Intertidal Ophiuroidea from the Saurashtra coastline, Gujarat, India

: Present communication reports the diversity of intertidal Ophiuroidea (Phylum: Echinodermata) from the intertidal zones of the Saurashtra coastline, Gujarat state. Saurashtra coastlines were extensively surveyed from January 2019 to March 2022 for the Ophiuroidea diversity. A total of nine species of Ophiuroidea belonging to eight genera and six families were noted from the intertidal zones of the Saurashtra coastline. Amongst these, Macrophiothrix variabilis, Ophiothrix savignyi and Ophiomaza cacaotica are newly observed species from the Gujarat coastline. The results of similarity indices show that each sampling site has a diverse variety of brittle star, making them spatially different from each other.


INTRODUCTION
The Ophiuroidea are known as brittle stars, basket stars (euryalids with branching arms) and snake stars (euryalids with non-branching arms). It is the largest group among extant living echinoderms, with 2,116 described species found in all oceans from the intertidal to the greatest depths (Stöhr et al. 2021). Among them, 160 species have been recorded from Indian waters (Samuel et al. 2017). Recently nine new brittle stars are reproted from India (Parameswaran et al. 2021). Macrophothrix aspidota was the first Ophiuroid reported from Gujarat (James 1969). After that, Ophioplocus imbricatus was recorded from Pirotan Island (Clark & Rowe 1971). A total of 12 species were reported from Gujarat (Sastry 2004;Gohil & Kundu 2012;Poriya 2015). The literature indicates that not many studies were conducted, nor significant data were available for the species diversity of intertidal ophiuroids from the Saurashtra coastline, Gujarat.
The present study aims to better document the species diversity of ophiuroids from the Saurashtra coastline, Gujarat. An extensive sampling effort in the rocky intertidal coastal zone was undertaken at eight localities around the Saurashtra coastline. Below, we discuss each species encountered and compare species composition between selected localities.

MATERIALS AND METHODS
Total of eight locations were chosen for ophiuroids sampling ( Figure 1, Table 1) during the low tide from January 2019 to March 2022. In situ photography of live specimens was carried out. Voucher specimens of some species were collected by direct hand-picking method from various habitats for further identification. Specimens were relaxed with magnesium chloride and fixed in 95% ethanol and 4% formalin. Encountered Ophiuroidea species preliminary identification was done with the monograph of Clark & Rowe (1971) and Cherbonnier & Guille (1978). Confirmed determinations up to species level was done using various research articles such as O'Hara et al. (2018) for family rank and above, Hoggett (1990) for Macrophiothrix, Thomas (1975) for Ophioplocus, and Clark (1953) for Ophionereis. Voucher specimens were deposited in the Museum of the Department of Biosciences, Saurashtra University.
In the present study, the Jaccard similarity index (J) was measured using R to compare the similarity and diversity of the different sampling sites.

Diversity of Intertidal Ophiuroidea:
In the present study, nine species of ophiuroids belonging to eight genera and six families were noted from the intertidal zones of the Saurashtra coastline (Table 2). Among these, only one species was reported from Simbor, three species each from Diu, Dhamlej, Mangrol, & Shivrajpur, five from Veraval, six from Dwarka, and seven species from Okha (Table 3). Systematic position, explanation, and habitation of noted ophiuroids are as follows:
Remarks: Commonly observed six arms O. sexradia at the Saurashtra coast, but we observed one specimen with seven arms. Specimens have small and imbricating scales and papillae, narrow and oval shaped radial shield, three to five elongate and blunt arm spines, one tentacle scale. Three to eight oral papillae on each side of jaw and one to six pair of dental papillae with one to seven square-tipped teeth.
Habitat: Rock crevices and under algal holdfast. Distribution: Common across the Indo-West Pacific (Clark & Rowe 1971).
Present study: Dwarka, Okha, and Shivrajpur   Remarks: Most common species of Saurashtra coast. Central primary plate is clearly visible, imbricating scales on disc. Radial shields separated proximally by a scale line, two tentacle scales, dorsal arm plate broader than long, three conical, erect, arm spines with serrated tip. Two oral papillae on each side, one distal long and opercular. A pair of infradental papillae with square tipped teeth.
Habitat: Rock crevices, underneath of rock and under the algal holdfast.
Distribution: Cosmopolitan distribution in cold to tropical and temperate ocean from intertidal to 1,300 m depth (Gage et al. 1983).
Remarks: Rarely observed at Saurashtra coast. Five imbricating greyish black blotches clearly observed on the central part of the disc. Radial shield barrel shaped, flat, and longer, two radial shields distally separated by a single scale line and only united at proximal part. Five conical shaped arm spines.

J TT
Habitat: Rock crevices, under the algal holdfast and within crevices of zoanthid bed.
Remarks: Brown-purple colour. Small papillae on disc. Scalene triangular-shaped radial shield, spines present on radial shield. Eight arm spines near to disc, but distal parts have less in number, middle 2 spines large & other short, broad base of spines & denticulate structure. Hexagonal-shaped dorsal arm plate, white dots in middle, ventral arm plate, hexagonal shaped but convex by side. Cluster of dental papillae with six-seven no. of teeth in a row present on each jaw.
Present study: This is the first record from Gujarat (Veraval and Okha).
Remarks: specimen has brown color disc and mustard yellow arms. Disc smooth, very large triangular radial shield present. Five arms with four to six conical shaped arm spines. Some of the arm plates are fragmented dorsally, trapezoid shaped. Ventral side octagonal shaped arm plate. Arms covered by thick skin. Two genital slit present. Triangular shaped oral shield. Cluster of numerous tooth papillae present on each jaw.
Present study: This is the first record from Gujarat (Simbor).
Remarks: This species differed from O. foveolata earlier reported by Sastry (2004). O. foveolata has conspicuous spines on the dorsal disc with few or no thorny stumps while This species has stumps/thorns, trifid. Bare radial shield having few thorns. Five arms with five/six denticulate arm spines. Tiny throns/stumps present on the proximal dorsal arm plate. Distal margin of the ventral arm plates is concave. Cluster of numerous dental papillae present on each jaw. Specimen has brown color disc and arms having pattern.
Present study: This is the first record from Gujarat (Mangrol).

DISCUSSION
The existing diversity of the intertidal Ophiuroidea from the Saurashtra coastline is described. Mainly rocky stations of the Saurashtra coastline were surveyed for the diversity estimation. Earlier 12 ophiuroids were reported from the Gujarat coast (Sastry 2004 www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.