Ensis Macha Research Articles

TWO NEW SPECIES OF AUSTROBDELLA (HIRUDINIDA: PISCICOLIDAE) FROM CHILE

Austrobdella coliumicus n. sp. is described from Coliumo Bay, Chile. It is characterized by a continuous, external coelomic canal (= marginal lacuna), 5 pairs of testisacs, accessory gland cells, a body not distinctly divided into trachelosome and urosome, 2 pairs of dorsal ocelli on the trachelosome, dorsal and ventral segmental ocelli present on the urosome, green overall pigmentation with transverse brown bands, and the absence of conducting tissue. Austrobdella coliumicus is distinguished from other species of Austrobdella by the presence of 2 pairs of ocelli on the trachelosome and a more cylindrical body. It is unusual that this leech was collected from inside the mantle cavity of the razor clam, Ensis macha. Austrobdella losmoliniensis n. sp. is described from the electric ray, Discopyge tschudii, collected at Los Molinos, Chile. It is characterized by a continuous, external coelomic canal; 5 pairs of testisacs; accessory gland cells; a body distinctly divided into trachelosome and urosome; 1 pair of eyes on the oral sucker; overall black pigmentation with unpigmented areas; and the absence of conducting tissue. Austrobdella losmoliniensis can be distinguished from other species of Austrobdella by the combination of 1 pair of eyes on the oral sucker and black pigmentation.

Morphometry, growth and reproduction of an Atlantic population of the razor clam <i>Ensis macha</i> (Molina, 1782)

Fil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Nacional Patagonico; Argentina. Universidad Nacional de la Patagonia San Juan Bosco; Argentina

Holocene molluscan assemblages in the Magellan region

In the Magellan region, much of the shoreline of the Beagle Channel coast (54°53´S; 67° - 68°W) is bordered by Holocene raised beaches, which contain a large number of molluscs and other shelled taxa. The purpose of this work is to document the presence of various molluscan assemblages deposited with little or no postmortem transportation. An epifaunal Chlamys patagonica palaeocommunity (ca. 8,000 - 7,000 BP) and three infaunal ( Tawera gayi, Ameghinomya antiqua - Hiatella solida and Ameghinomya antiqua - Ensis macha ) palaeocommunities (ca. 4,400 - 4,000 BP) were recognized. All the assemblages studied represent shallow, subtidal, cold-temperate environments. Based on comparisons with modern benthic communities in this region, these associations show that no remarkable ecologic and climatic changes occurred during the period ca. 8,000 - 4,000 BP. Thus, an apparent stability of modern marine communities over a period of several thousand years is suggested.