A new species within the Eurytemora affinis complex (Copepoda: Calanoida) from the Atlantic Coast of USA, with observations on eight morphologically different European populations

Abstract

Eurytemora carolleeae sp. nov. (Crustacea: Copepoda: Calaniformes) is described from the Chesapeake Bay, USA. The new species belongs to the Atlantic clade of the Eurytemora affinis complex outlined by previously published molecular work but poorly characterized morphologically. To discriminate E. carolleeae we compare specimens from the Atlantic USA clade with specimens from the type population of E. affinis (Poppe, 1880) from the Elbe River Estuary (Germany), as well as with eight other European coastal populations. Several important morphological characters clearly separate the North American E. cf. affinis from the European clade that include both sexes: a large outside orientated dent on the mandible, and clearly observable seta segmentation in the caudal rami and swimming legs. Unlike E. affinis, the newly described species possesses wing-like outgrowths on the genital double-somite and a very small spine near the distal seta insertion point in P5 in females. In males, the specific characters include naked dorsal and ventral sides of the caudal rami, and a cylindrical shape of exopod on the left P5, in contrast to a triangular shape of the segment in E. affinis. The new species was also found in Canada (St. Lawrence Estuary) and as an invasive species in the Baltic Sea. Eurytemora carolleeae is possibly widely distributed along the North American Atlantic coast, as well as in inland waters from Great Lakes to Mexico.

Eurytemora carolleeae in the Laurentian Great Lakes revealed by phylogenetic and morphological analysis

“…2c) and cylindrical shape (length/width (L/W) ratio >1.3) of the second segment of the exopod (also known as the basipod) on the left P5 (Fig. 2d) in the male to identify specimens of E. carolleeae as described in Alekseev and Souissi (2011). These characters were either easily seen under a dissecting microscope or when the P5 was placed under a coverslip on a slide and viewed under a compound microscope at higher magnification.…”

“…was first recorded in Lake Ontario at the genus level in 1958 (Anderson and Clayton, 1959) and thereafter reported as Eurytemora affinis Poppe 1880 in all the Great Lakes (Mills et al, 1993). However, the recent description (Alekseev and Souissi, 2011) of Eurytemora carolleeae Alekseev & Souissi, 2011 raised questions about the appropriate identification of the Eurytemora populations in the Great Lakes which the present study seeks to answer.…”

“…Phylogenetic analysis of North American Eurytemora collected from several marine and freshwater sites, including specimens from Lake Michigan and the Detroit River, revealed several distinct clades but did not distinguish any differences in the morphological characters of the specimens associated with the different clades using keys available at that time (Lee and Frost, 2002). Recently, Alekseev and Souissi (2011) identified E. carolleeae as a previously undescribed sibling species to E. affinis native to the North American Atlantic coast, with distinct characters to enable its morphological identification. E. carolleeae was also reported to be a potentially new invasive copepod in the Baltic Sea and European Atlantic coast estuaries first based on COI sequence data and then through taxonomic identification (Alekseev et al, 2009; Sukhikh et al, 2013).…”

“…E. carolleeae was also reported to be a potentially new invasive copepod in the Baltic Sea and European Atlantic coast estuaries first based on COI sequence data and then through taxonomic identification (Alekseev et al, 2009; Sukhikh et al, 2013). E. carolleeae observations in North America were from the Chesapeake Bay and the St. Lawrence estuary with the possibility of distributions in the inland waters of the Great Lakes to Mexico (Alekseev and Souissi, 2011). COI sequence data was used to corroborate the morphological identification of the E. carolleeae invasion of the Baltic Sea and European Atlantic coast estuaries (Sukhikh et al, 2013).…”

“…During an intensive collection of aquatic invertebrates for morphological and molecular identification in Western Lake Erie in 2012-2013, several specimens of Eurytemora were collected. Analysis of these specimens identified them as the recently described species E. carolleeae Alekseev and Souissi 2011. This result led us to assess E. carolleeae 's identifying features, geographic distribution and historical presence in the Laurentian Great Lakes in view of its recent description in 2011.…”