Observations sur Monobrachium drachi Marche-Marchad hydraire (Limnomedusae) à méduse non pélagique commensal d'un lamellibranche de la côte occidentale d'Afrique = Observations on Monobrachium drachi Marche-Marchad (Limnomedusae), a hydroid with a non-pelagic medusoid, commensal of a lamellibranch of the west coast of Africa
Marche-Marchad, I. (1975). Observations sur Monobrachium drachi Marche-Marchad hydraire (Limnomedusae) à méduse non pélagique commensal d'un lamellibranche de la côte occidentale d'Afrique = Observations on Monobrachium drachi Marche-Marchad (Limnomedusae), a hydroid with a non-pelagic medusoid, commensal of a lamellibranch of the west coast of Africa. Cah. Biol. Mar. 16(4): 569-584 (2plates)
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094, more
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| Abstract |
The gen Monobrachium is a commensal hydroid of some minute lamellibranchs. 3 spp are known (M. parasitum Mereschkowsky 1877, M. drachi Marche-Marchad 1963 and M. antarctica Robins 1972) in this gen of wide distribution from Arctica to Antarctica and even in California and the west coast of Africa (Senegal). M. drachi, commensal of the viviparous Cuna gambiensis Nickles is characterized by the presence of an hydrorhize without defensive zoids which covers as a regular net, all the surface of the shell. The hydranthe tentacle has a entodermal axis. The medusoid has 4 well developed radial canals along which spread 4 gonads, a vestigial circular canal and 4 rudimental short tentacles. The manubrium is very small and closed. The study in vivo shows that the medusoid is liberated and has a very short benthic life during which the genital products are liberated through the velar aperture. Fecundation is external; the number of eggs approaches 140 and their diam is 100 {mu}. The study in vivo reveals a strict adaptation of M. drachi to the ecology and ethology of its host C. gambiensis. |
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