Three species of marine hatchetfishes, Sternoptyx diaphana Hermann, S.obscura Garman, and S.pseudobscura Baird, were reported from the western North Pacific Ocean, based upon the materials collected by the R/V Tansei-Maru and Hakuho-Maru, Ocean Research.Institute, University of Tokyo. The morphological differences among the three species were tested by the statistical method proposed by Ito (1953) to test slope and positional differences of allometry line and proved to be significant at risk of 1 % level in many characters as presented in Table 3.These support the results of Baird (1971) who recognized three species in the genus Sternoptyx which had been usually treated monotypic.The key to the species in the western North Pacific Ocean are as follows.
The sharksucker, Echeneis naucrates Linnaeus was spawned from June 2nd to August 7th, and from September 18th to December 3rd in a tank of Oita Ecological Aquarium.Embryonic development and metamorphosis after hatching were observed. Spawning activities were continued for 30 minutes between 18: 20 and 20: 00.Lights for exhibition were put out at 18: 00.The spawning behavior was always repeated 2-5times with-in 30 min in the daily spawning period.The temperature of the breeding aquarium was regulated from 27.5 to 30.5°C. Fertilized eggs are transparent and free floating.Eggs are rather large, 2.62 mm in diameter, and nearly spherical in shape.One to five yellowish oil globules (2-3 in average) measuring 120 to 170 μ in diameter are found on one side of the vegetal pole.Time intervals of embryonic development after fertilization were summarized in Table 1. Mouth cleft appeared 2 days after hatching.The mouth and anus were well formed and open, the tail showed a fan-like shape and the yolk mass was completely absorbed on 4th day.On 6th day, the larvae attained 12.0 mm in total length and several pieces of small hooklike projections appeared on the anterior part of each jaw. When larvae measured up to 15-20.5 mm in total length 9 days after hatching, the epidermal boarding bulge appeared on the median line of the dorsal part of the body above the basal part of the pectoral fin.The caudal fin was twice as long as the head.The number of fin rays reached the fixed number of the species. Larvae grew to 29 30 mm in total length 12 days after hatching, and the epidermal bulging shifted to the upper part of the posterior margin of the eyes, forming a sucking disk in an oval shape.When larvae reached 34.0 mm in total length (14th day), the anterior margin of sucking disk extended above the middle of the eyes.On 15th to 20th day, the anterior margin of the sucking disk reached above the anterior margin of the eyes. Young fish grew to 41.0 55.0 mm in total length 20 N 27 days after hatching, and the anterior margin of the sucking disk reached the anterior margin of the upper jaw.In young fish, 80 mm in total length on.50th day, the sucking disk enlarged to a length longer than the head.The length of the tail reduced. |The first small scales appeared scattering on the lateral side of the young fish when they attained the size of 75.5 mm in total length.
Some serum constituents levels were examined before and after a single feeding in yellow-tail (Seriola quinqueradiata) fed on raw fish or a compound diet. In the group fed on raw fish, total protein, its fractions II and III, urea-N, total cholesterol, magnesium and phosphate-P levels returned to the pre-feeding values at 14 hrs, with the peaks at 6 to 10 hrs after feeding. The orange color index expressed in the arbitrary unit and triglyceride levels returned to the pre-feeding values at 18 hrs, via prominent and prolonged elevations with peaks at 6 hrs after feeding. Transitory declines at 1 hr after feeding were observed in the serum levels of total protein, total cholesterol, magnesium and phosphate-P. In the group fed on the compound diet, the absence of orange color, more prompt increases in triglyceride and NEFA, and decreases in calcium and phosphate-P levels were observed after feeding. The causes of these variations and the post-feeding time for blood sampling were discussed.