Schindleria brevipinguis, Watson & Walker, 2004

Watson, William & Walker, H. J., 2004, The World’s Smallest Vertebrate, Schindleria brevipinguis, A New Paedomorphic Species in the Family Schindleriidae (Perciformes: Gobioidei), Records of the Australian Museum 56 (2), pp. 139-142 : 140-141

Schindleria brevipinguis n.sp.

Fig. 1

Diagnosis. A small, stout, unpigmented Schindleria species, largest specimen 8.4 mm; body depth at pectoral-fin origin 9–12% of standard length and at anal-fin origin 9–14% SL.

Dorsal-fin rays 13, anal-fin rays 10–11; first dorsal-fin ray at myomere 18–20 and first anal-fin ray below dorsal-fin ray 4. Vertebrae 20 + 15–16 = 35–36, myomeres 19–20 + 14–16 = 34–36. Premaxillae and dentaries lack teeth. Males have a rod-like, flexible urogenital papilla lacking lobes, projections, or accessory papillae, with distal half tapering to a blunt point and usually anteriorly directed.

Description. Dorsal-fin rays 13 ( Table 1), anal-fin rays 10– 11, dorsal- and anal-fin rays spaced at intervals of approximately one ray per myomere; first dorsal-fin ray at myomere 18–20 (mode = 19), last ray at myomere 28–33 (31); first anal-fin ray at myomere 22, just before to just behind dorsal-fin ray 4 (usually below D 4), last ray below last dorsal-fin ray; pectoral-fin rays 14–16 (14); pelvic fins absent; principal caudal-fin rays 7 + 6, procurrent rays 5–6 + 5–6; all fin-rays unbranched; vertebrae 20 + 15–16 (20 + 16); myomeres 19–20 + 14–16 (20 + 16); branchiostegal rays 5; gill-rakers and teeth absent; gas bladder at myomeres 9–13 (10–12).

Head small, length averages 18% SL ( Table 2); snout short, length averages 23% of head length (HL); eye moderately large, slightly oval to round, length averages 30% HL and height averages 32% HL; gut moderately long and straight, preanal length averages 64% SL; dorsal-fin origin slightly anterior to level of anus, predorsal fin length averages 61% SL; caudal peduncle length averages 11% SL; elongate, but moderately deep-bodied compared with S. pietschmanni and S. praematura , body depth at pectoralfin origin averages 10% SL and at anal-fin origin 12% SL; unornamented, rod-like urogenital papilla of male tapers to a blunt point, usually with distal half anteriorly directed, resulting in a somewhat scythe-shaped appearance in lateral view, length in mature specimens averages 6% SL.

All specimens unpigmented apart from the eyes. A small species: the largest specimen, a mature female bearing approximately 12 large, somewhat irregularly shaped ova (mean diameter 0.4 mm, range about 0.3–0.5 mm), is 8.4 mm.

Etymology. From the Latin brevis, short, referring to the small size of this species, and pinguis, stout, referring to the deeper, broader body compared with the other Schindleria species. A common name suggested for the family is infantfishes, and for the species, stout infantfish.

Distribution. Currently known only from the Lizard Island- Carter reef area (c. 14°33–35' S 145°35' E) of the Great Barrier Reef, Queensland, Australia, and from Osprey Reef (13°47–55' S 146°35 –40'E), nearby in the Coral Sea.

Specimens were collected in oblique plankton net tows from the Great Barrier Reef and Osprey Reef lagoons in waters ranging from 15–30 m deep.

Remarks. Yoshino et al. (2000) suggested that at least eight Schindleria species, all different from Schindler’s original descriptions of S. pietschmanni and S. praematura , occur in the Ryukyu Islands, Japan. These were distinguished primarily by the morphology of the urogenital papilla of male specimens. Because females have less well-developed urogenital papillae, fewer types were identifiable; thus morphology of the male urogenital papilla was considered a key character for recognition of Schindleria species. In the case of Schindleria brevipinguis the male urogenital papilla is not critical to identification; both males and females are readily distinguishable from S. pietschmanni and S. praematura on the basis of several other morphological and meristic characters. Most useful among these are the number of dorsal- and anal-fin rays and relative positions of the dorsal and anal fins, as noted in the key above. Schindleria brevipinguis has a deeper body, averaging 10% and 12% SL at pectoral- and anal-fin origins, vs. 5% and 6%, respectively, in S. praematura and 6% at both locations in S. pietschmanni . Schindler (1930, 1931) gave slightly higher values for relative body depth of S. praematura and S. pietschmanni : 5.9—6.8% SL and 6.1— 7.5% SL, respectively, both still smaller than the relative body depth of S. brevipinguis . Schindleria brevipinguis has slightly larger eyes than S. pietschmanni , averaging about 30% HL vs. about 25% HL, and fewer preanal vertebrae than S. praematura : 20 vs. 23—25 ( Schindler, 1930), respectively. Schindleria brevipinguis apparently lacks teeth in the jaws while the other two have small, but readily discernible teeth in both jaws. Both S. pietschmanni and S. praematura typically have pigment dorsally on the gas bladder, but S. brevipinguis does not. The urogenital papilla of male S. brevipinguis is distinctly different from the papillae of male S. praematura and S. pietschmanni (cf. Fig. 1 ; Jones & Kumaran, 1964, fig. 2; Sardou, 1974, fig. 8) and thus is a useful ancillary character for identification of male specimens. Note that the urogenital papilla of male S. praematura from Hawaii we examined differs from that shown by Sardou (1974, fig. 4), and by Bruun (1940, fig. 2) for specimens from Madagascar and Samoa, respectively.

Figures

Fig. 1. Schindleria brevipinguis n.sp. (A) Holotype, AMS I.23552-006 (8.4 mm, female), from vicinity of Carter Reef, Great Barrier Reef, Queensland,Australia; (B) paratype, AMS I.26323-003 (6.6 mm, male; note that branchiostegal area is somewhat damaged) from Carter Reef vicinity, Great Barrier Reef.Enlarged lateral (left) and ventral (right) views of urogenital papilla are shown below paratype. Scale bar = 1 mm.