The present report aims the comparative morphology of two cyprinid fishes, Zacco platypus (Temminck et Schlegel) and Z.temminckii (Temminck et Schlegel), particularly with reference to the relative growth of two parts of the mouth which may be closely related to the capture of food, the floor of oral cavity, the gill raker, the pharyngeal bone, and the intestine.Through the detailed comparative study of these organs, the authors could make success in making clear the significance of the structural adaptations of these organs in the two species in relation to their feeding behaviors. The growth of two parts of mouth (length of upper jaw and width of lower jaw) was examined against changes of total length.Upon the relative growth method of analysis, it is clear that the sizes of these parts for Z.temminckii are obviously larger than those for Z.platypus.Therefore, it might be considered that Z.temminckii is capable of seizing larger food organisms. The prominent fleshy folds, called the oral folds, are present on the floor of oral cavity.Development of these folds varies in its extent according to the species.In Z.platypus, the folds develop gradually and increase in their number with growth of the fish.When the fish reaches about 90 mm in total length, all of the folds are highly elevated above the surface of the floor.In Z.temminckii, they are scarcely developed throughout the life history excepting the first two which are highly elevated in the fish measuring more than 60 mm in total length. The outer surfaces of oral folds are provided with prominent papillae.There are also some specific variations in the degree of development of these papillae.In Z.platypus, the first indication of formation of the papillae can be observed in the fish measuring about 45 mm in total length.With growth of the fish, they develop gradually and increase in their sizes.In Z.temminckii, the papillae appear on the outer surfaces of the first two folds when the fish exceeds 55 mm in total length, and increase gradually in their sizes.However, the rest of folds are furnished with minute papillae which are only sparsely set on their surfaces.It appears that the development of oral folds and their papillae is positively related to the herbivorous behavior of the fish. The modal number of gill rakers on the first arch is 11 in Z.platypus and 10 in Z.temminckii.In the former species, the gill rakers are rather slender, tapering gradually towards the pointed tips.While in the latter, the distal ends of gill rakers on the ceratohyal bone are truncated or the knob-like appearances when the fish reaches about 120 mm in total length. The dental formula of pharyngeal teeth is 1, 4, 4-4, 4, 2 in Z.platypus and 2, 4, 5-4, 4, 2 in Z.temminckii.From the statistical comparison of the growth of three parts of pharyngeal bone (length of bone, width of the same and length of the longest tooth) against changes of total length between Z.platypus and Z.temminckii, it is clear that the relative sizes of three parts for the latter species become obviously larger than those for the former when the fish exceeds about 45 mm in total length. Intestines of the two species bear a close resemblance to each other in their forms in the fish measuring less than 35 mm in total length.However, owing to the occurence of somewhat complicated coiling, the intestine of Z.platypus becomes longer than that of Z.temminckii when the fish exceeds 35 mm in total length.It is presumed that the elongation of the intestine of the former species is a structural adaptation for assimilating minute adherent algae. Considering from the facts described above, it may be deducible that the structures of feeding and digesting organs change ontogenetically in relation to the behavior of minute adherent algae feeding inkn-abstract=
The porcupine puffer, Diodon holacanthus Linnaeus, a well-known fish belonging to the family Diodontidae, inhabits the warm seas all over the world.However, both the behavior and life history of the puffer and its allies are virtually unknown.The present paper deals with the spawning behavior and the early life history of D.holacanthus based on observations at the Kanazawa Aqua-rium and the Marine Science Museum of Tokai University, from 1969 to 1975. Spawning and reproduction of the puffer was first observed at the end of May when the water temperature reached approximately 24.4°C, and was observed continuously until the end of August.The parental fishes, measuring 176-259 mm (in males) and 210-231 mm (in females) in total length, were reared for one or two years since they were collected from the coasts of Wakasa Bay and Noto Peninsula, the Sea of Japan (Fig.2, Table 1). Every day during the spawning season, in the afternoon or early evening, one or two males approach a female who remains motionless at the bottom of the rearing tank.The males, pressing their snouts against the belly of the female, incite her with their courtship behavior.The female is then slowly pushed upward towards the surface of the water by the males.Several other males also gather around the female and help to push her upward.If the female is not ready to spawn, she deserts the males and returns to the bottom alone.After repetition of such activities, the female spawns her eggs just below the surface of the water.And the eggs are fertilized simul-taneously by the males (Fig.1).Spawning always takes place between one female and four or five males with no exception, and occurs between 20: 52 and 23: 25 or at night at an undetermined time (Table 1). The fertilized eggs of D.holacanthus are buoyant, colorless, and spherical, measuring 1.62-1.86 mm in diameter.During egg development, a thick external membrane appears over the yolk of the eggs 45 hrs.after fertilization.The hatching takes place 103-118 hrs.after fertilization when the water temperature is 24.2-25.5°C.The newly hatched larvae, measuring 2.46-2.73 mm in total length, have 12+8=20 myotomes and float belly upward just beneath the surface of the water.The larvae are covered with a thick pliable shell excluding the caudal section.Ten days after hatching, the larvae, measuring 4.86-5.94 mm in total length, form fin rays and several tuber-cles on the body.These tubercles contain the rudiments of the spine.The shell over the body becomes indistinct or disappears (Fig.3). Thirteen days after hatching, small distinct spines can be observed in the tubercles.The fry, measuring 6.04-7.94 mm in total length, sometimes puff out their bellies.Twenty-five days after hatching, fused teeth and large irregular black speckles on the dorsal side are visible in fry measuring 20.3 mm in total length.Sixty-six days after hatching, the fry, measuring 46.5 mm in total length, have irregular speckles and pointed spines similar to those of the adult (Fig.4). The thick external membrane and pliable shell, which can be observed from 45 hrs.after ferti-lization to 10 days after hatching in D.holacanthus, closely resembles the rudiment of the shell which appear in the similar stages of the trunkfish, Ostracion tuberculatus (see Mito, 1962) and of the slender mola, Ranzania laevis (see Leis, 1977).The characteristics of the eggs and larvae of D.holacanthus bear no resemblance to those of the known puffers (except the slender mola, R.laevis) belonging to the same suborder Tetraodontoidei, but rather resemble the trunkfishes belonging to the suborder Balistoidei.These results are thought to suggest to the systematic relationships between Ostraciontidae, Diodontidae, and Molidae.
The sea bream, Gymnocranius griseus (Temminck et Schlegel), a coastal fish belonging to the family Lethrinidae, ranges from Sendai Bay in Japan to the Indo-West Pacific Ocean.The present paper deals with the mode of reproduction and early life history of the fish which were reared in an oceanarium (10×10×6 m, depth) at the Marine Science Museum of Tokai University in 1973. The seventeen parental fishes, measuring 290-340 mm in fork length, were collected from the coast of Suruga Bay and reared in the oceanarium for two or three years.Reproduction occurred during the months of May and June in the oceanarium when the water temperature ranged 18.0-26.5°C (Fig.1). Mutual courtship of the sea bream begins when one male attempts to lure a female who re-mains motionless in a small school of the fish close to the bottom.The male approaches the female and blocks her way, and then, he taps her belly with his snout.They ascend slowly together towards the surface of the water with the male under the female.If the female is not ready to spawn, the paired fishes return separately to the bottom.After several repetitions of this mutual courtship behavior, the paired fishes, when they reach the height of one or two meters below the surface of the water, take position themselves side by side.The eggs are spawned and are fertilized simultane-ously (Fig.2). Spawning occurs between 20: 30 and 21: 00 at the water temperature of 20.7-22.8°C. The characteristics of color of the sea bream can be divided into three distinct types and are interchangeable.One type, in which several wavy silver lines appear on the laterals, is observed only in the male during reproductive activity.The other two types are observed commonly in both sexes under normal conditions (Fig.3). Fertilized eggs of the sea bream are buoyant, spherical, and colorless, measuring 0.76-0.79 mm in diameter.Twenty-five hours after fertilization, an oil globule, which was spherical until that time, warps elliptically or deforms to a gourd-shape in the lateral view.The hatching takes place 38-40 hrs.after fertilization at the water temperature of 20.0-22.4°C.The newly hatched larvae, measuring 1.48-1.50 mm in total length, have 9+24=33 myotomes.The elliptical oil globule once again becomes spherical.Twenty-two hours after hatching, the larvae, measuring 2.35-2.40 mm in total length, have 5+19-20=24-25 myotomes (Fig.4). The warping of the oil globule in the yolk has been previously observed in early life stage of two lethrinid fishes, Lethrinus nematacanthus and L.choerorynchus (Mito, 1956;Akazaki et al., 1975;present authors, unpublished).However, in both lethrinids, the oil globule does not return to the spherical shape in the newly hatched larvae.Also the characteristics of the newly hatched larvae of G. griseus are compared with those of the two lethrinids and a few related fishes.
Thirty-six specimens of the dolphin, Coryphaena hippurus Linnaeus, 35 to 50cm in total length, were collected during September to October, 1975, off the coast of Kamogawa, Chiba Prefecture, Japan.They were kept in a big tank (17m×12m×3.5m).The water temperature in the tank was controled between 22.8°C and 25.4°C. Eleven specimens survived to grow up about 100cm in total length when their breeding behavior was observed.At the time when the first spawning was found, 8 specimens were survived.Twenty times of spawnings were observed from April 22 to July 13, 1976.The spawning was taken place mainly at the water surface by a pair of adults, although the pair was often accompanied by one to three dolphins.Every spawning occurred between 15: 35 and 17: 45. Fertilized eggs are transparent, floating, and spherical in shape, 1.40 to 1.65 mm in diameter.The eggs hatched out about 60 hours after fertilization at 24 to 25°C. The newly hatched larvae were 3.8 to 4.9 mm in total length.In 4 days after hatching the larvae began to eat Brachionus plicatilis.But all of them died within 9 days after hatching.
Twelve specimens of a goby were collected from Ishigakijima, Okinawa Prefecture, Japan.They were identified as Myersina macrostoma by Dr.Hoese of the Australian Museum through comparison with the holotype collected from the Philippines. Myersina macrostoma has hitherto been known only from the holotype described by Herre (1934).This record is the first from Japan. This species is thought to be closely related to the genus Cryptocentrus.The characteristic features of Myersina macrostoma are found in the gill-membranes and the vomer.Both sides of the gill-membranes are united across the isthmus.Both sides of the lateral anterior part of the under side of the vomer protrude posteriorly and interiorly as pointed processes, which were described as teeth in the original description.