Description: Body thin, long and narrow with a small vertically-narrowed oval eye and a terminal mouth. Pectoral fins length unknown, dorsal and anal-fin bases short, pelvic fins length unknown, caudal peduncle long and relatively narrow with 11-12 spindly procurrent caudal-fin rays. Markings mostly along the ventral midline: melanophores as streaks at the isthmus, the pelvic-fin insertion, and the mid-abdomen. There are four discrete melanophores along the base of the anal fin followed by a streak of melanophores along the ventral peduncle ending at the first procurrent caudal-fin rays. Melanophores are present at the base of most of the lower segmented caudal-fin rays extending well out along the fin rays. Head markings are limited to melanophores outlining the lower rim of the dentary at the tip of the lower jaw. Internal melanophores are present along the dorsal surface of the swim bladder.
Leptophilypnus fluviatilis? larva
Leptophilypnus fluviatilis? larva, bottom
Leptophilypnus fluviatilis? larva, middle
Diagnosis: A larva with the fin-ray count of D-VI,11 A-10 and numerous procurrent caudal-fin rays (11-12) could represent any of Erotelis smaragdus, Gobiomorus dormitor, Guavina guavina, or Leptophilypnus fluviatilis. This larva could possibly represent an earlier-stage larva of either Gobiomorus dormitor or Erotelis smaragdus, however several features support Leptophilypnus fluviatilis: this larva has no melanophores on the lateral caudal peduncle (characteristic of the other two genera, even at smaller sizes); this larva has 11 procurrent caudal-fin rays but small immature larvae of the other two genera do not have that full complement; and, lastly, the eyeball of the other two genera has a distinctive ventral extension not present on this larva, perhaps indicating that this larva is transitional at this small size. Larval Guavina guavina are distinctly shorter and wider-bodied. (PE)
Analogues: The eleotrid larvae share a long thin body with relatively short dorsal and anal-fin bases, numerous procurrent caudal-fin rays, and a long ventral midline streak from the isthmus to the mid-abdomen. This larval type resembles larval Dormitator maculatus with a delicate body and few markings, but has quite different fin-ray counts, with 11/10 vs. 9/10 and many more procurrent caudal-fin rays. It has a small and even oval eye, unlike pre-transitional larval Gobiomorus dormitor and Erotelis smaragdus which have a distinctive ventral extension. It is missing the characteristic patch of melanophores covering the caudal peduncle of larval Erotelis smaragdus and those on the upper half of the caudal fin of larval Gobiomorus dormitor. The few true gobies that share the numerous (>10) procurrent caudal-fin rays (notably Sicydium and Awaous banana) have distinctive internal melanophores that are absent on this larval type.
