Lynceus mallinensis, Pessacq, Pablo, Epele, Luis B. & Rogers, Christopher, 2011

Pessacq, Pablo, Epele, Luis B. & Rogers, Christopher, 2011, A new species of Lynceus (Crustacea: Branchiopoda: Laevicaudata) from Patagonia, with comments on laevicaudatan systematics, Zootaxa 3043, pp. 25-32 : 27-30

Lynceus mallinensis sp. nov.

(figs 1–2)

Etymology. “mallín” is the original inhabitants (the Mapuche people) word to designate the typical Patagonian wetlands.

Type locality. ARGENTINA: Chubut province: State Route 15, 28 km east of Cholila town, wetland by the side of road, (42º21’43.3” S, 71º08’59.8” W)

Type material. Holotype, male deposited in Museo de La Plata. Accession number 26.724. Data of collection: December 2006; Epele, Miserendino and Pessacq leg.,.

Allotype, female; same data as holotype, deposited: Museo de La Plata. Accession number 26.725.

Paratypes: same data as holotype, 11 females, 5 males, deposited: Museo de La Plata, Accession number e no. 26.726. 1 male and 2 females, same data as holotype, deposited: Collection of D. Christopher Rogers, Accession number #DCR-782.

Diagnosis. Male L. mallinensis is separated from all known American Lynceus species except L. brevifrons by the bifurcate rostral carina and the angulate rostrum in lateral view, rather than evenly curved. Male L. mallinensis also have four dorsal plumose setae on endite III of thoracopod I. The posterior margin of the male rostrum is covered with minute setae, a character only shared with L. brevifrons ( Martin & Belk 1988) within the American species. Male L. mallinensis is most readily separated from L. brevifrons by the length of the bifurcate region of the rostral keel, which is approximately 50% the rostral length in L. mallinensis and approximately 25% in L. brevifrons . The presence of a row of short thick spines near clasping edge in the third endite is shared with L. brachyurus .

Female L. mallinensis is separated from all known American female Lynceus except L. mucronatus by the rounded rostral apex, which is either apically acute or emarginated. Female L. mallinensis is separated from female L. rotundirostris by the lack of an umbo. Both L. mallinensis and L. mucronatus have a rounded rostral apex, which is narrowly rounded, with rounded lateral spines in L. mallinensis , and broadly rounded with subacute lateral and medial spines in L. mucronatus . Insufficient information is available concerning the female of L. tropicus Daday, 1927 to properly separate it from L. mallinensis .

Coloration: Heavily melanised. Carapace very dark brown, body nearly black with dark brown highlights.

Description. Male: Head (figs. 1A–C): subequal in size to body, finely punctate. Fornices broad, angulated. Setal fields closely spaced, subequal in size to compound eye. Compound eyes larger than adjoining setal fields, close set and just posterior of setal fields. Frontal pore centered between setal fields and compound eyes. Rostrum twice as wide as long, anteriorly angulate in lateral view. Lateral margins subparallel. Distal margin slightly convex and irregularly crenulate. Anteriolateral apical corners with short, narrow lobes. Rostral carina extending from between setal fields to distolateral lobes, bifurcate, with bifurcation beginning at rostrum midlength. Rostral disc distad of the carinal bifurcation covered by minute setae. Rostrum finely punctate posterior to rostral branches. First antenna (fig. 1H) with two antennomeres. Proximal antennomere short, cylindrical. Distal antennomere approximately twice the length of proximal and bearing numerous olfactory papillae, each with apical pore and cylindrical base. Second antennae (fig. 1G) biramous, large, well developed, exceeding length of rostrum by one fourth their length. Second antennal peduncle of first antennomere with few simple distal setae, peduncle of second antennomere with row of simple distal setae on anterior side. Posterior and anterior flagellae bearing shorter simple setae along anterior surfaces and much longer, plumose setae along posterior surfaces. Labrum large, well developed, dependent, clothed apically and posteriorly in fine setae. Mandible broadly spatulate, molar surface with 12 to 16 transverse ridges becoming larger in size posteriorly. Posterior most ridge prolonged into spine. First maxilla typical for genus. Second maxilla absent.

Carapace: with hinge line straight, flat, umbo lacking. Anterior margin broadly arcuate, curving evenly to ventral surface, then back to the posterior end. Posterior end with post hinge dorsal margin and posterior margin, slightly convergent and rounded apically. Valves roundly inflated laterally. Carapace surface completely smooth, lacking growth lines or punctae.

Thorax: thoracopod I (figs. 1D–F) modified as clasping appendage, right and left claspers equal in shape and size. Endite VI thin, arcuate, tapering to rounded apex, slightly curved, most of length closing against endite III. Endite V larger than endite IV, extending distally beyond base of endite VI, distal end covered with simple setae. Endite IV distally and anteriorly covered with simple setae, with two large dorsal plumose setae. Endite III a broad longitudinal plateau, margined with numerous short, stout spines, and four dorsal plumose setae. Thoracopod II unmodified. Remaining thoracopods, body and anal somite (figs. 1I –J) typical for genus (see Martin & Belk 1989). Posterior sclerotized hook-like process absent.

Measurements (mm, n=7): length: 4.6–5.0 (4.8 ± 0.18); height: 3.75–4.1 (3.93 ± 0.15); width 2.8–3.5 (3.11 ± 0.26).

Female: Head (figs. 2B–D): similar to male. Rostrum comparatively narrower than in male, gently curved in lateral view. Apical margin rounded with obscured lateral lobes. Carina long, not bifurcated, ending close to rostrum margin. Eyes widely joining on middle line, sensory fields and frontal pore same as male.

Carapace (figs. 2A, 2G): as in male, umbo lacking. Egg mass visible through the carapace.

Thoracopods: thoracopods XI and XII with exopod dorsal lobes cylindrical and extending dorsally beyond thoracic dorsum. Last three thoracic segments (figs. 2E–F) with a conjoined lateral lamellar process, with three subacute, conical, lateral lobes and one posterior flange.

Measurements (mm, n=10): length: 4.2–5.15 (4.85 ± 0.28); height: 3.4–4.2 (3.88 ± 0.22); width 2.85–3.4 (3.22 ± 0.16).

Variation. One female specimen possesses low, rounded flanges on the carapace margin (fig. 1G). One at the posteriodorsal angle and one at the posterioventral angle. These flanges are triangular in shape and apically rounded.

Egg: Spherical and smooth. 150 µm in diameter.

Characteristics of type locality. A temporary pool of about 50 m wide 100 m long and 0.2 m average depth. At the time of collection, the water temperature was 14.3 ºC, pH 8,08, water conductivity 170,8 µS cm -1, salinity 0.1 o/oo, dissolved O2 10,5 mg/l (102 % saturation), TN (total nitrogen) 419 µg.l -1, NO3 140 µg.l -1, NH4 4 µg.l -1, TP (total phosphorus) 36 µg.l -1, and SRP (soluble reactive phosphorus) 3 µg.l -1.

Distribution. Central steppe of Central Patagonia, close to the ecotone with the Subandean Patagonia (Andean Region, Patagonian Subregion, Chubut province, Argentina).