Pseudolaguvia ferula, Heok Hee Ng, 2006

Heok Hee Ng, 2006, Pseudolaguvia ferula, a new species of sisoroid catfish (Teleostei: Erethistidae) from India., Zootaxa 1229, pp. 59-68 : 60-66

Pseudolaguvia ferula sp. nov.

(Fig. 1)

Type material

Holotype: UMMZ 245985, 25.4 mm SL; India: West Bengal, Tista River at Tista Barrage, 26°45’10’’N 88°34’11’’E; A. Rao, 2005.

Paratypes: UMMZ 245986 (12), 19.6-24.8 mm SL ; ZRC 50398 (2), 21.8-23.0 mm SL; data as for holotype .

Diagnosis

Pseudolaguvia ferula differs from congeners in having a terete head and body (vs. slightly depressed body and strongly depressed head). This difference in body form is easily manifested in the head width (17.1-19.1% SL vs. 19.4-24.3). It can also be distinguished from congeners in having a smaller anterior fontanel (about one third the length of the frontals vs. at least half the length; Fig. 2), and very faint, poorly contrasting cream bands that are sometimes absent on some individuals (vs. sharply contrasting cream bands on a brown body). Pseudolaguvia ferula further differs from congeners except P. ribeiroi in having a shorter adipose-fin base (11.5-13.0% SL vs. 14.8-24.0), and, except from P. foveolata , in having the unculiferous ridges on the thoracic adhesive apparatus joined at their posterior ends (vs. separate; Fig. 3). It is further distinguished from P. foveolata in having fewer vertebrae (28-30 vs. 33) and a longer thoracic adhesive apparatus (reaching to midway between bases of last pectoral-fin ray and first pelvic-fin ray vs. to middle of pectoral-fin base), from P. inornata in having a slenderer body (12.1-13.8% SL vs. 13.9-16.1) and smaller eye (8.6-11.7% HL vs. 12.7-14.9), from P. kapuri in having a shorter pelvic fin (not reaching base of the first anal-fin ray vs. reaching; 13.0-14.7% SL vs. 15.3-17.9), and from P. muricata in having shorter dorsal and pectoral spines (17.3-18.7% SL vs. 21.2-26.7 and 20.2-24.3% SL vs. 26.8-35.7 respectively) and a smaller eye (8.6-11.7% HL vs. 11.4-15.1). Pseudolaguvia ferula is further distinguished from P. ribeiroi in having less distinct mesethmoid cornua (Fig. 2), from P. shawi in having a longer dorsal spine (17.3-18.7% SL vs. 13.4-16.7), and from P. tenebricosa and P. tuberculata in having a slenderer caudal peduncle (6.9-7.8% SL vs. 7.6-9.0).

Description

Biometric data as in Table 1. Head slightly depressed and terete, body terete. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from there to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally from there to end of caudal peduncle. Anterior fontanel small, approximately one third length of forntals. Supraoccipital spine reaching nuchal shield. Weberian lamina well developed, approximately same length as supraoccipital spine and extending parallel to either side of spine. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head. Orbit with free margin. Gill openings narrow, extending from posttemporal to isthmus. Branchiostegal membranes united at isthmus. Caudal peduncle of moderate length and depth. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin tuberculate. Lateral line complete and midlateral. Vertebrae 10+18=28 (1). 10+19=29 (4), 11+18=29 (5), 11+19=30* (4) or 10+20=30 (1). Abdomen with thoracic adhesive apparatus consisting of longitudinal, unculiferous ridges arranged in elliptical field and with prominent central median depression. Adhesive apparatus extending to midway between base of last pectoral-fin ray and pelvic-fin origin.

Mouth small, inferior and with papillate lips; upper jaw projecting beyond lower jaw. Oral teeth small and in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band consisting of single broad lunate patch across midline; with conical teeth very slightly exposed when mouth is closed. Dentary tooth band narrow, with conical teeth.

Barbels in four pairs. Nasal barbel very short and broad, extending to one third distance between its base and anterior orbital margin. Maxillary barbel slender, with broad skin flap at base and extending to base of pectoral-fin spine. Outer mandibular barbel with broad skin flap on dorsal margin and extending to base of pectoral-fin spine; inner mandibular barbel broad and shorter, reaching to vertical through posterior orbital margin.

Dorsal fin located about two-fifths along body; with 4,i (15) rays and straight margin. Dorsal-fin spine flattened, straight and robust; spine extending to line through base of pelvic fin. Anterior margin of spine smooth, posterior margin with 4-5 small serrations.

Pectoral fin with stout, blade-like spine, sharply pointed at tip, and with 7 (15) rays. Anterior spine margin with 11-15 small serrations. Posterior spine margin with 5-7 large serrations. Pectoral-fin margin straight anteriorly and posteriorly. Coracoid with short posterior processes, extending just beyond base of posteriormost pectoral-fin ray.

Pelvic-fin origin at vertical through middle of dorsal-fin base. Pelvic fin with i,5 (15) rays and straight margin; tip of adpressed fin not reaching anal-fin origin.

Adipose fin short, posterior end deeply incised. Fin located above anal-fin base. Anal fin with iii,6,i (15) rays, and straight anterior and posterior margins.

Caudal peduncle moderately deep. Caudal fin deeply forked, with i,7,7,i (15) principal rays; upper and lower lobes pointed, with lobes of equal length but lower lobe slightly broader than upper. Procurrent rays symmetrical, extending only slightly anterior to fin base.

Coloration

In 70% alcohol: dorsal and lateral surfaces of head and body grayish brown, fading to lighter grayish brown on lateral surfaces of head and dorsal and lateral surfaces of head and body, fading further to cream on ventral surfaces of head and body. Two series of faint, poorly contrasting cream bands on body: first between dorsal and adipose fins, and second on anterior half of caudal peduncle. Bands absent in some individuals, imparting uniform appearance to coloration. Dorsal fin, with brown base and stripe extending along entire length of dorsal spine, first soft ray and interradial membrane between. Pectoral and pelvic hyaline, with scattered melanophores forming faint transverse bands on middle third of fin. Anal fin hyaline, with brown along base and irregular brown stripe running along length of first and second branched anal-fin rays. Caudal fin hyaline, with brown base and subdistal brown stripe running along length of each lobe; brown band connected to brown color at base via brown median caudal rays in some individuals. Nasal and maxillary barbels brown dorsally, cream ventrally; all mandibular barbels cream.

Etymology

From the Latin ferula, meaning rod, in reference to the terete head and body in this species, which makes it considerably narrower than congeners. Used as a noun in the nominative singular.

Distribution and habitat

Known from the type locality in the Tista River in West Bengal, India (Fig. 4).

The Tista River where P. ferula was collected is wide (ca. 1 km), swift flowing, and with a mixed rocky/sandy bottom. Other fish species caught in the immediate vicinity are: Aspidoparia morar , Barilius bendelisis , B. shacra , B. vagra , Crossocheilus latius , Garra lissorhynchus (Cyprinidae), Psilorhynchus balitora , P. sucatio (Psilorhynchidae), Canthophrys gongota , Lepidocephalichthys guntea (Cobitidae), Acanthocobitis botia , Schistura savona (Balitoridae), Amblyceps mangois (Amblycipitidae), Batasio tengana (Bagridae), Erethistoides sicula (Erethistidae), Pseudolaguvia foveolata , P. ribeiroi , P. shawi (Erethistidae) and Parambassis ranga (Ambassidae).

Discussion

Three other species of Pseudolaguvia have been collected syntopically in the Brahmaputra River drainage with P. ferula : P. foveolata , P. ribeiroi and P. shawi . Pseudolaguvia ferula is clearly distinguished from these three species in having a narrower head as described in the diagnosis (Fig. 5). Pseudolaguvia ferula is additionally diagnosed from syntopic congeners in the size of the anterior fontanel, and the morphologies of the mesethmoid cornua and the thoracic adhesive apparatus as outlined in the diagnosis. Furthermore, the color pattern of P. ferula is different from the other three species: the color pattern of P. foveolata , P. ribeiroi and P. shawi consists of sharply contrasting cream bands on a brown body (although the bands are usually thinner in P. ribeiroi ), while P. ferula has very faint, poorly contrasting cream bands that are sometimes absent on some individuals.

Five of the nine species of Pseudolaguvia occur in the Brahmaputra River drainage ( P. ferula , P. foveolata , P. muricata , P. ribeiroi , and P. shawi ), of which P. ferula and P. foveolata are known from only a single locality. Collections in this area are poorly represented in museums and it was not possible to examine any more material to more accurately determine the geographical distribution of these species. Examination of the two species for which collections over the widest area exist ( P. ribeiroi and P. shawi ) indicate that no significant geographic variation exists for either morphometry or other morphological characters used in the diagnosis of P. ferula (making it unlikely that P. ferula is a geographical variant of another species). It has been shown that positive correlation exists between body size and geographic distribution once effects of latitude, longitude and phylogeny have been statistically accounted for (Taylor & Gotelli, 1994), and this may presumably be true for small, benthic catfishes like Pseudolaguvia , which presumably are less labile (and thus less able to disperse). The presumed reduced lability of Pseudolaguvia may account for the fact that Pseudolaguvia species are frequently syntopic within the Brahmaputra River drainage ( P. ribeiroi and P. shawi are often collected in the same habitat). Although this may also be true in other areas within the distribution of the genus, the fishes of these regions are too poorly sampled to verify this hypothesis.