Hypselodoris melanesica Gosliner & R. F. Johnson, 2018

Description

Living animals are moderately sized, reaching 30 mm in length. The body is translucent purple with a thin white band encircling the margin of the notum and foot. Five unipinnate gill branches are present on the notum (one large specimen had seven). Gill branches are light orange with a darker orange common base, and the base of the gill pocket is deep violet. Rhinophore bulbs are bright orange with a redder apex; the bulb has about 25 densely packed lamellae, and the base of the rhinophore sheath is deep violet to purple. Subcutaneous mantle glands are entirely absent.

Distribution

Known only from Papua New Guinea and the Solomon Islands.

Etymology

Named for Melanesia, the region to which this species is geographically restricted.

Remarks

In the molecular phylogeny Hypselodoris melanesica is always sister to Hypselodoris bullockii, but ABGD analysis groups it with H. bullockii; uncorrected p-distances for COI between these two species range between 2.0 and 2.6%, near the boundary of intra- and interspecific variation. H. bullockii is generally light pink to deep purple and any darker pigment at the base of the gill and rhinophores is diffuse and lacks distinct edges, whereas H. melanesica is always light purple and has well-defined narrow bands of darker pigment at the base of the rhinophores and gill, with a break in the band on the posterior side of the rhinophore base. Internally, H. melanesica has fewer radular teeth, shorter primary cusps, a shorter penial bulb, a longer ejaculatory duct and a longer vaginal duct than H. bullockii. The type locality is Southern Sek Island, Madang Lagoon, Papua New Guinea, 8 m depth.

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References

• Hypselodoris sp. 16, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• Hypselodoris melanesica, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• Hypselodoris melanesica sp. nov., Epstein H.E., Hallas J.M., Johnson R.F., Lopez A. & Gosliner T.M. (2019). Reading between the lines: revealing cryptic species diversity and colour patterns in Hypselodoris nudibranchs (Mollusca: Heterobranchia: Chromodorididae). Zoological Journal of the Linnean Society. 186(1): 116-189. https://doi.org/10.1093/zoolinnean/zly048