Sicydium altum Meek 1907: 149

Angulo, Arturo, Naranjo-Elizondo, Beatriz, Rojas, Emmanuel & Ley-López, Juan Manuel, 2017, Fishes from the Tirimbina Biological Reserve, La Virgen de Sarapiquí, Heredia, Costa Rica, Check List 13 (5), pp. 683-702 : 696-700

(29) Sicydium altum Meek 1907: 149 ; River goby (En), Chupapiedras (Sp)

Figure 7E

Body elongate; 2 rows of teeth on both jaws, minute and compressed in the upper jaw, recurved and conical in lower jaw; gill rakers absent; fins without strong spines; pelvic fins united into an almost circular or oval (wider than long) adhesive disc; 2 dorsal fins; caudal fin round- ed; general coloration greenish gray, darker dorsally, usually with 5 black bars on the back and the flanks, and paler, usually yellowish white, ventrally; dorsal and anal fins dark or transparent with free edges of spines pink or reddish, anal and caudal fins usually transparent, with external borders pink or reddish; maximum body length ca 140 mm SL.

Identification key to the fishes from the Tirimbina

Biological Reserve, La Virgen de Sarapiquí, Heredia,

Costa Rica

1 Body eel-like; scales absent; pectoral, pelvic and caudal fins absent; dorsal and anal fins vestigial, reduced to a rayless ridge ( Synbranchidae ) ................... Synbranchus marmoratus ( Fig. 4E)

1′ Body not eel-like; scales present (absent in members of Heptapteridae ); all fins present and well developed ................................................ 2

2(1′) Pelvic fins united into an adhesive disc (Gobi- idae) ................................................................. 3

2′ Pelvic fins separated, not in form of an adhesive disc ................................................................. 4

3(2) 2 or 3 rows of teeth on both jaws, conical; gill rakers present; pelvic adhesive disc oval, longer than width; general coloration yellowish brown .................................. Awaous banana ( Fig. 7D)

3′ 2 rows of teeth on both jaws, minute and com- pressed in upper jaw, recurved and conical in lower jaw; gill rakers absent; pelvic adhesive disc almost circular, or if oval, wider than long; general coloration greenish gray ................................... Sicydium altum ( Fig. 7E)

4(2′) 3 pairs of barbels; scales absent; adipose fin present, its base larger than base of dorsal fin ( Heptapteridae ) ............................................... 5

4′ Barbels absent; scales present; adipose fin ab- sent, if present (in members of Characidae and Bryconidae ), its base shorter than base of dorsal fin .................................................................... 7

5(4) Maxillary barbels relatively long (usually extending beyond pectoral fin origin, sometimes passing caudal fin origin); serrations present on both margins of pectoral fin spine ..................... Rhamdia guatemalensis ( Fig. 3A)

5′ Maxillary barbels relatively short (usually not extending beyond pectoral fin origin, or if pass- ing, not passing pelvic fin insertion; serrations present only on inner (posterior) margin of pectoral fin spine, or absent ................................. 6

6(5′) Maxillary barbels usually extending beyond dor- sal fin origin up to pelvic fin insertion; adipose fin base relatively long, occupying ca ≥75% of distance between dorsal fin insertion and origin of caudal fin. Rhamdia nicaraguensis ( Fig. 3C)

6 Maxillary barbels not extending beyond pectoral fin origin; adipose fin base relatively short, oc- cupying ca 50% of distance between dorsal fin insertion and origin of caudal fin ............................. Rhamdia laticauda ( Fig. 3B)

7(4′) Adipose fin present; general coloration silvery ( Characiformes ) .............................................. 8

7′ Adipose fin absent; general coloration variable, usually not silvery (except in Atherinopsidae ) ....................................................................... 12

8(7) Body strongly compressed; 2 pairs of external teeth on premaxillary; nape concave; anal fin very long with 42–50 rays ......................... Roeboides bouchellei ( Fig. 2D)

8′ Body robust, not strongly compressed; no ex- ternal teeth on premaxillary; nape convex or straight; anal fin relatively short, usually with <42 rays .......................................................... 9

9(8′) Body usually very elongate; upper jaw in ad- vance of lower jaw; upper jaw with 3 or 4 rows of teeth; maximum body length ca 500 mm SL ( Bryconidae ) .... Brycon costaricensis ( Fig. 2E)

9′ Body usually not very elongate; both jaws of equal length; upper jaw with 1 or 2 rows of teeth; maximum body length ca 150 mm SL ......... 10

10(9′) Snout length about ≥ eye diameter; jaws usually elongate, teeth unicuspid, and enlarged ...................... Astyanax bransfordii ( Figure 2A)

10′ Snout length usually <eye diameter; jaws not elongate; teeth multicuspid, usually not enlarged ....................................................................... 11

11(10′) Body usually less robust and elongated; third in- fraorbital less deep and not in contact with lower limb of preopercle, yields on pressure by dissecting needle; no spots on opercle; caudal peduncle usually thin … Astyanax nicaraguensis ( Fig. 2B)

11′ Body usually more robust and elongated; third infra- orbital deep and in contact with lower limb of the preopercle, does not yield when depressed; a diffuse violet spot present on opercle in live specimens; caudal peduncle usually thick ................ Eretmobrycon scleroparius ( Fig. 2C)

12(7′) 2 dorsal fins (first dorsal fin small and usu- ally inconspicuous in Atherinopsidae ); caudal fin forked or lunate ....................................... 13

12′ A single dorsal fin; caudal fin truncate or rounded ....................................................................... 15

13 Body very elongate and compressed; eye size ca 40% of head length; anal fin spine weak and flexible; a silver stripe present along mid-side of body in both live and preserved specimens; maximum body length ca 70 mm SL ( Atherinopsidae ) ..................... Atherinella hubbsi ( Fig. 3D)

13′ Body not very elongate and compressed, robust; eye size ca 25% of head length; anal fin spines (2) strong; no silver stripe along mid-side of body; maximum body length ca 700 mm SL ( Mugilidae ) ................................................... 14

14(13′) Mouth about terminal; second dorsal fin rays 9; anal fin rays 10; general coloration gray olive, darker dorsally, and paler, usually yellowish white ventrally; dark scale edges form crisscross lines on upper body; fins usually yellowish ..................... Agonostomus monticola ( Fig. 5A)

14′ Mouth ventral; second dorsal fin rays 10 or rare- ly 11; anal fin rays 11; general coloration silvery to grey green in adults, silvery white, with dark stripes on dorsal, anal and caudal fins in juve- niles; fins usually transparent, pinkish in some adult specimens ...... Joturus pichardi ( Fig. 5B)

15(12′) Body elongate and moderately deep; lateral line reduced to a series of individual pits along side of body; fins without spines; males with anal fin modified into a gonopodium; caudal fin usu- ally rounded; maximum body length ca 105 mm SL, usually less than 60 mm SL ( Poeciliidae ) ....................................................................... 16

15′ Body moderately elongate and deep; lateral line conspicuous, divided into 2 straight overlapping sections; fins with strong spines; males without gonopodium; caudal fin usually trun- cate; maximum body length ca 700 mm SL, usually> 60 mm SL ( Cichlidae ) ......................... 21

16(15) Body deeply compressed; ventral margin of the caudal peduncle sharp and compressed, scales forming a sheathed keel ................................... Alfaro cultratus ( Fig. 3E)

16′ Body not deeply compressed; ventral margin of caudal peduncle rounded with a series of scales along mid-line ............................................... 17

17(16′) Anal fin with a black blotch mainly covering it antero-basal portion; males with an moderately long gonopodium, usually 27–29% of SL ................... Brachyrhaphis parismina ( Fig. 3F)

17′ Anal fin clear or dusky, without a black blotch covering antero-basal portion; males with relatively long gonopodium, usually>29% of SL, or a relatively short gonopodium, usually <27% of SL ................................................................. 18

18 Males with asymmetric gonopodium, either dextral or sinistral; dorsal fin with first ray black and with wedge-shaped black base, usually with dusky posterior margin, in males the remaining fin is brilliant yellow; juveniles and adult males with 5–10 black bars on flanks ...................... Xenophallus umbratilis ( Fig. 4D)

18′ Males with symmetric gonopodium; dorsal fin not as described above; no black bars on sides ....................................................................... 19

19(18′) Teeth conical and well fixed in jaws; jaw bones firmly united; scales conspicuously bordered in black, giving a cross-hatch pattern to body (this pattern more intensive along mid-line of flanks and sometimes resembles a series of X’s along body); membranes of dorsal fin base with elon- gate black blotches; distal portion of dorsal fin usually orange ...................... Priapichthys annectens ( Fig. 4C)

19′ Teeth compressed and not firmly fixed in jaws; jaw bones weakly united; scales usually not as described above (cross-hatching pattern present in some specimens of Phallichthys amates ); dorsal fin without marks, or if present, not as described above ............................................ 20

20(19′) Body moderately elongate, deep, almost rhom- boid, moderately compressed; males with a long gonopodium, usually extending to caudal fin origin; sides usually uniformly colored, without rows of yellow dots; dorsal fin usually without spotting; females usually with a prominent black or purple blotch covering base of pelvic and/or anal fins; caudal fin usually not profusely spot- ted, even on its base ........................... Phallichthys amates ( Fig. 4A)

20′ Body elongate and moderately deep, robust; males with a short gonopodium, rarely extending beyond dorsal fin insertion; sides with 6–8, usu- ally 7, rows of yellow dots (1 per scale); dorsal fin usually with black spots and/or a black blotch on its base; females usually without a dark blotch covering base of pelvic and/or anal fins; caudal fin profusely spotted on base, often on entire fin ...................................... Poecilia gillii ( Fig. 4B)

21(15′) Predorsal profile of head usually curved, snout convex, rarely pointed; mouth inferior, usually ventral; teeth of outer rows compressed anteroposteriorly (incisors), at least at the tip ........ 22

21′ Predorsal profile of head usually straight or slightly curved, snout usually pointed or convex; mouth terminal, rarely inferior or ventral; teeth of outer rows sharp, conical and cylindrical ... 24

22(21) Teeth with flattened or truncate tips; iris usually bluish, silvery in a few specimens; mid-body with a broad dark bar, on a grayish brown back- ground (during breading season pattern reversed, that is, a white bar appears on a dark gray back- ground ............ Neetroplus nematopus ( Fig. 6C)

22′ Teeth spatulate with rounded tips; iris usually yellowish or reddish; mid-body dark bar absent ....................................................................... 23

23(22′) Anal fin spines 6–9; upper portion of the snout usually yellowish or in some adult specimens grayish blue-green, without black stripes join- ing the eyes; iris usually yellowish; mid-body usually with a large black blotch on mid-side crossed or not by a dark lateral stripe ................. Hypsophrys nicaraguensis ( Fig. 6B)

23′ Anal fin spines 4 or 5; upper portion of the snout usually gray olive and with 2 black stripes join- ing the eyes; iris usually reddish; mid-body black blotch absent, in turn, some specimens present 7–10 incomplete dark bars on flanks ................................. Tomocichla tuba ( Fig. 7C)

24(21′) Mouth relatively large, usually ca 30–40% of head length; maxillary extending to below the eye; lower jaw usually in advance of upper jaw; teeth enlarged, caniniform; maximum body length about 700 mm SL .............................. 25

24′ Mouth relatively short, usually <30% of head length; maxillary not extending to below eye; jaws of equal length, rarely upper jaw in advance of lower jaw; teeth somewhat enlarged, but no large canines; maximum body length ca 150 mm SL ................................................................. 27

25(24) Posterior edge of opercle usually with a conspicuous lobe at its lower angle; total gill rakers 14 or 15 ... Parachromis managuensis ( Fig. 7B)

25′ Posterior edge of opercle almost straight; total gill rakers 9–13 ............................................. 26

26(25′) Greatest body depth <head length; longitudinal scales 31–34; maximum body length ca 700 mm SL ......................... Parachromis dovii ( Fig. 6D)

26′ Greatest body depth ≥ head length; longitudinal scales 27–31; maximum body length ca 185 mm SL ................... Parachromis loisellei ( Fig. 7A)

27(24′) Snout relatively long, pointed, straight and pro- duced, usually ca 43–53% of head length; head and body with irregular iridescent blue spots or vermiculations; posterior portion of the flanks usually with 3–5 brown vertical bars separated by paler spaces; maximum body length ca 150 mm SL ............. Cribroheros alfari ( Figure 6A)

27′ Snout relatively short and convex, usually ca 33–43% of head length; no iridescent blue spots or vermiculations on head or body; flanks usu- ally with 6–8 diffuse or well defined black verti- cal bars; maximum body length ca 100 mm SL ....................................................................... 28

28 (27′) Iris bluish; opercular blotch absent; first vertical bar not Y-shaped; caudal blotch mainly on caudal peduncle ................ Amatitlania septemfasciata ( Fig. 5C)

28′ Iris usually golden or yellowish; opercular blotch present; first vertical bar Y-shaped; caudal blotch mainly on caudal fin base .............................. Amatitlania siquia ( Fig. 5D)