Japanese Journal of Ichthyology

Studies of fertilization in Clupea pallasi-VI. Fertilization of the egg deprived of the membrane

Ryuzo YANAGIMACHI

1957 Volume 6 Issue 3 Pages 41-47
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.41

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1) The fertilization of the Clupea egg is monospermic under normal conditions. It has been found that if the unfertilized egg is deprived of its membrane (cf. Fig.1) and then inseminated, numerous spermatozoa penetrate into the egg and take part in the mitotic process of the egg. The cleavage and ensuing development of such an egg is therefore almost invariably abnormal (cf. Figs.2 and 3).
2) The egg, once fertilized, cannot be fertilized again. However, if the membrane of the fertilized egg is removed, the egg becomes refertilizable. Spermatozoa penetrate into the previously fertilized egg and participate in the formation of the mitotic figures producing irregular cleavages characteristic of polyspermy (cf. Fig.5).
3) The artificially activated egg is incapable of fertilization under normal conditions. It has been shown that if the membrane of the egg is removed, the egg can be fertilized. Spermatozoa enter and cleavage takes place similar to that characteristic of polyspermy (cf. Fig.6).
4) In view of these findings it seems justifiable to consider that the egg-membrane prevents entrance of supernumerary spermatozoa and constitutes the pricipal mechanism for prevention of polyspermy.

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The Digestive Tube of an Omnivorous Cyprinoid Fish, Barbus stigma (CUV. & VAL.)

B.G. KAPOOR

1957 Volume 6 Issue 3 Pages 48-53
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.48

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Points of anatomical and histological interest are: (1) The digestive tube of Barbus stigma closely resembles to that of Catla catla. (2) The buccal cavity contains the maxillary valve and the rudimentary tongue; the anterior pharynx is respiratory and gustatory and the posterior is masticatory infunction; the oesophagus opensdirectly into the intestinal bulb; a sphinctermarks the boundary between the oesophagus and intestinal bulb; the intestine is not very much coiled and the rectum is not differentiated. (3) The buccal epithelium is characterised by the polygonal, fusiform and columnar cells. The basement membrane and stratum compactum are present. (4) The pharyngeal epithelium is packed with mucous cells and taste buds and is supported by a basement membrane and stratum compactum. The adipose tissue and striated muscle fibres in the submucosa are prominent. (5) The oesophageal lining is composed of differentiated stratified epithelium and abundant taste buds and mucous cells. The longitudinal muscle bundles are dispersed in the submucosa. The circular layer of striated muscles forms a thick coat. (6) The oeso-intestinal bulb region shows mixed epithelia. (7) The carp does not have a stomach as is shown by the absence of gastric glands and the point of entrance of the choledochal duct in the intestinal bulb. The structure of intestinal bulb is similar to that of intestine. At the anus the columnar epithelium of the intestine changes over to the stratified epithelium of the skin. (8) The multicellular glands are absent throughout the digestive tube.

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Some Experiments on the Chemical Changes in the Membrane of Salmon Eggs Occurring at the Time of Activation

Tadashi S. YAMAMOTO

1957 Volume 6 Issue 3 Pages 54-58
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.54

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A Study of the Lateral-line System in Fish I. Quantitative Analysis of Fiber Calibers in the Lateral-line Nerves of Fishes

Yoshikazu TSUKAMOTO, Shizuo YOSHINO

1957 Volume 6 Issue 3 Pages 59-64
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.59

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On the fishing condition and size of horse mackerel, Trachurus japonicus, taken in the Pacific coast of Tokushima Prefecture

Hideyuki HOTTA, Tadashi TAMURA

1957 Volume 6 Issue 3 Pages 65-70
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.65

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The present paper deals with the horse mackerel, Trachurus japonicus, in the vicinity of Hiwasa, which is located at the Pacific coast of Tokushima Prefecture, and both the seasonal change of catch and size composition of the fish in the several gears are considered.
The monthly change of the catch has indicated the existence of two considerably high peaks, viz. the peak in spring (April to June) and that of autumn (September to November). The catch of the former was more abundant than that of the latter and the catch in both seasons was occupied by the larger fish (over 20cm in body length). The smaller fish (10cm to 15cm in body length) appeared in summer (July and August) and the very small fish (under 5cm in body length) in both April and October. Therefore, the numder of spawning seasons was estimated as twice in a year. But the size-composition has indicated a considerable variation by fish-shool and with time of catch.
Judging from the monthly length-composition mentioned above, it is presumed that the spawning grounds were wide-spread and the spawning season extended over a long period.

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New, Rare or Uncommon Fishes from Japanese Waters. VI. Notes on the Rare Fishes of the Family Histiopteridae.

Tokiharu ABE

1957 Volume 6 Issue 3 Pages 71-74
Published: October 31, 1957
Released on J-STAGE: June 28, 2010

DOIhttps://doi.org/10.11369/jji1950.6.71

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