Parartemia laticaudata, Timms, Brian V, 2010
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Parartemia laticaudata sp. nov.
Etymology. To mark the unusually wide abdomen in males, and to a lesser extent in females, the specific epithet of laticaudata is based on the latin latus meaning wide and cauda meaning tail, and the name formatted to match that of P. longicaudata .
Holotype. Male, near Onslow, a unnamed salina near the salt works, (21 o 41 ’ 7 ”S, 115 o 04’ 25 ”E), 10 May 2006, B. Datson, WAM 45221 View Materials .
Allotype. Female, same collecting data as holotype, WAM 45222 View Materials .
Other material. 8 males, 5 females, Lake Way, about 20 km S of Wiluna, (26 o 43 ’ 21 ”S, 120 o 14 ’ 33 ”E) 12 March 2005, V. Campagna, WAM 45224 View Materials , 5 males, 5 females, Lake Miranda, about 30 km N of Leinster, (27 o 39 ’ 05”S, 120 o 34 ’ 07”E), 9 March 2004, V. Campagna, WAM 45225 View Materials ; 10 males, 1 female, Shark Bay, small gypsum lake at Useless Loop Salt Works,(26 o 14 ’ 13 ”S, 113 o 25 ’E), 10 August 2003, B. Datson, WAM 45226 View Materials ; 10 males, 10 females, small salina near Lake Carey, about 40 km S of Laverton, (29 o 00’ 24 ”S, 122 o 25 ’ 28 ”E), 25 March 2003, BVT, WAM 45227 View Materials ; 10 males, 10 females, Lake Raeside, about 22 km SE of Leonora, (29 o 00’ 30 ”S, 121 o 30 ’E), 22 January 2007, BVT, WAM 45228 View Materials .
Description. Male. Length 18 mm (head plus thorax 8 mm, abdomen 10 mm).
First antenna ( Fig 9 View FIGURE 9 A) filiform subequal in length to eye plus peduncle.
Second antenna. Basal antennomeres ( Fig 9 View FIGURE 9 A) of second antenna fused proximally at about 55 o from body axis. Ventral margin with paired linear ventral processes ( Fig 9 View FIGURE 9 A) a little more than twice as long as the average depth with ventral edge markedly concave and with both corners (ventrolateral and ventromedial) rounded and protruding, especially the ventrolateral. Margin of ventral processes with occasional short minute spines. Area between ventral processes with a small nipple-like medial process. No anterior processes, instead a convex ridge posterior and dorsal to the medial part of the ventral process ( Fig 9 View FIGURE 9 A). Distal antennomere ( Fig 9 View FIGURE 9 A) of second antenna about twice the length of basal antennomere, curved and tapering with a slight mesial thickening.
Thoracic segments ( Fig 9 View FIGURE 9 B) tumid laterally and increasing in width slightly from 1 to 11. Genital and especially abdominal segments tumid laterally, being particularly wide. Genital segments longer than thoracomeres, but slightly narrower than preceding thoracic segments, while first two abdominal segments widest and largest of all. Abdominal segments decreasing in width but increasing in length 1 to 6; last segment about 1.5 times length of first and half its width. Cercopods subequal in length to 5 th abdominal segment.
Gonopods ( Fig 9 View FIGURE 9 C) paired. Basal parts fused together and about twice diameter of free apical part. Each free portion with a prominent asymmetrical spine and a small digitiform process mediolaterally and positioned at about two-thirds the length of the apical tube.
Thoracopod 5 similar to that of P. longicaudata , but it differs in some details, particularly in having about 13 medial endopodal posterior setae each hooked terminally and with a strong one-sided pectin on apical half. The larger anterior setae (i.e. setae of endites 1, 4, 5 and 6) also different from usual in that their double pectins of spines are thinner and more numerous on one side than the other. Further, the endopodite, although convexly curved, is wider than high. First and eleventh thoracopods noticeably reduced in size and with 11 th lacking an epipodite and praeepipodite.
Female. Length 8.6 mm (head plus thorax 5 mm, abdomen 3.6 mm)
Head ( Fig 9 View FIGURE 9 E) with first antennae filiform and short, about half length of eye plus peduncle. Second antennae a little longer than labrum and narrowing gradually to a sharp apex. Naupliar eye prominent midway between compound eyes. Labrum with a prominent recurved spine.
Thorax ( Fig 9 View FIGURE 9 F) normal until thoracomere 9. This thoracomere widest of all and with three tumidities, one middorsal and one each laterally. Thoracomere 10 sclerotized dorsolaterally; dorsum not sclerotized, the two areas meeting in an arcshaped ridge. Segment 11 widened laterioposteriorly, this enlargement supporting the stump of thoracopod ventrally. Brood pouch with each lobe roughly oval, joined ventrally to a short gonopore borne on a posteriorly directed tubular structure. Abdominal segments oval in cross section, with first two much enlarged laterally, so that first segment as wide as thoracic segment 10. Abdominal segments decrease in diameter sequentially 1 to 6 and also increase slightly in length.
Fifth thoracopod as in male, but smaller and with fewer posterior setae, e.g. only 8 medial setae on endopodite, instead of about 13. First and 10 th thoracopods reduced to less than half size of thoracopods 3 – 9. First (Fig 7 E) with all components present but with exopod less protrusive then endopod, with long basal anterior setae of endites 4 and 5 and thick (3 times thicker then adjacent anterior setae) anterior seta of endite 1. Tenth thoracopod (Fig 7 F) without an epipodite and with much reduced endites, particularly 1 + 2 and 3. Exopod a little longer than endopod, but not to extent as in thoracopods 3–9. Eleventh thoracopod (Fig 7 G) markedly reduced to just a triangular base bearing two short setae.
Resting eggs round without any surface sculpturing, but clothed in minute hairs (V. Campagna, pers.comm.).
Variability. Reproductive males vary from 8.5 mm in Lake Miranda to 18.5 mm in the salina near Lake Carey, while ovigerous females vary from 7 mm in Lake Miranda to 13 mm in the Carey salina. Combined with the type material this gives male: female length ratios ranging from 1.21 to 2.01! One of the Miranda males has one gonopod everted. The everted gonopod ( Fig 9 View FIGURE 9 D) has an uneven bulbous part terminating in a small tubular section (equivalent to the proboscis mentioned in Brendonck, 1995). The bulbous section has 7 asymmetrical triangular denticles on one side and two on the other, but closer to the base. The most variable characteristic in males is the development of the medial process; in many specimens it is almost absent, thus giving the general appearance of a convex surface between the medial bases of the ventral processes. The width of the first and second segments of the abdomen is not quite as wide as the 11 th thoracomere or 1 st genital segment in some populations. Other variable features include the angle of fusion of the basal antennomeres which ranges from 10 o to 35 o, and the basal spine of the free portion of the gonopod is often an equilateral triangle rather than being asymmetrical.
In females the most concerning variability is in the relative development of the tumidities of thoracic segment 9 – they may be hardly present in some specimens, mainly immatures. Likewise the first abdominal segment is not always greater than 2.5 times the width of the 6 th segment; lower values of around 2 are seen mainly in immature females.
Differential diagnosis. Male P. laticaudata sp. nov. are distinctive with their unusually wide abdomens. Specimens with longer medial processes could be confused with P. contracta or P. informis , but both of these species, besides having a normal proportioned abdomens, have distinct anterior processes as opposed to none in P. laticaudata sp. nov. Specimens with no apparent medial processes could be confused with either P. longicaudata or P. boomeranga sp. nov. Again both of these have anterior processes, and furthermore P. longicaudata has long abdomen due in part to its long segment 6 (see description of P. longicaudata ).
Female P. laticaudata sp. nov. belongs to a group of species with distinct tumidities on later thoracic segments. In the case of P. laticaudata sp. nov. these are only on thoracomere 9 and consist of a medial and two lateral tumidities. This distinguishes it from P. purpurea sp. nov. which has two small lateral tumidities on thoracomere 7, from P. serventyi which has a single tumidity on thoracomere 8 and P. veronicae sp. nov. which has two lateral tumidities on thoracomere 10 and 4 on thoracomere 11. Parartemia informis , P. longcaudata and P. boomeranga sp. nov. have a tumidity on thoracomere 9, but it is single and each has lateral lobes on later thoracomeres, whereas Parartemia laticaudata sp. nov. lacks thoracic lateral lobes and has 3 tumidities on thoracomere 9.
Distribution and ecology. Parartemia laticaudata sp. nov. seems to be widespread in northern Western Australia and also in central Northern Territory (Timms et al. 2009), but is rarely collected because of the remoteness of this area. In Western Australia it has been found in the northern Goldfields, coastal Carnarvon, coastal Pilbara and also in Lake Disappointment in the Little Sandy Desert Bioregion ( Fig. 4 View FIGURE 4 ). Known field salinity range is 8 to 141 g /L (Timms et al. 2009).
The stress proteins p 26, artemin and hsp 70 have been found in the resting eggs of this species, as in Artemia franciscana eggs, but at lower concentrations ( Clegg and Campagna, 2006). Together with the presence of the disaccharide trehalose which protects against desiccation, these substances are important adaptations to withstand the severe saline environments in which they occur.
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