Typhleotris madagascariensis Petit, 1933

Sparks, John S. & Chakrabarty, Prosanta, 2012, Revision of the Endemic Malagasy Cavefish Genus Typhleotris (Teleostei: Gobiiformes: Milyeringidae), with Discussion of its Phylogenetic Placement and Description of a New Species, American Museum Novitates 2012 (3764), pp. 1-28 : 4-7

Typhleotris madagascariensis Petit, 1933

Figures 2 , 6A , 7A , 8A; table 1

LECTOTYPE: MNHN 1933-0060 , 43.8 mm SL; Mitoho sinkhole (aven de Mitoho), underground waters in Mahafaly, southwestern Madagascar, coll. Perrier de la Bâthie. Lectotype designated by Bauchot et al. (1991).

NONTYPE COMPARATIVE MATERIALS: AMNH 245603 , 1 ex., 44.8 mm SL, Mitoho Cave tourist camp, well at parking lot for Mitoho Cave , Parc National de Tsimanampetsotsa , northeast of Efoetse , 24°02′54.0″S, 043°45′07.6″E, southwestern Madagascar, MAD-6-2008, coll. J.S. Sparks, P.W. Willink, P. Chakrabarty, and S.B. Holtz, 7 June 2008. AMNH 245604 , 1 ex., 43.6 mm SL, Andranomalaza (Vintany) sinkhole, Parc National de Tsimanampetsotsa , northeast of Efoetse , 24°02′37.6″S, 043°45′19.6″E, southwestern Madagascar, MAD-5-2008, coll. J.S. Sparks, P.W. Willink, P. Chakrabarty, and S.B. Holtz, 7 June 2008. AMNH 245605 , 1 ex., 44.4 mm SL, Andranoilovy (Andranilove) Cave , Parc National de Tsimanampetsotsa , northeast of Efoetse , 24°03′15.9″S, 043°45′42.1″E, southwestern Madagascar, MAD-7-2008, coll. J.S. Sparks, P.W. Willink, P. Chakrabarty, and S.B. Holtz, 7 June 2008. AMNH 245606 , 1 ex., 56.7 mm SL, Andriamaniloke Cave , Parc National de Tsimanampetsotsa , northeast of Efoetse , 24°03′15.9″S, 043°45′42.1″E, southwestern Madagascar, MAD-82008, coll. J.S. Sparks, P.W. Willink, P. Chakrabarty, and S.B. Holtz, 7 June 2008. AMNH 245607 , 1 ex., 51.5 mm SL, data as for AMNH 245603. AMNH 245608 , 1 ex., 45.2 mm SL, data as for AMNH 245604. AMNH 245609 , 1 ex., 60.4 mm SL, data as for AMNH 245606. AMNH 245610 , 2 ex., 39.0–45.0 mm SL, 1 ex. C&S, Mitoho Cave, Parc National de Tsimanampetsotsa, northeast of Efoetse, 24°02′52.1″S, 043°45′11.5″E, southwestern Madagascar, MAD-4-2008, coll. J.S. Sparks, P.W. Willink, P. Chakrabarty, and S.B. Holtz, 7 June 2008. AMNH 245611 , 1 ex., 25.4 mm SL, data as for AMNH 245610 . AMNH 245687 , 1 ex., 44.2 mm SL, data as for AMNH 245604 . AMNH 245688 , 1 ex., 54.3 mm SL, data as for AMNH 245605 . BMNH 1981.11.9.21–22, 2 ex., Grotte de Lelia (Lalia), located north of Itampolo, southwest Madagascar, presented by J. Wilson . MNHN 1963-0174 , 2 ex., 51.0– 61.4 mm SL, Mikotsy [sic: should be Nikotsy sinkhole], just to the north of Itampolo, southwestern Madagascar, coll. De Saint-Ours. MNHN 1968-0167 , 2 ex., 50.3–81.4 mm SL, Tulear (Toliara) (no additional data provided), southwestern Madagascar, coll. A Kiener.

DIAGNOSIS: Distinguished from congeners by the presence of scales extending fully onto the head. Head is more or less fully scaled, including opercle and subopercle, cheek (suspensorium), snout (extent of squamation variable), preorbital and interorbital regions, and nape. Typhleotris madagascariensis is further distinguished from the new species by the absence of pigment on the body and fins, a shorter second predorsal length (56.2–64.1 vs. 64.9–69.0 in new species), and a more or less rounded head and snout in dorsal and lateral view (vs. strongly concave/indented in orbital region), and from T. pauliani by a pelvic count of I, 5 (vs. I, 4 in T. pauliani ) and the absence of spines in both the second dorsal and anal fins (vs. single spine present in both fins in T. pauliani ).

DESCRIPTION: Selected proportional measurements and meristic data presented in table 1. A generally small (<~ 80 mm SL) and elongate (BD <23% SL) gobioid, reaching relatively similar adult size as T. pauliani , although T. madagascariensis has a more elongate and less robust body. Body somewhat wide anteriorly and head dorsoventrally compressed, particularly rostrally. Head appearing smaller and more rounded than in congeners, which might be due to extent of squamation extending fully onto head. Body becoming progressively laterally compressed posteriorly. Caudal peduncle laterally compressed, elongate, and relatively shallow. Eyes lacking entirely, with ctenoid scales covering orbital opening in skull. Snout wide. Snout and anterior portion of head markedly elongate and shovellike, with a bony, armored appearance owing to enlarged sensory canals forming platelike subdivisions. On dorsal, lateral, and ventral sides of head numerous deep canals, lined with small pores. Anterior nostril short, wide, and tubular, located just posterior to upper lip; posterior nostril more or less slit like, but opening rather wide and oval. Lacrimal small, greatly reduced in size. Palatine elongate and very thin. Ventral margins of bones on cheek and operculum lined with densely arrayed short papillae, lending the bones a serrated appearance.

Mouth large, and gape wide. Oral jaw teeth small, conical, and slightly recurved; teeth numerous and arrayed in five or six closely set and irregular rows in anterior portion of mouth, and tapering to fewer rows of teeth posteriorly, as well as medially proximal to synthesis where tooth rows become noticeably constricted in both upper and lower jaws. Teeth present along full length of premaxillary arcade and dentary. Basihyal large, triangular, and fan shaped.

Nine or 10 thin, markedly elongate, medially denticulate, and distally tapering (to a point) gill rakers arrayed along lower limb of first arch. Four epibranchial rakers of similar morphology present on first arch. Gill rakers on arches 2–4 short, robust, and strongly denticulate dorsally; covered apically with short conical teeth. Fifth ceratobranchial elements separate, and densely toothed, as are upper pharyngobranchial toothplates. Fifth ceratobranchial and upper pharyngeal toothplates covered with small, robust conical teeth.

Head fully scaled, including snout (in some individuals scales extend rostrally almost to upper lip, to lateral ethmoid and median ethmoid). Squamation extends rostrally to anterior margin of frontal bones, where scale rows become constricted (narrow) medially. Scales sparsely arrayed over lateral ethmoid and median ethmoid (figs. 2, 6A, 7A, 8A). Laterally, ctenoid scales extend anteriorly over pterygoid elements to posterior portion of elongate, thin palatine. All scales on body and head strongly ctenoid, except on ventrum. Cycloid scales on ventrum extend from around anus and urogenital papilla to anterior margin of chest. Scales on belly and chest highly embedded and difficult to see in preserved specimens (i.e., can easily be seen in C&S individual, AMNH 245610, 39.0 mm SL). Scales on head, opercle, and dorsum strongly ctenoid. Scales becoming increasingly more embedded posteriorly on flank and dorsum, and on caudal peduncle to flexure, such that they may appear cycloid upon casual examination. All fins asquamate, except in some individuals a few scales may extend slightly onto base of caudal fin. Otherwise, body fully scaled to caudal fin, including regions both anterior and medial to pelvic fin. Scales arranged in irregular rows, uneven in size, with smallest on roof of head, and largest on operculum. Pectoral-fin axil and fleshy base asquamate.

It is worth noting that there is some intraspecific variation in scale morphology, as the two individuals from MNHN 1968-167 (50.3–81.4 mm SL, region: Toliara, locality: Tulear [no additional locality data provided], southwestern Madagascar, coll. A. Kiener) appear to have mostly cycloid scales covering the head (some ctenoid scales present on the operculum), whereas in all other available material the head is covered with ctenoid scales. Unfortunately, collection locality information for this lot is lacking, indicating only Tulear (Toliara), the largest city in the general region. These individuals may simply be aberrant in terms of scale morphology on the head, or this variation could be unique to an isolated population .

Two dorsal fins. First dorsal fin with five spines and second dorsal with eight or nine rays. Anal fin with eight rays. Spines lacking in both second dorsal and anal fins, only segmented and branched rays present. Pelvic-fin origin at about level or slightly anterior to vertical through pectoral-fin origin. Dorsal insertion of pectoral fin located just anterior to vertical through posterior margin of operculum. Pectoral fin with 14 to 16 rays. Anus located well anterior to vertical through origin of second dorsal fin. First dorsal fin small, rays feeble, and located at about level of vertical 1/3 distance through adducted pelvic fin. Anal-fin origin located posterior to vertical through origin of second dorsal. Urogenital papilla short, tubular, and narrow, not reaching anal fin when adducted. Pelvic formula I, 5. Pelvic and pectoral fins elongate, with long trailing rays. Pectoral-fin base well developed, portion surrounding proximal radials projecting from body as fleshy appendage. Caudal fin short, fanlike, and rounded distally. Vertebral count 24 or 25.

COLORATION AND PIGMENTATION PATTERN IN LIFE AND ALCOHOL (fig. 2): Body without pigment and uniformly white in coloration. In life, body is relatively translucent, whereas translucency is lost and body becomes an opaque white in alcohol. It is worth noting that all recently collected material is entirely lacking in pigment (e.g., fig. 2B), whereas some historical specimens (MNHN 1963-174, 2 ex., 50.3–81.4 mm SL; fig. 2C) appear to be somewhat light brownish overall. There is no way of knowing, unfortunately, whether this faint pigmentation is simply an artifact of preservation.

ETYMOLOGY: Named by Petit (1933) for the country of origin.

DISTRIBUTION AND HABITAT (figs. 1, 3): Restricted to subterranean habitats (caves, sinkholes, wells) within the Mahafaly Plateau karst formation, as well as isolated locations with Eocene limestone along the coastal plain below and to the west of the plateau, to the south of the large Onilahy River drainage basin. The geographic range of T. madagascariensis extends from wells near Ambilahilalika (approx. 23°52′S), located about midway between Soalara and Efoetse in the north, southward to Nikotsy sinkhole, located just to the north of Itampolo (24°40′S) (fig. 1). Reports from locals indicate the presence of blind, pigment-free Typhleotris southward to just north of the Linta River, which could extend the southern range limit of T. madagascariensis if confirmed through additional fieldwork.

REMARKS AND COMPARISONS: Typhleotris madagascariensis can be distinguished from congeners by the presence of a fully scaled head, whereas both T. pauliani and T. mararybe have scales extending anteriorly only up to the roof of the head and onto the operculum, not fully covering the cheek and not extending onto the anterior portions of the head, such as the orbital region, snout, and anterior portion of the frontal bones. This species can also be distinguished from congeners by the presence of strongly ctenoid scales on the flank and dorsum (vs. cycloid in congeners).

Whereas all previous accounts in the literature report the presence of an initial spine in the second dorsal and/or anal fins in T. madagascariensis (e.g., Petit, 1933 [anal fin only]; Arnoult, 1959a, 1959b [anal fin only]; Kiener, 1963 [both fins]), careful examination of the available preserved material indicates that these elements are not true spines, but segmented rays. Typhleotris pauliani does have a single true spine preceding the rays in both the second dorsal and anal fins as previously reported (e.g., Arnoult, 1959a, 1959b; Kiener, 1963).

Typhleotris madagascariensis appears to have a rather widespread range, and is known from several localities throughout the southern portion of the Mahafaly Plateau, south of the Onilahy River, but, unfortunately, the species is not common or abundant anywhere within its range. These cave and sinkhole habitats are fragile and rather ephemeral systems, although most are so isolated that there is little danger from human encroachment. Only the collection localities within Tsimanampetsotsa National Park, including the Mitoho Cave tourist site, Andranomalaza (Vintany) sinkhole, Andranoilovy (Andranilove) Cave, and Andriamaniloke Cave, are afforded any official protection from the Malagasy government, and receive few visitors annually due to their relative inaccessibility.

Figures

FIGURE 2. Typhleotris madagascariensis: A. Lateral view of lectotype, MNHN 1933-0060, 43.8 mm SL; Mitoho sinkhole, underground waters in Mahafaly, southwestern Madagascar. B. Recently collected specimen, AMNH 245610, from Mitoho Cave, 45.0 mm SL, in northern half of geographic range. C. Specimen from southern end of geographic range (Nikotsy sinkhole), near Itampolo, MNHN 1963-174, 61.4 mm SL.

FIGURE 6. Illustration of A. Typhleotris madagascariensis and B. T. pauliani after Arnoult (1959b), showing general body and fin shape, as well as differences in extent of head squamation between species.

FIGURE 7. Dorsal view of the anterior portion of the head in the three described species of Typhleotris: A. T. madagascariensis, AMNH 245603; B. T. pauliani, AMNH 245651; C. T. mararybe, AMNH 245601, holotype.