Yanagimachi Ryuzo

紀要類（bulletin）departmental bulletin pape

Yanagimachi, Ryuzo

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

THE LIFE-CYCLE OF PELTOGASTERELLA GRACILIS(RHIZOCEPHALA, CIRRIPEDIA)著者 Yanagimachi Ryuzojournal orpublication titleThe bulletin of the Marine Biological Stationof Asamushi, Tohoku Universityvolume 10number 2page range 109-110year 1961-03-25URL http://hdl.handle.net/10097/00131104BULLETIN OF THE MARINE BIOLOGICAL STATION OF ASAMUSHI, VOL. X, NO. 2, 1960 THE LIFE-CYCLE OF PELTOGASTERELLA GRACILIS (RHIZOCEPHALA, CIRRIPEDIA) By Rvuzo YANAGIMACI!I j!JJJ lliJ lllk "' Zoological Institute, Faculty of Science, Hokkaiilo University, Sapporo, japan The Rhizocephala are not hermaphrodites, but are females with extremely modified hyperparasitic larval males (Ichikawa and Yanagimachi 1958'', ~960''). The females of Peltogasterella gracilis (=P. socialis)''· although they all look alike, are in reality of two genetically different kinds, the male-producing and the female-producing. The male-producing female possesses 30A chromosomes and produces large eggs with 15A chromosomes. These eggs are fertilized by spermatozoa from the cypris-cell receptacles and develop, within the maternal mantle cavity, into large nauplius larvae. These nauplii have 30A chromosomes. The newly hatched nauplii undergo three successive moults and transform themselves into large cyprii. They are attracted to the juvenile females and affix themselves to the mantle open,ing. They do not simply attach to the mantle opening, but inject their internal cellular contents, through the antennules into the mantle cavity of the juveniles. The implanted cellular masses migrate through the cavity and eventually enter the cypris-cell receptacles where these cells multiply and trans-form themselves into spermatozoa with 15A chromosomes. These cyprii are the so-called larval cypris males which have been often misnamed the complemental males.u The female-producing female has 30A + X chromosomes and produces small eggs, half of these possessing 15A + X chromosomes and the other half possessing 15A chromosomes. These eggs are fertilized by spermatozoa and develop into small nauplii. Half of these nauplii have 30A chromosomes and the other half have 30A + X chromosomes. Externally, these two genetically different kinds of larvae show no visible structual difference. Both of these two kinds of small nauplii undergo three successive moults and transform themselves into small cyprii. These cyprii seek for the young host crabs (the hermit crab, Pagurus lanuginosus, and some others) and attach to the surface of the crabs' body. They are prospective females. The female cypris injects its internal cellular contents, through one of its antennules, into the body of the host. During a long, completely endoparasitic 109 110 R. YANAGIMACHI existence, each female which at first appears as a minute mass of undifferentiated cells constructes two major parts, i.e. root system and sac-like portion containing differentiated ovary. When the host crab moults, the endoparasitic female em-erges from the host's body, leaving the root system inside the body of the host. Thus, the female becomes partially exoparasitic and partially endoparasitic. The juvenile female at this stage awaits the arrival of the larval cypris males. When it receives the cellular materials of the males into its cypris-cell receptacles, it be-gins to grow rapidly. The juvenile female with 30A + X chromosomes develops into female-producing female, and the female with 30A chromosomes develops into male-producing female. After the last batch of larvae has been extruded, the external sac-like portion wrinkles up and falls off from the host's abdomen, leaving the root systein. The root system may produce new external sac-portions by a process of budding.'''' REFERENCES l) ICHIKAWA, A. and R, YANAGIMACHI, 1958. Annat. Zool, Japan., 31 : 82-96. 2) , 1960. Ibid., 33: 42-56. 3) REISHMAN, P.G., 1959. Proceedings (Ser. c), 62: 409-435. 4) PEREZ, C., 1931. C.R.Ac. Sci. Paris, 192: 1753--1755. 5) , 1932. Arch. Zoo!. !tal., 16: 1319-1329. 

THE LIFE-CYCLE OF PELTOGASTERELLA GRACILIS (RHIZOCEPHALA, CIRRIPEDIA)

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THE LIFE-CYCLE OF PELTOGASTERELLA GRACILIS (RHIZOCEPHALA, CIRRIPEDIA)

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