Abstract
Berthella currently comprises five valid species recorded from the western Atlantic, of which only Berthella agassizii (MacFarland, 1909) and Berthella stellata (Risso, 1826) have been recorded from Brazil. Two species of Berthellina occur in Brazil: Berthellina quadridens (Morch, 1963) and Berthellina circularis (Morch, 1863); however, based on a literature review and the anatomical study presented here, we only recognize B. circularis as occurring in the country. This study gives a detailed re-description of B. agassizii, B. stellata and B. circularis based on material from Brazil, and adds two new species to the genus, from the Brazilian coast, Berthella punctata sp. nov. and Berthellina ignis sp. nov. Berthellina circularis and B. quadridens are considered distinct species based on the denticulation of the radular teeth. B. quadridens presents the majority of teeth with two denticles, rarely three-four denticles, while in B. circularis from Brazil the radular teeth are highly denticulate with up to 17 denticles. Berthella and Berthellina do not form a monophyletic group, and cluster in a large polytomy within Pleurobranchidae. A detailed anatomical study is performed to improve the understanding of the evolutionary history of Pleurobranchidae. The comparison with available data on the odontophoric muscles of Pleurobranchoidea shows that Berthella and Berthellina present a pair of the muscle m10v that connects the mj with the ventral portion of the m5, while in Pleurobranchus and Pleurobranchaea the m10v connects the mj with the ventral portion of the m4; Berthella and Berthellina do not present the muscle m10d, which is present in Pleurobranchus and Pleurobranchaea. Based on these characters, Berthella seems to be more closely related to Berthellina than to Pleurobranchus.
Highlights
Members of Pleurobranchidae are generally characterized by body oval to elongated with centralized rhinophores, internalized plate-like shell, gill exposed on the right side of the body and veil trapezoidal
Berthella resembles Berthellina in the external morphology, but in characters of the radula, jaws and reproductive system, it is more similar to Pleurobranchus (WILLAN 1983)
Berthella currently comprises five valid species recorded from the western Atlantic, of which only Berthella agassizii (MacFarland, 1909) and Berthella stellata are recorded from Brazil (GARCÍA et al 2008, RIOS 2009)
Summary
Descriptions of the external morphology were based on living and preserved specimens. Very similar to B. agassizii as described above, with the following exceptions: Each jaw plate showing alternate rows formed by elongated elements without denticles with slight cruciform lateral expansion (18 elements transversal, in preserved specimen measuring 8 mm in length) Ducts of salivary glands entering pharynx musculature laterally to esophagus, opening into base of pharyngeal cavity between radula and jaw plates (Fig. 50); convoluted; without visible ampulla. (53) cerebro-pleural complex; (54-55) transverse cut of mantle; (55) linear spicule, black arrow indicates spicule; (56) radula and jaw plates; (57) detail of jaw elements, white arrow indicates small reflective circlet; (58-60) region near penis; (60) detail of penial papillae. Is very similar to Pleurobranchus caledonicus Risbec, 1928 from New Caledonia, which probably belongs to Berthella; both species have a brownish mantle, with a dark spot in the middle of the mantle surrounded by a light ring Berthella pellucidus: Thompson, 1970: 188, fig
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