Parartemia purpurea, Timms, Brian V, 2010

Timms, Brian V, 2010, Six new species of the brine shrimp Parartemia Sayce 1903 (Crustacea: Anostraca: Artemiina) in Western Australia, Zootaxa 2715, pp. 1-35 : 24-27

Parartemia purpurea sp. nov.

(Figs 4,7,11)

Parartemia n sp a Timms and Savage, 2004, p 22, 28; Timms 2009.

Etymology. This species is named for the distinct purple colouration of mature females, the name being derived from the Latin purpurea meaning purple.

Holotype. One male, 44 km NNE of Esperance, unnamed lake on Dempster Rd, (33o 28’ 58”S, 122o 00’ 38”E), 8 October 2008; BVT, WAM 45235.

Allotype. One female, same collecting data as holotype, WAM 45236.

Paratypes. Two males, two females, some collecting data as holotype, WAM 45237; two males, two females, same collecting data as holotype, AM 82976.

Other material. 10 males, 10 females, 23.5 km E of Scaddan, unnamed lake on East Lignite Rd, (33o 19’ 28”S, 121o 58’ 17”E), 2 August 2005, BVT, WAM 45238; 10 females, 38 km N of Esperance, unnamed lake on south side of Speddingup Rd, (33o 31’ 01”S, 121o 52’ 21”E), 8 October 2008, BVT, WAM 45239; 10 males, 10 females, all immature, 64.5 km NE of Esperance near Kau Rock, unnamed pond, (33o 24’ 32”S, 122o 20’ 00”E), 9 October 2008, BVT, WAM 45240; 10 males, 10 females, 80 km NE of Esperance in Beaumont Nature Reserve, unnamed lake, (33o 27’ 37”S, 122o 36’ 43”E), 5 September 2004, BVT, WAM 45241.

Description. Male. Length 21.5 mm (head plus thorax 7 mm, abdomen 14.5 mm)

First antenna ( Fig. 11 A) filiform, a little longer than eye plus peduncle.

Second antenna. Basal antennomeres ( Fig. 11 A) fused at about 75o to body axis. Ventral margin with paired ventral processes ( Fig. 11 A) about 3 times longer than deep, with distoventral corner rounded but not protruding and medioventral corner sharp, almost a right angle. Ventral process margin with well spaced minute spines, also a few such spines on dorsal surface of the processes. Medial margin of ventral processes about 1.2 times longer than lateral margin. Medial space between ventral processes narrow with parallel margins and terminating basally in a short notch. Ventrolaterally just lateral to basodistal margin of the ventral process a raised circular area, the conical mound, with numerous minute spines. Anterior processes ( Fig. 11 A) small, blunt triangular, about one quarter depth of ventral processes. Distal antennomere ( Fig. 11 A) almost twice as long as basal antennomere, curved medially, cylindrical and tapering to a sharp apex. Labrum lacking a spine.

Thoracomeres ( Fig 10 B) enveloped laterally in small fused lobes to form a narrow lateral flange along whole length of thorax. Thorax widest at thoracomeres 10 to 11, with lobe on first genital as wide as lobe on T11 anteriorly, but markedly narrowing posteriorly. No lobe on second genital segment. Eleven pairs of thoracopods, with first two reduced in size and last without an epipodite. Fifth thoracopod typical for the genus.

Gonopods ( Fig. 11 C) fused basally. Each apical free portion with a short hooked digitiform process inserted ventrolaterally at about three quarters the length of the free portion. No basal spine. A paratype with gonopod everted ( Fig. 11 D)— everted part a little longer than free basal portion, consisting of a basal wide cylindrical component and a tubular distal part of two diameters, a middle section narrower than basal tube and an apical, very narrow apical section. Whole expanded section naked except for a two recurved spines on a single base posteriolaterally on the wide cylindrical component.

Abdomen long, 2.1 times head plus thorax. Segments increasing in length and but hardy decreasing in diameter sequentially 1 to 6, with sixth 2.2 times the length and but only marginally narrower than first segment.

Telson inflated and not clearly demarked from sixth abdominal segment and cercopods about length of fourth abdominal segment and clothed with setae medially and laterally.

Female. 11 mm (head plus thorax 6.7 mm, abdomen 4.3 mm). In life, mature females coloured a deep purple, with the brood chambers a lesser intense colour.

Head ( Fig. 11 E) with first antenna filiform and slightly shorter than length of eye plus peduncle. Second antenna a little longer than twice eye plus peduncle length, somewhat flattened, and narrowing evenly to a sharp apex. Labrum with a prominent recurved spine.

Thoracomeres ( Fig. 11 F,G) 1 – 6 and 8 normal, thoracomere 7 with a lateral tumidity, thoracomeres 9 and 10 each with a dorsolateral lamella, with a sclerotized and denticulate margin. Dorsolateral lamella of thoracomere 9 asymmetrical, narrow dorsally and widest ventrolaterally and with subsidiary ventrolateral lamella, while lamella of segment 10 more symmetrical and more ventrolateral. Thoracomere 11 somewhat reduced.

Eleven pairs of thoracopods, 2nd and 10th pairs a little shorter than most, 1st about half size and 11th reduced to just a pair of stubs bearing a few spines.

First thoracopod (Fig. 7J) with all normal components, but endopod and particularly exopod reduced, so that both have fewer posterior seate than normal and exopod just protruding beyond endopod. Normal anterior setae, and with basal anterior setae of endite 4 enlarged, longer than adjacent posterior setae.

Fifth thoracopod of normal construction for Parartemia and similar to that in males.

Tenth thoracopod (Fig. 7K) with most structures reduced, particularly endites 1+2 and 3, endopod and praeepipodite, and with epipodite lacking. Exopodite of normal relative size and projecting well beyond the endopodite. Anterior setae of endites all present, but reduced in size.

Eleventh thoracopod (Fig. 7L) a stub with terminally what appears to be a very reduced endopod with five setae, and medially two protuberances, the distal one with two setae and a basal greater naked protuberance. These protuberances could be endites.

Brood pouch ( Fig. 11 F,G) lateral lobes oval structures in dorsal view but more quadrahedral laterally, and connected ventrally, with a posteriorly directed gonopore, borne on a tubular projection.

Abdomen segments typical for Parartemia , i.e. segments increase in length and decrease in diameter sequentially from segments 1 to 6. Surface denticulate.

Variability. Mature males vary in length from 16 to 23 mm. The basal antennomeres are fused at various angles, probably influenced by preservation, of 60–80o to body axis and while the frontal processes seem always to be small, blunt and triangular, the ventral processes vary so that the distoventral corner may protrude a little and the medial space varies from being almost closed to being open by a distance up to about one third the depth of the ventral processes. The medial margins of the ventral processes may not always be parallel, but occasionally are V-shaped or uneven. However, the angle of near 90o on the medioventral corner of the ventral processes varies little. The raised spinose area ventrolaterally to the basodistal margin of the ventral processes may be expressed as a conical mound or may be hardly present. The flange on the thoracic margins is generally present, but its widest part may be at thoracomere 10 or occasionally 11, i.e. more posterior than at thoracomere 8–9.

Abdomen length varies from 1.25 to 2.33 times head plus thorax length (average of 1.78 in 10 specimens). This length is due in part to the relatively long 6th segment which on average is 2.1 times length of 1st segment. The first ratio is greater than for P. longicaudata and the second only a little less than in P. longicaudata , the species supposedly with an extraordinary long abdomen (see earlier).

Mature females range in length from 9.6 to 11.2 mm, and while opaque white in preservation, in life are almost always a deep purple. The lateral tumidities on thoracomere 7 while usually prominent, are sometimes deflated and not noticeable. The lateral lamellae of thoracomere 9 and 10 vary in development, but the lamella of thoracomere 9 is always larger than that of thoracomere 10 and more dorsal in position.

Differential diagnosis. P. purpurea sp. nov. males are most similar to P. zietziana due to their broadly similar ventral processes and the shape of the medial area between these processes. However P. zietziana has digitiform anterior processes compared to short conical processes in P. purpurea sp. nov. The lateral and medial margins of the ventral processes are of similar length in P. zietziana , but the medial margin is about 1.2 times longer than lateral margin in P. purpurea sp. nov. The ventrolateral area at the basodistal margin of the ventral processes is different in the two species: in P. purpurea sp. nov. it is raised and very spinous, but in P. zietziana it hardly present, if at all. Finally the abdomen is relatively longer in most specimens of P. p u r p u re a sp. nov. (1.78 times) than in P. zietziana (1.30 in 10 specimens). The two species have different distributions separated by the Nullarbor Plain – P. zietziana occurs in central lowland Tasmania, southern Victoria, and southern South Australia to as far west as the eastern Eyre Peninsula, while P.purpurea sp. nov. occurs in the Esperance hinterland area of Western Australia (Timms et al., 2009).

Females are distinct from all other species due to the lack of dorsal swellings and horizontal lateral lobes on various thoracic segments, and the presence of lateral swellings on thoracomere 7 and vertical lateral flaps on thoracomere 9 and 10. Furthermore it is unusual in Parartemia females to have a vestige of thoracopod 11 as P. p u r p u re a sp. nov. does; closest species in this character is P. acidiphila with 3 terminal setae, P. laticaudata sp. nov. with two terminal spines and P. longicaudata with a subterminal spine.

Distribution and ecology. P. purpurea sp. nov. occurs in alkaline saline lakes in the Esperance hinterland, from about Grass Patch-Scadden eastwards for about 90 km to Beaumont Nature Reserve (Timms et al., 2009)( Fig. 4 ). It occurs over a salinity range of 20 to 235 g /L and in lakes with pH varying from 6.9 to 10.4 ( Timms, 2009b; Timms et al., 2009). Generally it occurs in late winter- spring as lakes fill with winterspring rains, reproduces in September and October with purple coloured females actively swimming in the shallows and depositing eggs. Occasionally summer rains fill the lakes, in which case P. purpurea sp. nov. responds as it does to a winter filling ( Timms, 2009b). Females are easily predated upon by waders (mainly Stilts, Avocets) as they swim conspicuously in shallow waters, so that sex ratios can become very biased towards males which tend to stay in deeper waters (author, unpublished observations). Presently it is common throughout this area as few lakes are salinised.

Figures

FIGURE 4. Map of Western Australia showing many places mentioned in the text and position of the type localities for each species.

FIGURE 10. Parartemia mouritzi sp. nov. A, male head with antennae ― basal segments forced apart to show median area clearly; B, male gonopods; C, female head; D dorsal view of female thorax and abdomen T 6 to T 11; E, lateral view of female thorax and abdomen T 4 to A 1. Scale bars 0.5 mm.

FIGURE 11. Parartemia purpurea sp. nov. A, male head with antennae; Aa detail of behind left ventral process, showing the conical mound; B, dorsal view of male thorax and genital segments, C, male gonopods; D, expanded gonopod; E, female head; F dorsal view of female thorax T 6 to A 1; G, lateral view of female thorax T 6 to A 1. Scale bars 0.5 mm.