Hetereleotris

Douglass F. Hoese & Helen K. Larson, 2005, Description of two new species of Hetereleotris (Gobiidae) from the south Pacific, with a revised key to species and synonymization of the genus Pascua with Hetereleotris., Zootaxa 1096, pp. 1-16 : 1-4

[[ Genus Hetereleotris ]]

The gobiid genus Hetereleotris is speciose in the western Indian Ocean. Smith (1958) placed a number of species in Monishia or in various genera, now regarded by Akihito & Meguro (1981) and Hoese (1986) as junior synonyms of Hetereleotris . Hoese & Winterbottom (1979) treated some species from South Africa, while Hoese (1986) revised the genus and recognized 13 species and synonymized several nominal genera. Subsequently Gill (1998) described an additional species from Mauritius. The present paper describes two new species from the south Pacific and redescribes Hetereleotris caudilinea (Randall) , in order to compare its characteristics with the two new taxa. Previously only a single species of Hetereleotris had been known from outside the Indian Ocean.

Tentatively the species are placed here in Hetereleotris based on the presence of 27 vertebrae and the closure of the first gill slit. Other genera with 27 vertebrae from the Indo-Pacific region include Psammogobius , Glossogobius , Bathygobius , Palutrus and Coryogalops . The vertebral counts are highly consistent within these genera, except for some dwarf species of Palutrus and Glossogobius which have 26 vertebrae and some species of Glossogobius , known from high altitudes of greater than 500m from New Guinea, which have 28 or 29 vertebrae. All of these also share a lobed mental frenum (highly modified and sometimes absent in Glossogobius ).

All three species described here share a number of characters not commonly found in Hetereleotris , particularly the flattened and elongate urogenital papilla of the males, the modified basicaudal scales (Fig. 1), the posterior nostril a simple pore or with only a slightly elevated margin anteriorly, two papillae just behind the mental frenum and the reduced transverse papilla pattern (Fig. 2). The modified urogenital papilla of males is similar to that described as the nonfimbriate condition for many species of Eviota (Lachner & Karnella 1980), a genus which has 25 or 26 vertebrae. The modified basicaudal scale is found in a number of species of New World gobies ( Böhlke & Robins 1968), which also have 27 vertebrae, but which have 11 precaudal vertebrae, rather than 10 as in the Indo-Pacific species. The closure of the first gill slit is rare, but also found in the eleotrid Thalasseleotris (Hoese & Larson, 1987), which bears a remarkable overall external similarity to the present species, but has 6 branchiostegal rays. Other species of Hetereleotris usually have the posterior nostril with an elevated rim or at the end of a short tube, two parallel rows of papillae behind the mental frenum, although in H. zanzibariensis , the number of papillae in each row can be as few as 3. A transverse and reduced transverse papilla pattern, similar to the new Hetereleotris species, also occur in Priolepis (Winterbottom & Burridge, 1992, 1993).

Despite these differences from typical Hetereleotris , the species are included here in that genus until a more thorough phylogenetic analysis of the Indo-Pacific genera (particularly those with 27 vertebrae) can be carried out. Examination of the osteology of one species described below shows it to be typical of other small gobiids and consistent with that described for Hetereleotris by Hoese (1986). Randall (2005) defined Pascua based on several characters. These are:

1 head width less than body depth (common to many gobioids and some species of Hetereleotris , such as H. tentaculata , and therefore not useful as a generic character);

2 1st gill slit closed by membrane - shared with all Hetereleotris ;

3 gill opening ending at level of ventral edge of pectoral-fin base - shared with all species of Hetereleotris and numerous other gobiid genera;

4 posterior nostril not tubular as in other Hetereleotris ;

5 a complete cephalic sensory system - complete is a misleading term, because many gobiid species have more head pores than this species and all Hetereleotris lack the posterior portion of the oculoscapular canal (above the operculum) and some species lack pores entirely;

6 reduced sensory papillae on cheek - species in other genera such as Priolepis show a similar variation from transverse to reduced transverse;

7 dorsal fins not completely separate - common to some other species of Hetereleotris ; in material of the species treated here the first dorsal fin connects to the base of the second dorsal fin, varying from attaching to the back just before the second dorsal fin to the basal one fifth of the spine of the second dorsal fin, which is similar to species of Hetereleotris , such as H. vulgaris and H. aporia as reported by Hoese and Winterbottom, 1979.

8 dorsal fin pterygiophores as in Bathygobius - common to most gobiines;

9 17 segmented caudal rays (14 branched) - 17 segmented rays is common to most gobioid fishes, we find 13-15 branched caudal rays for caudilinea and the species described here;

10 pectoral rays 20 or 21 - we find 18-21 rays for caudilinea and 17-21 for other species treated here and Hoese (1986) reported counts of 15 to 19 pectoral rays for Indian Ocean species of Hetereleotris ;

11 pelvic rays I,5 - common to most gobioid fishes, but some species of Hetereleotris have I,4;

12 fins completely separate, without frenum - common to most Hetereleotris ;

13 fifth pelvic ray unbranched and clearly shorter than fourth ray - we find the fifth ray sometimes with a branch at the tip, the shorter fifth ray is common to all Hetereleotris that have the fifth ray;

14 scales ctenoid, except a few anteriorly and on abdomen - common to numerous gobioid genera and some species of Hetereleotris ;

15 scales 24-29 in longitudinal series - we find 23-26 for H. caudilinea and 22-26 for all species studied here, Hetereleotris species vary from no scales to 52 in the longitudinal series;

16 no scales on head, nape, prepectoral area or chest - common to numerous gobiine genera and all other species of Hetereleotris .

Consequently only one of the characters reported appears to be consistent for the south Pacific species (no elevated posterior nasal tube). Evidence is presented below for other specialisations, but because of the variation of characteristics in Hetereleotris we do not consider that the Pacific species warrant generic separation. The genus needs to be thoroughly revised to take into account the range of characters and species.