A new species of Eurycletodes Sars, 1909 (Copepoda: Harpacticoida: Argestidae) from the southern hemisphere including remarks on the phylogeny of the genus and its subgenera

Abstract

This paper deals with taxonomy and phylogenetics of the genus Eurycletodes Sars, 1909 (Copepoda: Harpacticoida: Argestidae). Samples, collected from the southeast Atlantic on board RV ''Meteor'' during the cruises DIVA-1 (M48/1) and DIVA-2 (M63/2), contain specimens of Eurycletodes. Eurycletodes is characterized as a monophylum by A1 segments III ? IV fused, basal seta of md palp lost, exp of md palp reduced to 1 seta or completely lost. Similarly, the subgenera Eurycletodes (Eurycletodes) and Eurycletodes (Oligocletodes) are characterized as monophyletic by the loss of the inner seta on P1 exp2 (apomorphic to E. (E.)) and the absence of the inner seta on P5 endopodal lobe (apomorphic to E. (O.)). Eurycletodes profundus is renamed as E. (O.) profundus. Eurycletodes ephippiger is the only species of the genus without subgeneric designation. Eurycletodes (O.) diva sp. nov. is described. The new species differs from described species of the genus by a larger body size, P5 endopodal lobe only slightly protruding, last segment of A1 with 2 outer setae, furcal rami elongated between setae VII and IV. The occurrence of 2 specimens of Eurycletodes (O.) diva sp. nov. at 2 sites separated by the Walvis Ridge supports the hypothesis that geographic obstacles do not prevent harpacticoid copepods from spreading in the deep sea.

New species of Eurycletodes Sars, 1909 and Odiliacletodes Soyer, 1964 from the deep Gulf of California (Copepoda, Harpacticoida, Argestidae)

“…George (2011) proved the monophyly of the genus Fultonia , created the subfamily Argestinae Por, 1986 for Fultonia and Argestes , and transferred the genus Parargestes into the latter genus (the latter action was previously suggested by George (2008)). Menzel (2011a) demonstrated the monophyly of the genus Eurycletodes , and of its two subgenera, E. (Eurycletodes) and E. (Oligocletodes), and allocated the enigmatic E. profundus Becker, 1979 into the subgenus E. (Oligocletodes).…”

“…The family Argestidae, composed of 18 genera, is a typical deep-sea taxon (Hicks and Coull 1983, Huys and Conroy-Dalton 1997, George 2004) commonly found in muddy substrates, where it is one of the dominant harpacticoid taxa (Hicks and Coull 1983, George 2004, 2008, Menzel and George 2009, Menzel 2011a). Yet, some species of Argestes Sars, 1910, Argestigens Willey, 1935, Corallicletodes Soyer, 1966, Dizahavia Por, 1979, Eurycletodes , Fultonia Scott, 1902, Mesocletodes , and Parargestes Lang, 1944 have been reported from depths ranging from a few meters (e.g., 4.5 m for Dizahavia halophila Por, 1979, 35 m for Corallicletodes boutieri Soyer, 1966, 20 m for Eurycletodes (Oligocletodes) parasimilis, to less than 200 m (e.g., 91.44 m for Eurycletodes (O.) aculeatus (50 fathoms, not 50 m as in George (2004)), 150 m for Argestigens glacialis Lang, 1936, 180 m for Eurycletodes (O.) denticulatus, 60 m–120 m for Eurycletodes (Eurycletodes) laticauda) (for a complete list of depth range of the species of Argestidae and references see George (2004: 257–259, Table 2); for the genus Mesocletodes see Menzel et al (2011)).…”

“…The dissected parts were mounted on separate slides using lactophenol as mounting medium. Huys and Boxshall (1991) and Menzel (2011a) were followed for general terminology. Abbreviations used in the text:…”

“…For a more complete list of the bathymetric distribution of the family in general, and of Mesocletodes Sars, 1909 in particular, see George (2004) and Menzel and George (2012). Argestidae are common inhabitants of muddy substrates, are one of the dominant groups of meiobenthic deep-sea harpacticoids (Menzel and George 2009), and some of its genera, e.g., Mesocletodes and Eurycletodes Sars, 1909, are the most abundant in deep-sea samples, accounting for more than 25% of total abundance of Argestidae (Menzel 2011a). Due to their high abundance and high species richness, this family might play an important ecological role in the benthic realm and is a good subject for phylogenetic, biogeographical, and chorological investigations on deep-sea harpacticoids and meiofauna due to its worldwide distribution (Menzel and George 2009, George 2011).…”

“…Additionally, from Menzel et al (2011), Menzel and George (2012), and Gómez (2018) it is evident that the same species or closely related species are present in distant localities across vast areas of the world ocean, seemingly “ignoring” geographical barriers. Nevertheless, despite its importance, only few studies are available on the diversity of Argestidae and few of them have tackled the monophyly of the entire family and its constituent genera (e.g., Huys and Conroy-Dalton 1997, George 2004, 2008, 2011, Menzel and George 2009, Corgosinho and Martínez Arbizu 2010, Menzel 2011a, Menzel et al 2011). …”