Myja Bergh, 1896

Martynov, Alexander, Mehrotra, Rahul, Chavanich, Suchana, Nakano, Rie, Kashio, Sho, Lundin, Kennet, Picton, Bernard & Korshunova, Tatiana, 2019, The extraordinary genus Myja is not a tergipedid, but related to the Facelinidae s. str. with the addition of two new species from Japan (Mollusca, Nudibranchia), ZooKeys 818, pp. 89-116 : 89

Myja Bergh, 1896

Type species.

Myja longicornis Bergh, 1896.

Diagnosis.

One pair of anterior rows of cerata, posterior cerata in rows, few (1-3) peculiar club-shaped cerata per row, anus acleioproctic, rhinophores smooth, oral tentacles present, no anterior foot corners, cnidosacs present, pharynx moderately broad, jaws with wing-shaped anterior expansion, smooth masticatory edges, radula very small, uniserial, radular teeth very narrow, triangular with strong cusp, lateral denticles small, penis unarmed, supplementary glands absent.

Species included.

Myja cf. longicornis (Thailand), Myja karin sp. n. (Japan), Myja hyotan sp. n. (Japan).

Remarks.

All Myja specimens studied here clustered together (PP = 1, BS = 100) in a maximum-supported clade. This agrees well with the results of the morphological analysis. Inside the Myja clade clustered maximum-supported (PP = 1, BS = 100) Myja cf. longicornis and M. karin sp. n. clades and M. hyotan sp. n. clade. The ABGD analysis of the 16S data set run with two different models revealed three potential species: Myja cf. longicornis , M. karin sp. n., and M. hyotan sp. n. Additionally, molecular phylogenetic analysis revealed that Cratena peregrina (Gmelin, 1791) and Cratena minor Padula, Araújo, Matthews-Cascon & Schrödl, 2014 specimens clustered together on two maximum-supported (PP = 1, BS = 100) clades, which are not sister to each other. Furthermore, the Cratena minor clade is sister to the Myja clade but without high node support (PP = 1, BS = 68). It is assumed that further analysis with the addition of a larger number of species and genes will clarify the phylogenetic relationship in Cratena species and may reveal hidden paraphyly of the genus Cratena . It is important to note that in Padula et al. (2014), it is shown that the Sakuraeolis enosimensis clade was wedged between the C. minor and C. peregrina clades in the Maximum Likelihood phylogenetic tree based on H3 sequences. The morphological and molecular differences for the known Myja species are included below.