Eocyzicus richteri, Tippelt & Schwentner, 2018

Tippelt, Lisa & Schwentner, Martin, 2018, Taxonomic assessment of Australian Eocyzicus species (Crustacea: Branchiopoda: Spinicaudata), Zootaxa 4410 (3), pp. 401-452 : 420-424

Eocyzicus richteri sp. nov.

( Figs. 9 and 10 )

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

Etymology. The species is named in honor of Prof. Stefan Richter (University of Rostock). The work of Prof. Richter has significantly contributed to further our understanding of the evolution of Branchiopoda, which includes the first descriptions of Australian Eocyzicus species. In addition, he mentored and supported both authors of the present study, for which we are very thankful.

Type locality. Queensland, Currawinya National Park, turbid claypan South of North Kaponyee , 28°49´27.4´´S, 144°19´44.5´´E.

Type material. Holotype. Male (AM P.89626, GenBank KC583987 ).

Allotype. Female (AM P.89623, GenBank KC583984 ).

Paratypes. 3 males (AM P.89624, GenBank KC583985 ; AM P.89625, GenBank KC583986 ; AM P.89627, GenBank KC583988 ), collected by M. Schwentner, S. Richter and B. V. Timms, 24-II-2011.

Further material examined. New South Wales: 1 male (AM P.89620) Island claypan, Bloodwood Station, ca. 500m east of Freshwater Lake , 29° 29´S, 144° 50´E), 28-IX-2010 ; Queensland: 1 male (AM P.89615) Rockwell Station, Big Kangaroo Pan , 28° 57´S, 144° 58´E, 1999 ; 1 female (AM P.89617) Lower Lake Eliza, Muella Station , 29°25´28.9´´S, 145°03´41.8´´E, 20-II-2010 ; 1 male (AM P.89634) Claypan halfway on northern Fence of Bilby Pen, Currawinya National Park, 28°52´12.8´´S, 144°21´52.1´´E, 25-II-2011 ; 1 male (AM P.89630), 1 female (AM P.89629) Triops claypan, Currawinya National Park , 28°47´14.9´´S, 144°17´49.1´´E, 24-II-2011 ; 1 female (AM P.89631) Vegetated Island Claypan, Currawinya National Park, 28°47´14.0´´S, 144°17´45.7´´E, 24-II-2011 ; 1 female (AM P.89633) Claypan at old Wyara Junction, Currawinya National Park, 28°47´49.4´´S, 144°17´55.6´´E, 24-II-2011 ; South Australia: 1 male (AM P.89644) , 4 females (AM P.89642, AM P.89643, AM P.89645, AM P.89646) Stony claypan, 20 km north of Williams Creek , 28°51´30.1´´S, 136°09´49.1´´E, 12-III-2011 ; 1 male (AM P.89641), 1 female (AM P.89640) Cane grass swamp 26 km north of Oodnadatta , 27°24´18.0´´S, 135°21´00.1´´E, 11-III-2011 ; 1 male (AM P.89637) Cane grass swamp, 44 km west of Oodnadatta , 27°20´07.1´´S, 135°07´47.7´´E, 11-III-2011 .

Description. Holotype male ( Fig. 9 a, c and d ). Carapace. 3.5 mm high, 5.4 mm long, height/length ratio 0.65; height without "crowded" growth lines 3.3 mm; length without "crowded" growth lines 5.0 mm; shape oval; dorso-posterior corner nearly absent; 20 growth lines, of these 18 "non-crowded" and two "crowded"; umbo large, hemispheric, growth lines present ( Fig. 9a ).

Head. Condyle rounded, section between condyle and external eye contour straight; eye bulge absent, compound eye round; straight angle between head and rostrum; anterior margin of rostrum straight, transition between anterior and ventral margin rounded ( Fig. 9c ). Antennule with 27 lobules, closely arranged; reaches to 11th antennary segment. Antenna with 13 antennary segments, middle antennary segment anteriorly with three spines.

Thorax. 20 thorax segments, of these 18 "complete" and two "incomplete" ( Fig. 9d ); dorsal spines beginning at 11th thorax segment, eight thorax segments with dorsal spines; one dorsal spine at each thorax segment, first dorsal spine same size as following one; last dorsal spine smaller than preceding one, last "complete" thorax segment with dorsal spine ( Fig. 9d ).

Telson. 16 telsonic spines, of these one enlarged, telsonic spines end after base of apex; telson symmetric; telsonic filaments situated between fourth and fifth telsonic spine. Furca with five setae, shorter than proximal part of furca; small spine before row of spinules present, spinules short ( Fig. 9d ).

Allotype female ( Fig. 9b, e and f ). Carapace. 4.6 mm high, 6.4 mm long; height/length ratio 0.72; height without "crowded" growth lines 4.5 mm; length without "crowded" growth lines 6.2 mm; 21 growth lines, of these 20 "non-crowded" and one "crowded"; umbo cone-shaped ( Fig. 9b ).

Head. Section between condyle and external eye contour concave; eye bulge small; right angle between head and rostrum ( Fig. 9e ). Antennule with 17 lobules; reaches to sixth antennary segment. Antenna with middle antennary segment anteriorly with six spines.

Thorax. Dorsal spines beginning at 8th thorax segment, eleven thorax segments with dorsal spines; first dorsal spine smaller than following one.

Telson. 18 telsonic spines without enlarged, telsonic spines end at the base of apex; telsonic filaments situated between the 5th and 6th telsonic spine. Furca with two setae ( Fig. 9f ).

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

Variability. Males. Carapace. 2.9–5.0 mm high, 4.6–8.0 mm long, height/length ratio 0.59–0.69; height without "crowded" growth lines 2.2–4.7 mm, length without "crowded" growth lines 3.4–7.0 mm; dorso-posterior corner clearly present or nearly absent; 17–34 growth lines, of these 12–26 "non-crowded" and up to eight "crowded"; umbo small or large, cone-shaped or hemispheric.

Head. Section between condyle and external eye contour concave or straight; eye bulge absent or present, if present small or large, compound eye oval or round; acute or obtuse to straight angle between head and rostrum, anterior margin of rostrum straight or convex, transition between anterior and ventral margin rounded or angular ( Fig. 10a and b ). Antennule with 17–27 lobules, closely or widely arranged; reaches to 9th –12th antennary segment ( Fig. 10a ). Antenna with 11–13 antennary segments, middle antennary segment anteriorly with two to seven spines ( Fig. 10e ).

Thorax. 20–23 thorax segments, of these 18–21 "complete" and up to two "incomplete" ( Fig. 10f ); dorsal spines beginning at 7th –11th thorax segment, eight to twelve thorax segments with dorsal spines; first dorsal spine smaller than or same size as following one, last dorsal spine smaller than or same size as preceding one, last "complete" thorax segment with or without dorsal spine ( Fig. 10f ).

Telson. 11–19 telsonic spines, of these up to two enlarged, telsonic spines end before, at or after base of apex; telsonic filaments situated between second and sixth telsonic spine. Furca with four to ten setae, shorter than, as long as or longer than proximal part of furca; small spine before row of spinules present or absent, spinules short or long ( Fig. 10f ).

Variability. Females. Carapace. 3.3–5.1 mm high, 4.9–7.2 mm long, height/length ratio 0.65–0.72; height without "crowded" growth lines 3.1–5.1 mm, length without "crowded" growth lines 4.7–7.2 mm; dorso-posterior corner clearly present or nearly absent; 15–23 growth lines, of these 14–21 "non-crowded" and up to eight "crowded"; umbo small or large, cone-shaped or hemispheric, growth lines present or absent.

Head. Section between condyle and external eye contour concave or straight; eye bulge absent or present, if present small or large, compound eye oval or round; acute to right or straight angle between head and rostrum; anterior margin of rostrum straight or convex, transition between anterior and ventral margin rounded or angular. Antennule with 17–22 lobules, closely or widely arranged; reaches to 5th –9th antennary segment. Antenna with 10– 13 antennary segments, middle antennary segment anteriorly with four to six spines.

Thorax. 19–21 thorax segments, of these 18–19 "complete" and one or two "incomplete"; dorsal spines beginning at 5th –11th thorax segment, 9–14 thorax segments with dorsal spines; first dorsal spine smaller than or same size as following one, last dorsal spine smaller than or same size as preceding one, last "complete" thorax segment with or without dorsal spine.

Telson. 12–22 telsonic spines, of these no or one enlarged, telsonic spines end before, at or after base of apex; telsonic filaments situated between third and sixth telsonic spine. Furca with two to nine setae, shorter than, as long as or longer than proximal part of furca; small spine before row of spinules present or absent, spinules short or long.

Differential diagnosis. Genetically Eocyzicus richteri sp. nov. and its putative sister species E. breviantennus sp. nov. are differentiated in COI, but not in the two nuclear markers (Schwentner et al., 2014), which was interpreted as an indication of ongoing reproduction. However, both species can be distinguished morphologically by the total height and length of the carapace and the number of antennary segments ( Tables 1 and 2), which is further supported by correlation plots ( Figs. 4c and d ). Although E. breviantennus sp. nov. individuals were usually smaller, they were certainly adult (ovigerous females were present) and exhibited larger numbers for several countable characters (e.g. number of thorax segments; Fig. 4c ) than E. richteri sp. nov. Thus, morphological differences between these two species are not explainable by the putative age of the studied specimens. Consequently, the lack of differentiation in the two nuclear markers is assumed to be a result of ancestral polymorphism and incomplete lineage sorting rather than ongoing reproduction. The morphological data support the delimitation of these two species based on the BSC (Mayr, 1942), the PSC sensu Wheeler & Platnick (2000) and the ESC (Wiley & Mayden, 2000).

Distribution and ecology. Eocyzicus richteri sp. nov. occurs in fresh and turbid water bodies and is sympatrically distributed with Eocyzicus ubiquus sp. nov., E. phytophilus sp. nov., E. armatus sp. nov., E. parooensis and E. argillaquus and rarely syntopically with the latter.

Figures

FIGURE 4. Correlation plots.a, correlation between the total length of the carapace and the number of antennary segments. b, correlation between the number of "crowded" growth lines and the number of telsonic spines. c, correlation between total length of the carapace and the number of all thorax segments for E. richteri and E. breviantennus. d, correlation between total length of the carapace and the number of antennary segments for E. richteri sp. nov. and E. breviantennus sp. nov. Each point corresponds to one individual.

FIGURE 9. Eocyzicus richteri sp. nov. a, carapace of male holotype (AM P.89626). b, carapace of female allotype (AM P.89623). 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 10. Eocyzicus richteri sp. nov. male paratype (AM P.89627). a, head with antenna and antennules (left antenna removed).b, rostrum.c, second rightclasper,arrow indicatesthe scales at the tipof the movable finger.d, detail ofthe tip ofthe movable finger of second right clasper. e, third and fourth segment of the left antenna. f, telson, arrows indicate "incomplete" thorax segments. A1 = antennules, ds = dorsal spine, fu = furca, lp = large palpus, mf = movable finger, ro = rostrum, sc = scales, sp = spinules, tf = telsonic filaments, ts = telsonic spines.