Aspectos Reproductivos del Nemertino Malacobdella arrokeana endocomensal de Panopea abbreviata (Bivalvia, Hiatellidae) en el Golfo San José (Chubut, Argentina).

ESO VALERIA, BIGATTI GREGORIO, BAZTERRICA MARÍA C., CIOCCO NÉSTOR F. & PENCHASZADEH PABLO E.

Mar del Plata, Argentina

Congreso; V Jornadas Nacionales de Ciencias del Mar; 2003

Abstract. The annual gonadic cycle of the entocommensal nemertean Malacobdella arrokeana inhabiting Panopea abbreviata from San Jose gulf, Patagonia, Argentina, and the nemertean-host relationship were investigated. The nemertean population showed a sex ratio of 1:0.64, with females predominating. The number of M. arrokeana per clam ranged between 1 and 62 individuals, and showed monthly variations. Different stages of gonadic development were observed in the same nemertean individuals. Even when sexually mature individuals of both sexes were present all year round, spawning peaks took place during late summer and early spring, in coincidence with increasing water temperature, larger photoperiods and phytoplankton blooms. On the other hand, nemertean length decreased significantly with increasing clam length, suggesting a relationship between the number of entocommensals and the available space inside the clam. However, no significant correlation was found between the number of nemerteans per clam and P. abbreviata length. Our results suggest that M. arrokeana has no cannibalistic habits and confirm its entocommensal behavior.