Mollusca Research

New species of flamboyant shelled sea slugs

A collaborative international endeavour led to the description of beautiful species of tropical shelled sea slugs

Micromelo spp.
A–C. Micromelo undatus, (A) specimen from Brazil (ZMBN 103322), (B) specimen from Brazil (ZMBN 88216, isolate KF117), (C) specimen from Cape Verde (ZMBN 94146, isolate KF121). D. Micromelo guamensis, specimen from Panglao, the Philippines (MNHN 42238).
Manuel Malaquias
Micromelo spp.
E–G. Micromelo scriptus, (E) specimen from Taiwan (ZMBN 116943, isolate KF130), (F) specimen from Mozambique (ZMBN 94236, isolate KF124), (G) Specimen from Maui, Hawaiian Is. (CPIC 329, isolate KF2). H–J. Micromelo barbarae sp. nov., (H) specimen from Japan (ZMBN 106876, isolate KF128, paratype), (I) specimen from the Philippines (CASIZ 208475 A, isolate KF79, paratype), (J) specimen from the Philippines (holotype, NMP – 041297).
Manuel Malaquias

Main content

Molecular and morphological analyses reveal pseudocryptic diversity in Micromelo undatus (Bruguiere, 1792) (Gastropoda: Heterobranchia: Aplustridae)


This study resulted from the joint effort of researchers from the California State Polytechnic University, the California Academy of Sciences, the Bavarian State Collection of Zoology in Munich, and the Department of Natural History, University Museum of Bergen.


The genus Micromelo (family Aplustridae) occurs in almost all tropical and subtropical waters across the globe, with the exception of the Eastern Pacific. Most authors consider Micromelo undatus (Bruguiere, 1792) as the only valid species in this genus. This study examines populations of specimens identified as M. undatus across its geographic range, using morphological and genetic data from two  mitochondrial genes (16S and CO1) and one nuclear gene (Histone H3). The results reveal that M. undatus is a complex of four species with consistent genetic and anatomical differences. A literature review and evaluation of type material indicates that available names exist for three of the four species. Micromelo guamensis, M. undatus and M. scriptus are resurrected for species found in the Western Pacific, the Atlantic Ocean, and widespread in the Indo-Pacific, respectively. A new name is introduced for another species found in the Western Pacific, namely Micromelo barbarae sp. nov. and a neotype is designated for the type species of the genus M. undatus.