Aplysia parvula, MORCH, 1863

APLYSIA PARVULA MÖRCH, 1863 View in CoL

( FIGS 4A–B, 6A–B, 7A, 8D–I, 9B)

Aplysia parvula Mörch, 1863 View in CoL (ex. Guilding): 22–23. Type locality: St. Thomas or St. Vincent, US Virgin Islands. Syntype: ‘ West Indies,’ dry shell 8-mm long (NHMD 288589).

? Aplysia parva Eliot, 1899: 513 View in CoL [error for Aplysia parvula Mörch (1863) View in CoL ]. Type locality: Key West , Florida, USA . Type: untraceable.

Additional material examined: St. John , US Virgin Islands, 15 April 2006, one specimen 11 mm preserved length, leg. A. Valdés ( LACM 3642 About LACM , isolate HG11). Guana Island, British Virgin Islands, 4-m depth, 5 July 2000, one specimen 15 mm preserved length, leg. T. Zimmerman & G. Hendler ( LACM FP2.2007 About LACM - 3 About LACM ) .

Description: Morphological characteristics as in Aplysia parvula-atromarginata species complex description. Radular formula? × 6.9.1.9. 6 in an 11 mm preserved length specimen from the US Virgin Islands ( CPIC 00140, isolate HG11) and 29 × 6.10.1.10. 6 in a specimen from the British Virgin Islands ( LACM FP2.2007-3).

Range: North-eastern Atlantic, from the Virgin Islands to northern Brazil.

Remarks

In the present study we examined specimens from the Virgin Islands, Honduras and northern Brazil, which form a well-supported clade and are morphologically and genetically distinct from most other animals examined from the western Atlantic and the Caribbean region ( Fig. 2A). This clade is nested in a larger clade (species complex 1) also including animals from the western Pacific and St. Helena, each forming a well-supported clade. Animals in species complex 1 are morphologically distinct from other A. parvula s.l. species complexes ( Table 3). Although the ABGD analysis did not recover the three clades in species complex 1 as distinct species, haplotype network analyses revealed that they do not share mtDNA haplotypes and their geographic ranges do not overlap ( Fig. 3A). Because of this, the three clades of species complex 1 are here regarded as distinct species.

A review of the literature was conducted to determine the valid name for the north-western Atlantic species, including animals from the Virgin Islands, Honduras and Northern Brazil. Mörch (1863) introduced the name Aplysia parvula (assigned to Guilding), based on specimens collected from the US Virgin Islands. The shell was briefly described as solid, semitranslucent, white, convex, suboval, narrow, with a bent spire. Mörch (1863) also described two specimens: (1) a ‘flaccid’ specimen with a soft, narrow, fusiform body, having short parapodia fused together posteriorly and sub-lateral eyes, posterior to the base of the tentacles (= rhinophores), which are narrow and pointed; (2) a contracted specimen, with hard, rugose and wrinkled skin, shell foramen large and oval, surrounded by a black line as the margin of the parapodia. The characteristics of all of these animals match those of the specimens here examined from the north-western Atlantic included in this section and characterized by having narrow and elongate bodies with the mantle foramen centred and surrounded by a conspicuous black line. We are, therefore, confident that the name A. parvula should be applied to this species.

The original description of Aplysia parvula by Mörch (1863) was based on specimens collected in St. Thomas by Riise and Hornbeck and St. Vincent by Guilding. None of these specimens were found in the NHMD collections (K. Jensen, pers. comm.) and are probably lost. But Mörch (1863) also commented: ‘J’ai vu, en 1854, la coquille de cette espèce sous le nom indiqué, mais non publié à ma connaissance, dans la collection du Musée Britannique.’ This shell is, therefore, another syntype for this species, but is no longer at the NHMUK (A. Salvador, pers. comm.). However, a shell collected by Ørsted in 1849 in ‘Vestindien’ (= West Indies) with the notation ‘ Brit mus ’ written on the label and matching the size of the material described by Mörch, was located at the NHMD collections (K. Jensen, pers. comm.). This shell (NHMD 288589) is possibly a third syntype of A. parvula . The characteristics of this shell, which is elongate, narrow, widest near posterior end, with the posterior left side regularly curved, and the posterior right side conspicuously concave adjacent to protoconch, matches those of shells here regarded as A. parvula , providing additional confidence in the identification of these animals.

Engel (1936) divided Aplysia parvula into six different subspecies and restricted the use of the name A. parvula parvula to Atlantic animals, including records from St. Vincent identified by G. B. Sowerby II (1869) as A. rosea and from Key West, Florida by Eliot (1899) under the name A. parva (error for A. parvula ).