Reproductive biology and morphology of eggs and early larvae of the sicydiine goby Stiphodon percnopterygionus were investigated on Okinawa Island, southern Japan. Spawning season was estimated as being from May to December. Standard length at maturity was approximately 20 mm in both sexes, and batch fecundity was approximately 1000-10 000 per female. The egg masses, guarded by the male, were laid on the undersurface of stones in freshwater. The pyriform eggs had long-and short-axis diameters of 0.54-0.58 mm and 0.49-0.50 mm, respectively. Newly hatched larvae (1.20-1.32 mm notochord length: NL) were poorly developed, with large yolk sacs and unopened mouths. Three days after hatching (1.87-2.05 mm NL), eyes were fully pigmented and mouths were opened.

Reproductive biology and early development of two species of sleepers, Eleotris acanthopoma Bleeker, 1853, and E. fusca (Forster, 1801), were investigated in streams on Okinawa Island in southern Japan. Gonadal examination and morphology of the genital papillae indicated that E. acanthopoma matured at a smaller body size (ca. 28 mm in standard length) than E. fusca (ca. 50 mm). Mature ovaries were composed of oocytes that could be categorized into two size classes. Larger females of both species had several hundred thousand developed oocytes in the larger size class and may spawn them at one or several consecutive spawning events. Egg masses of both species were found in habitats typically occupied by adults and were deposited, often sparsely, on the underside of objects. Form of the egg masses and morphology of eggs and newly hatched larvae of both species were almost identical. Eggs were a nearly spherical pyriform in shape, with the widest diameters measuring approximately 0.4 mm. Newly hatched larvae were very small (1.0-1.4 mm in notochord length) and undeveloped. The mouth opened and the eyes became pigmented 3 days after hatching, and all of their yolk was consumed 4 days after hatching. Reproductive strategies of both species were characterized by high fecundity through production of small eggs and small newly hatched larvae, with high fecundity likely to mitigate the presumed increased risk associated with widespread larval dispersal.

The morphology of eggs and larvae of Awaous melanocephalus is described. The eggs measured 0.33-0.35 mm in long-axis diameter and 0.32-0.34 mm in short-axis diameter. Newly hatched larvae (0.90-0.99 mm in notochord length, NL; 0.93-1.04 mm in total length, TL) were poorly developed, lacking a mouth and having a large yolk sac and unpigmented eyes. The mouth opened and the eyes became fully pigmented 3 days after hatching (1.78-2.00 mm NL, 1.88-2.10 mm TL). The yolk sac was completely absorbed 5 days after hatching at a water temperature of 27º-28ºC.Key words Egg · Larva · Amphidromous goby · Awaous · Gobiidae length (TL), and yolk-sac diameter were measured using a micrometer after fi xation in 5% formalin solution. The sketched specimens were preserved in 70% ethanol and deposited in the collection of the University of the Ryukyus, Marine Science (URM). Results and DiscussionSixteen discrete nests were found in the Genka Stream from July to October 2005. Water temperature at the time nests were discovered ranged from 24.7º to 29.5ºC. Eggs being guarded by males (70-130 mm SL, n = 16) were attached to the surface of one or more stone(s) or rock(s) in a single layer by adhesive fi laments. The total area of egg masses in a single clutch ranged between 40 and 220 cm 2 . All the eggs in a nest appeared uniform in texture and color, suggesting that each nest consisted of a single clutch, and estimated to contain about 40 000-220 000 eggs (mean ± SD = 102 000 ± 54 000, n = 16). A positive relationship was observed between the SL of the guarding male and clutch size ( Fig. 1; r = 0.51, P < 0.05, n = 16). Eggs ranged between 0.33 and 0.35 mm (mean ± SD = 0.34 ± 0.01 mm, n = 10) in long-axis diameter and 0.32 to 0.34 mm (0.32 ± 0.01 mm, n = 10) in short-axis diameter ( Fig. 2A), and embryos hatched within 6 h after collection.Mean egg size in Awaous melanocephalus was similar to that reported for Hypseleotris compressa (0.30-0.32 mm in long-axis diameter; Auty, 1978), which are thought to be among the smallest known eggs in teleosts (Miller, 1984). The fi nding that A. melanocephalus spawns small eggs corroborates similar fi ndings in the conspecifi c Awaous guamensis (see Ha and Kinzie, 1996). However, A. melanocephalus differed from A. guamensis with respect to the guarding of egg masses. While the female is primarily re- IchthyologicalResearch

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