Adaptations morphologiques et biologiques chez un aphroditien interstitiel : pholoe swedmarki sp.n.

The first record of interstitial polychaetous annelids dates no more than forty years. Presently, the total number of interstitial species described is about one hundred. Up to the present, the large group of Aphroditoidea includes no interstitial representative. A few samples made by Pr Swedmark and M. Lasserre in Bermudas enable the discovery of an undescribed species of an interstitial Sigalionidae, Pholoe swedmarki Sp. n., together with two other interstitial species of Pisionidae and Syllidae, new to the western tropical atlantic. From a morphological point of view, the comparison of P. swedmarki sp. n. with the other species of the genus reveals some adaptations to the interstitial life: reduction of the body size, reduction or, at the contrary, enlargement of some appendages of the anterior part, lack of pigmentation. From the biological point of view, P. swedmarki sp. n. displays a remarkable group of characteristics : extreme reduction of the eggs numbers, extension of the reproductive period, pregnancy of the embryos and juveniles up to a very late ontogenetical stage. The hypothesis of an intra-elytral pregnancy, involving an internal fertilization, is discussed. By its morphology and biology, P. swedmarki sp. n. forms the first undeniable example of adaptation to the interstitial life among the Aphroditoidea. [NOT CONTROLLED OCR]