注記 |
The present paper, the fourth of the series of the pelagic fish eggs from Japanese waters, contains the figures and descriptions of the egg and larval development of 15 species belonging to the suborders Trachinina and Uranoscopina. Trachinina. The egg and larval development of 14 species belonging to this suborder are known from Japanese waters. These eggs are globular in shape, the egg membrane is smooth, without any conspicuous structure, the yolk not segmented, the perivitelline space narrow. According to the egg size, the number of oil globules and their size, and the process of the egg and larval development, these eggs can be divided into following three groups : (1) Neopercis sexfasciata (Temminck et Schlegel) and Parapercidae-type No. 1-9, (2) Trachinicae No. 1 and 2, and (3) Champsodon snyderi Franz and Chamspodon sp. Group (1). The eggs are rather small, measuring 0.63-0.99 mm in diameter, with a single oil globule measuring 0.13-0.24 mm in diameter. During the course of the egg development xanthophores and melanophores appear on the embryonal body and oil globule, but some species lack the melanophores on the oil globule. The oil globule of the newly hatched larva is situated in the posterior part of the yolk. The newly hatched larva has 7-8 large xanthophores on the dorsal and ventral median line of the body, and usually some of those on the dorsal side are situated opposite to ones on the ventral side. Soon after hatching these xanthophores scatter over the marginal fin usually accompanying the melanophores, and when the yolk is consumed, the pigment-cells on the marginal fin become faded. The number of myotomes of the hatched larva is 31-34. Group (2). The eggs closely resemble those of Trachinus vipera and T. draco reported by Ehrenbaum (1905), measuring 1.20-1.49 rnm in diameter. The egg of Trachinicae No. 1 contains 23-45 oil globules measuring 0.01-0.14mm in diameter, but Trachinicae No. 2 has only a single oil globule, 0.25-0.28 mm in diameter. In the egg development xanthophores appear on the embryonal body, yolk and marginal fin in the both species, and in Trachinicae No. 2 also appear on the oil globule. The melanophores appear on the embryonal body, yolk and oil globule in Trachinicae No. 2, while in Trachinicae No. 1 they are restricted to the embryonal body. The oil globule or oil globules of the newly hatched larvae are situated at the posterior part of the yolk. Before the yolk is completely consumed the ventral fins appear. The number of myotomes of the hatched larva is 25-27. Group (3). Ch a mpsodon snyderi and Champsopon sp. are already reported under the names of I. C, No. 6 and I. C, No. 7 respectively, in the previous paper (Mito, 1960). These eggs are moderate in size, measuring 1.09-1.19 mm in diameter, with a single oil globule measuring 0.17-0.21 mm in diameter, and usually accompanying a smaller single oil globule measuring 0.02-0.08 mm in diameter, in early developmental stages. A single spinous appendage appears at the upper posterior part of the operculum toward the late embryonic development, and it is as long as one ninth of total length of the body at hatching. During the course of the egg and larval development only the melanophores appear. The number of myotomes of the hatched larva is 30-32 in C. snyderi and 28 in C. sp. Uranoscopina. The egg and larval development of only a single species Uranoscopus japonicus Houttuyn is known from Japanese waters. It is already reported as III. A, No. 1 in the previous paper (Mito, 1960). The egg is large, globular, measuring 1.52-1.91 mm in diameter. The egg membrane is somewhat thick and with hexagonal mesh structure, measuring 0.03-0.05 mm in diameter of the mesh. The yolk is not segmented, containing 3-27 yellow oil globules measuring 0.02-0.09 mm in diameter. The perivitelline space is narrow. In the egg development melanophores and orange-red pigment-cells appear on the embryonal body, yolk and marginal fin. The hatched larva is plump, having 25-26 myotomes.
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