Parartemia triquetra, Timms, Brian V & Hudson, Peter, 2009

Timms, Brian V & Hudson, Peter, 2009, The brine shrimps (Artemia and Parartemia) of South Australia, including descriptions of four new species of Parartemia (Crustacea: Anostraca: Artemiina), Zootaxa 2248, pp. 47-68 : 57-60

Parartemia triquetra sp. nov.

(Figure 6)

Type material. Holotype. Male, SOUTH AUSTRALIA, Great Victoria Desert, Serpentine Lakes, a small salt lake 3 km from SA/WA border, (28o 30’11”S, 129o 01’57”E), 30 July 2006, J.A. Forrest, SAM C6764; Allotype. Female (ovigerous), same collecting data as holotype, SAM C6765; Paratypes. Two males, two females, same collecting data as holotype, SAM C6766; two males, two females, same collecting data as holotype, WAM 40319.

Other material. Eleven males, two females, SOUTH AUSTRALIA, Great Victoria Desert, Serpentine Lakes, a small salt lake 3 km from SA/WA border, (28o30’11”S, 129o01’57”E), 30 July 2006, J.A. Forrest, SAM C6767, C6768.

Description. Male. Length 19.5 mm (head plus thorax 8 mm, abdomen 11.5 mm).

Head (Fig.6A) with first antenna filiform, subequal in length to eye plus peduncle. Basal antennomere of second antenna fused proximally near right angles to body axis. Frontal edge of fused basal antennomeres with paired ventral processes (VP, Fig. 6A) with a granular surface (GS,Fig. 6B) and edged with numerous small denticles. Ventral processes deeply concave between rounded lateral corners and large anteriorly aligned triangular medial corner with a bulge about midway on its medial edge. Lateral edge of ventral process about a quarter the depth of medial edge, and depth at maximum concavity about one-sixth depth of medial edge. A small conical mound surfaced with small denticles lies posterioventral to ventral process lateral edge (CM, Fig. 6B). Medial surface between ventral processes slightly domed (i.e. convex) and with a small nipple-like medial process. Anterior surface of fused basal antennomeres with ridges on either side of centreline each terminating in prominent conical anterior process (length 2 times basal width) surfaced with small denticles (AP, Fig. 6A). Distal antennomere of second antenna a little longer than basal antennomere, approximately cylindrical and tapering to a sharp apex. Surface granular (GS,Fig.6B). This antennomere with a swelling at about two-thirds along its length affecting curvature of whole antennomere, so the inner surface with a very flat sigmoidal curvature. Labrum without a spine.

Thorax, particularly segments 7 to 11, with asymmetrical lateral lobes (L, Fig.6B). First genital segment expanded a little, but even so a major difference between widths of last thoracic and first genital segments. Eleven pairs of thoracopods, first, second and eleventh not as large as the others. Fifth thoracopod similar to the standard Parartemia type as described here for P. acidiphila , but with many fewer (c. 25) posterior setae on endopodite.

Gonopods (Fig. 6C) paired, basal parts fused together and not much thicker than distal apical tube in lateral view, but wider by at least two times ventrally. Basal part with a broadly based triangular protrusion apically (DP, Fig. 6C) and apical tube with a small unhooked digitiform process subapically. No specimens with gonopod extended or everted.

Abdominal segments increasing in length and narrowing 1 to 6, particularly 5 and 6, so 6th segment about twice the length of first. Cercopods fringed with long setae medially and laterally and length subequal to 5th abdominal segment.

Description. Female. Length 15 mm.

Head (Fig. 6D) with first antenna filiform about two-thirds the length of eye plus peduncle. Second antenna a little longer than eye plus peduncle, flattened and terminating in an evenly narrowing and almost symmetrical apex. Labrum with a prominent recurved spine.

Posterior thoracic segments (Figs 6F,G) with lateral lobes on 5th to 11th segments, symmetrical on segments 5 to 8, asymmetrically bulging on segment 9, and all fused laterally. Segments 10 and 11 with smaller free triangular lobes. Segment 10 with a small swelling dorsolaterally and segment 11 with a similar swelling laterally (S, Figs 6F,G). Segments 8 to 11 denticulate dorsally, also lobes of segments 5 to 7 (Fig. 6F). Brood pouches oval, separated dorsally and joined ventrally to an oviduct subequal in length to depth of brood pouch and containing many smooth surfaced eggs.

Thorax with 11 pairs of thoracopods, the 11th represented by small triangular stumps without setae. Thoracopods similar in structure to those of male, except the reduced tenth pair. Tenth thoracopod (Fig. 6H) with standard number and relative size of the anterior setae and first 6 posterior setae of endopodite. However posterior setae reduced in number, with 10 on endites 1+2, 2 on endite 3, none of endites 4 to 6, 14 altogether on endopodite, and about 20 on the exopod. Both exopodite and praepipodite reduced, and epipodite absent.

Surface of abdominal segments papillate, otherwise proportions as in male.

Etymology. The specific name is from the latin ‘triquetrus’ meaning triangular. This refers to the triangular medial corner of the transverse process of the male, which is unusual shape among Parartemia species, the only other known species with a similar, but smaller structure is P. contracta Linder, 1941 .

Variability. Male length varies from 18 to 22 mm and female length from 11 to 15 mm in the only collection available for study. All males in the collection have a mesial swelling on the distal segment of the second antenna and hence a distinctive curvature of the claspers.

Differential diagnosis. The male is distinctive among Parartemia in having the second antennomere of second antenna (the claspers) with a mesial swelling beyond half its length, and the inner corner of the frontal processes being prominent and triangular. The lateral swellings on posterior thoracic segments is shared by only a few species (e.g. P. cylindrifera in which they are large, and P. auriciforma n sp. and P. yarleensis n. sp. in which they are small). The anterior processes are more robust than in most species of Parartemia , except in an undescribed species in Lake Carey, WA, (known as Parartemia sp x, Timms et al, 2007 and B. Timms, unpublished data). Females, like those of P. acidiphila , also lack dorsal and dorsolateral swellings on thoracic segments 8 and 9 (e.g. P. serventyi , P. longicaudata and many of the undescribed species of Parartemia in WA (Timms, 2004)) and there are no segments with narrow sclerotised ridges (e.g. P. zietziana ). Several other species of Parartemia ( P. cylindrifera , P. serventyi , P. informis , P. m i n u t a P. auriciforma n. sp. and P. yarleensis n. sp.) lack an 11th pair of thoracopods. Dorsally, thoracic segments are like those in P. acidiphila FIGURE 6. Parartemia triquetra n. sp. Male A-D, Holotype; Female, E-H, Allotype; both Serpentine Lakes, SA. A, anterior view of head with first and second antennae (VP = ventral processes; AP = anterior processes); B, posterior view of one side of second antenna showing the conical mound (CM) and granulation of ventral process and distal antennomere; C, dorsal view of thoracic segments 7-11, the genital segments, and first abdominal segment (L = lobes); D, gonopods with genital segments and subapical spine and digitiform processes (DP); E, anterior view of head; F, dorsal view of thoracic segments 5-11, genital segments, brood pouches and first abdominal segment (S = swellings); G, lateral view of brood pouch region and adjacent thorax (L = lobes; S = swellings); H, 10th thoracopod with anterior setae. Scale bars 1 mm.

but both 10th and 11th segments have free lobes and that on segment 9 is asymmetrical, whereas in P. acidiphila only the 11th segment has a free lobe and the 9th lobe is square. Moreover the last four thoracic segments have denticulate surface, whereas in P. acidiphila only the last two segments are so structured. Like three of the new species of Parartemia described here ( P. acidiphila n. sp., P. auriciforma n. sp., and P. yarleensis n. sp.) brood chambers are round to oval and without significant posterior lobes.

Type locality. A small lake in the Serpentine Lakes system on the SA/WA border in the Great Victoria Desert. Other than being episodic and saline, nothing is known of it.

Distribution. Known only from type locality ( Fig. 4 ). It is not even known whether it lives in other parts of the of the Serpentine Lakes system.

Figures

FIGURE 4. Map of South Australia showing sites where the new species were found. Key: P. acidiphila n. sp. ˔; P. auriciforma n. sp. ˑ; P. triquetra n. sp. ♦; P. yarleeensis n. sp. ․.