The tripterygiid blenny,
Tripterygion etheostoma Jordan and Snyder is one of the common blennies in the rocky shore of the central and southern Japan.It feeds on creeping copepods, tiny shells, crab larvae, and annelid larvae.It grows to 60mm in full grown size. It shows the sexual dimorphism in coloration.The spawning season seems to extend from April to November in the shore of Nomozaki (Lat.32°35.3'N, Long.129°45.5'E), near Nagasaki.
From the rocky shore of Nomozaki, 34 adults, comprising 11 males and 23 females were collected and kept in a table aquarium for the spawning experiment during the period from March 27 to November 19, 1971.During the above period, 21 spawnings were observed in the aquarium.
In the actual spawning, a male parent first occupied one of the six stones previously set on the aquarium bottom for the spawning bed and guarded the stones for the fish intruders.The male cleaned filaments of the tiny prostrate alga,
Gelidium pusillum growing on the stone surface.A female came to the boundary of the stone and displayed itself to the male.The male induced the female to the algal zone on the stone.After the pairing, the male instantly demonstrated quick half-circling movement around the algal zone.The female entered into the center of the movement and spawned the first egg there.
The female rather sparsely deposited the eggs among the algal filaments on the stone spawning bed at intervals 17 to 69 sec.The inseminating behavior of the male instantly followed each oviposition.
After the spawning, the female left the spawning bed, whereas the male guarded eggs without fanning action.
Four of 11 males kept in the aquarium alternatively participated in 3 to 9 spawnings by various females in the period from 4 to 39 days.In a spawning, there were several egg masses in different developmental stages and each egg mass comprised from 24 to 518 eggs.
The eggs were about 1 mm in average diameter, and each egg was provided with sticky filaments entangled on algal filaments growing on the stone spawning bed.
An egg mass deposited among filaments of tiny prostrate algae, comprising
Herposiphonia tenella and others, was collected from a tide pool on the rocky shore of Nomozaki on August 24, 1972, together with the male parent guarding it.
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