Baeolidia

Carmona, Leila, Pola, Marta, Gosliner, Terrence M. & Cervera, Juan Lucas, 2014, Review of Baeolidia, the largest genus of Aeolidiidae (Mollusca: Nudibranchia), with the description of five new species, Zootaxa 3802 (4), pp. 477-514 : 505-506

Baeolidia vs Spurilla , Berghia and Limenandra

The aeolidid genera Spurilla , Berghia and Baeolidia were considered to be closely related. Indeed, Odhner (1939) placed Spurilla and Berghia in a new family called Spurillidae , including Baeolidia ten years later and overlooking Limenandra (Odhner in Franc 1968). In the manner of Odhner (in Franc 1968), many authors regarded Limenandra as a junior synonym of Baeolidia . Recently, the molecular phylogeny of Aeolidiidae ( Carmona et al. 2013) rejected the validity of Spurillidae sensu Odhner and the synonymy of Limenandra with Baeolidia .

However, the morphological differences among these genera have not been well defined.

Despite difficulties in finding synapomorphies for some genera within Aeolidiidae , it is possible to differentiate Baeolidia , Spurilla , Berghia and Limenandra based on some features. Regarding body size and morphology, we could divide these genera in two groups: Spurilla and Baeolidia , and Berghia and Limenandra ( Fig. 15 ). The body of the members of the first group is quite broad although species of Baeolidia are usually smaller and wider than species of Spurilla . On the other hand, Berghia and Limenandra species are both slender but Limenandra species are more cylindrical. The rhinophorial ornamentation is also very useful to separate these genera. Although Berghia , Baeolidia and Limenandra were supposed to have papillate rhinophores, we could find consistent differences in the morphology of the papillae. While the rhinophorial papillae of Berghia are usually asymmetrical, being more or less rounded on posterior side, and elongate and perpendicular to rhinophores on their lateral sides (see figure 2 of Carmona et al. 2014b), in Limenandra they are bifurcated (see figure 4 of Carmona et al., 2014c). In Baeolidia , we find more variability in the morphology of these papillae and in the ornamentation of the rhinophores in general ( Fig. 2 ). However, due to the particular rhinophores together with other morphological features, Baeolidia cannot be confounded with Spurilla , Limenandra , and Berghia . Although the arrangement of the cerata is not appropriate to separate genera in Aeolidiidae ( Carmona et al. 2013) , the morphology of the cerata may give some information. Our research suggests that all the Berghia species have cylindrical cerata, with a round apex and uniform diameter throughout most of their length ( Carmona et al. 2014b); the cerata of Limenandra may have papillae over their surface ( Carmona et al. 2014c); Spurilla has cerata that are recurved inwards ( Carmona et al. 2014a), which are also present in some species of Baeolidia . However, the latter usually have leaf-shaped cerata, being broad at their base and narrowing towards the apices.

Regarding the radular morphology ( Fig. 16 ), only Limenandra is easily recognizable from the remaining genera ( Fig. 16 C). The radular teeth of Spurilla , Berghia and Baeolidia are very similar, corresponding with the radular teeth represented in the Figure 17. Although there is quite a lot of intrageneric variability, Figure 16 depicts the archetypical radular teeth for each genus.

In terms of biogeography, so far Berghia is the only genus restricted to one ocean basin (Atlantic- Mediterranean) ( Fig. 18 A) although the occurrence of otherwise Indo-Pacific Baeolidia in the Atlantic Ocean with B. cryoporos would need further comparatives studies ( Fig. 18 B).

In order to facilitate the identification of these four genera, here we present a small key based on external characters and distribution.

1 Rhinophores perfoliate........................................................................... Spurilla - Rhinophores ribbed..................................................................... Baeolidia macleayi - Rhinophores smooth..................................................................... Baeolidia ransoni - Rhinophores papillate................................................................................. 2 2 Notum with colouration pattern of concentric circles................................................. Limenandra - Notum without colouration pattern of concentric circles...................................................... 3 3 Cerata cylindrical.................................................................................... 4 - Cerata non-cylindrical................................................................................. 5 4 Indo-Pacific distribution..................................................................... Baeolidia dela - Atlantic-Mediterranean distribution................................................................. Berghia 5 Remaining species of Baeolidia .

Figures

FIGURE 2. Photographs of the living animals. A, B, Baeolidia moebii: (A) specimen from the Philippines, photo by Terrence M. Gosliner, CASIZ 177602; (B) specimen from Mozambique, photo by Yara Tibiriça, MNCN 15.05 / 63447; (C) Baeolidia macleayi, specimen from Australia, photo by Terrence M. Gosliner, CASIZ 71923; (D-E) Baeolidia japonica: (D) specimen from Japan, photo by Akira Kawahara, CASIZ 1814520; (E) specimen from Marshall Islands, photo by Scott Johnson, CASIZ 186795; (F) Baeolidia ransoni, specimen from the Philippines, photo by Terrence M. Gosliner, CASIZ 186208.

FIGURE 15. Schematic representation of differences of body shape among the genera Spurilla (A), drawing of Ascensión Cespedosa; Berghia (B), drawing of Ascensión Cespedosa; Limenandra (C), taken from Haefelfinger & Stamm (1958); and Baeolidia (D), taken from Rudman (1982).

FIGURE 16. Comparison of the radular morphology among the genera Spurilla (A), Berghia (B), Limenandra (C) and Baeolidia (D).

FIGURE 18. Map of the range of the different species of Spurilla, Berghia, Limenandra, and Baeolidia. A. Berghia and Limenandra. B. Spurilla and Baeolidia. Abbreviation: Isolated records of Baeolidia cryporos (star) and Spurilla braziliana (square).