The Persian Gulf is considered an extreme marine environment due to its hyperthermic and hypersaline conditions. The environment in the southwestern coast of the Persian Gulf is particularly extreme. This shallow-water region and the associated mangrove settings has hyperarid conditions with temperature and salinity reaching values as high as 49˚C and 75 parts per thousand, levels much higher than the East coast of the Gulf. The southwestern coast forms an isolated marine province with a high rate of marine endemism and lower species richness than the eastern coast of Persian Gulf, the latter receives an influx of waters from the Indian Ocean which results in a higher diversity of species. The high rate of endemism found in the western coast of Persian Gulf, and the as yet, low number of taxonomic descriptions for the region, indicate potential for the discovery of species new-to-science.
In a paper published in the journal PLoS One on 13 May 2020, Bruno Welter Giraldes of the Environmental Science Centre at Qatar University, Claire Goodwin of the Huntsman Marine Science Centre and the University of New Brunswick, Noora Al-Fardi, Amanda Engmann, and Alexandra Leitão, also of the Environmental Science Centre at Qatar University, Asma Ahmed, Kamelia Ahmed, Hadil Abdulkader, and Halah Al-Korbi of the Biomedical Science Department at Qatar University, Hala Sultan Saif Al Easa of the Department of Chemistry and Earth Sciences at Qatar University, Nahla Ahmed Eltai of the Biomedical Research Centre at Qatar University, and Pejman Hanifi-Moghaddam, also of the Biomedical Science Department at Qatar University, describe two new species of Demosponge from the Mangroves of Qatar.
Marine ecosystems have considerable potential for bioprospecting, and several new drugs are described and isolated every year, yet these natural resources, which can produce economic and societal benefits, remain largely unexplored. A significant majority of new marine natural products have come from Sponges (Phylum Porifera). Chemical compounds isolated from Sponges have been found to have anti-inflammatory, antibiotic, anticancer and anticoagulant properties. Sponges are multicellular invertebrates that have evolved as filter feeders in aquatic environments. Sponges naturally process a huge volume of water daily and as a consequence, may concentrate a wide variety of pathogens. Due to this, Sponges have developed effective defence systems based on bioactive secondary metabolites including antibacterial substances.
Despite their economic importance, virtually nothing is known about Sponge diversity in the coastal areas in the Gulf, with only a few Sponge records from the Arabian Sea and adjacent area. Environmental stress has been shown to concentrate toxins in Sponges, and higher temperatures to be related with the bioactivity. Therefore, the study of marine Sponges in the extreme, hyperarid conditions found in the Southwest of Persian Gulf has potential for both the discovery of potential bioactive metabolites and species new to science.
Shallow-water hyperarid Mangrove ecosystems were studied at Al-Khor and Al-Dhakira, Qatar. These areas do not experience any input of fresh water, but saline tidal channels are present. Areas of Seagrass and Oyster beds, interspersed with rocky substrate, surround and extend out from the Mangroves in the shallow subtidal zone (less than 1 m). The coastal zones of Qatar are characteristic by gently sloping shores and a large tidal range which result in large intertidal and shallow subtidal zones.
Collection localities in Qatar: (A) the location of Qatar within the Persian Gulf; (B) the location of the studied Mangrove settings and the other locations around Qatar that were searched for Sponge species; (C) the studied Mangrove settings in Al-Khor and Al-Dhakira highlighting the large area with shallow depth around the Mangrove; (D) schematic profile of the Mangrove ecosystem in the coastal intertidal zone with the forest area and the shallow subtidal zone with patches of Seagrass and Oyster-beds (rocks). Giraldes et al. (2020).
Sponges were collected in the intertidal and subtidal zones in the studied arid Mangrove ecosystem. Most specimens were collected by snorkelling and freediving at the edge of tidal mangrove channels. Field studies did not involve endangered or protected species and there is no specific permission required for collection of Porifera in these locations. Specimens were photographed in situ using underwater cameras. Large pieces of each species were transported to the laboratory and preserved in 70% ethanol. Methods for identification followed standard taxonomic procedures.
After the first taxonomic identification, more than 50 freediving and snorkelling expeditions were performed in the tidal channels surrounding Mangroves, and Seagrasses, to identify zonation and distribution of the described species. In addition several dives were undertaken in shallow subtidal zones around Qatar, including Um-Bab, Dukhan and Janan Island in the west Coast, Shamal, Al-Ruwais and Fuwarit in the North coast and Al-Khor, Al-Dhakira, Doha, Al-Alyia Island, Al-Wakrah and Sea-Line in the east coast. Visual identification of Sponges was performed based on the general shape, texture and colour of the described new species.
The first new species described is placed in the genus Chalinula, and given the specific name qatari, for the general type locality, Qatar, and its colouration, which is similar to that of the Qatari flag. Chalinula qatari is a thinly encrusting Sponge with a thickness of around 4 mm and a maximum observed diameter of 40 cm. Oscular chimneys (raised oscula, large openings to the outside through which the current of water
exits after passing through the spongocoel, having been absorbed through
much smaller dermal pores) were present on some specimens. These had the form of small cones around 6 mm in diameter with an elevation of around 8 mm. Oscules were 2–5 mm in diameter. Oscular chimneys were observed mainly in the specimens in the Mangrove roots. Most living specimens are a vivid maroon colour, however, those living in stressful situations, such as intertidal specimens in summer conditions, may bleach to a pale yellow. The choanosomal skeleton (supporting skeleton of spicules) is an anisotropic reticulation with paucispicular primary tracts, 1–3 spicules in diameter. The secondary tracts are unispicular, usually about two spicules long. There is no ectosomal skeleton, the ends of the primary tracts of the choanosome project beyond the surface, rendering it slightly hispid.
Chalinula qatari, morphology, skeleton and spiculation. Morphology: Living specimens (A) attached to Mangrove pneumatophores in the riparian zone, (B), (C) in the intertidal zone, (D) under limestone in the channels between the Mangroves. Skeleton and spicules: (E) choanosomal skeleton; (F) embryos; (G) ascending spicule tracts; (H) oxeas, showing immature thinner forms; (I) choanosomal skeleton showing thickness of encrustation on a Mangrove root; (J) embryo; (K) Cross section of ectosome (specialised ectosomal skeleton absent); (L) choanosomal skeleton showing length of secondary spicule tracts; (M) close up of ascending primary spicule tract. Electronic microscopy of (N) large, thick oxea (O) thinner oxea. Giraldes et al. (2020).
Chalinula qatari is currently only known from the holotype and paratype localities in the Mangroves at Al-Dhakira and Al-khor, planted Mangrove in the Al-Wakrah in the south of Doha, and in the Mangroves at Shamal in the north-east of Qatar. All locations are on the east coast of Qatar, south-western coast of the Arabian/Persian Gulf.
Chalinula qatari is described from a holotype (when describing a new species one specimen is designated the holotype; all future specimens determined to belong to the same species as this holotype therefore bellong to the species) collected from a pneumatophore (breathing root) of a Mangrove in a tidal-channel at Al-Khor, Qatar, at a depth of 30 cm, as well as two paratypes from the intertidal zone at Al-Dhakira, also found encrusting pneumatophores.
Extracts from Chalinula qatari did not show any antibacterial bioactivity against the test pathogens. No significant differences in skeletal morphology or spiculation were observed between the paratypes. The proportion of smaller young oxeas did vary amongst the paratypes; with each specimens presenting a different ratio of large and thin spicules. Embryos with young spicules were visible in some individuals. these were always concentrated in the basal layer. The skeleton of Chalinula qatari comprises oxeas (spicules pointed at both ends) 69.2-96.2 μm in length by 1.1-4.0 μm in width.
The species was found growing on the pneumatophores of the Mangrove Avicennia marina in the intertidal and subtidal zones along tidal channels, and on the underside of limestone rocks in tidal channels. It was also found in Seagrass and Algal beds connected directly with the Mangrove habitat. Chalinula qatari is currently only known from the holotype and paratype localities in the Mangroves at Al-Dhakira and Al-khor, as well as planted Mangroves in the Al-Wakrah in the south of Doha, and in the Mangroves at Shamal in the north-east of Qatar. All locations are on the east coast of Qatar, south-western coast of the Persian Gulf.
The possession of an isodictyal skeleton of diactinal megascleres, and a regular anisotropic reticulation with recognisable ascending primary tracts, places this species in Order Haplosclerida. The presence of a choanosomal skeleton with unispicular secondary lines assigns this species to Family Chalinidae. Within the Chalinidae, Giraldes et al. assign this species to genus Chalinula on the basis that the secondary tracts of the choanosomal skeleton are mostly two spicules long and multispicular fibre tracts are not present throughout the Sponge.
The second new species is placed in the genus Suberites, and given the specific name luna; the species was nicknamed the ‘Moon-surface Sponge’ by the collectors due to its appearance. The name reflects both this and the importance of the Moon in the Muslim culture.
Suberites luna, morphology, skeleton and spiculation: (A), (B) growing on Mangrove pneumatophores in the riparian zone; (C) just collected and cut; (D) large compound oscule; (E) large specimens close to Seagrass; (F) specimen just collected. Slides of fresh specimens, (G) cross section of choanosomal skeleton; (H) plumose choanosomal skeleton in cross section, (I) palisade of subtylostyles in the ectosome. Slide in cross section of dried specimen showing plumose choanosomal skeleton (J). Electronic Microscopy, (K), (L), (M) showing different head shapes of the subtylostyles; (N) the subtylostyles types (I), (II) and (III). Giraldes et al. (2020).
Suberites luna is a massive globular-lobate sponge, with some large specimens 20–60 cm diameter and 10–20 cm high. The sponge exterior is dense and compact. The interior choanosomal tissue has many pores and is cavernous. Oscules are infrequent, the largest observed was around 8 mm in diameter and was on the apex of a lobe. These Sponges have a velvety surface with macroscopically smooth appearance; they are cmpact, firm, slightly compressible and elastic, and hard to tear. A slime is produced when torn. The live colour is greenish-black and internally a yellowish orange.
The skeleton is plumose (made of primary fibres or spicule tracts from which skeletal elements obliquely radiate) with ascending tracts of large subtylostyles (slender accessory spicules). An ectosomal skeleton is formed of a palisade of smaller subtylostyles. Subtylostyles are 10-843 μm by 2.9-13.1 μm. A multimodal pattern of spicule length was observed, with three main sizes of tylostyles (subtylostyles): (I) smaller spicules 110-196 long by 2.9-5.9 μm wide, most likely ectosomal in distribution; (II) robust subtylostyles 400–500 long by 5-13.1 μm wide, found in the sub-ectosomal choanosomal skeleton; (III) long subtylostyles, over 600 μm in length by 5.6-10.4 μm wide, part of the deep choanosomal skeleton forming the ascending tracts in the plumose skeleton.
Suberites luna has been recorded from Mangrove ecosystems on the east coast of Qatar from Shamal to
Al-Wakrah, in the south-western coast of the Persian Gulf. The species
is described from a holotype collected from the pneumatophore of a
Mangrove in a tidal channel at Al-Khor, Qatar, and four paratypes, one
collected from a rock/sand substrate in the hyperarid Mangrove bay at Al-Khor,
and three collected from shells and soft rock on sand substrate in the
Seagrass peripheral to the hyperarid Mangrove at Al-Dhakira, Qatar.
Suberites luna is found on hard substrates in Mangrove and Seagrass habitats in the subtidal zone. Observed on the pneumatophores of Avicennia marina in the channels of the riparian zone of the arid Mangrove ecosystems. Often found close to Chalinula qatari. Very abundant with large specimens (more than 50 cm diameter) in the subtidal zone around the Mangroves, and at the edges of the seagrass habitat. Found in soft sediment, but mostly attached to small pieces of hard substrate within the sediment, such as small soft-rocks and shells. There was a higher abundance of this species at sites with low current.
Significant differences in skeleton and spiculation of the paratypes was not observed. However, there was some variation in external form with some specimens being much larger and more lobate than others. This species is included within the Family Suberitidae and Genus Suberites, due to its massively globular-lobate shape, possession of a spicule complement consisting only of tylostyles, and the presence of an ectosomal palisade formed of bouquets of smaller tylostyles than those of the choanosome.
Extracts taken from some specimens of Suberites luna showed antibiotic activity against three species of bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis), others were effective against only one species (Enterococcus faecalis) of the bacteria tested in Giraldes et al.'s study, while others showed no antibacterial activity against any of the bacterial strains.
The discovery of Suberites luna and Chalinula qatari on Mangroves on the west coast of the Persian Gulf highlights the lack of taxonomic study of Sponge species in the Gulf but also the biogeographic isolation of the studied hyperarid mangrove habitats. These two species new to science, together with the other endemic species that have been found in this habitat support the concept that the west coast of the Persian Gulf is an isolated marine province. Theoretically, the intense hyperarid conditions found in the west coast of Persian Gulf create a biogeographic barrier that isolates an endemic biodiversity adapted to the intense temperature and salinity conditions. The deeper waters and constant water input from the Indian Ocean result in less extreme arid conditions on the eastern coast of the
Suberites luna is found on hard substrates in Mangrove and Seagrass habitats in the subtidal zone. Observed on the pneumatophores of Avicennia marina in the channels of the riparian zone of the arid Mangrove ecosystems. Often found close to Chalinula qatari. Very abundant with large specimens (more than 50 cm diameter) in the subtidal zone around the Mangroves, and at the edges of the seagrass habitat. Found in soft sediment, but mostly attached to small pieces of hard substrate within the sediment, such as small soft-rocks and shells. There was a higher abundance of this species at sites with low current.
Significant differences in skeleton and spiculation of the paratypes was not observed. However, there was some variation in external form with some specimens being much larger and more lobate than others. This species is included within the Family Suberitidae and Genus Suberites, due to its massively globular-lobate shape, possession of a spicule complement consisting only of tylostyles, and the presence of an ectosomal palisade formed of bouquets of smaller tylostyles than those of the choanosome.
Extracts taken from some specimens of Suberites luna showed antibiotic activity against three species of bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis), others were effective against only one species (Enterococcus faecalis) of the bacteria tested in Giraldes et al.'s study, while others showed no antibacterial activity against any of the bacterial strains.
The discovery of Suberites luna and Chalinula qatari on Mangroves on the west coast of the Persian Gulf highlights the lack of taxonomic study of Sponge species in the Gulf but also the biogeographic isolation of the studied hyperarid mangrove habitats. These two species new to science, together with the other endemic species that have been found in this habitat support the concept that the west coast of the Persian Gulf is an isolated marine province. Theoretically, the intense hyperarid conditions found in the west coast of Persian Gulf create a biogeographic barrier that isolates an endemic biodiversity adapted to the intense temperature and salinity conditions. The deeper waters and constant water input from the Indian Ocean result in less extreme arid conditions on the eastern coast of the