Eocyzicus parvus, Tippelt & Schwentner, 2018

Tippelt, Lisa & Schwentner, Martin, 2018, Taxonomic assessment of Australian Eocyzicus species (Crustacea: Branchiopoda: Spinicaudata), Zootaxa 4410 (3), pp. 401-452 : 430-433

Eocyzicus parvus sp. nov.

( Figs. 15 and 16 )

Eocyzicus lineage T Schwentner et al., 2014, 2015b

Etymology. The Latin word " parvus " means small and refers to the size of the carapace, which is smaller than in other Australian Eocyzicus species (see Tables 1 and 2).

Type locality. Queensland, Bulloo River catchment, roadside dugout with yellow lilies, 27°58´26.8´´S, 144°18´34.9´´E.

Type material. Holotype. Male (AM P.91862, no GenBank number).

Allotype. Female (AM P.89457, GenBank KC583822 ).

Paratypes. 1 male (AM P.89456, GenBank KC583821 ), 3 females (AM P.89454, GenBank KC583819 ; AM P.89455, GenBank KC583820 ; AM P.89458, GenBank KC583823 ), collected by M. Schwentner, S. Richter and B. V. Timms, 27-II-2011.

Further material examined: no material from other localities available

Description: Holotype male ( Fig. 15 a, c and d ). Carapace. 2.5 mm high, 4.0 mm long, height/length ratio 0.63; height without "crowded" growth lines 2.5 mm, length without "crowded" growth lines 4.0 mm; shape oval; dorso-posterior corner clearly present; nine growth lines, all "non-crowded"; umbo small; hemispheric, growth lines absent ( Fig. 15a ).

Head. Condyle rounded, section between condyle and external eye contour straight; eye bulge absent, compound eye oval; acute angle between head and rostrum; anterior margin of rostrum straight, transition between anterior and ventral margin angular ( Fig. 15c ). Antennule with 17 lobules, widely arranged; reaches to 9th antennary segment. Antenna with ten antennary segments, middle antennary segment anteriorly with two spines.

Thorax. 21 thorax segments, of these 19 "complete" and two "incomplete" ( Fig. 15d ); dorsal spines beginning at 7th thorax segment, thirteen thorax segments with dorsal spines; one dorsal spine at each thorax segment, first dorsal spine smaller than following one, last dorsal spine smaller than preceding one, last "complete" thorax segment with dorsal spine ( Fig. 15d ).

Telson. 14 telsonic spines, of these two enlarged; telsonic spines end at base of apex; telson symmetric; telsonic filaments situated between third and fourth telsonic spine. Furca with five setae, longer than proximal part of furca; small spine before row of spinules present, spinules short ( Fig. 15d ).

Allotype female ( Fig. 15b, e and f ). Carapace. 2.8 mm high, 4.2 mm long, height/length ratio 0.67; height without "crowded" growth lines 2.8 mm; length without "crowded" growth lines 4.2 mm; dorso-posterior corner nearly absent ( Fig. 15b ).

Head. Compound eye round; right angle between head and rostrum; anterior margin of rostrum convex, transition between anterior and ventral margin of rostrum rounded ( Fig. 15e ). Antennule with 20 lobules, closely arranged; reaches to 7th antennary segment. Antenna with eleven antennary segments, middle antennary segment anteriorly with five spines.

Thorax. 13 thorax segments with dorsal spines.

Telson. 16 telsonic spines, of these three enlarged. Furca with two setae, shorter than proximal part of furca ( Fig. 15f ).

Ovigerous flagella situated at 9th and 10th thorax segment.

Variability. Males. Carapace. 3.7–4.0 mm long, height/length ratio 0.63–0.68; length without "crowded" growth lines 3.7–4.0 mm long; dorso-posterior corner clearly present or nearly absent.

Head. Compound eye oval or round; anterior margin of rostrum straight or convex; transition between anterior and ventral margin rounded or angular. Antennule with 15–17 lobules, closely or widely arranged; reaches to 8th or 9th antennary segment. Antenna with middle antennary segment anteriorly with two or four spines.

Thorax. 21 or 22 thorax segments, of these 19 or 20 "complete" and two "incomplete"; dorsal spines beginning at 7th or 9th thorax segment; eleven or thirteen thorax segments with dorsal spines, last "complete" thorax segment with or without dorsal spine.

Telson. 14 or 16 telsonic spines, of these two or three enlarged. Furca with four or five setae, as long as or longer than proximal part of furca; small spine before row of spinules present or absent.

Variability. Females. Carapace. 2.3–2.8 mm high, 3.3–4.2 mm long, height/length ratio 0.67–0.73; height without "crowded" growth lines 2.3–2.8 mm, length without "crowded" growth lines 3.3–4.2 mm; dorso-posterior corner clearly present or nearly absent; eight or nine growth lines, all "non-crowded".

Head. Compound eye oval or round; acute to obtuse angle between head and rostrum; anterior margin of rostrum straight or convex, transition between anterior and ventral margin rounded or angular ( Fig. 16a ). Antennule with 17–20 lobules, reaches to 5th–8th antennary segment. Antenna with ten or eleven antennary segments ( Fig. 16c ), middle antennary segment anteriorly with four or five spines ( Fig. 16d ).

Thorax. 19–22 thorax segments, of these 18–20 "complete" and one or two "incomplete" ( Fig. 16b ); dorsal spines beginning at 6th –8th thorax segment, 12 or 13 thorax segments with dorsal spines; last dorsal spine smaller or same size as preceding one.

Telson. 12–16 telsonic spines, of these two to four enlarged, telsonic spines end before or at base of apex; telsonic filaments situated between the second and fourth telsonic spine. Furca with two to five setae, shorter than, as long as or longer than proximal part of furca ( Fig. 16b ).

Differential diagnosis. Eocyzicus parvus sp. nov. can be morphologically clearly differentiated from all other Australian Eocyzicus species by its size, the small number of growth lines and the number of setae on the furca. No egg bearing females were among the examined individuals. Thus, it is possible that the studied individuals are not fully matured. The morphologic and genetic differentiation from its putative sister species E. phytophilus sp. nov. (with which it occurs sympatrically) support its species status based on the PSC sensu Wheeler & Platnick (2000), the ESC (Wiley & Mayden, 2000) and the BSC (Mayr, 1942).

Distribution and ecology. The only locality from which Eocyzicus parvus sp. nov. is known is a fresh and clear pool with yellow lilies. This species occurs sympatrically with Eocyzicus ubiquus sp. nov., E. phytophilus sp. nov. and E. argillaquus .

Figures

FIGURE 15. Eocyzicus parvus sp. nov. a, carapace of male holotype (AM P.91862). b, carapace of female allotype (AM P.89457). c, head of male holotype. d, telson of male holotype. e, head of female allotype. f, telson of female allotype. ce = compound eye, co = condylus, ds = dorsal spine, fu = furca, gl = growth lines, is = „incomplete" thorax segments, md = mandible, ro = rostrum, sp = spinules, tf = telsonicfilaments, ts = telsonic spines, um = umbo.

FIGURE 16. Eocyzicus parvus sp. nov. female paratype (AM P.89455). a, rostrum (left antenna removed). b, telson, arrow indicates "incomplete" thorax segment. c, right antenna. d, fifth and sixth segment of the right antenna. A1 = antennules, ds = dorsal spine, fu = furca, ro = rostrum, sp = spinules, tf = telsonic filaments, ts = telsonic spines.