Patterns of Cryptic Diversity and Phylogeography in Four Freshwater Copepod Crustaceans in European Lakes

Comparative phylogeography has become a powerful approach in exploring hidden or cryptic diversity within widespread species and understanding how historical and biogeographical factors shape the modern patterns of their distribution. Most comparative phylogeographic studies so far focus on terrestrial and vertebrate taxa, while aquatic invertebrates (and especially freshwater invertebrates) remain unstudied. In this article, we explore and compare the patterns of molecular diversity and phylogeographic structure of four widespread freshwater copepod crustaceans in European water bodies: the harpacticoids Attheyella crassa, Canthocamptus staphylinus and Nitokra hibernica, and the cyclopoid Eucyclops serrulatus, using sequence data from mtDNA COI and nuclear ITS/18S rRNA genes. The three taxa A. crassa, C. staphylinus and E. serrulatus each consist of deeply diverged clusters and are deemed to represent complexes of species with largely (but not completely) non-overlapping distributions, while in N. hibernica only little differentiation was found, which may however reflect the geographically more restricted sampling. However, the geographical patterns of subdivision differ. The divisions in A. crassa and E. serrulatus follow an east–west pattern in Northern Europe whereas that in C. staphylinus has more of a north–south pattern, with a distinct Fennoscandian clade. The deep mitochondrial splits among populations of A. crassa, C. staphylinus and E. serrulatus (model-corrected distances 26–36%) suggest that divergence of the lineages predate the Pleistocene glaciations. This study provides an insight into cryptic diversity and biogeographic distribution of freshwater copepods.

Taxonomic status of Macaronesian Eucyclops agiloides azorensis (Arthropoda: Crustacea: Copepoda) revisited – morphology suggests a Palearctic origin

Macaronesia, with the exception of the Azores, is one of the few Palearctic provinces where basic taxonomic information on the freshwater copepods is still lacking. We redescribed Eucyclops azorensis, a cyclopid crustacean so far known only in the Azores, and report the occurrence of this species in Algeria and Madeira Island. Eucyclops azorensis was formerly considered to be a subspecies of E. agiloides (East Africa); therefore, the latter species is redescribed here as well based on type and non-type material. Morphological comparisons between E. azorensis, E. agiloides and other taxa (E. serrulatus and E. roseus), assumed to be closely related to our target species, support a closer relationship between E. azorensis and E. serrulatus (Palearctic) than between E. azorensis and E. agiloides (Afrotropical). The slight differences between E. azorensis and E. serrulatus in the surface ornamentation of the antennal coxobasis and intercoxal sclerites of legs 1 and 4 suggest a relatively young separation of these lineages. Eucyclops agiloides is morphologically close to E. roseus (temperate and subtropical Asia, southeastern Europe, East Africa). The numerous and clear-cut differences indicate a species rather than subspecies-level differentiation between E. agiloides and E. roseus, unlike what was formerly proposed in the taxonomic literature.

Late postnaupliar development of the freshwater copepods Lovenula falicifera and Metadiaptomus colonialis (Calanoida: Diaptomidae) from South Africa

The life cycle of calanoid copepods consists of eggs hatching into nauplii (6 stages) which then moult into copepodids (5 stages), followed by the final moult into the adult female and male. The family Diaptomidae contains two subfamilies, Diaptominae and Paradiaptominae, with paradiaptomids almost exclusively consisting of African taxa. The copepodid stages III, IV and V were described for some freshwater diaptomine genera (i.e., Eudiaptomus Kiefer, 1932, Aglaodiaptomus Light, 1938, Skistodiaptomus Light, 1939, Leptodiaptomus Light, 1938, Megadiaptomus Kiefer, 1936 and Diaptomus Westwood, 1836). Copepods collected from Turfloop Dam, South Africa, with a plankton net were fixed and preserved in 70% ethanol. Calanoid copepods were studied under stereo- and light microscopes, using the wooden slide technique and features drawn. Examined specimens were identified as the copepodid stages of two African species, Lovenula falcifera (Lovén, 1845) and Metadiaptomus colonialis (van Douwe, 1914). Copepodids of the two species can be distinguished by their body size and the structure and size of the maxillipeds. The description and illustrations of three postnaupliar stages (CoIII, CoIV and CoV) are provided for both species. The identification of different stages is based on the number of urosomites, antennule development, the segmentation of legs 1–4, and the development of the fifth leg. These copepodids are compared with those of other described diaptomid genera.