Rostanga pulchra MacFarland, 1905

Cetra, Nicolás & Roche, Andrea, 2023, Nudibranchia (Mollusca: Gastropoda) from San Matías Gulf, Northern Argentine Patagonia, Zootaxa 5244 (5), pp. 455-473 : 458

Rostanga pulchra MacFarland, 1905

( Figures 2B , 3B, 3C )

Material examined. Argentina, San Matías gulf, Caleta Los Hornitos, REDE 2009 , one specimen, 110m (MLP-Ma 14654) .

Description. Length up to 25 mm, body oval, uniform reddish orange, densely covered with thin caryophyllidia. Rhinophores with approximately ten vertical lamellae and apical knob. Oral tentacles short and conical.Ten unipinnate gill leaves around the anal papilla ( Figure 2B ). Foot broad and bilabiate. Radular formula is 60 x 30.44.0.44.30. (MLP-Ma 14654). Innermost teeth small with up to eight pointed denticles on the inner edge. Lateral teeth increase in size, becoming longer and thinner. Marginal teeth very thin and elongated, divided in the form of fine threads in the upper third ( Figures 3B, 3C ).

Geographic distribution and depth range. Recorded from Eastern Pacific and Southern South America. Alaska to Mexico ( Schrödl 2003), central Chile ( Schrödl 1996, 1997a, 1999) and Bahía Camarones, Argentina ( Schrödl 2003). Found on rocky bottoms between four and 110 m depth.

Remarks. Rostanga pulchra is clearly distinguishable from other nudibranchs in this study by the orange color of the mantle and the lamellate rhinophores. The material studied matches the original description of R. pulchra from Monterey Bay, California ( MacFarland 1905). R. pulchra has a disjunct geographic distribution in America, with a great geographic gap between north and south. Marcus & Marcus (1969) extended its distribution from Chile to Argentina, with one specimen collected in Camarones bay (44°45’57´´S; 65°34’47´´W) at 102 m depth. Schrödl (1996, 1997a) confirmed the presence of R. pulchra in the southern hemisphere. R. pulchra is very similar to its congener Rostanga byga Marcus, 1958 recorded from northern Brazil to Patagonia. According to Muniain & Valdés (2000) and Schrödl & Grau (2006) the differences between R. pulchra and R. byga are the presence of white dots on the central notum in R. byga and the double number of lamellae in the rhinophores.

Figures

FIGURE 2. (A) Doris fontainii, (B) Rostanga pulchra, (C) Diaulula punctuolata, (D) egg mass of Diaulula punctuolata, (E) Gargamella immaculata, (F) egg mass of Gargamella immaculata, (G) Geitodoris patagonica, (H) egg mass of Geitodoris patagonica.

FIGURE 3. Scanning electron micrographs. (A) Doris fontainii (MLP-MA 14653): radular teeth; (B-C) Rostanga pulchra (MLP-Ma 14654): (B) radular teeth (C) detail of the lateral teeth; (D) Diaulula punctuolata (MLP-Ma 14655): radular teeth; (E-F) Geitodoris patagonica (MLP-Ma 14656): (E) lateral and marginal teeth (F) detail of the marginal teeth.