Gobiosoma seminudum ( Günther 1861 )

Tornabene, Luke & Van Tassell, James L., 2014, Redescription of the goby genus Gobiosoma (Teleostei: Gobiidae: Gobiosomatini), with the synonymy of the genus Enypnias, Journal of Natural History 48 (23 - 24), pp. 1413-1437 : 1425-1429

Gobiosoma seminudum ( Günther 1861)

Silt goby

( Figures 3B– 5 )

Gobius seminudus Günther, 1861: 554 , also appearing as new in Günther 1862: 372

Enypnias seminudus Jordan and Evermann, 1898: 2231, 2233–2234 (proposed Gobius seiminudus as type species for Enypnias , a subgenus of Garmannia ).

Type locality

Pacific coast of Central America .

Material examined

USNM 407407 , 1 of 2, 29.99 mm SL, El Salvador, Jiquilisco Bay, Bahia De Jiquilisco , C. Baldwin et al., 31 March 2001 ; USNM 407106 , 1 , 29.03 mm SL, El Salvador, Isla Meanguera, Golfo de Fonseca , C. Baldwin et al., 9 March 2001 ; AMNH 254722 , 1 , 20.1 mm SL, El Salvador, Isla Meanguera, Golfo de Fonseca , J. Van Tassell et al., 8 March 2001 ; AMNH 256784 , 1 , 29.0 mm SL, Panama, Bahia Piña , J. Van Tassell et al., 21 December 2002 ; AMNH 256871 , 4 of 8, 19.6–24.2 mm SL, Panama, Rio Mosquitos , Isla del Rey, J. Van Tassell et al., 22 December 2002 ; AMNH 258315 , 1 , 28.6 mm SL, El Salvador, Gulf of Fonseca, Isla Martin Perez , J. Van Tassell et al., 9 March 2001 ; AMNH 258316 , 1 , 34.5 mm SL, Panama, La Palma, San Miguel Estuary , J. Van Tassell et al., 19 December 2002 ; AMNH 258317 , 1 , 22.5 mm SL, Panama, Rio Mosquitos , Isla del Rey, J. Van Tassell et al., 22 December 2002 ; AMNH 258318 , 1 , 25.5 mm SL, Panama, Rio Mosquitos , Isla del Rey, J. Van Tassell et al., 22 December 2002 ; AMNH 258319 , 3 + 1 C&S, 21.3– 35.56 mm SL, Panama, Rio Mosquitos , Isla del Rey, J. Van Tassell et al., 22 December 2002 ; AMNH 258320 , 3 of 5, 20.5–33.0 mm SL, El Salvador, Estero north of Isla Perico, Bahia de La Union, Golfo de Fonseca , J. Van Tassell et al., 12 March 2001 ; AMNH 258423 , 2 , 24.13–25.78 mm SL, El Salvador, Estero El Tamarindo, north entrance to Golfo de Fonseca , J. Van Tassell et al., 10 March 2001 ; AMNH 258321 , 1 of 5, 26.1 mm SL, El Salvador, Isla Meanguera, Golfo de Fonseca , J. Van Tassell et al., 8 March 2001 ; AMNH 258322 , 1 of 5, 25.1 mm SL, El Salvador, Isla Meanguera, Golfo de Fonseca , J. Van Tassell et al., 8 March 2001 ; BMNH 1861.8 .13.22, syntypes, 8, west coast of Central American , Capt. Dow .

Diagnosis

A species of Gobiosoma distinguished by the following characters: prominent barbel adjacent to anterior nare; a pair of barbels on the tip of snout; mental frenum produced into two prominent barbels; first dorsal fin without greatly elongate or filamentous spines; second dorsal fin I,13–14; side of body heavily scaled from caudal peduncle extending to or just falling short of axil of pectoral fin; scales on body cycloid; sensory head pores B', C(s), D(s), E, F, H', K', L' usually present (pore C sometimes absent); three preopercular pores present.

Description

Body and head slightly dorsoventrally depressed; body depth at origin of first dorsal fin 16.8–25.0; least depth of caudal peduncle 11.3–14.8; caudal peduncle length 17.97–22.8.

Fins. Counts for first and second dorsal, anal, and pectoral fins include counts from Böhlke and Robins (1968): first dorsal fin VII* (32); second dorsal fin I,12 (1), I,13* (12), I, 14* (26); anal fin I,9 (2), I,10* (34), I,11 (1); pectoral fin rays 19 (4), 20 (23), 21 (20); pectoral fin length 19.9–26.0; pelvic fin I,5* (20); pelvic fins completely united by a membrane along their entire length, forming cup-like disc with well-developed, smooth anterior frenum; caudal fin rounded to truncate; segmented caudal fin rays 17 (17); branched caudal fin rays 14 (2), 15 (10), 16 (5); caudal fin length 21.2–26.8.

Scales. Head, nape, abdomen, pre-pelvic area and pectoral fin base without scales; side of body with scales extending from base of caudal fin anteriorly to, or just short of, axis of pectoral fin; scales on side of the body cycloid; lateral scale rows 33–59; transverse scale rows 11–17; base of caudal fin typically with four to six scales; two scales dorsal and ventral edge of base of caudal fin slightly larger than other basicaudal scales, sometimes with very reduced cteni.

Head. Head length 28.4–32.4; post orbital length 06.7–19.2; eye diameter 6.7–8.8; upper-jaw length 8.2–14.1; snout length 5.1–8.1; interorbital width 2.2–4.7; tongue broadly truncate; teeth in upper jaw typically in three rows anteriorly, becoming two rows posteriorly, with inner and outermost rows enlarged and regularly spaced, middle row irregularly spaced and much smaller; outermost row of teeth in upper jaw extending to end of premaxilla or nearly so; teeth in lower jaw arranged in three rows anteriorly, becoming two rows posteriorly; teeth at anterior end of lower jaw with enlarged and regularly spaced inner and outermost rows, middle row irregularly spaced and much smaller; gill opening extends ventrally to just anterior of the pectoral fin base; anterior nare on short stout tube; anterior nare with flap on rim of tube in one specimen; posterior nare on a tube shorter than anterior nare, often nearly flush with snout; tip of snout with pair of barbels, length approximately equal to onethird to two-thirds diameter of pupil; barbel present adjacent to anterior nare, length approximately equal to one-third to one-half diameter of pupil; lateral edges of mental frenum produced into two prominent barbels, length approximately equal to half to entire diameter of pupil.

Sensory pores and papillae ( Figure 3B ). Head pores B', C(s), D(s), E, F, H', K', L' present in most individuals; interorbital pore C absent in several individuals from El Salvador; preopercular pores M', N, O' present; six transverse rows of papillae beneath eye; first transverse row beginning beneath anterior margin of eye; last two transverse rows short, beginning at posteroventral corner of eye just anterior to pore F; longitudinal papillae row b beginning at vertical through posterior margin of eye; longitudinal row papillae row d terminating at transverse row that bisects papillae row b; papillae row n not continuous across nape, but in two separate segments.

Select osteological characters. Vertebrae 27 (11 precaudal + 16 caudal); pterygiophore formula of first dorsal fin 3–221110; first two anal pterygiophores inserted anterior to haemal arch; hypurals 1–2 fused with hypurals 3–4 and terminal vertebral element; one epural; ventral post-cleithra absent; braincase circular in shape; supraoccipital with prominent lateral wings that articulate with sphenotic.

Colour in females ( Figure 4 ). Background of body grey; body with a series of dark dots down lateral midline, several dots often connected appearing as dashes; side of body with pale areas that vary in intensity and shape, sometimes appearing as distinct pale diagonal bars on dark background ( Figure 4A, B ), other times appearing as haphazardly spaced pale blotches on dark background ( Figure 4D ), or as a mottling of indistinct light and dark grey patches ( Figure 4C,E ); first dorsal fin uniformly dusky with very narrow pale stripe near distal margin, and two small pale patches near base; second dorsal fin highly variable, ranging from mottled to possessing completely or broken pale horizontal stripes on a dark background; caudal fin variously pigmented with broken dark vertical bars or densely mottled; side of face, operculum, and nape mottled with areas of dark pigment on pale background; pectoral fin base uniformly pale or lightly mottled with prominent dark spot on upper portion on base; pectoral rays dusky, with pigment slightly darker near base of rays than on remainder of fin; anal fin lightly pigmented to uniformly pale.

Colour in males ( Figure 5 ). Head, body and pectoral fins uniformly drab brown or dark grey; body often with a series of dark dots down lateral midline, several dots often connected appearing as dashes; dorsal fin dark brown, often with narrow pale stripe near distal margin; second dorsal fin with heavy mottling to uniformly dark brown; caudal fin dusky to dark brown, with distal tips of rays lighter than remainder of fin; dark vertical bar over base of caudal rays and poster margin of caudal peduncle; anal fin typically uniformly dark brown.

Habitat

Gobiosoma seminudum is known to occur in rocky or mangrove tide pools, as well as other intertidal and shallow subtidal areas where rock, shell and mud are present.

Distribution

Gobiosoma seminudum is known only from the Pacific coast of Central America as far south as southern Panama. Two lots of specimens exist from the Gulf of California, Mexico: UAZ 69-42-8, Sinaloa; and UCLA W51-36 (currently at SIO), Mazatlan. These records represent the northernmost extent of the range.

Comparisons

Gobiosoma seminudum can be distinguished from its eastern Pacific congeners G. paradoxum , G.hildebrandi and G.chiquita by the presence of barbels near the anterior nare, on the tip of the snout, and on the mental frenum. Gobiosoma homochroma also lacks barbels on the mental frenum. Gobiosoma nudum possess barbels near the anterior nare and mental frenum, but differs from G.seminudum primarily in lacking scales on the side of the body (with the exception of a small patch under the pectoral fin base) versus being heavily scaled. The elevated number of second dorsal fin elements in G.seminudum (primarily I,13–14) further distinguish it from all other eastern Pacific Gobiosoma (I,12 or less) except G.aceras . This species is the only eastern Pacific species of Gobiosoma to possess sensory pores K' and L' and the associated canal segment over the operculum. This character coupled with the absence of distinct dark and light wide vertical bars on the body of both sexes, and the presence of cycloid versus ctenoid scales, easily distinguish G.seminudum from its closest relative G.aceras .

Figures

Figure 3. (A, B) Sensory papillae and head pore patterns in Gobiosoma aceras (A), and Gobiosoma seminudum (B). Drawings by J.L. Van Tassell, or modified from unpublished drawings by Isaac Ginsburg.

Figure 4. (A)–(E). Gobiosoma seminudum females. (A)–(D) G. seminudum females from El Salvador; (E) G. seminudum female from Panama. Photos by J.L. Van Tassell.

Figure 5. (A,B) Gobiosoma seminudum males. (A) G. seminudum male from El Salvador; (B) G. seminudum male from Panama. Photos by J. L. Van Tassell.