Reproductive Biology and Early Development of Two Species of Sleeper, Eleotris acanthopoma and Eleotris fusca (Teleostei: Eleotridae)¹

Abstract

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.

Diel and Seasonal Occurrence Patterns of Drifting Fish Larvae in the Teima Stream, Okinawa Island

“…All small undeveloped type larvae were at an almost uniform newly hatched stage. Their 1-day-old larvae are larger (1.5-1.8 mm NL) and show features distinguishing them from newly hatched larvae (Yamasaki and Tachihara 2006, 2007, Maeda et al 2008), but we did not find these older larvae. Thus, all larvae we observed probably passed through the sampling site within hours of hatching.…”

“…They most likely comprised Eleotris acanthopoma, Eleotris fusca, Sicyopterus japonicus, Stiphodon percnopterygionus, Stenogobius sp., and Awaous melanocephalus, because only these fishes among those found in the upper reaches of the sampling site are known to hatch in such undeveloped stages (Dô tu and Mito 1955, Yamasaki and Tachihara 2006, 2007, Maeda et al 2008our unpubl. data).…”

Comparative larval development of three amphidromous Rhinogobius species, making reference to their habitat preferences and migration biology

“…(e.g. Maeda et al 2008;Yamasaki et al 2011), they are thought to be adapted to longer downstream migrations by having a somewhat 'early hatch' and a larger yolk. Rhinogobius sp.…”

Life-history characteristics of eleotrid fishes of the western hemisphere, and perils of life in a vanishing environment

“…The family Eleotridae is that of principal interest in the present discussion. There is significant evidence of amphidromy in a number of species of eleotrid fishes from, Australia, Japan, New Zealand and a number of Pacific islands including Guam and the Hawaiian Islands (Radke and Kinzie 1987; Barker and Lambert 1988;Chubb et al 1998;Radtke et al 1988Radtke et al , 1999Fitzsimons et al 1990Fitzsimons et al , 2002Iguchi and Mizuno 1990;McDowall et al 1994;Tate 1997;Nishimoto and Kuamo'o 1997;Waters et al 2000;Closs et al 2003;McDowall 2003McDowall , 2004McDowall , 2007aMcDowall , 2009bKeith et al 2006;Maeda et al 2008. It was pointed out by McDowall (2007a) that amphidromy is most common among island fish faunas.…”