ÉTUDE MORPHOLOGIQUE D'ACTINOPOSTHIA BEKLEMISCHEVI N. SP. (TURBELLARIA ACOELA)

• Main Author: MAMKAEV, Yu. V.
• Format: Text
• Language: unknown
• Published: Station Biologique de Roscoff (SBR) 1965
• Subjects: Kandalaksha; White Sea
• Online Access: https://dx.doi.org/10.21411/cbm.a.1a85efde; http://application.sb-roscoff.fr/cbm/doi/10.21411/CBM.A.1A85EFDE

The paper contains a description of Actinoposthia beklemischevi n. sp. (Haploposthiidae) found in August 1962 in fine sand (Mo = 0,l-0,2 mm) of the low littoral of Rjazhkov Island (the Gulf of Kandalaksha, White Sea). Spindle- form or cylindrical, colourless body; 0,5-0,7 mm long; syncytial epidermis with mucous glands; well developed frontal glands opening together as a frontal organ nervous system with a ganglious mass around the statocyst, but without distinct ganglions, and with a diffuse plexus; weak cutaneous musculature with an outer layer of circular fibres, inner layer with longitudinal ones; retractors of the fore end well developed; mouth without pharynx in the end of the front third of the body; diffuse lateral testes and ventral ovary with large eggs; male copulatory organ consisting of a voluminous seminal vesicle, of a penis with a stylet formed by 7 long spicules and of a short antrum opening near posterior end of the body; without a female copulatory organ. The division of layers of the body into the epicytium, ectocytium and endocytium is absent. The body consists of a peripheral syncytium representing a united whole and of a extensive cavity with the sexual and cambial cells. The cells of neoblast type are differentiated in the peritheral syncytium and immigrate into the cavity. The morphological analysis of the animals at the various stages of their maturity shows that at first the animals function as males, then become hermaphrodites and at last females, the male copulatory organ being lost.