Tritonia odhneri Er. Marcus, 1959

Cetra, Nicolás & Roche, Andrea, 2023, Nudibranchia (Mollusca: Gastropoda) from San Matías Gulf, Northern Argentine Patagonia, Zootaxa 5244 (5), pp. 455-473 : 469-470

Tritonia odhneri Er. Marcus, 1959

( Figures 6F , 7E, 7F )

Material examined. Argentina, San Matías gulf: Caleta Los Hornitos, two specimens, 65 m, BENTOS 2008; one specimen, REDE , 2004; ten specimens, REDE 2005, 133 m; nineteen specimens, REDE 2009 ; Plataforma , one specimen, 9 m, 03/11/2017 (ESCM-Ma-10); sixty specimens, San Matías gulf, ( MACN 21311 ) .

Diagnosis. Length up to 90 mm, elongated body slightly angled laterally, pink or orange coloration. Dorsum covered with irregular spots. Oral tentacles bilobed with several finger-like processes on each lobe. Lamellar rhinophores with lobed folds; abundant dorsolateral gills of different sizes ( Figure 6F ). Radular formula is 58 x 64.1.1.1.1.64 (ESCM-Ma-10). Rachidian teeth broad and tricuspid, all cusps strong. First lateral teeth broad-based with a short cusp. Outer lateral teeth simple, without cusps ( Figures 7E, 7F ). Mandibles are large with denticles on the chewing edges.

Geographic distribution and depth range. From northern Uruguay to Central Chile; San Jorge gulf, Argentina ( García-Matucheski & Muniain 2011); Gulf of Ancud to Coliumo Bay ( Schrödl 2003). Found on rocky bottoms between four and 25 m depth.

Remarks. The morphological characteristics of the specimens examined in this work agree with the original description of Tritonia odhneri Marcus, 1959 . The Chilean and Argentinean populations of warm-adapted T. odhneri may be geographically separated, but still appear morphologically identical ( Schrödl 2009). Moles et al. (2021) consider that Tritonia odhneri is a single species distributed around Cape Horn, Chile or that it is undergoing a process of speciation. This species was previously confused with the similarly colored Marionia cucullata (Couthouy, 1852) found in northern Argentina and Brazil but molecular analysis confirmed that they are distinct ( Moles et al. 2021). Although M. cucullata has been mentioned by Scarabino (1977) in the SMG, it has not been collected again and no material of the species belonging to the gulf has been found in the museum collections consulted. A comparative revision of South Atlantic Tritonia species is needed.

Figures

FIGURE 6. (A) Berghia rissodominguezi, (B) egg mass of Berghia rissodominguezi, (C) Doto uva, (D) egg mass of Doto uva, (E) Coryphella cf. verta, (F) Tritonia odhneri.

FIGURE 7. Scanning electron micrographs. (A) Berghia rissodominguezi (ESCM-Ma-37): radular teeth; (B) Coryphella cf. verta (ESCM-Ma-82): radular teeth; (C-D) Doto uva (MLP-Ma 14657): (C) radular teeth, (D) detail of the central teeth; (E-F) Tritonia odhneri (ESCM-Ma-10): (E) radular teeth, (F) detail of the central and lateral teeth.