Daphnia longispina

DAPHNIA LONGISPINA View in CoL (O. F. MÜLLER, 1776)

( FIGS 4 View Figure 4 , 5 View Figure 5 , TABLE 3)

Diagnosis

Adult male: Dorsal margin strongly convex, elevated above head ( Fig. 4D View Figure 4 ). Posterior head margin straight, with a distinct step-like prominence in distal half of margin ( Fig. 4E View Figure 4 ). Postero-ventral head angle as a rudimentary rostrum. Ventral margin of head slightly concave; anterior-most extremity occupied with optic vesicle. Eye very large. Labrum with a very large distal labral plate ( Fig. 4F View Figure 4 ). Valve with antero-ventral portion having numerous setae submarginally on inner face of valve ( Fig. 4G View Figure 4 ). Postero-ventral portion of valve with small marginal denticles and submarginal row of setules ( Fig. 4I–K View Figure 4 ). Abdomen with small mounds of subequal size on first and second segment, such mound on third segment low ( Fig. 5A View Figure 5 ). Postabdomen with long and slightly concave pre-anal margin, its distal portion with paired teeth strongly increasing in size distally; gonopore opens laterally, without a genital papilla. On outer surface of postabdominal claws, pectens consist of setules only ( Fig. 5B View Figure 5 ). Antenna I with antennular seta very small (but length> 0.5 diameter of antenna I), located at a small distance from distal end of antenna I body; male seta (flagellum) distally on antenna body without a post-aesthetasc process; this seta subequal in length with longest aesthetasc ( Fig. 5C View Figure 5 ). Limb I with outer distal lobe (ODL) smallest seta minute, largest seta as in other species; inner distal lobe (IDL) with a very short, bent copulatory hook, and two setae of different size ( Fig. 5E View Figure 5 ); endite 3 with setae 2 and 2′ equally long, setae 3 and 4 as in other taxa ( Fig. 5D View Figure 5 ). Limb II with anterior seta 1 armed by short, robust spinules ( Fig. 5F View Figure 5 ). Limb V exopod with seta 2 somewhat shorter than seta 1 ( Fig. 5G View Figure 5 ). Size of adult males 1.1–1.4 mm (not including caudal spine length).

Type locality

Unknown water body in Zealand, Denmark ( Petrusek et al., 2008) .

Type material

Apparently lost.

Material examined here

Many parthenogenetic, ephippial females and males from pond 2, Fredericksdal area, in the vicinity of Copenhagen, Denmark, collected on 11 October 2003 by N. M. Korovchinsky and J. Olesen, AAK 2008-052.

Comments

We had only a single formalin-preserved sample with a population containing males from Denmark, and we assume that such specimens belong to D. longispina sensu stricto, because: (1) the morphology of females from this population ( Fig. 4A–C, L, M View Figure 4 ) is longispina like in the ‘conventional’ understanding ( Benzie, 2005): lacking a helmet and dorsal crest, lacking pigmentation, lacking a body to antenna I, lacking a pecten of strong teeth on the postabdominal claw etc. (which does not mean that this is the same taxon as was proposed by O. F. Müller!); and (2) the sample was taken from the exact pond group studied by O. F. Müller ( Frey, 1980).

Petrusek et al. (2008) proposed that the label ‘ D. longispina ’ was incorrectly assigned because D. longispina sensu Taylor et al. (1996) ( D. lacustris sensu Nilssen et al., 2007 ) is presently absent from ‘the region’ of Müller’s D. longispina . J. P. Nilssen has spent substantial time sampling in Denmark, and A. Petrusek (personal communication) also invested extensive sampling effort, but no population of D. longispina sensu Taylor et al. ( Taylor et al., 1996) was detected. However, the type location in Denmark is flanked by known sites for D. longispina sensu Taylor et al. ( Taylor et al., 1996) from southern Norway and Poland. Nevertheless, we need a further revision of the D. longispina complex before the designation of a neotype, the full redescription of the morphology (including sexual stages with an extensive population sample) and genotyping are complete.