A NEW GENUS AND NEW SPECIES OF GOBIOID FISH ( GOBIIDAE : GOBIONELLINAE ) FROM SUNDERBANS , INDIA

Updated information on fish fauna of India resulted in summarising that the Indian waters are represented by 69 genera and 174 species of gobioid fishes (Perciformes, Gobiidae). The subfamily Gobione11inae comprises of 13 genera and 33 species in India. While working on the gobioid fishes of Indian Sundarbans (latitude 21 °13' 22°40' N. and longitude 88°03'89°06' E.),the first author came across few specimens of an interesting goby. After careful examination that turned out to be an undescribed species. However, no known genus could accommodate the new species and that warranted erecting a new taxon in generic level. The other gobies of Indian Sundarbans are dealt elsewhere (Chatterjee et al., in press) reporting 44 species and 35 genera from the region. The new genus and the new species have been initially described by the first author (Chatterjee, 1978) in his doctoral thesis and the name is also appeared in MandaI & Nandi (1989) and Talwar et al. (1992), but it is not formally published to be treated as 'available' under the provisions of the International Code of Zoological Nomenclature. The new species is hereunder described as Awaouichthys menoni sp. nov. with the genus Awaouichthys gen. nov.


INTRODUCTION
Updated information on fish fauna of India resulted in summarising that the Indian waters are represented by 69 genera and 174 species of gobioid fishes (Perciformes, Gobiidae).The subfamily Gobione11inae comprises of 13 genera and 33 species in India.While working on the gobioid fishes of Indian Sundarbans (latitude 21 °13' -22°40' N. and longitude 88°03'-89°06' E.),the first author came across few specimens of an interesting goby.After careful examination that turned out to be an undescribed species.However, no known genus could accommodate the new species and that warranted erecting a new taxon in generic level.The other gobies of Indian Sundarbans are dealt elsewhere (Chatterjee et al., in press) reporting 44 species and 35 genera from the region.The new genus and the new species have been initially described by the first author (Chatterjee, 1978) in his doctoral thesis and the name is also appeared in MandaI & Nandi (1989) and Talwar et al. (1992), but it is not formally published to be treated as 'available' under the provisions of the International Code of Zoological Nomenclature.The new species is hereunder described as Awaouichthys menoni sp.nov.with the genus Awaouichthys gen.nov.

Awouichthys menoni sp. nov. Holotype
The studied materials were collected from the Patibonia Island near Frasergunge (21°34' N, 88°16' E), from a tidal channel connected to Edward's creek, in the Gangetic delta, West Bengal.The materials were deposited with the National Zoological Collection, Zoological Survey of India, Kolkata.
Body covered with ctenoid scales.Head scaled above posterior to the eyes.Pre operculum and operculum naked.Tongue free, anterior margin notched.Anterior nostril tubular.Sensory canalpores on head absent, except for two interorbital pores.Pit organs in longitudinal as well as transverse lines.Gill-opening extending ventrally, gill membranes united across isthmus forming a free fold.Mouth sub horizontal, lips thick.No teeth on prevomer or palatine bones.Jaw teeth multiserial, close-set, in 5 -6 rows, outer row somewhat enlarged, no canine.Inner margin of shoulder girdle with some fleshy cirri.First dorsal fin with 6 weak spines.Ventral fins united, basal membrane present.Pectoral fin without free silky rays.Total elements in the second dorsal fin lOll.Total anal fin elements 9 -10, caudal fin rounded.Chin and snout without barbels.
Relationship : Awaouichthys shows close relationship with the genus Awaous Valenciennes in having fleshy cirri in the inner margin of shoulder girdle, very long snout, eyes situated high on head and head with no sensory canal-pore.However, union of gill-membranes across isthmus forming Type species: Awaouichthys menoni sp.nov.
Etymology: The genus is named for its close similarities with the genus Awaous Valenciennes.
Diagnosis : A gobioid fish distinguished in having fleshy cirri in the inner margin of shoulder girdle; head without sensory canal-pore, except for two interorbital pores; gill membranes of both sides united across isthmus forming a free fold; very long snout, about 37.3% head length; 19 or 20 predorsal scales; 44-46 scales in longitudinal series; scales absent from operculum and preoperculum.
Pit organs : Pair of head pores anteriorly in interorbital region present, other cephalic pores absent.In infraocular region, there is about 5 transverse lines radiating from the lower margin of eye and 2 longitudinal lines, the upper longitudinal line originates from below the posterior half of the eye and lower line extends anterior to the lower jaw.A single transverse line present on operculum.One line originates in front of eye and curves down to reach anterior nostril.One short line vertically connects the posteriormost infraocular line to the opercular pit line (fig. 2).Colour in alcohol: Light brown.Lateral and dorsal sides of body with darker blotches and irregular streaks.Dorsal side of head with indistinct blackish markings.First dorsal fin with 3 distinct horizontal bands, and a blackish blotch at its posterior extremity; second dorsal fin with about three horizontal bands; caudal fin barred; ventral, pectoral and anal fins yellowish brown.
Locality: Patibonia Island, Fraserganj in the Gangetic delta, West Bengal.Etymology: The species is named in the honour of the eminent Ichthyologist of the Zoological Survey of India, Late Dr. A.G.K. Menon, who confirmed the status of the specimens.

DISCUSSIONS
The sensory canal on head and presence of two head pores anteriorly in the interorbital region along with well-developed basal membrane of the pelvic fin prompted us to place it in the subfamily Gobionellinae (Perciformes, Gobiidae).As discussed in the relationship paragraph under the genus character, the new genus is very close to Awaous in shape, size and in having fleshy cirri in the inner margin of shoulder girdle, but distinctly differs by the presence of gill-membranes of both sidefused across isthmus forming a free fold, as in case of the genus Psammogobius.There is no pore on snout, whereas, the genus Awaous is supposed to have two pairs of pores on snout (Larson and Murdy, 2001).Further, presence of 15 segmented rays in the caudal fin distinguishes it from many closely related genera.Distinction of the genus itself makes the described species distinct from all species of Gobioid fishes known in the region and elsewhere.
The subfamily Gobionellinae is distinguished from all other gobies in having dorsal and anal fins separated from caudal fin; both dorsal fins typically separate; lower jaw typically possessing more than one row of teeth; pelvic frenum simple, not folded forward, frenum without fleshy lobes around pelvic-fin spines; paired anterior interorbital pores present or head pores completely lacking; if head pores absent, then body fully scaly or mostly scaly.
A key to the Indian genera ( 14) of the subfamily is presented here for easy identification of the new genus with Chiramenu jluviatilis Rao is treated as an Awaous species following Froece and Pauly (2012) and Eschmeyer (2012).
Key to the genera of subfamily Gobionellinae found in India:
First dorsal fin height shorter than body depth, third ray longest.Second dorsal fin lower than body, third ray longest.Second dorsal and anal fin lower than first dorsal fin and pointed posteriorly.Pectoral fin pointed, length of the rays 22.2 -26.4 % in standard length.Ventral fins united, basal membrane present, well developed.Caudal fin rounded, 29.8-31.4% in standard length.