Garra regressus, Stiassny & Getahun, 2007

Stiassny, Melanie L. J. & Getahun, Abebe, 2007, An overview of labeonin relationships and the phylogenetic placement of the Afro-Asian genus Garra Hamilton, 1922 (Teleostei: Cyprinidae), with the description of five new species of Garra from Ethiopia, and a key to all African species, Zoological Journal of the Linnean Society 150 (1), pp. 41-83 : 53-55

GARRA REGRESSUS SP. NOV. ( FIG. 11 ; TABLE 2)

Garra microstoma Getahun, 2000 , nomen nudum [p. 92, unpubl. PhD thesis, preoccupied by Garra microstoma Mai (1978) and valid as Discogobio microstoma ( Mai, 1978) ( Kottelat, 2001) ]

Diagnosis: Unique among African Garra in possession of a small, acutely pointed head, narrow mouth, regressed rostral cap, and a fully exposed upper jaw.

Description: Morphometric and meristic data for holotype and two paratypes given in Table 2. Maximum size: 121.8 mm SL (holotype, AMNH 228487). Currently known only from type series. All specimens relatively slender (body depth 19.8–20.6, m. 20.1% SL) and elongate, greatest body depth located at level of dorsal-fin origin. Head relatively short (19.7–21.0, m. 20.5% SL), snout acutely pointed and often studded with small tubercles, mouth narrow. Eye positioned a little posterior on head. Dorsal head profile rising steeply over snout, dorsum of head more-orless flattened, dorsal body profile smoothly convex to dorsal-fin origin. Disc type A, weakly developed and inconspicuous, without free posterior margin. Rostral cap thin and regressed leaving upper jaw exposed. Two pairs of small barbels, maxillary pair usually longest. Thirty-nine pored scales along lateral line; either eight or nine predorsal scales anterior to dorsal fin; either three or four scales from lateral line to origin of pelvic fin; either four or five scales from lateral line to origin of dorsal fin. Chest asquamate, belly with a few deeply embedded scales, and postpelvic region fully scaled. Dorsal-fin rays iii, seven, inserted well anterior to pelvic fin, with short subacuminate tip, first and second branched rays longest, extending slightly beyond last ray; posterior margin straight, posteriormost ray not extending to tip of pelvic fin. Predorsal length (distance between dorsal-fin origin and tip of snout) 44.0–46.3% SL. Anal-fin rays iii, five, with short subacuminate tip; posterior margin straight. Pectoral-fin rays iv, 11; pectoral length 17.5–21.0% SL. Vent located relatively close to anal fin (vent distance 19.3–23.8, mean 21.9%). Intestine very short (SL 108–116% Int.L). Gas bladder well developed and large (posterior chamber 21.7–24.9% SL).

ARTIFICIAL KEY TO GARRA OF THE AFRICAN CONTINENT

1. Two pairs of barbels (maxillary and rostral) .................................................................................................................. 2 Single pair of (maxillary) barbels......................................................................................... Garra duobarbis ( Ethiopia)

2. Rostral fold ventrally expanded and covering upper jaw; mouth broad .......................................................................3 Rostral fold not ventrally expanded and upper jaw exposed; mouth narrow................................................................. ............................................................................................................................. Garra regressus ( Ethiopia, Lake Tana)

3. Mental disc moderately to very well developed, with free lateral and posterior margins ( Fig. 1B, C ) ......................4 Mental disc reduced to a central callus, sometimes with a narrow free posterior margin, but entirely lacking free lateral margins and papillate periphery ( Fig. 1A ) ........................................................................................................ 14

4. Chest with either many, or some scattered scales ..........................................................................................................5 Chest asquamate ............................................................................................................................................................... 6

5. Lateral line scales 34–35; vent located close to anal fin (vent distance 8.6–19.1% of distance between anterior end of anal- and pelvic-fin insertions); eye median ............................... Garra quadrimaculata ( Ethiopia, Eritrea, Somalia) Lateral line scales 40–42; vent located relatively far from anal fin (vent distance 29.3–30.2% of distance between anterior end of anal- and pelvic-fin insertions); eye posterior .... Garra hindii ( Cameroon, Congo *, Kenya, Uganda)

6. Post-pelvic region asquamate ........................................................................................................................................... 7 Post-pelvic region scaled ................................................................................................................................................... 9

7. Body either with distinct midlateral band, or darker dorsally than ventrally; black spots in basal membrane of dorsal fin; predorsal region only partially scaled; region between vent and anal fin scaled ............................................8 Uniformly pale body coloration; no markings in dorsal fin; fully scaled predorsal region; no scales between vent and anal fin ........................................................................................................ Garra blanfordii ( Ethiopia, Eritrea, Sudan)

8. Between five and nine scales in predorsal region; body depth 14.9–16.8, m. 16.0% SL; intestine short (SL 95.0– 102.0% Int.L) .................................................................................................................................. Garra geba ( Ethiopia) Between zero and three scales in predorsal region; body depth 15.6–23.9, m. 20.4% SL; intestine moderately long (SL 39.0–42.0% Int.L) ......................... Garra dembeensis ( Cameroon, Chad, Egypt, Ethiopia, Kenya, Nigeria, Tanzania)

9. Predorsal region either naked or only partially scaled ................................................................................................ 10 Predorsal region fully scaled .......................................................................................................................................... 11

10. Body and head markedly dorso-ventrally flattened (body depth 10.6–15.0, m. 11.9% SL); gas bladder extremely reduced, posterior chamber 3.1–3.8% SL................................................................. Garra congoensis ( Angola, Congo *) Body depth 15.8–22.3, m. 17.8% SL; posterior chamber of gas bladder 6.2–10.0% SL ................................................. ............................................... Garra ornata ( Cameroon, Central African Republic, Congo *, Gabon, Guinea, Nigeria)

11. Either 29 or 30 scales on the lateral line; body depth 29.1–30.9, m. 30.0% SL; 27–28 vertebrae................................ .............................................................................................................................................. Garra ethelwynnae ( Eritrea) More than 34 scales on the lateral line; body depth less than 28.0% SL; more than 30 vertebrae ......................... 12

12. Disc moderately developed (type B); dark ash-grey midlateral band to base of caudal peduncle; belly scaled; no tubercles on snout .............................................................................................................. Garra aethiopica ( Ethiopia) Disc well developed (type C); body more-or-less uniformly dark on flanks; belly either asquamate or with only a few embedded scales; tubercles on snout ............................................................................................................................. 13

13. Some scales on belly; distance from vent to anal fin 10.3–16.9, m. 13.6% of distance between anal- and pelvic-fin insertions; eye either median, or posterior in large specimens ......................................... Garra makiensis ( Ethiopia) Belly asquamate; distance from vent to anal fin 19.2–29.5, m. 18.2% of distance of anal- and pelvic-fin insertions; eye median........................................................................................................................................ Garra ignestii ( Ethiopia)

14. Post-pelvic region asquamate, Ethiopian distribution.................................................................................................. 15 Post-pelvic region scaled, found in Cameroon and Tchad............................................................................................ 16

15. Length of caudal peduncle 20.4–22.3, m. 20.2% SL; either 39 or 40 scales in lateral line; intestine short (SL 62.7–79% Int.L); spots in basal membrane of dorsal fin either absent or small and faint ........................................... ..................................................................................................................................... Garra tana ( Ethiopia, Lake Tana) Length of caudal peduncle 13.3–20.7, m. 16.8% SL; 37–38 scales in lateral line; intestine longer (SL 40–56% Int.L); either four or five elongate black spots in basal membrane of dorsal fin....................................................................... ................................................................................................... Garra dembecha ( Ethiopia, Eritrea, Kenya, Tanzania)

16. Vent close to anal fin (vent distance 13.3–17.4% of distance between pelvic- and anal-fin insertions) ....................... ............................................................................................................................................ Garra lancrenonensis ( Tchad) Vent situated relatively far from anal fin (vent distance 28.5–30.6% of distance between pelvic- and anal-fin insertions) ............................................................................................................................ Garra allostoma ( Cameroon)

Colour in preservation: Body dark brown dorsally, somewhat lighter brown below lateral line but not markedly so. In largest specimen ( Fig. 11 ) traces of a dark midlateral band evident. Head, snout, cheek, and opercle: dark brown. Lips, lower cheek, gular region, and branchiostegal membranes: pale yellow brown. Dorsal and anal fins dark brown distally, paler proximally, with pale, creamy subacuminate tips. Either four or five discrete black spots between rays in basal membrane of dorsal fin. Caudal fin uniformly dark brown. Pelvic and pectoral fins light brown with pale leading edges.

Distribution and habitat: Currently known from region of Gerima in southern part of Lake Tana, Ethiopia. Specimens were collected by trawl in papyrus beds close to shore (25–30 m) in water c. 2.5 m in depth.

Etymology: Regressus , from the Latin regress, meaning to go back, in reference to the regressed rostral cap characteristic of the species.

Material examined – type material: Holotype of G. regressus, AMNH 228487, 121.8 mm SL, Lake Tana, Gerima , c. 30 m off shore (11°35′N, 37°24′E); paratypes of G. regressus, AMNH 228487, two ex., one ex. C & S, 94.7–115.6 mm SL, same data as holotype.

Figures

Figure 1. Range of variation in disc type among African Garra: (A) type-A disc, weakly developed; (B) type-B disc, intermediate development; (C) type-C disc, well-developed.

Figure 11. Garra regressus, holotype, AMNH 228487, 121.8 mm standard length.