Eurycercus cf. nigracanthus

Bekker, Eugeniya I. & Kotov, Alexey A., 2016, A revision of the subgenus Eurycercus (Teretifrons) Frey, 1975 (Crustacea: Cladocera) in the Holarctic with description of a new species from Russian Arctic, Zootaxa 4147 (4), pp. 351-376 : 360

Eurycercus cf. nigracanthus from Churchil

( Figs 6–8 )

Material examined. All from Manitoba, Canada: 8 parthenogenetic ♀♀ from Pond X, Churchill, coll. in 15.08.2006, AAK M-2773. 2 parthenogenetic ♀♀ from TP-1, tundra pond, Churchill, coll. in 0 8.2006, AAK M- 2772. 2 parthenogenetic ♀♀ from TP-3, tundra pond, Churchill, coll. in 0 8.2006, AAK M-2771.

Comments. Using genetic barcoding, Jeffrey et al. (2011) detected two species of Eurycercus in Churchill vicinities: Eurycercus longirostris and E. cf. longirostris . Subsequent COI -based study ( Bekker et al. 2012) revealed that the latter was identified wrongly and in reality belongs to an undescribed species of E. ( Teretifrons ), different from both E. glacialis and E. nigracanthus , and grouped with a good statistical support with the former against the latter. Dr M. Elías-Gutiérrez, one of authors of the paper recorded above (Jeffrey et al. 2011), kindly provided us with a material on the aforementioned wrongly identified taxon. But our morphologic study led to conclusion that these populations could be identified as E. nigracanthus . Different hypotheses could be proposed to explain such controversy: (1) in reality, E. nigracanthus is present in Churchill region, it was missed by Jeffrey et al (2011), and only these specimens were sent to us; (2) our " E. nigracanthus " is in reality a specific undescribed species which could not be diagnosed based on morphological characters; (3) both Jeffrey et al. (2011) and us dealt with a hybrid population of E. nigracanthus x undescribed species which has a nigracanthus -like morphology, but a non- nigracanthus mitochondrial genome. This problem needs further investigation.

Figures

FIGURE 6. Eurycercus cf. nigracanthus, parthenogenetic female from tundra pond TP- 3, Churchill, Manitoba, Canada. A – B, lateral view. C, head, lateral view. D, head shield. E, head pores. Scale bar denotes 1 mm.

FIGURE 7. Eurycercus cf. nigracanthus, parthenogenetic female from tundra pond TP- 3, Churchill, Manitoba, Canada. A, postabdomen. B, its distal portion. C, postabdominal claw. D, antenna I. E, antenna II. F, proximal segments of exopod. G, limb I. H, IDL of limb I. I, limb II. J, distal armature of its gnathobase. Scale bar denotes 1 mm for A; 0.1 mm for B – J.

FIGURE 8. Eurycercus cf. nigracanthus, limbs of parthenogenetic female from tundra pond TP- 3, Churchill, Manitoba, Canada. A, limb III. B, distal armature of its gnathobase. C, limb IV. D, distal armature of its gnathobase. E, limb V, F, its gnathobase. Scale bar denotes 0.1 mm.