A new genus and two new species of monstrilloid copepods (Copepoda: Monstrillidae): integrating morphological, molecular phylogenetic, and ecological evidence

Abstract

Caromiobenellagen. nov., represented by males of two new species of monstrilloid copepods (Copepoda: Monstrillidae), Caromiobenella castoreasp. nov. (type species) and C. polluxeasp. nov., is established based on morphological, molecular, and ecological evidence. The genus is characterized by the following new combination of morphological characters: 1) relatively short cephalothorax, 2) inconspicuous oral papilla located anteriorly, 3) last antennular segment modified into serrate ridges on the inner distal margin with a general absence of branched setae, 4) modified spinous element 2d 2 (elongated, biplumose or both), and 5) two pairs of prominent, crater-like, concave depressions on the anterior dorsum of the cephalothorax. These characters are also shared by several other nominal species hitherto assigned to MonstrillaDana, 1849. Molecular analyses of mitochondrial cytochrome c oxidase subunit I (mtCOI) genes and nuclear 28S ribosomal RNA (28S rRNA) genes indicate both that these species are distinct from each other and that, as a group, they are isolated from other known monstrilloid genera. Furthermore, previous studies have shown that one of these species differs from other species of Monstrilla in utilizing a different group of invertebrate hosts, namely gastropods. Based on this integrated data, the new genus comprises six additional species: C. helgolandica (Claus, 1863) comb. nov., C. serricornis (Sars, 1921) comb. nov., C. arctica (Davis & Green, 1974) comb. nov., C. hamatapex (Grygier & Ohtsuka, 1995) comb. nov., C. pygmaea (Suárez-Morales, 2000) comb. nov., and C. patagonica (Suárez-Morales, Ramírez & Derisio, 2008) comb. nov.