Tanganikallabes alboperca, Wright & Bailey, 2012

Wright, Jeremy J. & Bailey, Reeve M., 2012, Systematic revision of the formerly monotypic genus Tanganikallabes (Siluriformes: Clariidae), Zoological Journal of the Linnean Society 165 (1), pp. 121-142 : 129-131

TANGANIKALLABES ALBOPERCA SP. NOV.

( FIGS 3B, E , 4B , 5B , 9 , 10 , 11B; TABLES 3, 4)

Diagnosis: Tanganikallabes alboperca sp. nov. is distinguished from all congeners by its relatively shorter pelvic fins (6.0–7.7% SL versus 7.1–9.3% SL in other Tanganikallabes species ), which do not reach past the origin of the anal fin when adpressed (versus reaching past the anal fin origin in all other Tanganikallabes species ). It is also distinct from other Tanganikallabes species in the presence of a well-defined, depigmented border on the operculum, which extends from the upper margin of the operculum all the way to the union of the gill membranes at the isthmus (border absent in T. mortiauxi and T. stewarti sp. nov.).

Tanganikallabes alboperca sp. nov. is further distinguished from T. mortiauxi by its premaxillary toothpad shape (uniformly thin, broad crescent versus widest point anteroposteriorly thicker than the premaxillary toothpad in T. mortiauxi ; Fig. 4 ), io-iv and the suprapreopercle consisting of multiple separate elements (versus a single element in T. mortiauxi ; Figs 3 , 5 ), the extensions of the lateral ethmoid not reaching io-ii when viewed from above (versus nearly or completely overlying io-ii in T. mortiauxi ; Fig. 3 ), its incomplete lateral line (versus complete in T. mortiauxi ), shorter pectoral fin spine (3.6–5.3% SL versus 5.6–8.8% SL in T. mortiauxi ), generally lower number of dorsal fin rays [65–74 (modally 70) versus 72–81 (modally 80) in T. mortiauxi ], smaller eye (0.8– 1.6% SL versus 1.8–3.0% SL in T. mortiauxi ), and lack of a free lower orbital margin. Tanganikallabes alboperca sp. nov. is further separated from T. stewarti sp. nov. by having a relatively deeper body (body depth at anus 11.7–14.6% SL versus 8.7–10.9% SL in T. stewarti sp. nov.), longer lateral line (see below description of T. stewarti sp. nov.), greater preanal length (45.2– 49.0% SL versus 42.4–44.8% SL in T. stewarti sp. nov.), and by generally having a lower number of anal fin rays [55–63 (modally 59) versus 63–69 (modally 65) in T. stewarti sp. nov.].

Description: Morphometric data in Table 4, frequency distributions of selected meristic data in Table 3. Maximum TL 180 mm, SL 160 mm. Body elongate, moderately compressed posterior to origin of dorsal fin. Predorsal slightly convex, with small indentation formed by curvature and insertion of cheek muscles on skull. Prepelvic profile slightly convex. Skin on body forming numerous vertical ridges and folds; extending onto and encasing all fins.

Head depressed and broad; skin thick; lateral cranial muscles hypertrophied, forming trough in centre of head over bones of skull. Snout short, with bluntly rounded margin when viewed dorsally; acute, narrow margin when viewed laterally. Anterior nostrils tubular; posterior nostrils poorly visible, located at posterior base of nasal barbel. Opercular flap extending over base of pectoral fin spine. Eye small, located dorsolaterally; circular; lacking free margin. Interorbital area broad, flat.

fin i,5; tip of adpressed fin does not reach beyond origin of anal fin. Anal fin elongate, with 55–63 branched rays; posterior margin not joined with caudal fin. Caudal fin i,7,8,i; rounded.

Coloration in alcohol: Dorsum and flanks uniformly light to dark brown, ventral surfaces noticeably lighter ( Fig. 9 ). All barbels pigmented as body on their proximal half, distal half lacking pigmentation. All fins with brownish bases and narrow, depigmented border; border wider in younger specimens. Operculum with wide, depigmented margin, extending onto underside of head.

Distribution: Lake Tanganyika. Tanganikallabes alboperca sp. nov. is apparently distributed lakewide, although existing collections come only from the extreme southern and northern areas of the lake ( Fig. 10 ).

Habitat: Habitat details for this species are absent for the collections examined. It is likely to inhabit rocky bottoms, over a range of depths, as is the case for T. mortiauxi .

Mouth terminal; lips narrow and papillate; jaws equal, or upper jaw slightly longer. Mandibular, premaxillary, and vomerine teeth pointed, unicuspid, arranged in multiple transverse rows. Toothpads granular in appearance because of embedding of teeth in fleshy pad for most of their length. Mandibular toothpad wide, crescentic. Premaxillary toothpad broadly curved, rectangular, noticeably wider than vomerine toothpad. Vomerine toothpad located immediately posterior to premaxillary; narrow; broadly curved; crescentic.

Nasal barbel short; not extending to any aspect of opercular flap. Maxillary barbel occasionally extends beyond margin of opercular flap, but is usually shorter. Lateral mandibular barbel extending to, or slightly beyond, lower opercular margin. Medial mandibular barbel short, slightly over half the lateral mandibular barbel length. All barbels smooth, with very narrow basal membrane.

Dorsal fin elongate, lacking spine, with 65–74 soft rays; origin located well behind vertical through posterior tip of adpressed pectoral fin; posterior margin not joined with caudal fin. Pectoral fin I,7,8; strong spine, well-developed venom glands present; spine approximately half the length of pectoral fin; posterior margin of spine with between zero and five very small, retrorse serrations. Adipose fin absent. Pelvic Diet: The stomachs of three specimens (from UMMZ 199937 and UMMZ 199861) contained, collectively, fish eggs (species indeterminate), the remains of a single platythelphusid crab, and insect larvae.

Etymology: The specific epithet, alboperca , is a combination of the latin adjective alba, meaning white, and the noun operculum, meaning lid or cover, a reference to the distinctive depigmented posterior margin seen in the operculum of this species. Gender: feminine.

Material examined: Holotype: UMMZ 199936 (153 mm SL), E. side of Nyika Bay , N. side of Nkumbula Island, Zambia Lake Tanganyika, 31.X.1970 . Paratypes: UMMZ 199937 (7 alc, 1 c&s; 102– 155 mm SL), collection data as for holotype ; UMMZ 199861 (27 alc, 2 c&s; 47–152 mm SL), N. end of Nkumbula Island , 2 km N. of Mpulungu, Zambia, Lake Tanganyika, 1.XI.1970 ; UMMZ 196021 (2 alc; 122–146 mm SL), Zambia, Lake Tanganyika (no additional data) ; SAIAB 76160 (3 alc; 66– 145 mm SL), Mbita Island (north-west end), 8°45.18′S, 31°05.07′E, Zambia, Lake Tanganyika, 29.II.2004 ; SAIAB 86974 (1 alc; 115 mm SL), Sumbu , 8.5167°S, 30.4833°E, Zambia. Lake Tanganyika, 00 . V.1983; SAIAB 86968 (1 alc; 105 mm SL), Chimba , 08°25.27′S, 30°27.44′E, Zambia, Lake Tanganyika, 07.III.2004 ; SAIAB 80225 (1 alc; 99 mm SL), Chituta Bay , cliffs, bottom of bay on west side, 8°43.82′S, 31°9.41′E, Zambia, Lake Tanganyika, 09.III.2004 ; MRAC 125751 (1 alc; 104 mm SL), Luhanga, Lake Tanganyika , 13.II.1959 ; MRAC 78025.0013 , 78025.0014 (2 alc; 83–104 mm SL), Cape Kabeyeye, Zambia, Lake Tanganyika , I.1978 ; MRAC 78025 . 0013, 78025.0014 (1 alc; 93 mm SL), Cape Kabeyeye, Zambia, Lake Tanganyika , I.1978 ; MRAC 76004.0566 (1 alc; 126 mm SL), Cape Nunda, southern Lake Tanganyika , Zambia, 6.I.1976 ; MRAC 130952– 130970 (4 alc; 141–161 mm SL), Kalungwe, Lake Tanganyika , 11.VII.1961 ; MRAC 187088 (1 alc; 104 mm SL), Nkumbula Island , Lake Tanganyika, Zambia, 14.VII.1965 ; MRAC 81062.0001 (1 alc; 146 mm SL), Kabimba, 50 km N. Albertville, Lake Tanganyika , Democratic Republic of Congo, 7.IV.1981 .

Figures

Figure 3. Cranial morphology of Tanganikallabes species (and Clarias gariepinus for comparison), showing interspecific differences in orbital and lateral ethmoid morphology, as well as overall reductions of cranial osteology. A, Tanganikallabes mortiauxi (UMMZ 199862), in which infraorbital iv (io-iv) is composed of a single element and the extensions of the lateral ethmoid nearly overlie io-ii. B, C, Tanganikallabes alboperca sp. nov. (UMMZ 199861) and Tanganikallabes stewarti sp. nov. (UMMZ 196154), respectively, in which io-iv consists of two elements and the extensions of the lateral ethmoid do not reach io-ii. D, Clarias gariepinus, UMMZ 166654. E, Drawing of T. alboperca sp. nov. skull (UMMZ 199861), more clearly showing delimitations of cranial elements in Tanganikallabes.

Figure 4. Toothpad morphology of Tanganikallabes species: A, Tanganikallabes mortiauxi; B, Tanganikallabes alboperca sp. nov. and Tanganikallabes stewarti sp. nov.

Figure 5. Condition of the suprapreopercle in Tanganikallabes species. A, Tanganikallabes mortiauxi (UMMZ 199862), in which the suprapreopercle is composed of a single element. B, Tanganikallabes alboperca sp. nov. (UMMZ 199861), in which the suprapreopercle is clearly composed of multiple elements. This condition is also found in Tanganikallabes stewarti sp. nov.

Figure 9. Dorsal, lateral, and ventral views of Tanganikallabes alboperca sp. nov., Holotype, UMMZ 199862, 153 mm standard length. Scale bar: 1 cm.

Figure 10. Known distribution of Tanganikallabes alboperca sp. nov. T denotes the type locality.

Figure 11. Differences in the extent of lateral line between (A) Tanganikallabes stewarti sp. nov. and (B) Tanganikallabes alboperca sp. nov. White arrows indicate the posterior terminus of the lateral line.