Acanthaster benziei: A new species of Crown-of-thorns Starfish from the Red Sea.

Crown-of-thorns Starfish, Acanthaster spp., are highly distinctive Starfish found across the tropical Indo-Pacific region from the east coast of Africa to the west coast of Mexico, which get their popular name from the covering of long, venomous spines found in most species. They are typically corallivorous, feeding on Coral Polyps by extruding their stomachs and digesting them externally. Notably, Crown-of-thorns Starfish can undergo sudden rapid population increases, known as outbreaks, which can lead to large areas of Coral Reefs being denuded of their living Polyps, something of great concern to conservationists at a time when Coral Reefs are facing a range of other threats, which has led to them being one of the most extensively studied groups of Marine Invertebrates.

Crown-of-thorns Starfish were first described by the German naturalist Georg Eberhard Rumphius in 1705, and given their own generic name, Acanthaster, by the French palaeontologist François Louis Paul Gervais  in 1841. For a long while, only two species were described within the genus, Acanthaster planci, the typical, long-spined, venomous, corallovorous form, and Acanthaster brevispinus, a shorter-spined, non-venomous form, which does not feed on Corals. However, genetic studies carried out within the past three decades have shown that Acanthaster planci is in fact a species cluster, made up of a number of physically very similar species (cryptospecies), which are nevertheless genetically distinct, which often appear to have diverged from one-another a long time ago. 

Based upon this, it was suggested that the original species should be split into four different species, each inhabiting a different geographical area; the Pacific, the Southern Indian Ocean, the Northern Indian Ocean and the Red Sea, which each of these species probably needing further division into several subspecies. Subsequent studies have indeed confirmed that the Pacific, North Indian Ocean, and South Indian Ocean populations are in fact separate species, although genetic material from the Red Sea population has not, until now, been available.

In a paper published in the journal Zootaxa on 17 November 2022, Gert Wörheide of the Department of Earth and Environmental Sciences Palaeontology and Geobiology, and the GeoBio-Center at Ludwig-Maximilians-Universität München, and the Bavarian State Collection of Palaeontology and Geology, Emilie Kaltenbacher and Zara-Louise Cowan, also of the Department of Earth and Environmental Sciences Palaeontology and Geobiology at Ludwig-Maximilians-Universität München, and Gerhard Haszprunar, also of the GeoBio-Center at Ludwig-Maximilians-Universität München, and of the Bavarian Zoological State Collections, describe the Red Sea population of Crown-of-thorns Starfish as a new population.

The new species is named Acanthaster benziei in honour of marine biologist John Benzie, for his extensive work on Crown-of-thorns Starfish. The description is based upon four specimens collected from species within the territorial waters of Saudi Arabia by  Sara Campana and OliverVoigt in 2017.

Typical colouration of Acanthaster benziei. (A) GW4081 (Paratype, hiding during the day under a crevice), Al-Lith, Saudi Arabia, (B)–(D) Thuwal Reefs, Saudi Arabia. Approximate diameter of specimens is 25–30 cm. Oliver Voigt & Gert Wörheide in Wörheide (2022).

Acanthaster benziei is a large Starfish with a convex disk and 11-14 arms (the range for the genus being 10-25), of uneven lengths, and tapering to a point. Each arm has two rows of ambulacral tube feet, which have flattened tips and lack suckers. The central disk of the species is 28-65 mm across, with an aboral (upper surface) covered in papulae (pimples) arranged in an apparently random manner. Both surfaces are covered in calcareous ossicles (plates) and spines. These Starfish are grey-green to grey-purple in colour, although the aboral spines are orange or red. The papulae on the aboral surface of the central disk can form darker patterns, giving this surface a 'bulls-eye' appearance.

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Astrolirus patricki: A new species of Sponge-associated Starfish, from the seamounts of the northwest Pacific.

Seamounts are deep-sea biomes in the global ocean which harbor diverse habitats and benthic communities. Sponges are one of the dominant benthic groups in seamount ecosystems, playing important ecological roles by providing habitat and settlement substrate for other seamount invertebrates, such as Molluscs, Hydrozoans and Echinoderms. Suspension-feeding Brittle Stars and Crinoids with long and flexible arms are often observed perching on or wrapped around Sponges. 

In a paper published in the journal PeerJ on 27 May 2020, Ruiyan Zhang of the School of Oceanography at Shanghai Jiao Tong University and the Key Laboratory of Marine Ecosystem Dynamics at the Second Institute of Oceanography of the Ministry of Natural Resources, Yadong Zhou, also of the Key Laboratory of Marine Ecosystem Dynamics at the Second Institute of Oceanography of the Ministry of Natural Resources, Ning Xiao of the Laboratory of Marine Organism Taxonomy and Phylogeny of the Institute of Oceanology and the Center for Ocean Mega-Science of the Chinese Academy of Sciences, and Chunsheng Wang, also of the School of Oceanography at Shanghai Jiao Tong University, the Key Laboratory of Marine Ecosystem Dynamics and the State Key Laboratory of Satellite Ocean Environment Dynamics at the Second Institute of Oceanography of the Ministry of Natural Resources, describe a new Starfish species, which was found attaching to deep-sea Sponges, based upon five specimens from northwestern Pacific seamounts.

Species of the family Brisingidae possess 7 20 spiny arms that are up to about 40 times the length of the disk radius. As exclusive deep-sea inhabitants, their long arms and spines potentially equip them to be excellent suspension feeders, stretching out and gathering food particles in the water column in the resource-diluted deep ocean. The Brisingidae is composed of 62 extant species designated into 10 genera. The genus Astrolirus currently contains only one species, Astrolirus panamensis, and is differentiated from the other genera based on the presence of intercostal plates on arms and a pair of marginal plates between the first adambulacral plates. Astrolirus panamensis was discovered in the eastern Pacific Ocean at 1820- 2418 m depth, with 1 eight-armed specimen and 27 nine-armed specimens of varying size (disc diameter 6- 26 mm) reported. Thereafter, Astrolirus has seldomly been reported or investigated. 

The new species is named Astrolirus patricki, in honour of the character `Patrick Star' in the famous cartoon `SpongeBob Squarepants', who always spends time with his best friend `SpongeBob', a benthic Sponge. Since all specimens of the new species were observed in situ living on Sponges, it was name by Patrick to reflect this curious relationship.

In situ photographs of Astrolirus patricki. Zhang et al. (2020).

All five specimens of the new species are seven-armed and were captured from Hexactinellid Sponges. Occasionally 2- 3 individuals were spotted on the same Sponge along with numbers of Ophiuroids and Crinoids. The new species differs greatly from Astrolirus panamensis in morphological characters and living habitat.

During the COMRA (China Ocean Mineral Resources R & D Association) cruises DY31, DY37, DY41, DY56 and a seamount cruise in the northwestern Pacific Ocean seamounts from 2013 to 2019, five specimens of the new species were collected by mechanical arms or siphon-pumps equipped on Human operated vehicles and remote operated vehicles. Specimens were photographed in situ and on board by digital cameras. Tube feet tissues were extracted from each specimen and frozen in -80°C refrigerator or liquid nitrogen for later molecular experiments, while other parts of specimens were preserved in 100% ethanol for morphological examinations. Morphological identification was conducted under a stereoscopic microscope. 

Astrolirus patricki has seven robust arms. The tntercostal integument is densely covered by irregular, abutting plates. There is no conection between proximal arm plates. The first pair of adambulacral plates is separated by a pair of marginal plates. A large interradial plate above the first marginal plates, is visible from the abactinal side, covered by scattered spinelets. The mouth spines and proximal adambulacral spines are robust, and densely distributed. There are 3-4 uboral spines and 1-2 subambulacral spines, the proximal ones of which are truncate and capitate. There is one lateral spine to each adambulacral plate, starting from about the 8th. There is a pair of gonads to each arm.

Astrolirus patricki, abactinal view. (A) Paratype RSIOAS028. (B) Paratype RSIOAS003. (C), (D), (H), holotype RSIOAS044, (C) Abactinal surface of disk and proximal part of arms, with red arrow pointing at the madreporite body, white arrow at the interradial plate and yellow arrows at the marginal plates. The red frame indicates the proximal region of arm connecting the disk and genital region, where pedicellariae do no form regular costae. (D) Abactinal surface of arm genital area with mosaic plating, red arrows show the costae bands. (E) Paratype RSIOAS003, abactinal surface of arm genital area, red arrows show the costae bands. (F) Paratype RSIOAS052, zoom in view of the abactinal disk, showing the multiple sharp spinelets on disk plates. (G) Paratype RSIOAS052, a piece of dissected skin from abactinal disk, shot from the inner side of the skin, showing the small round disk plates. (H) Abactinal surface at the middle of arm, black arrows indicate the pedicellariae bands. Zhang et ai. (2020).

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Asterodiscides fourmanoiri: A Starfish known only from southern Madagascar reported off the coast of Pakistan.

Starfish (Asteroidea) are benthic marine Echinoderms found across the globe. They have a simple bodyplan, with a central disk that has the mouth on the underside, surrounded by (usually) five arms, each with a double row of tube feet underneath. The upper surface of the Starfish is covered by an articulated armoured exoskeleton made up of thousands of small calcite plates. The animal moves by means of a water vascular system, which enables it to inflate and deflate the tube feet as required. There are currently around 1900 described species of living Starfish, grouped into 370 genera. The genus Amphiaster contains eighteen species of deepwater Starfish found in the Indian and western Pacific oceans, including Asterodiscides fourmanoiri, which is known only from waters off the Sainte Luce Reserve in southeast Madagascar.

In a paper published in  the Summer 2019 edition of Iranian Journal of Fisheries Sciences, Mohammad Reza Mirzaei, Arezoo Vahabnezhad and Fereidoon Owfi of the Iranian Fisheries Science Research Institute, record the presence of Asterodiscides fourmanoiri on the southern coast of Pakistan.

Mirzaei et al. report discovering Asterodiscides fourmanoiri living at a depth of between 83 and 85 m on a sand and rock seafloor trawl near Gwadar Bay in the northern Oman Sea, based upon a single specimen recovered from a sample trawl by the Research Vessel Ferdows in October 2016. This represents a significant extension of the known range of the species, making it likely that it is found elsewhere in the waters of the Indian Ocean.

Specimen of Asterodiscides fourmanoiri recovered from the coast of Pakistan in 2016. Mizaeri et al. (2019).

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Acanthaster solaris: Using Environmental DNA to track the Crown-of-Thorns Starfish.

The Great Barrier Reef on Australia’s east coast is the world’s largest marine protected area, a World Heritage Site and a biodiversity hotspot of global importance. Despite this, the reef is estimated to have lost more than 50% of its Corals during the past three decades. Much of this is due to global warming, and the accompanying acidification of the seawater, but other factors are important. One of these has been repeated outbreaks of the Crown-of-Thorns Starfish, Acanthaster solaris, a Coral-consuming Echinoderm credited with having caused 42% of Coral loss on the Great Barrier Reef prior to the bleaching events of 2016-17. The Crown-of-Thorns Starfish has entered a boom-and-bust population cycle since the 1960s, with outbreaks producing huge numbers of Starfish that consume all the available food (i.e. Coral) then die out due to starvation. The precise cause of these booms is unclear, but probably linked to the life-cycle of the Starfish, which produce planktonic larvae, with the most likely explanation being greater numbers of larvae surviving because of increased food availability due to nutrients from agricultural runoff, or increased larval survival due to a reduced number of predators caused by overfishing. This makes Starfish booms of great interest to conservationists trying to protect the Great Barrier Reef, who need to detect new outbreaks as quickly as possible in order to take remedial action.

 

 An adult Crown-of-Thorns Starfish predating Coral. Hall et al. (2017).

 

In a paper published in the journal Coral Reefs on 12 September 2018, Sven Uthicke of the Australian Institute of Marine Science, Miles Lamare of the Department of Marine Science at the University of Otago, and Jason Doyle, also of the Australian Institute of Marine Science, describe the results of a trial of a method which used environmental DNA to track populations of the Crown-of-Thorns Starfish.

Environmental DNA (or eDNA) is DNA shed into the environment by an organism via shed skin cells, and excretion of mucus, urine or faeces. The detection of eDNA has become a standard methodology for detecting invasive of endangered species in freshwater environments, but the much larger volume of the oceans, which means that the eDNA will be significantly more diluted by the water, makes detecting eDNA in marine environments considerably harder, and the technique has yet to be successfully applied in this setting.

In order to establish the amount of eDNA produced by Crown-of-Thorns Starfish a single individual was placed in a 10 000 litre seawater tank at the Australian Institute of Marine Science’s National Sea Simulator. This tank had continuous through-flow of water at a rate that would replace all the water twice a day, and the Starfish was kept in it and monitored for one week. This was then repeated with two Starfish, then three, up to a maximum of sixteen, in order to calibrate the methods used for eDNA detection.

Seawater was then collected on four field trips between June 2016 and August 2017, covering reefs in the Cooktown, Innisfail and Ingham to Townsville regions, and tested for levels of Crown-of-Thorns Starfish eDNA. The areas covered included two reefs where there had previously been Starfish outbreaks, two where the Starfish had never been observed, five reefs with active outbreaks, and two reefs without outbreaks, but which were 50-65 km from a reef where and outbreak was ongoing.

No Crown-of-Thorns Starfish eDNA was detected at any site where the Starfish were not present, but it was found in the samples from all the reefs where the Starfish were observed. Furthermore, the levels of eDNA found in the samples closely reflected the known densities of Starfish on these reefs, indicating that the test is both a viable method for detecting the Starfish and a reliable way to estimate their population density.

Density estimates of Acanthaster solaris (left) and eDNA concentration on 11 reefs of the Great Barrier Reef, Australia. Uthicke et al. (2018). 

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Sertulaster keslingi and Delicaster hotchkissi: Two new species of Starfish from the Ordovician and Carboniferous of eastern North America.

Starfish, Asteroidea, are important members of benthic invertebrate communities, often playing a major role in shaping marine ecosystems. They have a long fossil record, having first appeared in the Ordovician, but this record is extremely sparse due to the nature of their exoskeletons, which are made up of large numbers of tiny elements, which become disarticulated very easily upon the death of the animal, and when fossils are exposed at the surface. This makes it very hard to understand the evolutionary history of Starfish as a group, due to the limited number of preserved skeletons.

In a paper published in the Journal of Paleontology on 7 November  2018, Daniel Blake of the Department of Geology at the University of Illinois, and Joseph Koniecki of Ann Arbor in Michigan describe two new species of Starfish from the Ordovician and Carboniferous of eastern North America.

The first new species is named Sertulaster keslingi, where ‘Sertulaster’ means ‘garlanded star’ in reference to the primary circlet of skeletal plates, which resembles a garland, and ‘keslingi’ honours palaeontologist Robert Kesling for his work on ancient Starfish and other Echinoderms. The species is described from four partially complete specimens, one from the Verulam Formation at the LaFarge Belleville Quarry, near Belleville in Ontario, and three from the upper Bobcaygeon Formation of the Kirkfield Quarry at Kirkfield, Ontario; both formations are Late Ordovician in age. These specimens have an arm-tip radius of up to 15 mm, and a body radius of up to 5 mm.

(1)–(6) Sertulaster keslingi, family Palaeasteridae; specimens wetted to delineate ossicular shapes and arrangements. Surfaces are finely pustulate but enlarged spine bases are lacking. (1)–(3) Holotype UMMP 74694: (1) complete specimen, central disk ossicles lost or collapsed into disk interior; arrow at superomarginal (SM) series; (2) inclined view, inset primary circlet interradial (upper arrow) abuts two radials, primary circlet does not include supplemental ossicles; the interradial bears two ventrally directed flanges and is separated by two upright disk superomarginals from axillary (lower arrow), which lies between two arm marginal series; no intermarginal series is developed; (3) dorsal aspect, radial (arrow) at head of carinal series. (4) Paratype UMMP 74695, arrow at SM series; (5) paratype UMMP 74696, left arrow at SM series, right arrow at axillary, is beneath enlarged disk SM pair; (6) paratype UMMP 74697, arrow at SM series. (7) Eriaster ibexensis, is most similar to Sertulaster among known palaeasterid genera; overall view of holotype; primary circlet ossicle (left arrow) is subcircular and pustulate; enlarged carinal series ossicles extend to the arm tip and overlie marginal and intermarginal series (right arrow. Scales bars are 5 mm. Blake & Konieki (2018). 

The second species described is placed in the genus Delicaster, and given the specific name hotchkissi, in honour of palaeontologist Frederick Hotchkiss for his work on Starfish and other Echinoderms, including obtaining the specimen from which Delicaster hotchkissi is described. The species is described from a single specimen from the shale above the Willow Point Limestone Member of the Pennsylvanian (Carboniferous) Canyon Series at Bridgeport Clay Pit in Wise County, Texas. This specimen has a maximum arm radius of about 30 mm and an inner body radius of 12 mm, though this is likely to have been increased by flattening during burial.

Delicaster hotchkissi, holotype and only known specimen, YPM IP 238703. The two columns of figures illustrate the opposite surfaces of the single-known specimen, rotated 180° about the “vertical” axis. Disk ossicles are in disarray although arm intervals are largely intact. (1) The two more complete arms showing primarily marginal and ambulacral ossicular form in dorsal aspect, axillaries at arrows; (2) axillary at left arrow, madreporite immediately beyond axillary at right arrow; (3) disk region, ossicles largely disrupted; axillaries marked by two upper arrows, madreporite near upper left arrow; primary circlet ossicles and adradial face of ambulacral at two lower right arrows; (4) arm to left exposes the ventral surface; arm to right is exposed in dorsal view, folded across the ventral disk surface; adambulacral series at upper right arrow belongs to an arm obscured by the folded arm; lower arrows locate adambulacral ossicles; (5),upper left arm; adambulacral double series along midline is partially obscured and disrupted; adambulacral spines at arrow; (6) proximal interval of folded arm, partially displaced axillaries at arrows to left; small pustules along dorsal edge of marginals (middle arrow); adambulacral series in ventral view, ossicular outlines rectangular with transverse series of spine bases (right arrow). Scale bars are 10 mm. Blake & Konieki (2018).

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Thousands of Starfish wash up on beaches in east England.

Thousands of Starfish, Asteroidea, have washed up on beaches in the east of England this week. The Starfish have been seen on beaches in Ramsgate and Broadstairs on the Isle of Thanet in East Kent, as well as in parts of East Yorkshire, further to the north. While the strandings have largely been of Starfish, other benthic (bottom dwelling) invertebrates, such as Sea Urchins and Lobster, as well as some Fish have also been observed.

Mass stranding of Starfish on a beach in Ramsgate, Kent. Lara Maiklem/SWNS.

While the cause of the strandings is impossible to confirm, it is likely to have been related to a severe storm from the east earlier in the week. The storm brought with it both very low temperatures and high winds, which is likely to have stirred up sediments on the sea bottom, making it difficult for benthic invertebrates such as Starfish to breath, while at the same time cooling them down, which makes them lethargic and unable to escape.

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A mass death of Starfish in the Late Cretaceous of Morocco.

Starfish (Asteroidea) are benthic marine Echinoderms found across the globe. They have a simple bodyplan, with a central disk that has the mouth on the underside, surrounded by (usually) five arms, each with a double row of tube feet underneath. The upper surface of the Starfish is covered by an articulated armoured exoskeleton made up of thousands of small calcite plates. The animal moves by means of a water vascular system, which enables it to inflate and deflate the tube feet as required. The earliest Starfish appear in the fossil record in the Ordovician, however they are not common fossils, as the skeleton is made up of a large number of very small components, and tends to disarticulate rapidly after death.

In a paper published in the journal Palaeontology on 7 May 2013, Any Gale of the School of Earth and Environmental Sciences at the University of Portsmouth and Loïc Villier of the Laboratoire de Géologie des Systèmes et des Réservoirs Carbonatés at the Université de Provence describe a site at Bakrit in the Middle Atlas of Morocco where a very large number of Starfish belonging to a single (new) species are preserved as in a limestone concretion apparently representing a mass mortality event.

The Starfish are given the specific Cretasterias reticulatus, where 'Cretasterias' means 'Cretaceous Starfish' and 'reticulatus' refers to their reticulated skeleton. There are thousands of individuals present in the slabs recovered from the site, averaging 60-140 mm across, and essentially similar in morphology to modern Starfish.

Specimens of the Starfish Cretasterias reticulatus on a slab from the Late Cretaceous of Bakrit in the Middle Atlas. Gale & Villier (2013).

The Starfish in the slab appear to have died in a single mass mortality event, probably when they were swept into a marine gully during a storm and buried rapidly. Such mortality events are not unusual in modern Starfish, many species of which will undergo spectacular population explosions when suitable conditions arise, followed by mass deaths when conditions change again.

See also A new species of Sea Cucumber from the Kermadec Islands, Coral decline on the Great Barrier Reef, A new species of Crinoid from the Southern Ocean, A Brittle Star from the Late Jurassic of Southern Germany and A possible bilaterally symmetrical Echinoderm from Spain.

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