| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
J. Moll. Stud. (1999), 65, 399-409
© The Malacological Society of London
1999
THE GENUS BERTHELLA BLAINVILLE, 1825 (NOTASPIDEA: PLEUROBRANCHIDAE) FROM MAGELLANIC WATERS
Zoologische Staatssammlung München, Münchhausenstr. 21, 81247 München, Germany
Only two notaspidean species are known from cold-temperate waters of South America. Both belong to the pleurobranchid genus Berthella Blainville, 1825, but their taxonomy is confused. This study gives detailed anatomical data on 13 specimens of B. platei Bergh, 1898, recently collected from southern Chile and two specimens from the Beagle Channel area dredged during the International Victor Hensen Magellan Expedition, 1994. The major difference from previous descriptions is the absence of a vaginal duct connecting the seminal receptacles with the female glands. Berthella platei has three genital openings, but not a doridoidean-like triaulic genital arrangement; allosperm must exit from the vagina and enter the nidamental duct by an external groove. The anal opening is situated above the anterior half of the gill basement membrane. In its coloration, porous and notal texture, wider mantle and more anterior anus position B. platei clearly differs from the original description of B. patagonica (Orbigny, 1837) from Argentina. Re-examination of museum material shows that Bergh (1898) erroneously used central Chilean B. platei for his anatomical redescription of B. patagonica. One museum specimen of Berthella patagonica determined by Melvill & Standen from the Falklands is shown to be B. platei. Berthella platei thus ranges from central Chile to southernmost Patagonia and seems separated geographically from B. patagonica which is only known from northern Patagonia. The taxonomy of the latter species still remains unclear and requires reassessment.
(Received 8 July 1998; accepted 19 November 1998)