Nocticola vagus: A new species of parthenogenetic Nocticolid Cockroach from Florida and Vienna.

Nocticolids are a small group (39 described species in ten genera) of Cockroaches found in tropical Africa, Southeast Asia, Papua-New Guinea, and Australia. They differ from other Cockroach groups in that they are flattened laterally rather than horizontally. Nocticolids are rather cryptic in their habits, and the group is not well studied in the wild; most of what we know about their biology comes from studies of colonies in labs, or the pet trade.

In a paper published in the journal Zootaxa on 5 May 2025, Junkai Wang of the Department of Entomology at Michigan State University, Alan Jeon of the Natural History Museum at Auburn University, and Anthony Cognato, also of the Department of Entomology at Michigan State University, describe a new, and apparently invasive, species of Nocticolid Cockroach from Florida and Vienna.

The new species was originally detected in the wild at University Park in Miami Dade County, Florida, where Alan Jeon collected several female specimens in June 2020.  In captivity, these were found to reproduce parthenogenetically, i.e. the female Cockroaches laid eggs without mating, which hatched into new females, also capable of producing fertile eggs without mating. This trait has not previously been recorded in Nocticolid Cockroaches, although it is known in several other Cockroach groups.

Because Nocticolid Cockroaches are not thought to be indigenous to the Americas, Wang et al. carried out a genetic analysis, in which they also included specimens from the US pet trade, which weren being traded under the name Nocticola sp. 'Malaysia', as well as specimens from a greenhouse at Schönbrunn  Zoo in  Vienna, Austria, where another all female colony of Nocticolid Cockroaches was reported.

The genetic study recovered all three populations as the same species, which Wang et al. name Nocticola vagus, where 'vagus' means 'wandering' in Latin, in reeference to the known distribution of the species. The original location of the Cockroaches traded as Nocticola sp. 'Malaysia' is unknown, but Nocticola vagus was recovered as the sister species to an un-named specimen from Vietnam in the genetic study. Thus, it is likely that the species originates in Southeast Asia, and possibly with a range that includes Peninsula Malaysia. A morphological comparison was more difficult, as many species of Nocticola are known only from male specimens, whereas all known specimens of Nocticola vagus are female.

Nocticola vagus female holotype. Habitus (A) frontal, (B) dorsal, (C) lateral, (D) ventral view and ootheca (E) lateral view. Wang et al. (2025).

Specimens of Nocticola vagus are described as 'small' (although Wang et al.do not provide measurements, and yellow or brown in colour. Their bodies are covered in short sensilla chaetica (sensory bristles). Each eye has eight ommatidia (the individual lenses of an Insect's compound eye), and the maxillary palps (mouthparts) each have five segments, making them almost as long as the head. 

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Amasa parviseta: A new and highly invasive species of Ambrosia Beetle from Australia, South America, and Europe.

Ambrosia Beetles are one of the most diverse groups of Bark Beetles, with over 1300 described species in 43 genera, found throughout the world's tropical and temperate regions. The biology of these Beetles enables them to colonise new areas rapidly, with many species considered to be highly invasive pests, causing significant economic and ecological damage in forests, orchards, nurseries as well as urban and suburban gardens. This is because the Beetles bore into the wood of trees and cultivate gardens of Fungus, feeding on an ambrosia produced by the Fungus rather than the wood of the tree. This means that, unlike most wood-boring Insects, they are not tied to a single species of tree, although some species and genera are restricted to a single family of hosts. The reproductive cycle of the Beetles also favours dispersal, with diploid females mating with haploid males within their birth tree before dispersing to new trees to lay eggs. 

The taxonomy of Ambrosia Beetles can be challenging, due to the small size of these Insects, and their wood boring lifestyle, which means both that they are out of sight and that they are not under any evolutionary pressure to become visually distinct. Members of the genus Amasa can be distinguished from other genera by their truncated abdomens and elytra (wing cases) which have a distinct declivity (downward fold) at the rear. However, telling species apart can be difficult, particularly as most species are known only from a single, or very small number of, specimen(s) held in widely distributed collections. There are currently 47 species of Amasa, from across tropical Asia and Oceania; two species from Madagascar have been assigned to the species, but this is probably erroneous. 

In 2011 a species of Amasa found infesting a Eucalyptus grandis plantation in São Paulo State,  Brazil, was provisionally identified as Amasa truncata, a widespread invasive species, although further investigation led to the conclusion that this was a morphologically similar, but unknown, species. This new Beetle was reported from Minas Gerais State in Brazil as well as in neighbouring Uruguay in 2015. In 2016 it was reported from Valparaíso in Chile, and by 2018 it had reached Argentina.

Similar specimens found in Cádiz, Spain, in 2009, were initially identified as Amasa  resecta, but again were later shown not to belong to this species. In 2018 the same species was found in Antibes,  France, and in 2019 in Lisbon,  Portugal. A genetic analysis of specimens collected in France found them to be 100% identical to members of an unknown species from New South Wales.

In a paper published in the journal Zootaxa on 12 January 2024, Miloš Knížek of the Forest Protection Service at the Forestry and Game Management Research Institute, and Sarah Smith of the Department of Entomology at Michigan State University, formally describe the unknown Amasa species based upon specimens from Australia, South America, and Europe.

The new species is named Amasa parviseta, where 'parviseta' means 'small hairs' as the hairs on the elytral  declivity is almost hairless, with only a few microscopic hairs. The new species is described on the basis of specimens from New South Wales, the Australian Capital Territory, and Queensland in Australia, Alpes-Maritimes Department in France, Galicia in Spain, São Paulo State in Brazil, and Tacuarembó Department in Uraguay. It is also thought to be present in Corsica, Portugal, Minas Gerais, Argentina, and Chile.

Amasa parviseta paratype female from Ponteverda Spain (Miloš Knížek collection) (1) habitus dorsal view; (2) habitus lateral view; (3) elytral declivity part; (4) elytral declivital face; (5) lateral detail of elytral declivity with microscopic hair-like setae visible on the lateral edge of the declivity and on the apices of tubercles on the declivital face. Antonín Knížek in Knížek & Smith (2024).

Females of Amasa parviseta are 2.38–3.00 mm long and light brown in colour, with slightly darker elytra. Males are unknown. The species was found on Eucalyptus trees and in Eucalyptus leaf litter; some were captured in traps in mixed Eucalyptus and Pine woodland. 

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The impact of landscape change on the Greater One-horned Rhinoceros in Chitwan National Park, Nepal.

Human populations have risen sharply in South Asia in the past century, leading to a greater demand for land for agricultural and other purposes. This has had a profound impact on the wildlife of the region, as areas of uncultivated land have shrunk and become fragmented. Even in areas which have not been formally 'claimed' by Human populations, habitats are often degraded by activities such as fire-setting, Cattle grazing, and the collection of thatch and timber. 

The Chitwan National Park in Nepal contains slightly over 950 km² of 'wild' landscape providing a habitat to large Mammals such as Greater One-horned Rhinoceros, Rhinoceros unicornis, Asian Elephant, Elephas maximus, Gaur, Bos gaurus, and Bengal Tiger, Panthera tigris. However, while in theory protected from Human actions, both this environment and the buffer zone surrounding in (in which only a limited range of Human activities are allowed), are coming being altered by Human pressures, leading to changes in the numbers and distributions of the Animals within the park.

Five species of Rhinoceros still survive on Earth. The most numerous of these, the White Rhinoceros, Ceratotherium simum, currently has a population estimated to be between 17 212 and 18 915, and is found in semi-arid grasslands in Southern Africa. The Black Rhinoceros, Diceros bicornis, has an estimated population of between 5366 and 5630 individuals, found in dry woodland savannah, although with a population fragmented and largely confined to protected reserves. The Greater One-horned Rhinoceros, Rhinoceros unicornis, is the most numerous surviving Asian Rhinoceros, with a population of over 3700, inhabit the moist riverine grasslands and alluvial floodplains of Ganges, Brahmaputra, and Sindh rivers and their tributaries. Less than 80 Sumatran Rhinoceros, Dicerorrhinus sumentransis, are thought to be alive today, living in the rainforests of Sumatra, Peninsula Malaysia, and Borneo. An estimated 75 Javan Rhinoceros, Rhinoceros sondaicus, still survive in the lowland forests of the Ujung Kulon National Park, on the westernmost tip of Java. 

The Sumatran and Javan Rhinoceros are the two rarest large Mammals surviving, and both are currently classified as Critically Endangered under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species. The Greater One-horned Rhinoceros was formerly classified as Endangered, but was downgraded to Vulnerable following a significant recovery of the population of this species in the Kaziranga National Park in India. The Black Rhinoceros is still considered to be Critically Endangered, due to its highly fragmented population, and the threat of poaching, while the White Rhinoceros is Near Threatened.

There are currently 752 known Rhinoceros with Nepal, 694 of which are found within the Chitwan National Park, where they inhabit the riverine grasslands of Reu, Rapti and Narayani rivers, while the remaining 17 are found within the Suklaphanta National Park, where they are found in mixed riverine forests and tall grasslands associated with the Chaudhar and Mahakali rivers. Greater One-horned Rhinoceros favour areas close to rivers, wallowing in riverbeds and feeding grasslands and open woodlands. They will occasionally retreat into more dense woodland to seek shelter during monsoons, and rarely visit croplands to feed on aggricultural products. Their favoured enviroment is grassland dominated by Wild Sugercane, Saccharum spontaneum.

An adult Greater One-horned Rhinoceros with a calf in the Chitwan National Park in April 2015. Sumanth Kuduvalli/Felis Creations/WWF.

In a paper published in the Asian Journal of Conservation Biology in July 2023, Prayag Raj Kuikel and Khadga Basnet of the Central Department of Zoology at Tribhuvan University, present the results of a study of changing land use by Greater One-horned Rhinoceros in the Chitwan National Park, in response to changing habitats within the park.

Previous studies of Rhinoceros in the Chitwan National Park have shown that their distribution has changed in recent years with the majority shifting from the eastern part of the park to the western part, but no attention has been given to date to the cause of this shift. 

The Chitwan National Park was Nepal's first national park, created in 1973, and was made a UNESCO World Heritage Site for the international significance of its unique wetlands in 1984. The park comprises a variety of lowland ecosystems within the wider Inner Tarai ecozone, including the Churia and Someshwor hills, the flood plains of the Reu, Rapti and Narayani rivers, and numerous ox-bow lakes. The eastern boundary of the park abuts the Parsa National Park.

Chitwan National Park, Nepal. Kuikel & Basnet (2023). 

Kuikel and Basnet looked at the way in which the Rhinoceros were using the landscape, and the way in which that landscape changed over time, using field observations, satellite data, and geographical information systems. The landscape was divided into a series of categories,  river area, sparse forest, dense forest, riverbed, bushes, cultivable land, and barren land, and Landsat images from 1993, 2000, 2010 and 2014, were used to track the way that these had changed over time.

Fieldwork was carried out in the Chitwan National Park between December 2016 and September 2017, both on foot, by canoe, and on Elephant back. This was done to provide ground truth of environmental interpretations of landscape type, as well as to carry out direct observations of Rhinoceros. Direct observations of Rhinoceros were made in both the eastern and western regions of the park, while the presence of Rhinoceros on islands in the Narayani River was confirmed by the identification of dung. Animals were classified as calves if they were under four years old, subadults if they were four-to-six-year old, and adults if they were over six. Sightings of Rhinoceros were mapped against landscape type using Arc GIS software.

Most prior studies of Greater One-horned Rhinoceros have concluded that their preferred habitat is riverine grasslands, so Kuikel and Basnet concentrated their efforts on the grasslands associated with the Reu, Rapti and Narayani rivers. The use of each landscape type was calculated by the number of Rhinoceros sightings there as a total of the whole. Areas infested by the invasive Climbing Hemp Vine, Mikania micrantha, was also mapped, as was the condition of the land, state of water bodies, and areas of drought or flood, and variations in vegetation cover.

Kuikel and Basnet found that dense forest cover increased by 196 km² between 1993 and 2014, while grassland and sparse forest decreased by 154 km², and cultivatable land decreased by 56 km². Baren land increased by 56 km², and river cover increased by 14 km², while other land cover types remained roughly constant.

In line with predictions, 49% of all Rhinoceros sightings occurred in open forest or grassland environments, with 38% in riverine forests, 10% in rivers, and 3% in dense forests. The two land cover forms which increased the most in the park were both largely unused by Rhinoceros.

While the over the entire area of the park the areas favoured by Rhinoceros decreased, in the western part of the area there was an increase in river area, and therefore also in land in close proximity to rivers, as well as in the amount of land covered by pure stands of Wild Sugarcane. Infestations of Climbing Hemp Vine covered 23.3% of the land area in the eastern area and 18.3% in the western area, with this particularly affecting rivers, riverine forests, and grasslands. The eastern area was also affected by drought, which was apparently driven by vegetative succession; forms of vegetation which were not washed away by the annual floods had taken hold, leading to the formation of new dykes, which altered the flow of waterways. Only seventeen areas where found in the eastern area where the annual flood cleared areas of vegetation in the eastern part of the park, compared to 32 in the western part. These areas were those colonised each year by Wild Sugarcane, creating the favoured environment for Rhinoceros.

A Greater One-horned Rhinoceros feeding in a stand of Wild Sugarcane in the Chitwan National Park, Nepal. Tripadvisor.

The habitat favoured by Rhinoceros in the Chitwan National Park is steadily decreasing, and it is likely that following current conservation practices will cause it to decrease further. Dense forest and baren areas, both avoided by Rhinoceros, are increasing within the park, while grasslands and mixed woodland, which are important Rhinoceros habitats, are decreasing. Human behaviour is generally assumed to be the major cause of habitat loss for species such as Rhinoceros, though in the case of the Chitwan National Park, the major problem appears to be vegetative succession in undisturbed land. This has been made words by the rapid spread of the invasive Climbing Hemp Vine, as well as indiscriminate fire setting and overgrazing of domestic Animals (leading to the formation of barren areas.

Greater One-horned Rhinoceros require flood plain grasslands and open forest in order to thrive. They also utilise the rivers themselves. In the Chitwan National Park areas formerly utilised for agriculture have been returned to nature, creating new habitats, but over time flood plain grasslands develop into open woodland, and then dense woodland, effectively excluding the Rhinoceros. 

Over time the eastern part of the park has dried and become more heavily forested, while the amount of wetlands in the western part of the reserve has increased slightly, causing the Rhinoceros to shift towards the western end of the park. While the Rhinoceros are currently finding suitable habitats in the west of the park, the general trend is towards drying and afforestation across the whole area, with the spread of the invasive Climbing Hemp Vine, which supplants native species such as Wild Sugarcane, the main food of the Rhinoceros also impacting the available space for the species. 

Kuikel and Basnet recommend that future conservation efforts in the Chitwan National Park include the maintenance of stable wetlands and a management plan for the invasive Climbing Hemp Vine.

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Trying to identify an invasive colonial Sea Squirt from the Gulf of California.

Invasive species are one of the greatest challenges faced by conservationists today, often rapidly taking over ecosystems where they have no natural enemies and displacing endangered or commercially important local species in the process. The first step in controlling an invasive species is identifying it, which enables appropriate control systems to be introduced. However, this is often difficult and complicated, as invasive species are not necessarily well understood, or even known, in their own ecosystems. This is particularly true in marine environments, where our taxonomic understanding of many groups is poor, and increasingly plagued by a lack of skills as few young scientists are attracted into the field. This is despite the problem of invasive species being particularly acute in marine environments, where international shipping traffic has made it easy for many benthic 'fouling' organisms to rapidly establish global distributions.

Ascidians, or Sea Squirts, are the most abundant class of the Subphylum Tunicata and are distributed along shorelines worldwide. They are sessile marine invertebrates and are widely used as a model organism for developmental and evolutionary studies. Ascidians exhibit multiple morphological characteristics, from small colonial to colorful and large solitary forms. They are divided into three major well-accepted orders, namely, Phlebobranchia, Aplousobranchia, and Stolidobranchia, based on the branchial sac morphology of the adults. However, the class Ascidiacea is paraphyletic (i.e. not everything thought to be descended from the last common ancestor of the group is considered to be an Ascidian) with the  Phlebobranchia and Aplousobranchia showing a close relationship with Thaliaceae (Pyrosomes, Salps, and Doliolids), a non-Ascidian Tunicate class, whereas the Stolidobranchia remains a distinct and monophyletic group. Over the course of several decades, the Ascidiacea have been shown to be an important class of ecological species because of their invasive potential along with their ability to adapt to new environments. Transportation of Ascidians attached to ship hulls as fouling material and within the ballast water of ships has enabled them to invade many new territories. This phenomenon has major impacts on local marine biodiversity as well as aquaculture industries. Therefore, the Ascidiacea are now considered as important model species for the study of non-indigenous species worldwide.

Sea Squirts are particularly problematic from a taxonomic point of view, with a simple body plan which provides few diagnostic features, and very few scientists specializing in their taxonomy. To make matters worse, the group appears to be rife with cryptic species (i.e. species which are physically identical or nearly identical, but biologically distinct), so that many identified species are likely to be clusters of similar-looking species, often with different ecological constraints. Many species of Sea Squirt have proven to be adept at colonizing new environments, where they are often identified as new species, so that particularly successful invasive species often have several different names, further adding to the taxonomic confusion within the group. A combination of careful physical examination and genetic analysis can hopefully unravel some of these problems, particularly in the identifying of pseudo-indigenous species, i.e. invasive species thought to be native to their new habitat because their origin is unknown.

Eleven invasive species of Sea Squirt had been identified from Mexican waters by 2014, five of them from the Gulf of California. In 2015, a colonial Sea Squirt previously unknown to the region was identified in Ensenada de La Paz, which spread rapidly, causing a mass mortality event in Pen Shells, Atrina maura, a Bivalve species commercially important locally, whose large shells provided an ideal substrate for the invaders. The Pen Shell fishery was already suffering from over-harvesting, with a moratorium on their collection introduced in 2013 to allow the population to recover, something which appears to have been significantly hampered by the arrival of the Ascidians (no significant variation in other environmental variables was detected which coincided with the die-back). A subsequent biofouling experiment carried out in Bahía de La Paz found that the Sea Squirts, tentatively identified as Distaplia cf. stylifera, were the most abundant macro-organisms settling on a series of silicone resin coated metal panels placed in the water for two months. Furthermore, the Sea Squirt colonies provided a substrate upon which 28 species of epibiont Polychaete Worms were able to settle, further adding to the biofouling. Subsequent studies of the Sea Squirts, which have continued to suppress Shellfish populations, and become a serious biofouling problem in the area, have used the name Distaplia stylifera, although this is only an assumption, based upon a rough similarity to descriptions and the fact that it is a common invasive species. No formal taxonomic identification of the invader has been attempted to date, something which may be hampering efforts to find an effective control.

In a paper published in the journal ZooKeys on 5 April 2023, Betzabé Moreno-Dávila and Leonardo Huato-Soberanis of the Programa de Ecología Pesquera at the Centro de Investigaciones Biológicas del Noroeste, Jaime Gómez-Gutiérrez of the Departamento de Plancton y Ecología Marina at the Instituto Politécnico Nacional, Carolina Galván-Tirado of the Consejo Nacional de Ciencia y Tecnología, Carlos Sánchez of the Departamento de Ciencias Marinas y Costeras at the Universidad Autónoma de Baja California, Teresa Alcoverro of the Department of Marine Ecology at the Centre for Advanced Studies of Blanes, Eduardo Balart, also of the Programa de Ecología Pesquera at the Centro de Investigaciones Biológicas del Noroeste, and Xavier Turon, also of the Department of Marine Ecology at the Centre for Advanced Studies of Blanes, present the results of a study of the invasive Sea Squirt from Ensenada de La Paz, which examines the Mexican species' morphology and compares it to previous descriptions from other parts of the world, as well as attempting a genetic analysis.

Bahía de La Paz is located on the southeastern tip of the Baja California Peninsula. The Ensenada de La Paz is separated from Bahía de La Paz by a 12 km long sandbar known as El Mogote. The Ensenada de La Paz has an area of about 45 km² and a maximum depth of 10 km and a bottom covered by patches of sand and mud-silt. The Ensenada de La Paz and the Bahía de La Paz are connected by a shallow channel about 1 km wide and 4 km long, upon which are seven yacht docks associated with the city of La Paz, while at the entrance lies the Pichilingue commercial harbour.

(A) Area of study in Ensenada de La Paz located in the southern part of Bahía La Paz, Baja California Sur, Mexico. (B) Both bodies of water are located on the southwest coast of the Gulf of California, Mexico. (C) Sampling sites and potential sources of dispersal of Tunicates (circles). Moreno-Dávila et al. (2023).

Colonies representing three different colour-morphs of the invasive Sea Squirt (white, orange, and purple) were collected from four sites within the Ensenada de La Paz, for a total of twelve colonies, which were preserved for morphological analysis as well as having their DNA extracted for genetic analysis. The colonies were found growing at depths of 0.5-3 m, growing on the shells of Sea Pens, a PVC pipe, buoys, a rope, and wooden docks.

'Distaplia stylifera' from Ensenada de La Paz. (A) Live orange colony. (B) Live purple colony. (C), (D) Typical mushroom-shaped colonies. (E) Zooid. Scales bars: 10 mm (A), (B); 2.5 mm (C), (D); 1 mm (E). Moreno-Dávila et al. (2023).

The colonies were predominantly orange, and approximately mushroom-shaped, with mottled white markings around the common cloacal-aperture, with purple and white colonies also present within the population. They reach a maximum of about 2 cm, with the head having a diameter of up to 2.5 cm. The colonies are more heavily pigmented around their tips than at the base, with pigment only remaining in this area after preservation. The tunics of the colonies are firm, and the stalks sometimes branch, so that two or more colonies share a common base; some colonies lack stalks altogether, forming cushion-shaped masses that spread over the substrate. The head of each colony is shared by one or more zooid systems, each sharing a common cloacal-aperture, which is surrounded by a single or double ring of zooids.

The zooids are up to 5 mm in length, excluding the gonadal sacs. Each zooid is divided into a thorax and abdomen. Two sacs are attached to this structure, a smaller one, containing the gonads, is attached to the right posterior side of the abdomen. The second sac contains embryos and developing larvae, and is often longer than the zooid. This second sac is attached to the posterior part of the pharynx by a thin peduncle.

'Distaplia stylifera'. (A) Zooid (thorax and abdomen). (B) Thorax. (C) Dissected thorax. (D), (E) Stomach. (F) Gonads. (G) Larvae. (H) Enlargement of one larva showing two pigmented spots. Scale bars: 10 mm (A); 0.5 mm (B), (C), (F), (G); 0.25 mm (D), (E). All images except (F) correspond to stained zooids. Moreno-Dávila et al. (2023).

The oral siphon on the thorax is smooth-rimmed or has six slight lobulations, and a large atrial opening which exposes most of the branchial sac. A  wide flap-like lid with smooth or lobed margins called the atrial languet lies on top of the atrial opening. This languet is crossed by several transverse muscular bands. Each side of the thorax has about 30 bands of longitudinal muscle. About 14 simple oral tentacles are also present on the thorax. The pharynx has four stigmata rows clearly divided by parastigmatic vessels, with the first two rows typically having 18-19 stigmata, and the posterior two rows having 15-16. Three simple dorsal languets are found between these rows, slightly displaced to the left.

'Distaplia stylifera' (A) Zooid (thorax and abdomen). (B) Abdomen. (C) Larva. Abbreviatures: a. anus; am. ampullae; ap. adhesive papillae; oc. ocellus; o. oocyte; pv. parastigmatic vessels; pg. pyloric gland vesicle; sc. statocyte; sg. stigmata; st. stomach; t. testes. Scales bars: 1 cm (A); 0.5 mm (B), (C). Moreno-Dávila et al. (2023).

Within the abdomen lies an elongated and curved stomach, the wall of which has more than 20 fine longitudinal plications (folds), which can be seen on the inner and outer surfaces when the specimens are sectioned, although they are sometimes interrupted or divided. A short post-stomach connects to an enlarged mid-intestine at the bottom of the gut-loop. The distal intestine runs to the anterior, and ends in a bilobed anus at the base of the atrial aperture. A pyloric (mucus) gland between the stomach and the intestine and continues anteriorly forming sinuous tubules over the intestine in front of the stomach.

The gonads are held within a pedunculated sac, with one or two oocytes at the bottom, above which lie a cluster of five or six elongated or wedge-shaped testes. A  common sperm duct arises posteriorly from the cluster of testes, but turns anteriorly at its very beginning, without overlapping the oocytes.

All of the colonies examined had larvae incubating in long sacs that reach posteriorly deeper than the zooids themselves in the colonies. These sacs typically contained one or two well developed larvae, about 1.3 mm in length, plus three embryos. When fully developed the larvae reach about 1.5 mm, and possess three adhesive papillae, two dorsal and one ventral, with a globular ampulla each in the stalks. The four rows of stigmata have developed by this stage, with an incipient abdomen folded under the branchial sac. A sensory vesicle contains two pigmented spots, with a larger one above and a smaller one below, though these can be hard to differentiate, as they are close together and the larvae are not transparent. 

Distaplia stylifera was originally described in the Red Sea, and subsequently has been recorded from several areas of the Indo-Pacific, Australia, the Philippines, and the South China Sea, as well as. under the possible synonym Distaplia mikropnoa, from Palau. There have been reports from the Mediterranean, although these are considered dubious. It has also been reported in the Western Atlantic, from the coast of North Carolina south as far as Jamaica, and at several locations in the Caribbean, and possible further south around Sao Paulo in Brazil. It has not, however, previously been reported from the Eastern Pacific.

Sites of previous records of Distaplia stylifera: (1) Red Sea, 1874 (type locality). Indo-Pacific; (2)-(9). Mediterranean, (10). Western Atlantic Ocean, (11)-(18). Eastern Pacific Ocean, (19) present study. The type locality in the Red Sea and the record of the present study are indicated with stars. Moreno-Dávila et al. (2023).

Despite successful amplification of DNA apparently collected from the Ascidian colonies, all of this proved, upon analysis, to be closer to that of Algae, Bacteria, or Fungi, than to any Animal, despite great care being taken to avoid any contamination. For this reason the taxonomic comparison had to be made entirely upon physical examination of the specimens, and comparison to other members of the genus Distaplia.

The taxonomy of the genus Distaplia is mainly based on characters such as colony shape, arrangement of zooids in systems, presence or not of gonadal sac, stigmata per row, stomach shape and external surface, and muscle arrangement. Based upon these criteria, the Ensenada de La Paz specimens would appear to be entirely consistent with Distaplia stylifera. However, Moreno-Dávila et al. note that the original description of the species was made in 1874, and like a lot of descriptions from this period, was a lot less detailed than descriptions made by modern taxonomists. Furthermore, that description was made upon a specimen that was probably a juvenile, lacking larvae and having under-developed gonads. 

Descriptions of populations of modern populations of 'Distaplia stylifera' show some variation, making it possible that the global population is in fact a cluster of closely related species. Notably, the specimens collected at Ensenada de La Paz all had parastigmatic vessels, something also reported in almost all specimens collected from Australia, as well as specimens collected from the Caribbean. An absence of such vessels has been noted in specimens from Madagascar, and it has been suggested that the presence or absence of these vessels might be a feature which can be used to differentiate between Distaplia stylifera and Distaplia mikropnoa. However, a number of other features can be used to differentiate Distaplia mikropnoa, which include a long double rows of zooids converging to the terminal common cloacal apertures, a long post-pyloric part of the gut loop, and a lack of a gastric reservoir. Furthermore, in Distaplia mikropnoa the course of the gastro-intestinal ducts that does not cross from the stomach to the ascending limb of the gut loop but extends down the descending loop. Based upon this, Patricia Kott concluded that the two species are both valid, but that they have widely confused within the literature. Notably, she concluded that the Palau population belonged to Distaplia stylifera rather than Distaplia mikropnoa.

Oval follicles have been suggested as another feature which could be used to differentiate the two species, with specimens which have up to 15 oval follicles assigned to Distaplia mikropnoa, while those having only five or six, which would include the Ensenada de La Paz population, belong to Distaplia stylifera. 

The sperm duct is another feature apparently variable in populations assigned to Distaplia stylifera, with some populations having a sperm duct running posteriorly and making one or several loops over the oocytes before turning anteriorly, while in other populations, including the Ensenada de La Paz population, it is straight. Furthermore, in some populations, including Ensenada de La Paz, the gonadal sac is attached via a peduncle, while in others it is almost flush with the abdomen, separated by a wide neck. 

Moreno-Dávila et al. suggest that this wide range of variable features indicate that 'Distaplia stylifera' is probably a cluster of closely related species, often mistaken with the closely related Distaplia mikropnoa. This probably cannot be resolved without a more detailed taxonomic study, using both morphological and genetic methods to analyse populations from different regions of the world. Nevertheless, the reporting of a member of the species cluster from the Eastern Pacific represents a significant range-expansion for a group previously known from tropical regions of the Western Atlantic, Indian Ocean, and Western Pacific. 

Moreno-Dávila et al. were unable to extract DNA from their specimens of 'Distaplia stylifera', and note that no records exist within the GenBank and BOLD public databases. The co-generic Distaplia bermudensis is present in these databases, and shows a 14–20% genetic variance between different populations and morphotypes, indicating either a remarkable level of genetic variation within a single species, or that Distaplia bermudensis is also a species cluster. 

This taxonomic uncertainty makes it difficult to assess to what extent the different populations of 'Distaplia stylifera' represent introductions or local species, although Moreno-Dávila et al. note that the populations from North Carolina and the Caribbean appear to strongly favour lagoons and artificial structures, which is behaviour typical of invasive fouling organisms, and that this population appears to be expanding southwards to the coast of Brazil, where again it has been found only on artificial substrates. 

Despite this uncertainty, Moreno-Dávila et al. believe that the Ensenada de La Paz population does represent a high-impact invasive species, and given the absence of any other known populations of 'Distaplia stylifera' in the Eastern Pacific, and the behavioural similarities of this species to the Western Atlantic populations, one which has probably arrived via the Panama Canal. probably crossing the canal on a large ship, then secondarily transferring to a smaller vessel capable of entering the harbours around La Paz. 

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Aplonis opaca: The Såli (or Micronesian Starling) holds on despite the presence of the invasive Brown Treesnake on Guam.

Invasive species present one of the biggest challenges for conservation biologists, with many endemic species threatened by the arrival of invasive predators or competitors. Such organisms typically arrive in an area where local species are naïve to their behaviour, and undergo an explosive ecological release, being freed from their own predators and pathogens whilst at the same time able to exploit local prey which have no defences against them. Species on oceanic islands are often particularly vulnerable to the arrival of invasive predators, and are also often home to highly endemic species, not found anywhere else, which means that the arrival of a novel predator on such an island can quite often lead to a cascade of extinctions. Among Vertebrates, island-dwelling Bird species appear to be particularly vulnerable to such effects, with widespread loss of native Bird species across island systems such as Hawai’i, New Zealand, and the Mascarenes.

However, where species are not completely wiped out, they can respond positively to predator control programs, with the recovery of Bird species recorded on many small islands where invasive Mammal species have been removed. Such programs are difficult to run on larger islands however, and in such cases species recovery is often limited to fenced-off areas where the predators have been removed, although the presence of wild populations in such areas greatly increases the availability of recruits to repopulate the rest of the island, should this later become possible.

The predatory Brown Treesnake, Boiga irregularis, was introduced to Guam, an island in the Mariana Archipelago, shortly after the end of World War II, since which time nine of the island's eleven indigenous Bird species have been wiped out. By the early 1990s, there were an estimated 5000-10 000 Brown Treesnakes per square kilometre on Guam, with 1-2 million thought to be living on island in total. Despite this, some Birds have managed to survive on the island, notably the endangered Yåyaguak (or Mariana Swiftlet), Aerodramus bartschi, which is a cave-roosting Bird, difficult for the Snakes to attack, and the locally endangered Såli (or Micronesian Starling), Aplonis opaca, a cavity-nesting Bird found across the Marianas. The omnivorous Såli is an important seed-disperser, and therefore critical to the ecology of the island, where it was formerly found in all habitats, but underwent a catastrophic decline after the introduction of the Brown Treesnake, with the last recorded survey of the species, carried out in the early 1990s, finding only 60-120 Birds remaining on Guam, almost all of which resided on Andersen Air Force Base on the northeast of the island.

Despite a lack of formal assessment since this time, the Såli is known to still be present on Guam, with the population around Andersen Air Force Base thought to have expanded due to Snake control measures. The species is known to be suffering high fledgeling mortality, again due to the Snakes, but has recently been seen in urban areas in northern and central Guam, where it has not been seen since the 1980s, leading to hopes that these Birds may be expanding back into parts of their former range, despite a lack of Snake control.

In a paper published in the journal Bird Conservation International on 1 March 2021, Henry Pollock of the School of Global Environmental Sustainability at Colorado State University, Martin Kastner of the Department of Ecology, Evolution, and Organismal Biology at Iowa State University, Gary Wiles of Olympia in Washington State, Hugo Thierry, also of the Department of Ecology, Evolution, and Organismal Biology at Iowa State University, Laura Barhart Dueñas of the Division of Aquatic and Wildlife Resources at the Guam Department of Agriculture, Eben Paxton of the Pacific Island Ecosystems Research Center of the U.S. Geological Survey. Nicole Suckow, also of the School of Global Environmental Sustainability at Colorado State University, Jeff Quitugua also of the Division of Aquatic and Wildlife Resources at the Guam Department of Agriculture, and Haldre Rogers, again of the Department of Ecology, Evolution, and Organismal Biology at Iowa State University, present the results of a study of an island-wide survey of the distribution and abundance of the Såli on Guam, 

At 541 km², Guam is the largest island in Micronesia, as well as the most populated, with a population of about 160 000 people in 2010, and the most developed, with about 20% of the . The northern part of the island is covered by a limestone plateau, with karst forest, and the majority of the island's Human population and urbanised areas, while the southern part is dominated by volcanic geological features, with areas of savanna and ravine forest, and a more sparse Human population.

Previous studies have established that Såli roosting on Andersen Air Force Base range widely throughout the forested areas along the eastern and southern perimeter of the base during the day, but return to the developed area around 3.00 pm, where they are relatively sedentary and easier to count. In 2017-8 over 350 Birds from the Air Force Base population were colour-banded, providing a basis for future population estimates based upon resighting of these Birds; a number of Birds were also radio-tagged, all of which used forest extensively and travelled off-base but returned to the core roosting area at night.

 

The study area on Andersen Air Force Base and the search areas used for the standardised area searches. The developed areas of Andersen Air Force Base were divided into 28 search areas, comprising three types of habitats (forest search areas FO₀₁, FO₀₂, and FO₀₃ were included in the closest adjacent search area): urban (UR), residential housing (HW, HE, HN), and golf course (GC). Inset depicts the island of Guam, with the study area indicated by the white rectangle. Pollock et al. (2021).

Pollock et al. divided the main developed area of Andersen Air Force Base into 28 search areas of roughly similar size, comprising three habitat types: urban, residential housing, and golf course. Every day two areas were chosen at random, and each of these was observed by two fieldworkers, who traversed the search area together, to increase overall detection probability and the accuracy of colour-band identifications. Adjacent search areas were never searched on the same day, to minimise the risk of double-counting Birds. Observers also remained in constant contact during surveys, and communicated movements of any Birds throughout a given search area. All Birds detected in the search areas were logged, along with data on their ages and any banding information; the open nature of the landscape made it relatively easy to approach and visually observe Birds detected by sound.

In order to study the distribution of the Såli away from Andersen Air Force Base, Pollock et al. combined data from transect surveys with recorded opportunistic sightings of the Birds. They excluded the small, but stable, population of Såli known to be present on the nearby island of Cocos. Three data sources were consulted for data on opportunistic sightings, the eBird website, which enables members of the public to record Bird sightings anywhere in the world, a database if sightings maintained by the Guam Division of Aquatic and Wildlife Resources, and a personal database maintained by Martin Kastner. All of the sightings in the Division of Aquatic and Wildlife Resources database were confirmed by biologists from the department, and all of the sightings recorded in Martin Kastner's database were made by scientists familiar with the species.

 

A Såli (or Micronesian Starling), Aplonis opaca, on Cocos Island, Guam. Joseph Mancuso/eBird.

A total of 46 transect surveys were carried out in April–May 2018. Each transect route was visited once, with 19 of the routes having been previously used in a Division of Aquatic and Wildlife Resources survey in 1985, ten surveys were carried out in rural areas with little development (two northern, three central, and five southern), and nine in suburban areas within a kilometre of forest (five northern and four central). The transects were an average of 5189 m in length, with ten-minute surveys being carried out at ten points spaced roughly evenly along these lines. A further 27 transects were carried out in areas where sightings of Såli had recently been recorded by the Division of Aquatic and Wildlife Resources; these surveys were only 500 m in length, and did not overlap with the longer surveys. All but one of these short surveys were carried out within 500 m of an area of forest, with surveys carried out at six points roughly 100 m apart on the transect.

Pollock et al. found 16 previous studies that mentioned either the abundance or distribution of Såli on Guam published between 1901 and 1995. Twelve of these were published prior to 1970, and invariably described the Såli as very common. By 1978–1979 the species was rare on the southern part of the island, and uncommon on the northern and central parts. The first attempt at assessing the population of the Birds on Guam was carried out in 1981, and counted 1667 Såli in a series of surveys, which was extrapolated to a total of 15 132–18 602 Birds on the island. By this time Såli were completely absent from the southern part of the island, and in the central part, only a single small population was found, around the village of Hagåtña. This survey only found an estimated 231 individuals living at and around Andersen Air Force Base.

Subsequent surveys found almost no Såli on the island, and by the early 1990s it was estimated that only 60–120 Birds remained, including 50–100 living on Andersen Air Force Base, and the nearby areas of Mt. Santa Rosa and Gayinero, Yigo. Smaller groups of Birds, totalling no more than five individuals, were present at the Conventional Weapons Storage Area (now called ‘Munitions Storage Area’), and Naval Computer and Telecommunications Area Master Station (now called ‘Naval Base Guam Telecommunications Site’), as well as a scattering of solitary Birds along the southern coast.

 

Såli distribution on the island of Guam during the last three population surveys. Panel (a) indicates results from the 15 search areas surveyed in 1981. Panel (b) indicates results from the island-wide population assessment conducted between 1992-1994. Panel (c) indicates the current distribution on the island as derived from opportunistic sightings and the Andersen Air Force Base area search in 2018. Pollock et al. (2021).

During their three week-long surveys of Såli around Andersen Air Force Base, Pollock et al. counted 683, 609, and 844 Birds, respectively. However, in forests along the southern and eastern peripheries of the base they only counted 3–6 Birds each week. The Såli appeared to be concentrated towards the centre of the base’s main developed area, with less Birds in peripheral search areas adjacent to forest edge. Less than 5% of the Birds counted were banded, including 42 unique individuals, with 13 re-sightings of Birds seen in week one in week 2, and four re-sightings of Birds seen in weeks one or two in week 3. Extrapolating from this, Pollock et al. conclude about 50 ringed Birds remain on Andersen Air Force Base, out of a total population of about 1391, 91.1% of which are adults and subadults.

Pollock et al. compiled records of sightings of Såli at 64 unique locations across Guam from 2005 to 2019, these were largely concentrated in villages of northern and central Guam, with a few sightings around the southernmost tip of the island. A total of 64 sightings were recorded in 12 of the island's 19 villages, representing 156 Birds. The Birds were more common in urbanised areas, including the island’s main business districts (particularly at large malls and shopping centres), as well as urban parks and residential areas. No Birds were sighted more than 2 km from a built-up area or major road. The Birds were most frequently seen perched on power lines, power poles, buildings, and trees. Ten nests were observed outside the Air Base, all on lamp posts or power poles.

Duromg the transect surveys, Pollock et al. made 91 observations of Såli on 20 of the 29 surveys. All sightings were on the northern and central parts of the island, with the majority around the Air Force Base and the island of Yigo. No Såli were detected in the southern villages of Merizo or Umatac, despite these being the closest points to the island of Cocos, with its own population of the Birds. 

 

Satellite imagery of the island of Guam showing the locations of, panel (a), both long (white) and short (orange) transect surveys and, panel (b), the island’s 19 villages. Panel (b) lists the villages where Såli were detected (pink polygons) or not (red polygons) during transect surveys. Pollock et al. (2021).

Based upon the results of the sightings records and survey results, Pollock conclude there are currently around 1450–1490 Såli living on the island of Guam. This includes 30–40 individuals living around the villages of Yigo and Dededo on northern Guam, 20–30 Birds in Hagåtña, and 10–20 in Tamuning-Tumon-Harmon, in the central part of the island, as well as up to ten further Birds living outside of these areas; the remainder of the population being resident at Andersen Air Force Base.

Pollock et al. have produced the first update on the distribution and abundance of Såli on Guam since the 1990s. They record a 15-fold increase in population size since the last population survey took place, with the population up from about 100 to about 1500, although 93-96% of the population is concentrated at a single location, Andersen Air Force Base. Despite this uneven distribution, the Såli do appear to be in the process of recolonising urbanised areas elsewhere in northern and central Guam, with a few isolated Birds being seen on southern parts of the island. 

Away from Andersen Air Force Base almost all sightings of Såli occur in urbanised areas, with the overwhelming majority of such sightings. It is, however, unclear how well established the Birds are in areas away from the Base, as while the majority of these sightings were of pairs or small groups of Birds, indicating a potential for breeding, very few nests or juveniles were seen. This is further complicated by the fact that, apart from at Hagåtña, almost all of these sightings occurred at shopping malls, which might indicate that the (highly mobile) Birds are exploiting a new food source rather than settling in these areas.

For any Bird to survive on Guam today, they need to be able to avoid Brown Treesnakes. This means there are two major factors likely to influence the long-term survival of the Såli on Guam; Snake control measures, and the Birds increasing adaptation to urban areas. Snake control measures have been in place at Andersen Air Force Base since 1993, with thousands of Snakes being removed from the site each year, which has clearly benefitted the Såli. Similar Snake eradication programs are in place at other military installations on the island, but these sites are all much smaller, and do not seem to have created suitable safe environments.

Brown Treesnakes avoid brightly lit area, brightly lit areas, and open spaces such as lawns and car parks, and urbanised areas seem to have become refugia for the Såli on Guam. Recorded nesting by the Birds occurs in solitary trees, building cavities, lamp posts and artificial nest boxes. 

Snake eradication programs on Guam are largely restricted to military instillations, and Guam International Airport, and although other urban areas clearly present some refuge from the Snakes, most also include patches of vegetation, where the Snakes are found. Most urban areas are known to have fairly high Snake populations, with the largest Snakes often found in such areas, where there is an abundance of prey. However, even the limited protection presented by these areas appears to be beneficial, with the Birds apparently becoming re-established here.

Whatever the current successes of the Såli, the Snake control measures currently present on Guam are unlikely to protect the species in the long run, as these are intended to protect the island's electrical infrastructure and prevent the spread of the Snakes to new islands, rather than to eradicate them. The number of Snakes captured at Andersen Air Force Base has remained steady since the 1990s, indicating the overall population of Snakes has been uneffected, and a constant supply of new recruits exists to replace any Snakes removed. In addition, studies have shown that, even on Andersen Air Force Base, very few fledgling Såli survive to adulthood, due to predation by both Brown Treesnakes and Domestic Cats, leaving the Bird population unusually skewed towards older Birds. The Såli have failed to recolonise the extensive suburban areas on the east-central Guam, despite the high Human population here. The Birds are also largely absent from the sparsely-populated central and southern parts of the island. This strongly suggests that the Birds will be unable to repopulate the island properly without a more extensive Snake control program being implemented. 

One action that has clearly proven beneficial to the Såli has been the provision of nest boxes. These provide additional nesting opportunities for cavity-nesting Birds such as the Såli, and can offer protection from both the elements and predators. Such boxes have been placed on Andersen Air Force Base since the 1990s, with at least 50 predator-resistant boxes in place at any one time since 2015, which is thought to have allowed the fledging of about 900 Birds. However, fledgelings still suffer very high predation rates from both Brown Treesnakes and Domestic Cats, and there are still more nests in natural cavities than in nest boxes, so it is unclear how much of an impact this program has on the overall population.

The survival of the Såli is considered essential for ecosystem functioning on Guam. These omnivorous Birds are the only surviving native frugivores on the island, and as such are vital for the distribution of the seeds of many Plants, and subsequently the ability of the indigenous forests to regenerate. The ability of these Birds to survive in urban areas is beneficial for the species itself, but clearly of limited value to the island's forests. Thus, plans for rewilding efforts on Guam will require extensive application of Snake-control measures if they are to resume their natural ecological function.

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