Description of four new species of Mesocletodes Sars, 1909 (Copepoda, Harpacticoida, Argestidae) and redescription of Mesocletodes robustus Por, 1965 from the South Atlantic, including remarks on the Mesocletodes abyssicola-group

Abstract

The present paper focuses on taxonomic and phylogenetic investigations of the family Argestidae Por, 1986. Samples, collected during the cruise DIVA 1 (M48/1) to the Angola Basin on board of RV “Meteor” (2000), contain amongst others several specimens belonging to the Mesocletodes abyssicola-group (Harpacticoida, Argestidae) which includes ten species so far. This paper deals with the description of Mesocletodes angolaensis sp. nov., M. bicornis sp. nov., M. dorsiprocessus sp. nov. and M. meteorensis sp. nov. as well as the redescription of Mesocletodes robustus Por, 1965. The four new species bear cuticular processes on the cephalothorax and/or telson, as is characteristic for the Mesocletodes abyssicola-group. These processes are supposed to be of high phylogenetic value, since they do not occur in any other taxon within the Argestidae, and are always inserted at the same position. Therefore, the Mesocletodes abyssicola-group is herein considered monophyletic.

Copepodid and adult Argestidae Por, 1986 (Copepoda: Harpacticoida) in the southeastern Atlantic deep sea: diversity and community structure at the species level

“…Whereas it is easy to connect males and females for most genera of Argestidae, extreme sexual dimorphism makes it very difficult or nearly impossible for species of Mesocletodes (Por 1986a;Menzel and George 2009), which is the most abundant genus of Argestidae in deepsea samples (cf. Coull 1972;Menzel per sobs).…”

“…17, Argestidae sp. 23, Eurycletodes (E.) EURY 6, Mesocletodes angolaensis Menzel and George, 2009, Mesocletodes sp. 7, Mesocletodes sp.…”

“…20, Table 2). Therefore, they covered latitudes from the northernmost Guinea Basin (equator) to the Menzel and George, 2009). Many species of Argestidae that are absent from the NAB but present in one of the other investigated stations were found in the southern Angola Basin (Menzel et al 2011;Menzel 2011a, b).…”

“…Moreover, some studies showed that species present in the Angola Basin are also present in other oceanic regions such as the South and North Atlantic, Southern Ocean, Pacific Ocean, the Indian Ocean, and the eastern Mediterranean Sea. This applies to both meiofauna such as Copepoda Harpacticoida (Gheerardyn and VeitKöhler 2009;Menzel et al 2011;Menzel 2011a;Menzel and George 2009) and Nematoda (Miljutin et al 2010), and macrofauna such as Isopoda (Brandt et al 2005;Brökeland 2010;Brökeland et al 2010;Brökeland and Wägele 2004) and Polychaeta (Fiege et al 2010). Therefore, it is expected that the distribution range of several Argestidae includes the NAB as well.…”

“…Their high abundance, high species richness, and worldwide distribution make them eminently suitable for phylogenetic and biogeographical investigations at species level. Therefore, Argestidae may constitute an appropriate representative group even for generalized meiobenthic deep-sea research (Menzel and George 2009). …”