Garra

Garra View in CoL

The genus Garra comprises small fishes widely distributed in West South and Southeast Asia, and tropical Africa. The genus is highly diverse, with approximately 190 species currently recognised, while many others await formal description. It is the most speciose genus of Cyprinids in West Asia, with 42 species. The diversity of Garra in West Asia has long been significantly underestimated, as several species exhibit highly similar meristic character states and even the complex gular discs behind the mouth exhibit minimal consistent interspecific variation. Recent molecular studies have greatly contributed to the understanding of the diversity of this genus.

Most Garra species can be readily distinguished from other cyprinids by a prominent, uniquely shaped gular disc on the skin behind the lower jaw. This gular disc is structured into an anteromedian fold and a central callus. Garra species are often adapted to swift-flowing mountain streams, where they are aided in maintaining their position in the current by the gular disc and the lateral position of their large, paired fins. Furthermore, the air bladder is often reduced to reduce buoyancy. Rheophilic, current-loving species usually have a very large gular disc, but the gular disc can be reduced or even absent in some species that do not reside in fast currents.

The presence of a gular disc has long been regarded as the most important diagnostic character for Garra . Recent phylogenetic studies suggested that its presence is a plesiomorphic condition (an ancestral character state) in a range of labeonine cyprinids. This is evidenced by the fact that several labeonine lineages that lack the gular disc are nested within lineages that have a gular disc. Historically, species without a gular disc have been excluded from Garra . In West Asia, such species were previously placed in Hemigrammocapoeta and Iranocypris , but looking more closely, all of these still have remnants of some elements of the gular disc. It has long been suggested that they are closely related to Garra , and the “absence” of the gular disc is a secondary, adaptive character state in these fishes. This was recently supported by molecular data, which indicated that Hemigrammocapoeta species do not form a monophyletic lineage, but the species are related to three different groups of Garra species. All former Hemigrammocapoeta , Iranocypris , Tylognathus , and Typhlogarra from West Asia are included here within the genus Garra .

All Garra species feed on periphyton, plants, and detritus but are opportunistic feeders when other food sources are readily available. In streams where Garra are common, they have a substantial effect on the stream ecosystem by permanently grazing almost all surfaces. In West Asia, most species of Garra are ubiquitous inhabitants of streams and rivers. Still, they also occur in springs, lakes with stony shores, and even in marshes with dense vegetation. In southern Iran and the Arabian Peninsula, Garra are typically found in isolated pools in wadis that are otherwise dry, except when rain floods the river courses. They also occur in subterranean habitats.

Many species of Garra display prominent tubercles on the snout. The function of these tubercles has been discussed extensively, and it is generally believed that they function in territoriality and social interaction. In several species of Garra , the outer tubercles on the snout are enlarged and serve a social function. In most species, only some individuals develop prominent tubercles, and this character state is not associated with the sex of individuals. It has been proposed that individuals holding a territory develop tubercles, and those without territory do not. It has also been suggested that the snout tubercles may reduce the impact of rushing waters. However, these hypotheses remain untested.

Further reading. Menon 1964 (diversity and biogeography); Krupp 1985d (phylogenetic position of Hemigrammocapoeta ); Stiassny & Getahun 2007 (diversity in Africa); Yang et al. 2012 (phylogeny of Labeonines); Hamidan et al. 2014 ( Iranocypris ); Behrens-Chapuis et al. 2015 (molecular phylogeny); Esmaeili et al. 2016c; Zamani-Faradonbe et al. 2021b ( Iran); Hashemzadeh Segherloo et al. 2016a (convergent reduction of gular disc; phylogeny).

Keys to species Garra in West Asia

Please note that the gular disc is present in all species; it is only incompletely developed in some.

Central Anatolia, Mediterranean, and Dead Sea basins

1a - Gular disc incompletely developed. ………………2

1b - Gular disc fully developed. ………………7

2a - No barbels; a papillate and elevated mental pad behind lower jaw. ………………3

2b - One or two pairs of barbels; no mental pad behind lower jaw. ………………4

3a - 9–15 gill rakers; few papillae on mental pad. ……………… G. kemali

3b - 15–17 gill rakers; many papillae on mental pad. ……………… G. klatti

4a - 8½ branched dorsal rays; two pairs of barbels; lateral line complete. ……………… G. nanus 4b - 7½ branched dorsal rays; one pair of barbels; lateral line incomplete. ………………5

5a - Skin behind lower jaw continuous, with a shallow depression in middle; chin behind lateral lobes rounded anteriorly, not reaching between lateral lobes. ……………… G. festai

5b - Skin behind lower jaw with a wide lateral lobe, very narrow, almost split in middle; chin between lateral lobes strongly pointed anteriorly, reaching deeply between lateral lobes. ………………6

6a - Skin behind lower jaw with lateral lobe strongly papillate on entire surface; scale in rows 2–3 above and below lateral line densely pigmented in middle, forming indistinct stripes; wide orange or reddish lateral stripe from eye to caudal base in live nuptial male. ……………… G. culiciphaga

6b - Skin behind lower jaw with lateral lobe smooth or with indistinct furrows, papillate in middle in some indi- viduals; scale in rows 2–3 above and below lateral line not more densely pigmented in middle, without stripes; live nuptial male with plain golden flank. ……………… G. caudomaculata

7a - One pair of barbels. ……………… G. variabilis

7b - Two pairs of barbels. ………………8

8a - 7½ branched dorsal rays; a small field of tubercles behind upper, posterior eye margin; 31−32+1−2 later- al-line scales; no black blotch on flank at middle of pos- terior caudal peduncle. ……………… G. ghorensis

8b - 8½ branched dorsal rays; no tubercles behind upper, posterior eye margin; 33−36+1−2 lateral-line scales; a black blotch on flank at middle of posterior caudal peduncle at least visible in juveniles. ………………9

Persian Gulf basin and endorheic basins in Iran, including Hari drainage

1a - Subterranean, body whitish, orange or pink; eye reduced and invisible externally. ………………2

1b - Epigean, body brown or grey, usually mottled; eye fully developed. ………………5

2a - Gular disc incompletely developed. ……………… G. typhlops

2b - Gular disc completely developed. ………………3

3a - Lateral line complete or almost complete, with

28−35 scales. ……………… G. widdowsoni

3b - Body completely naked or few scales present at pelvic base and on flank. ………………4

4a - Scales present at pelvic base, often isolated scales on flank; lateral line reduced, no visible pores. ……………… G. tashanensis

4b - Body completely naked; lateral line on body well developed with 28−35 pores. ……………… G. lorestanensis

5a - Lateral and distal margin of labrum of gular disc fused with skin of chin. ……………… G. elegans

9a - Snout blunt; body depth at dorsal origin 18–21 % SL. ……………… G. turcica

9b - Snout slightly pointed; body depth at dorsal origin

21–26 % SL. ………………10

10a - 12–17 gill rakers on lower limb of first gill arch; 5–6, rarely 4 scales between tip of pectoral and pelvic origin; maximum head width 64–72 % HL. ……………… G. jordanica View Figure

10b - 17–21 gill rakers on lower limb of first gill arch; 2–3, rarely 4 scales between tip of pectoral and pelvic origin; maximum head width 73–82 % HL. ……………… G. orontesi

5b - Lateral and distal margin of labrum of gular disc free from skin of chin. ………………6

6a - Barbels absent. ……………… G. roseae

6b - One or two pairs of barbels present. ………………7

7a - One pair of barbels; if two pairs, rostral barbel very small, sometimes just a tubercle. ………………8

7b - Two pairs of normally developed barbels. ………………10

8a - 20−26 gill rakers. ……………… G. variabilis

8b - 10−16 gill rakers. ………………9

9a - Predorsal midline, chest, and belly almost without scales. ……………… G. nudiventris

9b - Predorsal midline, chest, and belly fully covered by scales. ……………… G. rossica

10a - 8+8 branched caudal rays. ……………… G. persica

10b - 9+8 branched caudal rays. ………………11 11a - Usually 8½ branched dorsal rays. ………………12

11b - Usually 7½ branched dorsal rays. ………………13

12a - 32–38 total lateral-line scales. ……………… G. gymnothorax / G. rufa

12b - 30–33 total lateral-line scales. ……………… G. tiam

13a - 11–16 total gill rakers. ……………… G. rezai

13b - 16–24 total gill rakers. ………………14

Hajar Mountains of United Arab Emirates and northern Oman

1a - Subterranean, whitish or pink, eye reduced and invisible externally. ……………… G. cavernicola

1b - Epigean, brown or grey eye fully developed. ………………2

2a - Tip of dorsal white. ………………3

2b - Tip of dorsal similar to middle and proximal part of fin. ………………4

3a - A pale- or deeply orange spot at upper opercle; middle caudal rays bold black, membranes white; 15–18 gill rakers on lower limb of first gill arch. ……………… G. barreimiae

Saudi Arabia, Yemen and Dhofar (Oman)

1a - Subterranean, whitish or pink; eye small. ……………… G. dunsirei

1b - Epigean, brown, grey, often mottled; eye fully developed. ………………2

2a - A deep groove between tip of snout and nostrils;

12 circumpeduncular scales. ……………… G. mamshuqa

2b - A shallow groove between tip of snout and nostrils or groove absent; 12−20 circumpeduncular scales. ………………3

14a - Usually two scales between anus and anal origin. ……………… G. amirhosseini

14b - Usually three scales between anus and anal origin. ………………15

15a - Posterior margin of scales on chest not embedded in skin. ……………… G. hormuzensis

15b - Posterior margin of scales on chest embedded in skin. ……………… G. meymehensis

3b - No orange spot at upper opercle; middle caudal rays and membranes same colour as other caudal rays and membranes or slightly darker; 10–14 gill rakers on lower limb of first gill arch. ……………… G. shamal

4a - Flank strongly mottled, with individual or series of orange scales. ……………… G. sharq

4b - Flank usually plain greenish, brown, black, rarely with a midlateral stripe or faint mottling, never with orange midlateral scales. ………………5

5a - Flank scales with bold, dark-brown or grey margins. ……………… G. longipinnis

5b - Flank scales same colour as centers of scales or with very indistinct dark-brown or grey margins. ……………… G. gallagheri

3a - 36−39 total lateral-line scales; 20, very rarely 18, circumpeduncular scales. ……………… G. buettikeri

3b - 30−36 total lateral-line scales; 12−18 circumpeduncular scales. ………………4

4a - Dorsal dark-grey or black; 8½ branched dorsal rays. ……………… G. sahilia

4b - Dorsal hyaline or pale-brown with black spots at bases of branched rays; 7½ branched dorsal rays. ………………5 5a - Chest and belly naked. ……………… G. lautior

5b - Chest and belly covered by scales at least to level of pectoral base. ………………6

6a - Usually 16−18 circumpeduncular scales; tubercles on snout usually present. ……………… G. tibanica

6b - Usually 14−16 circumpeduncular scales; tubercles on snout absent. ………………7

7a - 8−13 gill rakers on lower limb of first gill arch; gular disc wider than long; prominent hump on back in some individuals. ……………… G. sindhae

7b - 12−15 gill rakers on lower limb of first gill arch (10−13 in Laggashaylon); gular disc longer than wide; without hump on back. ……………… G. smartae