Aplysia undefined-1

Golestani, Haleh, Crocetta, Fabio, Padula, Vinicius, Camacho-García, Yolanda, Langeneck, Joachim, Poursanidis, Dimitris, Pola, Marta, Yokeş, M. Baki, Cervera, Juan Lucas, Jung, Dae-Wui, Gosliner, Terrence M., Araya, Juan Francisco, Hooker, Yuri, Schrödl, Michael & Valdés, Ángel, 2019, The little Aplysia coming of age: from one species to a complex of species complexes in Aplysia parvula (Mollusca: Gastropoda: Heterobranchia), Zoological Journal of the Linnean Society 187, pp. 279-330 : 300-301

APLYSIA SP. 1

( FIG. 6D–F)

Description: External morphological characteristics as in Aplysia parvula – atromarginata species complex description. Internal anatomy not examined.

Range: Appears to be endemic to St. Helena, south Atlantic Ocean.

Remarks: Specimens from St. Helena sequenced for this study were found to form a monophyletic group and were recovered as a distinct species. However, due to the lack of specimens for morphological examination, this species is not formally named here.

SPECIES COMPLEX 2

( FIGS 10–13)

Diagnosis

External anatomy: Animal slender, elongate, much wider in visceral region, narrowing abruptly towards head and tail ( Fig. 10); visceral hump small, rounded, well differentiated from rest of body, occupying less than 1/5 of body length; mantle foramen large, oval, on posterior left side of visceral hump, not elevated; parapodia broad, fused posteriorly, typically joined high up, forming several shallow folds; rhinophores and oral tentacles elongate, enrolled, with conspicuous flat posterior projection in oral tentacles; siphon narrow, elongate, typically protruding above parapodia. Colour yellowish to brownish red, completely covered with white dots, often aggregated in dense concentrations; parapodia edged in white, with submarginal black band, interrupted with white spots; rhinophores and oral tentacles with conspicuously dark tips; mantle foramen with dark inner edge interrupted with white patches ( Fig. 10).

Internal anatomy: Shell elongated, narrow, widest near posterior end; posterior left side regularly curved, posterior right side slightly concave adjacent to protoconch ( Fig. 11); rachidian tooth with robust, broad, triangular central cusp bearing multiple sharp denticles, 2–4 lateral cusps on each side of central cusp, lacking denticles ( Figs. 12A, 12D, 12G); each lateral tooth with central cusp denticulated on both sides, larger tooth or secondary cusp near base; up to four simple outer teeth ( Figs. 12B, 12E, 12H); jaw with cylindrical, elongated elements with no cusps at tips ( Figs. 12G, 12F, 12I). Penis elongate with two retractor muscles, and two papillae on the tip ( Fig. 13).

Remarks

Species in this complex are clearly different morphologically from other species of Aplysia parvula s.l. The most obvious external differences are the elongate, slender body, with a small, rounded visceral hump that is well-differentiated from the rest of the body, the presence of a dark parapodial margin interrupted with white spots and a large mantle foramen on the posterior left side of the visceral hump. Internally, species in this complex are characterized by having a penis with two papillae at the tip.

Molecular data recovered two well-supported clades in this species complex: one including specimens collected in the Atlantic Ocean and adjacent Indian Ocean ( Madagascar and Mozambique) and the other including specimens from the tropical western Pacific Ocean (Okinawa and Vanuatu). We have no observed consistent morphological differences between these two clades.