Current Trends in Oceanography and Marine Science A Review on Taxonomy of Lakshadweep Sponges and its Checklist

Sponges its Checklist. Curr Trends Oceanogr


Introduction
Sponge is one of the oldest group of multicellular animal found on the earth [1]. They are one of the highly diverse and successful group of marine benthic communities around the world [2]. Sponge is one of the dominnent associated species in coral reef ecosystem [3] and they help to bind the live corals to the reef frames, also helps to regeneration of broken reefs, sheltering microbial symbionts of nitrifying and photosynthesizing acivities and protecting from erosion processes [4][5][6].
The spongiology in India started with freshwater sponges by Carter [7][8][9] and followed by Bowerbank [10] with marine sponges. Even though India has rich history of sponge studies, from the Lakshadweep Island group, studies are very meagre. Burton [11] studied off Kilten Island sponges and latter Thomas [12][13][14][15][16][17][18][19] studied the Lakshadweep Islands sponges in detail. These studies reported 91 species of sponges from 10 islands of this location. The next detailed study was carried out by George et al. [20] after three decades. The studies after Thomas [19], most of the work of these Islands were sponge metabolites and associated microbial studies along with that few distribution studies as an extension of the earlier studies were reported. Feby and Nair [21] studied sponge associated Dysidea granulosa Bergquist, 1965 and Sigmadocia (Haliclona) fibulata Schmidt, 1862 bacterial distribution in the Kavaratti Island. Gopi and Ajithkumar [22] reported 21 species of sponges from Agatti Island, of which 19, were new report. Prabhakaran et al., [23] reported 22 species of sponges from seagrass meadows of Minicoy Island and Rocktim et al., [24] reported a new record of sponges from Bangaram and Thinnakara island.
Since, the long gap in the studies of the sponges of Lakshadweep Islands and its inconsistency in terminology makes a perplexing situation for the upcoming researchers. This may be due to not available of updates checklist, some species name change because of the revised classification of sponges by Morrow and Cárdenas [25] as well as differences of opinion are available on about the number of sponge species recorded from Lakshadweep offshore regions. An attempt was initiated to compile the literature on sponge species and its distribution for Lakshdweep Islands waters and prepared a checklist to update the sponge taxonomy status in these Islands.

Materials and Methods
The existing published literatures were compiled and extracted the status of sponge studies in the waters of Lakshadweep Islands marine environments. The collected results were interpreted and brought out as a checklist of sponges of Lakshadweep. The taxon identified in these texts were verified with World Porifera Data Base [26] and the World Register of Marine Species [27]. The taxonomy of the reported taxon was updated based on the revised porifera classification proposed by Morrow and Cardenas [25].

Discussion
Off the cost of Kiltan Island, the first sponge report from Lakshadweep islands was made [11]. This sponge species were the collections of R.I.M.S. "Investigator" expedition. After that, it took about 40 years to get an attention to the sponge fauna of these Island ecosystems by Thomas [12]. This work was a Ph.D. thesis and it's an unpublished data. However, Central Marine Fisheries Research Institutes (CMFRI) reference sponge specimens catalogue mentioned only 10 species from Lakshadweep, which was published by Thomas [13]. A subsequent study by Thomas [19] mentioned that 11 sponge species were identified from the Minicoy Island of Lakshadweep. So, the 11 th specimen mentioned by Thomas [12,19] was not clear from these literatures.
Subsequently, a series of publications from Thomas [14][15][16][17] described about 41 species of sponges exclusively from Minicoy Islands of Lakshadweep. Among the 41 species, 3 identified up to genus and 20 species are remaining in the same name as he mentioned, and the rest of the 18 species have got synonym or transferred to new names.
The most acknowledged research article on the sponge of Lakshadweep was published by Thomas [19] with a compiled report of 91 sponges from 10 islands of Lakshadweep, including his previous studies from these Islands. But this paper has not provided any detailed systematic account of the sponge species for these 91 sponges. At present, 44 species Out of 91 sponges mentioned in this paper got their synonym or transferred to new names.
Furthermore, from the 91 sponges of Lakshadweep 8 sponges identified only up to genus level, namely Myxilla sp, Pseudosuberties sp, Phycopsis sp1, Phycosis sp2, Agelas sp, Bubaris sp, Hippospongia sp, Thorectopsamma sp and 2 got the same name according to the current systematics, i.e, Aka laccadivensis and Damirrina laccadivensis are accepted as Zyzzya fuliginosa. This is the reason in many papers, a number of the sponge species available from these Islands became 82. While going through the distribution table of Thomas [19] suggested that distributional data of 2 sponge species are missing, i.e. the species Ecionemia acervus and Thoosa armata. The species described as Tedani anhelan have an unrecognized author, which was repeated in all other publications of Thomas too.
The work done by Gopi and Ajithkumar [22] from Agatti Island, suggested that they identified 21 species, of which 14 species were new to Agatti Island and 3 were identified only to genus level and remaining 4 species were reported by Thomas [19]. Furthermore, from their identification, 12 specimens mentioned the species name with wrong author or year. This information leads to confusion among the researchers on sponges. The lists of the Species mention with a wrong author name or year are mentioned in the  Prabhakar et al. [23] reported 22 species of sponges from the seagrass associated environment of Minicoy Island, Lakshadweep. Among them, 16 was identified to species level and the remaining 6 identified only to genus level. Of the 16 species, 5 species, namely, Haliclona pigmentifera, Gelliodes cellaria, Trcinia comana, Sypha ciliata and Xenospongia sp. were not reported from Lakshadweep Island before this study and three more species, namely, Haliclona tenrmosa, Rhavdastrella globostella and Tethya diploderma were the first report of Minicoy Island. However, the detailed taxonomy was not presented for the above species mentioned in this article. Gopi and Ajithkumar [22] and Prabhakar et al. [23] reported four species of calcareous sponges Pericharax heteroraphis (Poléjaeff, 1883), Leucetta chagosensis (Dendy, 1913), Clathrina sp., and Sycon ciliatum (Fabricius, 1780). However, they did not mention any description of this species. But, latter the species Leucetta chagosensis (Dendy, 1913) was described by van Soest and de Voogd [33] from Minicoy and Kavarati Islands.
A recent short communication of Rocktim et al., [24] reported coral killing sponges outbreak, Terpios hoshinota (Rützler and Muzik, 1993) from Bangaram and Thinnakara Islands, which was also a first report of the Lakshadweep Islands.
George et al. [20] reported 101 species of sponges from the Indian nearshore waters. Among them, 38 sponges were reported from Lakshadweep Islands. Out of reported species from Lakshadweep 24 species were first reports. However, the cursory analysis of data in this article suggested that, 25 species were new to Lakshadweep Island, 6 species were reported in previous works of these Islands and the remaining 3 species were identified up to genus and the last 4 species are aff. species.

Conclusion
This study concluded that, a total of 145 species of sponges is recorded in 19 published papers from Lakshadweep Islands. Except Hexactinellida all the three remaining Classes are recorded from these Islands. Demosponges has the most predominant Class followed by 4 records of Calcarea from these locations and a single record off Class Homoscleromorpha was observed. The major contributions of these records were contributed by Thomas. It is interesting to note that every author got one or more new records from these islands proves that the diversity of the sponges in this location are enormous and the detailed and intensive study is needed to reveal the sponge diversity of these Islands.