Parasaccogaster melanomycter ( Cohen, 1981 )

Nielsen, Jørgen G., Schwarzhans, Werner & Cohen, Daniel M., 2012, Revision of Hastatobythites and Saccogaster (Teleostei, Bythitidae) with three new species and a new genus, Zootaxa 3579, pp. 1-36 : 27-29

Parasaccogaster melanomycter ( Cohen, 1981)

Figs. 19 , 20 , 26 , Table 1 , 2, 7

Saccogaster melanomycter Cohen 1981: 374 , figs. 1–2 (type locality: Gairaca Bay, Caribbean Columbia). Saccogaster melanomycter: Cohen 1987: 2 ; Nielsen et al. 1999: 110.

Material examined (1 specimen, 66 mm SL). Holotype: MCZ 47362, 66 mm SL, female, Santa Maria, Gairaca Bay (Encenada de Gayraca), Caribbean Columbia, coral reef, 8 m, 1968.

Diagnosis. Parasaccogaster melanomycter differs from the other two Parasaccogaster species by the sooty black nasal chambers, few anal fin rays (37 vs. 49–54), few vertebrae (45 vs. 54–58) and a wider head (12.0 % SL vs. 7.7–9.8 % SL). Also the following combination of characters is diagnostic: A pair of sub-dermal spines fused to form a broad ridge on frontal just behind eyes, a small, median, sub-dermal, ethmoidal spine just in front of eyes and an antero-ventrally directed spine at lower angle of preopercle (all spines covered by skin); three developed rakers on anterior gill arch only slightly larger than the spiny knobs, gill filaments 7–8 times length of developed rakers; pectoral peduncle slightly prolonged; palatines with several tooth rows; precaudal vertebrae 16 and total vertebrae 45; fin rays in dorsal 74, anal 37, caudal 10 and pectoral 18.

Similarity. Parasaccogaster melanomycter differs from the two other species of the genus in the stouter body shape, fewer vertebrae (45 vs 54–58), fewer anal fin rays (37 vs 49–54) and wider head (12.0 % SL vs 7.7–9.8 % SL). Also the fusion of the paired frontal spines is not observed in any other species of the genera studied here.

Description. The principal meristic and morphometric characters are shown in Table 7 . Body rather compressed with pointed, slightly compressed head and tapering tail. Skin thick and opaque. Scales absent. Lateral line continuous, originating above and anterior to upper angle of gill opening and descending to midline beyond midpoint of body. Its course marked by narrow unpigmented line with widely spaced, small papillae; about 12 dark papillae to level of vent and further posteriorly pale papillae difficult to count. Dorsal fin origin above middle of pectoral fin and anal fin origin well behind midpoint of fish. Pectoral fin reaching 1/3 to anal fin; pectoral peduncle longer than broad and adnate to body. Anterior gill arch ( Fig. 20 D) with five low, spiny knobs on upper branch, one slightly developed raker in angle and lower branch with two slightly developed rakers with a low knob in between and followed by five partly united knobs, two shallow, likewise partly united knobs, and four well developed separate knobs after a small break. Longest gill filaments about 2–3 three times length of developed rakers. Two pseudobranchial filaments. Body cavity nearly filled with two distended ovaries packed with apparently unfertilized eggs of about 1 mm in diameter.

Axial skeleton (from radiograph): Number of precaudal vertebrae 16. Anterior neural spine very short and nos. 2–4 very long. Neural spines 2–8 much depressed and with blunt tips. Parapophyses developed on vertebrae 6–16. Pleural ribs on vertebrae 3–11.

Dentition: Palatines with rows of pointed teeth, inner row with larger teeth. Vomer with a boomerang-shaped band of sharp-pointed teeth, inner row with larger teeth. Premaxillaries with a narrow band of granular teeth and an inner row of enlarged, needle-like teeth. Dentaries with irregular row of small, slightly compressed teeth and an inner row of larger, pointed teeth.

Head morphology ( Fig. 20 A–C, E–F): A pair of fused, sub-dermal spines on frontal plate above and just behind eyes, a small, thin, compressed, sub-dermal, ethmoidal spine in midline of snout and broad, blunt, subdermal spine above eyes. Frontal plate with rough sub-dermal texture. Opercular spine pointed, covered by skin, not reaching hind margin of operculum. Antero-ventrally directed spine at lower angle of preopercle below skin. Anterior nostril placed close to upper lip, not tubular; posterior nostril twice as large as anterior nostril, positioned at some distance from eye. Head pores: 1 supraorbital pore at tip of snout, 1 small posterior supraorbital pore above base of opercular spine, 2 anterior infraorbital pores below and in front of eye, 2 anterior mandibular pores at tip of jaw. Head with pointed snout, sunk-in eye covered by window of translucent skin, and many small, dark papillae on occiput and cheeks. Upper jaw ends well behind eye with posterior part vertically expanded. Nasal chambers sooty black about equal in size to orbit.

Otolith: Dissolved.

Coloration: Color light brown, darker dorsally and on caudal section. Dorsal and anal fins with narrow, pale rim. Nasal chamber lined with sooty, black pigment, separated from eye by white area. Head papillae darker than skin color.

Biology and distribution ( Fig. 26 ). Parasaccogaster melanomycter is only known from the holotype caught at a depth of 8 m on a coral reef in Gairaca Bay, Caribbean Columbia. It is the only species of the three genera here reviewed living on a shallow reef.

Figures

FIGURE 19. Parasaccogaster melanomycter, holotype, MCZ 47362, SL 66 mm (photo A. Williston).

FIGURE 20. Parasaccogaster melanomycter, holotype: A—Lateral view of head. B—Lateral radiograph of head (photo A. Williston). C—Dorsal view of head. D—Anterior right gill arch. E—and F—Lateral and dorsal views of head (CT photographs A. Williston).

FIGURE 26. Geographic distribution of Parasaccogaster and Saccogaster in East Pacific and West Atlantic waters. Each marking may represent more than one locality.