Fig 1.
Phylogenetic tree of aeolidacean nudibranchs based on concatenated molecular data (COI + 16S + 28S + H3) represented by Bayesian Inference (BI).
The aeolidacean families are highlighted. The brackish-water living, but non-related taxa Bohuslania gen. n. and Tenellia are indicated as “BW”. Numbers above branches represent posterior probabilities from Bayesian Inference. Numbers below branches indicate bootstrap values for Maximum Likelihood.
Fig 2.
Morphology of Bohuslania matsmichaeli gen. n., sp. n.
A, Dorsal appearance of the holotype; B. Ventral appearance holotype; C. Living specimen and its egg mass in situ; D, Pharynx and jaws (Paratype GNM 9024); E, Masticatory processes of jaws with denticles; F, Radula, central teeth (Holotype); G, Reproductive system of the holotype (non-destructive SEM with “nano-coating”); H, copulative organ (same technique as in G); I, Scheme of reproductive system. Scales: 10 μm (F, G, H), 500 μm (I). Abbreviations: a–ampulla, fgm–female gland mass, fgo–female opening, hd–hermaphroditic duct, p–penis, pg–penial gland, pr–prostate, ps–penial sheath, rsp–proximal receptaculum seminis, vd–vas deferens, v–vagina.
Fig 3.
The haplotype network based on cytochrome c oxidase subunit I molecular data showing genetic mutations occurring within family Cuthonidae and brackish-waters aeolidacean nudibranch Tenellia adspersa of the family Trinchesiidae.
Fig 4.
Ontogenetic and phylogenetic framework for evidence of parallel paedomorphosis driven-evolution within the brackish-water nudibranchs of the families Cuthonidae (Bohuslania gen. n.) and Trinchesiidae (Tenellia adspersa).
Adults (14 and 20 mm) of marine species Cuthona nana and C. divae respectively, considerably differ from adults of brackish-water Bohuslania matsmichaeli gen. n., sp. n., whereas juveniles of C. nana (6 mm length) and C. divae (5 mm length) are similar to the adult of B. matsmichaeli (10 mm length) by presence of only 3–4 anterior ceratal rows and absence of numerous pre-rhinophoral digestive gland branches. Because Bohuslania, compared to Cuthona, does not develop further to reach the stage with numerous anterior ceratal rows, this stage is considered missing in Bohuslania (indicated by “X” on the scheme) due to heterochronic developmental shifts leading to the adult paedomorphic external morphology. The brackish-water species Tenellia adspersa (adult, 6 mm length) demonstrates a striking paedomorphic feature in presence of secondary oral veil. However, it belongs to the family Trinchesiidae which is more distantly related to the family Cuthonidae according to the present molecular phylogenetic analysis (Figs 1 and 2). Since the appearance of the small oral veil occurs in earlier ontogeny of aeolidacean nudibranchs and predates formation of oral tentacles and numerous anterior ceratal rows, the two stages of development of external features are considered as missing in Tenellia adspersa (indicated by two “X” on the scheme).
Table 1.
List of samples, localities, and voucher references.
Table 2.
Primers.