Eurycercus nigracanthus Hann, 1990

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 : 358-359

publication ID

https://doi.org/ 10.11646/zootaxa.4147.4.1

publication LSID

lsid:zoobank.org:pub:550E60AC-54F6-4FB4-8A79-058A0996B598

DOI

https://doi.org/10.5281/zenodo.5631051

persistent identifier

https://treatment.plazi.org/id/03CD879F-9C37-FF8A-56A3-2B45E290FED3

treatment provided by

Plazi

scientific name

Eurycercus nigracanthus Hann, 1990
status

 

Eurycercus nigracanthus Hann, 1990 View in CoL

( Figs 4–5 View FIGURE 4 View FIGURE 5 )

Eurycercus (Teretifrons) sp. in Frey & Hann 1985, P. 327.

Eurycercus nigracanthus Hann 1990 View in CoL , P. 2150, Figs 16–40; Bekker 2012, P. 125–130, Figs 41–42.

Type locality. “ Weiss Pond , Avalon Peninsula , Newfoundland , Canada ” ( Hann 1990). Unfortunately, the coordinates represented by Hann (1990) are apparently wrong.

Type material. Holotype. Parthenogenetic female, USNM 243306.

Paratypes. 2 adult males, USNM 243307. 2 juvenile males (instar II) USNM 243308. 2 juvenile males (instar I), USNM 243309. 2 parthenogenetic females, USNM 243310.

Other material examined here. All from Newfoundland and Labrador, Canada: 20 parthenogenetic ♀♀ from Oxen Pond (appr. N47.5713°, W52.7623°), coll. in 28.08.1984 by D.G. Frey, DGF 7051. 14 parthenogenetic ♀♀ from Round Pond (appr. N47.7°, W52.81°), N of St GoogleMaps . Johnes, coll. in 28.08.1984 by D.G. Frey, DGF 7055. 7 parthenogenetic ♀♀ from Pond along Hgy 1. (appr. N47.36°, W53.05°), 1.5 miles S of Butterpot Provincial Park, coll. in 0 5.09.1984 by D.G. Frey, DGF 7109. 5 parthenogenetic ♀♀ from Fen Pool (appr. N46.88°, W54.11°), East side of road from Cape St. Marys to Hgy 100, coll. in 11.091984 by D.G. Frey, DGF 7135a–b. 22 parthenogenetic ♀♀ from a water body (appr. N47.6°, W52.7°) near Hgy. 1 opposite truck weighing station W of St GoogleMaps . John's, coll. in 0 9.1984 by D.G. Frey, DGF 7167- II. 45 parthenogenetic ♀♀ from Pond-G (N49.4931°, W56.4655°), coll. in 30.06.2005 by L.J. Hovind & M. Faustova, DJT 20-115, AAK M-1177, and AAK M-0536.

Diagnosis. In lateral view body sub-ovoid ( Fig. 4 View FIGURE 4 A), maximum height of the body in its middle portion (BH/ BL= 0.64–0.74; VL/BL=0.80–0.89). In anterior of dorsal view, body not compressed laterally, median dorsal keel absent ( Fig. 4 View FIGURE 4 B–C). Rostrum relatively long ( Fig. 4 View FIGURE 4 D). Ocellus small. Dorsal head pores located on a pancake-like projection on dorsal margin of head and slightly protrude beyond the edge of the head shield ( Fig. 4 View FIGURE 4 E). Lateral head pores small and subcircular ( Fig. 4 View FIGURE 4 F). Labrum with a large median keel, with angled apex, projecting beyond distal end of antenna I ( Fig. 4 View FIGURE 4 D). Armature of valve margin as in other species ( Fig. 4 View FIGURE 4 G–I). Postabdomen large (PL/BL= 0.41–0.45), relatively broad ( PH /PL= 0.46–0.54) with almost parallel ventral and dorsal margin ( Fig. 5 View FIGURE 5 A) and deep embayment ( Fig. 5 View FIGURE 5 B). Preanal teeth more elongated, pointed (NT=118–121), in most cases dark, strongly chitinized; rudimentary teeth up to bases of postabdominal setae ( Fig. 5 View FIGURE 5 C). Teeth in distal part of postanal margin large, long, predominantly double ( Fig. 5 View FIGURE 5 B). Teeth in distal part of anal margin – proximal part of postanal margin short, almost all of them single. Postabdominal claw relatively robust (CL/PL=0. 23–0.26) with two basal spines (DS/CL=0.28–0.30; BS/CL=0.11; BS/DS=0.40–0.50). Antenna I elongated (AL/BL=0.10–0.11; AL/DA=4.67– 4.87); antennular sensory seta arising in antenna I distal part ( Fig. 5 View FIGURE 5 D). Numerous short rows of minute denticles encircling antennular surface. On antenna II spine situated on proximal segment of exopod equal in length or slightly longer than second segment ( Fig. 5 View FIGURE 5 E). IDL of limb I supplied three bisegmented setae, one of them a relatively strong hook-like seta, its diameter at base equal or slightly more than diameter at base of longest setae IDL ( Fig. 5 View FIGURE 5 F). The smallest of the three setae relatively short, its length two or more times less than longest setae IDL. IDL with groups of spinulae: 10–12 long distal spinulae; 11–15 long proximal spinulae and 7–10 very short basal spinulae; marginal spinulae absent ( Fig. 5 View FIGURE 5 F). Eight setae in filter plate II, 10 setae in filter plate III; 9–10 setae in filter plate IV, 8–9 setae in filter plate V. Exopodite IV with 8 setae; exopodite V with 8 setae. Intestine with a double loop, posterior intestinal caecum absent.

Ephippial female and ephippum. Slight median keel on valves, whole valves are involved in ephippium formation. Ephippia in our fixed material were almost unpigmented additionally as compared with parthenogenetic female.

Adult male. As in other species of the subgenus, see Hann (1990).

Size. Juvenile and adult parthenogenetic females in our material 2.3–4.5 mm. Juvenile females 1.2–3.2 mm, adult parthenogenetic females 3.7–5.8 mm, adult males 1.8–2.1 mm ( Hann, 1990).

Differential diagnisis. Among the species of Eurycercus (Teretifrons) , E. nigracanthus is unique having a ring of major head pore projects above head shield, but no projection in middle of major head pore. In contrast to E. chernovi sp.nov., it has 10 setae in exopodite IV and 8 setae in exopodite V.

Distribution. It is found in Labrador and Newfoundland, Cape Breton Island and Nova Scotia ( Hann 1990). But a real range of its distribution in North America is not clear, i.e. see below. Comments. The species was adequately described by Hann (1990) except few details which are discussed below.

Kingdom

Animalia

Phylum

Arthropoda

Class

Branchiopoda

Order

Diplostraca

Family

Eurycercidae

Genus

Eurycercus

Loc

Eurycercus nigracanthus Hann, 1990

Bekker, Eugeniya I. & Kotov, Alexey A. 2016
2016
Loc

Eurycercus nigracanthus

Hann 1990
1990
GBIF Dataset (for parent article) Darwin Core Archive (for parent article) View in SIBiLS Plain XML RDF