Cobitis, Linnaeus, 1758

Cobitis View in CoL

Cobitis comprises approximately 126 species, distributed between Portugal and Morocco in the west and Korea and Japan in the east. In West Asia, 31 species have been documented, most of which are found in Anatolia. In conjunction with Greece, this region represents a significant diversity hotspot of the genus. Male Cobitis have one or two laminar projections on the dorsal surface of the anterior pectoral rays (lamina circularis, plural: laminae circularis; also known as Canestrini scales). Examining the lamina circularis in Cobitis requires preparation, as it is covered by skin. In species with two laminae, these may be very small, particularly the outer lamina, which may be a small lateral enlargement or a lateral crest on the fin ray. It should be noted that the inner lamina is not necessarily scale-shaped.

Cobitis is notable for exhibiting minimal morphological variation. Most species exhibit superficial similarities, share identical meristic characters, and display comparable structural characteristics, including fin position, mouth shape and structure, nares, lateral-line length, and squamation pattern. Species differentiation is primarily achieved through colour patterns, organised by the Gambetta zones relatively conservatively. Several species have a notable divergence from the typical configuration of the Gambetta zones. This is evidenced by the fragmentation of the blotches within these zones, the blurring of the borders between them, and the gradual convergence of different zones. Notably, this process of dissociating the colour pattern of the Gambetta zones is ontogenetic. In young fish, the colour pattern is often well organised in the Gambetta zones, whereas in adults, particularly in adult females, a pattern of dissociated blotches is observed. The degree to which the Gambetta zones’ colour patterns are dissociated depends on the species and particular populations. For instance, considerable individual variation is observed in the colour pattern of C. battalgilae , which spans almost the entire spectrum of variation observed in Cobitis . Additionally, considerable variation is observed among different populations of C. strumicae , C. phrygica , C. simplicispina and C. turcica , with almost every population displaying distinct characteristics. In C. dorademiri and C. sipahilerae , only a small proportion of individuals exhibit a dissociated colour pattern, with most individuals displaying a highly similar phenotype.

Cobitis are typically associated with fine substrates (sand, mud) from which they feed. They burrow in the substrate to hide. A specialised filter-feeding mechanism enables Cobitis to separate fine organic particles and small benthic organisms (e.g., copepods, worms, insect larvae) from the substrate. Cobitis can swallow air, with oxygen being absorbed through the gut walls. The spawning behaviour is consistent in the few species of Cobitis in which it has been observed. The male follows the female, and after both enter dense vegetation (e.g., filamentous algae), the male forms a complete ring around the female’s body behind the dorsal as the female releases the eggs. The eggs of most species are not sticky but swell to 2.5–3.5 mm in diameter and, due to this large size, are retained in the vegetation. The free larvae have large external gill filaments. The biology of almost all Cobitis species in West Asia remains unstudied, and there is much work to be done in the future.

Some Cobitis species of Central and Eastern Europe occur as a multitude of hybridogenous lineages. These hybrid lineages, made up of nearly only female individuals, reproduce by gynogenesis, often including polyploid individuals. They are described as sperm-parasites, as they are dependent on males of bisexually reproducing lineages that serve as sperm donors, with the sperm serving only to induce the development of their eggs. Such hybridogenous lineages have yet to be reported from West Asia, but their occurrence cannot be excluded. The presence of highly biased sex ratios may serve as an indicator.

Further reading. Gambetta 1934 (pigmentation pattern); Bohlen 2003a, b (reproduction); Ludwig et al. 2001 (molecular phylogeny); Bohlen et al. 2006 (molecular phylogeny); Geiger et al. 2014 (molecular diversity in the Mediterranean); Perdices et al. 2018 (molecular diversity); Freyhof et al. 2018c (species diversity in West Asia).

Keys to species of Cobitis in West Asia

Persian Gulf basin

1a - Male with two laminae circularis. ………………2

1b - Male with one lamina circularis. ………………3

2a - Blotches in Z4 between vertical of pectoral origin and dorsal base squarish, irregularly shaped, roundish, and usually widely separated; blotches in Z4 posterior to dorsal base not fused into stripes, restricted to one row; pelvic axillary lobe present. ……………… C. elazigensis

2b - Blotches in Z4 between vertical of pectoral origin until caudal–peduncle comma-shaped, densely set, often fused into short stripes or dissociated into a wide band of several rows of blotches; axillary pelvic lobe absent. ……………… C. linea

3a - Large, usually horizontally elongated, dark-brown blotches in anterior part of Z4, roundish or vertically elongated on caudal–peduncle. ……………… C. avicennae

3b - Minute, roundish, dark-grey dots in Z4. ……………… C. kellei

Caspian basin

1a - Subdorsal scales with a large focal zone (about ½ of maximum scale diameter). ……………… C. amphilekta

1b - Subdorsal scales with a small focal zone (about or less than ⅒ of maximum scale diameter). ………………2

2a - Plate of lamina circularis not reaching end of third segment of attached pectoral ray; dark-brown spot at upper caudal base poorly developed. ……………… C. derzhavini

2b - Plate of lamina circularis reaching to or beyond end of third segment of attached pectoral ray; dark-brown spot at upper caudal base well developed. ………………3

3a - Base of lamina circularis widely connected to pectoral ray; cheek between eye and opercle strongly pigmented. ……………… C. saniae

3b - Base of lamina circularis with a narrow connection to pectoral ray; cheek between eye and opercle poorly pigmented or unpigmented. ……………… C. faridpaki

Southern Black Sea basin and endorheic Anatolian basins of Lakes Akşehir, Eber, and Ilgın

1a - Male with 2 laminae circularis. ……………… C. simplicispina

1b - Male with 1 lamina circularis. ………………2

2a - Pigmentation in Z3 reduced to about head length in male or pigmentation in Z3 as wide as or narrower than pigmentation in Z2. ……………… C. splendens

2b - Pigmentation in Z3 usually complete, reaching much behind dorsal base and or pigmentation in Z3 wider than pigmentation in Z2. ……………… C. satunini

Southern Marmara and eastern Aegean basins south to Eşen

1a - Male with 2 laminae circularis. ………………2

1b - Male with 1 lamina circularis. ………………6

2a - Two brown or black spots at upper and lower caudal base. ……………… C. strumicae

2b - One or no black spot at upper and lower caudal base. ………………3

3a - External part of suborbital spine simple; no black spot at upper caudal base; colour pattern on flank often dissociated, not following Gambetta zones in most, but not all, individuals and populations. ……………… C. phrygica

3b - External part of suborbital spine bifurcate; back spot at upper caudal base present, often very small, rarely absent; colour pattern on flank following Gambetta zones in all populations except in few individuals. ………………4

4a - Pigmentation below Z4 absent except some small spots at caudal–peduncle, also above anal base in few individuals; caudal–peduncle depth 1.2–1.7 times in caudal–peduncle length. ……………… C. indus

4b - Pigmentation below Z4 present, if restricted to anal base, then caudal–peduncle depth 1.0–1.2 times in caudal– peduncle length. ………………5

5a - Pigmentation below Z4 restricted to a short line or few dots below pectoral and a second short line on lower caudal–peduncle. ……………… C. dorademiri

5b - Pigmentation below Z4 usually present along complete flank. ……………… C. afifeae

6a - Blotches in Z2 and Z4 very small, indistinct or confluent; flank pigmented below zone Z4; body brownish. ……………… C. puncticulata

6b - Blotches in Z2 and Z4 well separated, fused into a bold stripe in some individuals; flank without pigmentation below zone Z4; body pale-yellowish or whitish. ………………7

7a - Focal zone of subdorsal scale large, about ⅓–½ of vertical scale diameter. ……………… C. satunini

7b - Focal zone of subdorsal scale small, about ⅒–⅓ of vertical scale diameter. ………………8

8a - 25–36, small, comma-shaped blotches in Z4 along anterior and middle part of flank blotches squarish or irregularly shaped on posterior part of flank, rarely fused into short stripes. ……………… C. troasensis

8b - 12–18 roundish, triangular, squarish, or horizontally elongate blotches in Z4, often densely set and fused into short stripes along anterior and middle part of flank, blotches vertically elongate on posterior part of flank. ………………9

9a - Black spot at upper caudal base roundish or ovoid, larger than eye diameter in male; Z3 fully covered by very small spots forming a sand-like pattern, especially in female. ……………… C. emrei

9b - Black spot at upper caudal base absent or comma-shaped, smaller than eye diameter in male and female; Z3 with a row or a narrow band of small spots not forming a sand-like pattern. ……………… C. fahireae

Mediterranean basin east of Eşen and endorheic basins in Central Anatolia (excluding basins of Lakes Akşehir, Eber, and Ilgın)

1a - Male with 1 lamina circularis. ……………… C. bilseli

1b - Male with 2 laminae circularis. ………………2

2a - No black spot at upper caudal base. ………………3

2b - Black spot present at upper caudal base, often very small and best seen in live individuals. ………………4

3a - A bold-brown stripe in Z4 between head and vertical of anal origin; flank below Z4 unpigmented; external part of suborbital spine bifurcate. ……………… C. evreni

3b - A series of midlateral blotches in Z4 or Gambetta zones dissociated into a pattern of many irregularly shaped small or medium-sized spots and blotches; flank below Z4 usually pigmented; external part of suborbital spine simple. ……………… C. phrygica

4a - Back plain cream-brown, few individuals with 1–3 narrow, squarish, brown bars. ……………… C. sipahilerae

4b - Back with 3–8 large, roundish, dark-brown blotches or blotches fused into a dark-brown stripe on back or blotches dissociated into a marbled pattern. ………………5

5a - Flank pattern not organised in Gambetta zones, completely disorganised into a pattern of many small spots and blotches. ………………6

5b - Flank pattern well organised in four Gambetta zones, blotches in Z4 organised in a wide band or two rows of spots, and blotches in some individuals or populations. ………………7

6a - Mental lobe long, reaching to or beyond lower lip; caudal truncate; prepelvic length 53–56 % SL; preanal distance

75–78 % SL in female. ……………… C. turcica

6b - Mental lobe short, not reaching beyond lower lip; caudal slightly rounded; prepelvic length 58–59 % SL; preanal distance 81–82 % SL in female. ……………… C. joergbohleni

7a - External part of suborbital spine simple; two distinct rows of small blotches in Z4, one along lateral midline and one distinctly below. ……………… C. pirii

7b - External part of suborbital spine bifurcate, simple in some individuals of C. battalgilae , one row of large blotches in Z4 or blotches in Z4 dissociated into a band of spots and blotches or spots and blotches of Z4 completely dissociated, not forming two rows. ………………8

8a - A series of large, horizontally elongate blotches in Z4, adjacent blotches often fused to each other; blotches in Z4 not vertically or horizontally dissociated. ……………… C. erkakanae

8b - A series of roundish, squarish, comma-shaped, or vertically elongated blotches in Z4, rarely blotches horizontally elongate or fused into short stripes in some individuals (in C. levantina ); blotches in Z4 often vertically and horizontally dissociated into several rows or a wide band of small blotches and spots. ………………9

9a - Blotches in Z4 usually vertically elongate or squarish, often dissociated into a band of small irregularly shaped blotches and spots; interorbital distance 14–16 % HL in male. ……………… C. battalgilae

9b - Blotches in Z 4 in a single row, roundish, irregularly shaped, horizontally elongate or squarish anterior to dorsal origin, often fused into a stripe, not dissociated into a band of small spots or small blotches; interorbital distance 7–11 % HL in male. ………………10

10a - Blotches in Z2 irregularly shaped, often ½ of size or as large as in Z3, often blotches in Z2 and Z3 about size of eye or pupil diameter, Z2, and Z3 usually forming one marbled pattern; many small, dark-brown spots or blotches on lower part of caudal–peduncle, reaching forward to pectoral base in some individuals. ……………… C. levantina

10b - Z2 with small brown spots, always much smaller than blotches in Z3, much smaller than eye or pupil diameter, Z2 and Z3 well separated; no pigmentation or very few isolated brown spots below Z4 and on lower caudal–peduncle. ………………11

11a - Anterior to dorsal origin, blotches in Z2 and Z4 almost always well separated from each other; Z1 and Z2 always well distinguished; prepelvic length 56–60 % SL in female; caudal–peduncle length 11–14 % SL in female. ……………… C. aliyeae

11b - Anterior to dorsal origin, blotches in Z2 usually fused into short, irregularly shaped stripes or forming a mottled band of irregularly shaped, small blotches and spots, Z4 fused into a stripe in few individuals; Z1 and Z2 usually fused into a mottled band; prepelvic length 53–55 % SL in female; caudal–peduncle length 15–19 % SL in female. ……………… C. anabelae