Eurycercus microdontus Frey, 1978

Bekker, Eugeniya I., Kotov, Alexey A. & Taylor, Derek J., 2012, A revision of the subgenus Eurycercus (Eurycercus) Baird, 1843 emend. nov. (Cladocera: Eurycercidae) in the Holarctic with the description of a new species from Alaska, Zootaxa 3206 (1), pp. 1-40 : 19

Eurycercus microdontus Frey, 1978

Eurycercus microdontus Frey, 1978, p. 8 –22, Figs 2 –17, 19–28, 30–35.

Type locality. "Lake June in Winter, Highlands Co., Florida ” ( Frey 1978), USA. Approximate geographic coordinates: 27.3, -81.4.

Holotype. A parthenogenetic female 1.67 mm long in alcohol, USNM 151210 .

Paratypes. Two parthenogenetic females in alcohol and one mounted in glycerine jelly, USNM 151210 . Two parthenogenetic females in alcohol and one in glycerine jelly, NHM 1974 . 716-718. All other specimens and exuvial fragments in DGF .

Material examined here. Many females from U.S.A. (Florida, South Carolina and North Carolina). Full list will be represented in a special future publication concerning a revision of the lamellatus -like forms worldwide .

Diagnosis. Parthenogenetic female. Dorsal head pores on a transverse fold in posterior portion of head shield with an indentation behind it. In anterior view, body strongly compressed laterally, median keel sharp, passes through whole carapace dorsum and actually begins on the head behind head pores. Dorsal margin of head flattened between compound eye and head pore region. Rostrum short. Ocellus minute. Lateral head pore small, rounded. Labrum with a median keel of moderate size, terminating in a widely rounded apex reaching distal end of antenna I. Postabdomen with sub-parallel dorsal and ventral margins, preanal teeth pointed. Spines at base of pre-claw portion predominantly clustered. Antenna I with antennular sensory seta arising in middle. Denticles in rows encircling antennular surface small. On antenna II, spine situated on proximal segment of exopod shorter than second segment. Limb I IDL with a hook-like seta markedly thicker than longest seta, the smallest IDL seta short. IDL with distal, proximal, marginal and basal group spinules. Eight setae in filter plate II, 9 setae in filter plate III; 9 setae in filter plate IV, 8 setae in filter plate V.

Full description. See Frey (1978).

Comments. It is a characteristic taxon from the south of the U.S.A., and is the most laterally compressed among all species of the genus.

Distribution. Southern states of the U.S.A. The species is recorded from North Carolina, South Carolina, Georgia, Florida, Louisiana and Texas ( Frey 1978).

Ecology. Frey (1978) reported this taxon only from lakes, but he also said that "the smaller water bodies, such as ponds, back-waters, slow streams, etc., particularly those with an abundance opf macrophytes, and hence some protection against predation by fishes, will yield many records of the species when they are studied intensively" ( Frey 1978, p. 24). Our study confirms this idea as we also found E. microdontus in ponds.

Figures

FIGURE 2. Characteristic traits of different species of Eurycercus (Eurycercus) emend. nov. A–B, E. longirostris, dorsal view and dorsal head pores in lateral view. C–D, E. lamellatus, dorsal view and dorsal head pores in lateral view. E–F, E. beringi sp. nov., dorsal view and dorsal head pores in lateral view. Rather schematic, not to scale.