Revision of the genus Evansula T. Scott, 1906 (Copepoda, Harpacticoida, Cylindropsyllidae) with a description of three new species

Abstract

A revision of the marine mesopsammic genus Evansula T. Scott (Copepoda, Harpacticoida, Cylindropsyllidae) is presented. Analysis of type and newly collected material, using both light and scanning electron microscopy, revealed that the genus consists of a complex of morphologically similar species, which frequently occur sympatrically. Redescriptions are provided for E. incerta T. Scott (type), E. pygmaea T. Scott and E. arenicola Nicholls, and published records are reviewed. Three new species, previously confused with either E. incerta ( E. polaris sp. nov. , E. spinosa sp. nov. ) or E. pygmaea ( E. cumbraensis sp. nov. ) are described from north-western European waters. Scanning electron microscopy revealed that the reported plumosity of certain setae on the P5 is, in reality, a biofouling artefact caused by site-specific, epibiotic, filamentous bacteria. Evansula is the only cylindropsyllid genus that has retained inner setae on the P4 endopod and exhibits the ancestral complement of seven setae on the male P5. Its early divergence within the family is further evidenced by the absence of two sexually dimorphic structures in the male, the apomorphic presence of which supports the monophyly of the residual genera: (1) the spinous process on the P2 basis, and (2) the secretory pore on the anterior surface of the male P3 exp-2. The Cylindropsyllidae has recently been relegated to subfamilial status, and as a result was subsumed within the Canthocamptidae. The evidence employed to justify this course of action is critically evaluated and proven essentially unsound. Consequently, the Cylindropsyllidae is reinstated here as a valid taxon.

Taxonomic review of the genus Stenocaris Sars (Copepoda, Harpacticoida, Cylindropsyllidae), with (re)descriptions of two Stenocaris species from the Far East

“…This taxonomic confusion might have been resulted from the long-accepted simple criteria used to distinguish cylindropsyllid genera, such as segmentation of the thoracic legs and the degree of development of the maxilliped. However, recent researches have clarified the characteristics of the body and caudal rami, the nature of the mouth appendages, the sexually dimorphic structures of P2–P3, and the setation pattern of the swimming legs as well as P5 in both sexes to (re-)define the general classification of the family Cylindropsyllidae ( Huys & Conroy-Dalton, 1993 ; Moura & Pottek, 1998 ; Huys & Conroy-Dalton, 2006a , 2006b ; Kornev & Chertoprud, 2008 ; Richter, 2019 ). In addition, Richter (2019) recognized that any apomorphies for the genus have not been defined.…”

“…Abbreviations used in the text, tables and figure captions are as follows: acro, acrothek composed of one aesthetasc and two setae (fused basally); ae, aesthetasc; apo, apophysis; EXP(ENP)1(2, 3), first (second, third) exopodal (endopodal) segment; P1–P6, first to sixth thoracic leg. We also followed Huys & Conroy-Dalton’s (2006b) designations for armature elements on the fifth leg (innermost = seta a , second innermost = seta b … outermost = seta h in females and seta f in males) to compare their positions and modifications in other genera or species.…”

“…Since Lang’s (1948) familial concept of the Cylindropsyllidae (a subfamily at that time), the genus Stenocaris Sars, 1909, had until the 1970s served as a repository to accommodate more advanced cylindropsyllid harpacticoids ( i.e ., retaining a slender-type maxilliped with a geniculate claw, a non-prehensile endopod of the first leg, the second and third legs with reduced endopod segmentation), without any morphologic or phylogenetic inference. Therefore, the monophyly of this genus is questionable ( Huys, 1988 ; Huys & Conroy-Dalton, 1993 , 2006b ) and apomorphies have not been defined ( Richter, 2019 ). These taxonomical problems were partially resolved by the following contributions.…”

The genus Cletocamptus (Harpacticoida, Canthocamptidae): a reappraisal, with proposal of a new subfamily, a new genus, and a new species

“…With 864 species distributed in 58 valid genera (WoRMS 2021), the Canthocamptidae is currently one of the most species-rich families within Harpacticoida. The Canthocamptidae is not a natural assemblage and could be divided into several families (Huys et al 1996;Gómez Noguera and Fiers 1997;Boxshall and Halsey 2004;Huys and Conroy-Dalton 2006). The taxonomy and the phylogenetic relationships are immersed in chaos, and the different canthocamptid subfamilies are seldom mentioned in the recent literature probably because the genera described more recently are difficult to attribute to any of the existing subfamilies, and if forced, the subfamilial diagnoses have often to be widened more to include, probably unrelated taxa, exacerbating the already complicated systematics of the group.…”

Ameiridae Boeck and Argestidae Por revisited, with establishment of Parameiropsidae, a new family of Harpacticoida (Crustacea, Copepoda) from deep-sea sediments

“…Fiers 1990;Huys 1990; Communicated by Peter Funch. Moura 1994; Huys and Lee 1998;Willen 2000;Lee and Huys 2002;Seifried 2003;Seifried and Schminke 2003;Huys and Conroy-Dalton 2006;Huys et al 2009). Recently, diVerent researchers have disagreed about the total number of families within this order.…”