On the Development and Growth of Neocaridina denticulata DE HAAN

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  • ミナミヌカエビ(タエビ)Neocaridina denticulata De HAANの発生および成長について

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1) Neocaridina denticulata DE HAAN is not most popular fresh water shrimp in the south-west of Japan, but owing to the diffusion of the insecticides in the paddy-field after the war, it is going to be annihilated. On the one hand the demand to this shrimp has increased as it is the most desirable live-bait in the coastal sea. We has studied about the behavior of this shrimp since the autumn of 1958 to know the way of its propagation and in this paper we report about the development and growth of this shrimp. 2) We collected this shrimp from the pools among the mountains in the neighbouring of Sasebo city. 3) Our shrimp has many variations in body color but the many are semitransparent grey green, the blackish brown comparatively and the reddish sometimes. 4) The differences of both sexes in the adult of this shrimp are following, (1) the size distribution of females is larger than males, (2) at the Ist pleopod of this shrimp the exopodite is normal slender form and the endopodite is very large and pear-shaped in male, but in female the endopodite is smaller and more slender than the exopodite and is not seen the special form such as male, (3) at the 2nd pleopod the endopodite and exopodite are almost same size in female but in male the exopodite is larger and the other is very smaller, and the endopodite is attached to the enlarged and thickened appendix masculina which has many setae. 5) Our shrimp has the special number in the dorsal and ventral teeth at rostrum, in the spines of the both sides at the dorsal face of telson and in the spines at the terminal margin of telson as the tables show. 6) After hibernation the male molts at the middle of April and the female spawns the eggs and holds this eggs in his pleopods, and the hatching is performed in the period from the middle decade of May to the last decade of June, this is the first hatching season in this year. 7) The egg of this shrimp is larger than the other, and the number of eggs in this species is very few in comparison with the other and there is a positive correlation between the body length and the number of eggs. After the spawning the eggs adhere in the pleopods by the elastic fibroid egg handle. 8) The shape of the young shrimp after the hatching is almost the same to the parent except the telson and uropods as the PLATE Ⅷ shows. This shrimp does not metamorphose. 9) The figures of the body, antennas, mandible, maxillas, maxillipeds, pereiopods. pleopods, telson and uropods are shown at PLATES in the each larval stages. 10) In the shrimp after the 5th molting (after about 10 days from the hatching), there. is no yolk in the carapace and the color of the excrement changes so it is seemed that the shrimp after the 5th molting begins to take the food. Its growth from this. stage is rapidly. 11) In the young shrimp which grows up about 11mm in body length after a month from the hatching, the characteristic of the sex already appears and the both sexes can be distinguished by Ist and 2nd pleopods, it is guessed that the gonad matures in both. sexes since this time. 12) The shrimp which grows up about 16 mm in body length after two monthes front the hatching molts the eggs which has held between the pleopods, namely this is the second hatching season in this year and it is the period from the first decade of August to the middle decade of September. The molting and development of this larval shrimp which had hatched out in this hatching season is same to that in the first hatching season. And the parent shrimp in the first hatching season does not perform the spawning and hatching. 13) The growth curve of this shrimp is indicated in Fig. 6. 14) This shrimp has been alive more than two years at least. 15) This shrimp is very delicate to the chemicals such as insecticides, but is not so delicate for the change of natural environments such as the water temperature and its growth is rapidly and the period which reaches to the sexual maturity is short and its food at the breeding is the rice-bram and so on which is very easy to receive, So the propagation of this shrimp is not difficult.


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