Preliminary translation by J. B. Sochasky

Transcription

1 ^ %^ ïq yc]" FISHERIES RESEARCH BOARD OF CANADA Translation Series No Ki30_^"RTxsG ry^ STUDY OF A POPULATION OF CARCINUS MAENAS L. FROM THE COASTS OF THE ENGLISH CHANNEL: GENITAL OVARIAN CYCLE By N. Démeusy i Original title: Etude d'une population de Carcinus maenas L. des côtes de la Manche: cycle génital ovarien. From: Comptes Rendus Hebdomadaire des Séances de l'academie des Sciences de Paris. Vol. 256, pp , Preliminary translation by J. B. Sochasky Distributed by Fisheries Research Board of Canada Biological Station, St. Andrews, N.B pages typescript

2 This is a preliminary translation originally prepared for personal use. It is not a definitive English version of the article, and it has not been checked or approved by the author.

3 Demeusy, N Etude d'une population de Carcinus maenas L. des c6tes de la Manche: cycle genital ovarien. C. R. Hebd. Séances Acad. Sc.i. Paris 256: [Study of a population of Carcinus maenas L. from the coasts of the English Channel: genital ovarian cycle. Fish. Res. Bd. Can., Transi. Ser. No ] The information collected until now on the annual ovarian cycle of a crab as common as Carainus maenas has nearly always been in consequence of observations limited both in time and in the range [échelle] of sizes of the individuals. For the same reason they are the fruit of extrapolations and hypotheses to a great extent. It is nevertheless commonly acknowled.ged that this brachyuran decapod oviposits o.nce per year on our coasts and that, as in most crustaceans, oviposition is followed by molting. But we have recently (Démeusy 1962) had the opportunity to point out the presence of a population of Careinus maenas in the vicinity of Luc-sur-Mer (Calvados) extremely well represented at the place called "Quillot" and atthe same time the fact that.certain of its representatives, held in the lab [maintenus en elevage], can undergo two successive vitellogeneses, without the interpolation of a molt. On the other hand, we should recall that eyestalk ablation in mature females from Roscoff (Finistere) brings various results, the heterogeneity of the reactions having remained unexplained until then (Demeusy 1958). All of these reasons have lead [incitée] us to examine, as closely as possible, the normal correlations between vitellogenesis, embryonic development and intermolt duration. Monthly collections, made at the spring tides have allowed us to statistically follow the population during the course of an entire year. For each female, we noted the cephalothoracic length, the approach or.absence of ecdysis, the developmental stage of the ovaries, the possible presence on the pleopods of empty shells from their embryoes, and, in the females during the incubation period, the degree of maturity of the oviposited eggs. Graphs [graphiques] putting the genital- development of the population in a condensed form [concrétisant] will be published subsequently. ResuZts.y- In spite of an interpretation sometimes rendered weak by the uneven size of the collections, it is evident that the adult female popula'tion has a generally well marked molting period (summer). Only the youngest individuals continue to molt until the approach of winter. The period of oviposition is very loose [lâche] (winter, spring, summer). This is connected with a variable behavior of the females according to their size and a.ge.

4 The smallest from among them (from the attainment of puberty until 28 or 30 mm long) show a complex genital activity, because of the interference at certain times of the year of the processes of molting and vitellogenesis. From the time of being juvenile, the contribution of these females, massive in summer, is continued truly until the beginning of winter. It undergoes a decline until finally revived in spring. From the end of summer, two fates are in store for them. Some ripen [page 4096] their ovaries, others remain at genital arrest [repos genital]. This duality of genital state observed similarly at Roscoff (Démeusy 1958), is maintained until the following June. However, oviposition is rare in winter and involves principally the largest of these individuals; the most intense period of oviposition in this range of females occurs in spring. Barring disappearance 19 winter, by migration or burial of the small ovigerous [oeuvees] females, all takes place as if a great proportion of the individuals, although in complete genital development, were capable of molting. They should thus increase the rank [rangs] of the females of average size. Their vitellogenesis would thus extend, at this time of the year, over several intermolts. During winter, the intermolt duration happens to be lengthened, vitellogenesis occurs during a single intermolt, thus explaining the spring oviposition. As for the individuals with transparent ovaries, they develop after a variable number of ecdyses. -- The females of average size (from to mm) have a much more standardized ovarian cycle. They all begin [les atteignant toutes] genital development starting at the end of the summer molting period. The main part of the oviposition occurs from December to February, indeed certain individuals provided with later molts, oviposit again in spring. In such a case, a long period [temps] of ovarian arrest [repos des ovaires] continuing until the end of the coming [suivant] summer follows for a large percentage of them. The remainder undergo a second ovarian growth after oviposition without an intermediary molt,,which happens to confirm our previous observations (Démeusy 1962). -- The females of large size (36-38 to 55 mm) undergo two ovarian cycles [pousées] in a year without an interpolating molt. The first is concomitant with that of the average female. So is oviposition. A very large proportion of these individuals develop again and a second maturity can be attained at the beginning of summer. However the not very high number of ovipositions observed in summer allows one to suppose a high mortality amongst these females.

5 CoraoZusions. Discussion. m- The annual cycle of ovarian maturation shows various modalities according to the size of the individuals and for some of them according to the seasons. This has the effect [ceci a pour effet] of di stri buting ovi posi ti on over a great part of the year. For these diverse modalities there are corresponding [correspondent alors] modifications in the correlations [relations] between molting and vitellogenesis: The processes of molting and vitellogenesis very certainly interfere in most of the young individuals, at the very least from the end of summer until the-beginning of winter. Observations undertaken on animals held in the lab [maintenus en élevage] should [doivent venir] confirm this point of view. The two processes are distinctly separate in the older females. The long period of arrest [repos] which follows the winter oviposition corresponds to an intermolt of the "anecd sis" type of Carlisle (1954, Knowles and Car.lisle 1956T. It is a question then of a somatique arrest repos] as well as genital because no re eneration, or even [page 4097] any natural or experimental ^by eyestalk ablation) basal growth can take place during this period, just as we have confirmed it. There is a predominance of one process (vitellogenesis) over the other (molting) in females at the end of growth. One witnesses in such a case the disappearance of the genital arrest [repos] phase. This gradation in the appearance of an antagonism between molting and vitellogenesis as a function of age of the individual adult, reflects without any doubt a hormonal control undergoing parallel fluctuations. REFERENCES CARLISLE, D. B J. Mar. Biol. Ass. U.K. 33: DEMEUSY, N Arch. Zool. Exp. Gen. 95(3): DEMEUSY, N C.R. Acad. Sci. Paris. 255: KNOWLES, F.G.W. and CARLISLE, D.B Biol. Rev. Cambridge Phil. Soc. 31: