NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
Studies on a New Trypanorhynchan Larva, Callotetrarhynchus sp., Parasitic on Cultured Yellowtail-XII
Free Proglottid
Kenji NAKAJIMASyuzo EGUSA
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1972 Volume 38 Issue 12 Pages 1333-1340

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Abstract

Observations were made on the movement and gravidity of free proglottides of Callotetrarhynchus sp. separated from the strobila of the adult in the valvular intestines of Triakis scyllia. The results are as follows: 1) Mature proglottides which still joined to the terminal of the strobila are 4.05-6.50×1.28-2.14mm in size and have no sperms either in the vas deferens or in the vagina and no ova in the narrow uterus. 2) Mature proglottides separate from the strobila before fertilisation at the posterior part of the valvular intestine. 3) In the initial stage, free proglottides immediately after separation, often have the cirrus protruded and the ductus ejaculatorius filled with sperms. 4) Free proglottides after receiving sperms move toward the anterior part of the valvular intestine and many fertilized eggs appear in the spread uterus of the proglottid. 5) All the free proglottides in the anterior part of the valvular intestine are completely gravid and larger in size than mature proglottides, being 5.33-7.65×2.00-3.75mm. 6) When the number of the fertilized eggs reaches about 40-60 thousand in the uterus, gravid proglottides start to return to the posterior part of the valvular intestine and finally escape into the sea from the anus of the host. 7) When gravid proglottides contact with sea water, the spawning pore is opened immediately on the dorsal side of the vertex of the uterus and the majority of the fertilized eggs are jetted out from the pore instantly. 8) Free proglottides are found in the valvular intestine of host sharks 12 to 30 days after administration of the bladder worms, plerocercus of Callotetrarhynchus sp.. 9) From these observations, it is concluded that the present species is hyperapolytic.

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© The Japanese Society of Fisheries Science
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