Parartemia longicaudata Linder, 1941, Linder, 1941

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: 3-9

publication ID

http://doi.org/ 10.5281/zenodo.199709

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http://treatment.plazi.org/id/5D556922-6440-6550-FF0B-A255FCB4FD09

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Plazi

scientific name

Parartemia longicaudata Linder, 1941
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Parartemia longicaudata Linder, 1941  

( Figs. 1–4 View FIGURE 1. P View FIGURE 4 )

Linder (1941) provides a brief description of males of this species, based on six poorly preserved specimens which have subsequently been lost from the WAM. Given that the female was unknown at the time of description, there are no types and that it is similar to one of the new species described below, P. longicaudata   is herein redescribed and a neotype designated.

Neotype. one male, Pink Lake, Esperance, (33 o 50 ’ 42 ”S, 121 o 49 ’ 39 ”E), 7 October 2008, BVT, WAM 45203 View Materials .

Topotypes. 1 female, same collecting data as neotype, WAM 45204 View Materials ; 2 males, 2 females, same collecting data as neotype, WAM 45205 View Materials ; 2 males, 2 females, some collecting data as neotype, AM P 82971 View Materials

Other material. 7 males, 6 females, small roadside salt lake southeast of Yarra Yarra Lake, 5 km W of Winchester, (29 o 46 ’ 17 ”S, 115 o 52 ’ 31 ”E), 14 September 2003, BVT, WAM 45206 View Materials ; 5 males, 3 females, small roadside salt lake 18 km S of Lake Grace, (33 o 15 ’ 50 ”S, 118 o 28 ’ 09”E), 28 July 2008, BVT, WAM 45207 View Materials ; 7 males, 3 females, Lake Carmody, southern end, (32 o 32 ’ 48 ”S, 119 o 21 ’ 50 ”E), 12 August 2008, BVT, WAM 45208 View Materials ; 10 males, 10 females, Esperance hinterland, North Speddingup Road, small lake 9 km E of railway, (33 o 30 ’ 56 ”S, 121 o 52 ’ 12 ”E), 2 August 2005; BVT, WAM 45209 View Materials ; 20 males, 20 females, Israelite Bay, Daringdella Lake, (33 o 39 ’S, 123 o 49 ’E), 31 January 2007, BVT, WAM 45210 View Materials .

Description. Male. Length 24.6 mm (head plus thorax 10 mm, abdomen 14.6 mm).

First antenna ( Fig 1 View FIGURE 1. P A) filiform, almost twice as long as eye plus peduncle and subequal in length to basal antennomere of second antenna.

FIGURE 2. P. longicaudata   . Male, 5 th thoracopod. Length 3.2 mm (without setae). Main diagram shows posterior setae (PS) and subsidiary diagram of endites shows anterior setae ( AS). Some setae enlarged. Key: End = endite, Edp = endopodite, Exp = exopodite, Epp = epipodite, Pep = praeepipodite.

Second antenna. Basal antennomeres ( Fig 1 View FIGURE 1. P A) fused at about 45 o to body axis. Ventral margin with paired ventral processes ( Fig 1 View FIGURE 1. P A) about 1.5 times longer than high. Distoventral corner of ventral processes broadly rounded and slightly protruding while medial edge thickened cylindrically and also protruded, but more expressed and narrowly rounded. Ventral process margin clothed in well spaced minute spines. Medial space between ventral processes a little narrower than their length and domed. Anterior process ( Fig 1 View FIGURE 1. P A) digitiform, small and subequal to ventral process depth. Distal antennomere almost twice as long as basal antennomere, somewhat curved medially, cylindrical and tapering to a sharp apex. Labrum lacking a spine.

Thoracic segments ( Fig 1 View FIGURE 1. P B) with small lateral lobes, increasing in size posteriorly and reaching a maximum on segment 11. Lateral bulge on first genital segment even greater than 11 th lobe, so that maximum body width in genital segments. Eleven pairs of thoracopods, with first two reduced in size and last without an epipodite.

Fifth thoracopod (Fig. 2) with endite 1 + 2 and 3 evenly curved, the former about 3 times the size of the later. Endite 1 anterior seta about as two-thirds as long as adjacent posterior setae (shown enlarged in Fig. 2) and with few setae. Endite 2 anterior seta very short, about same length as base of anterior seta 1. Its spine even shorter and both weakly setose apically. Endite 3 anterior seta about four times length of anterior setae 2; both it and its subequal spine weakly setose apically. Endites 1 to 3 with posterior setae long and thin, clothed with numerous short setules and numbering about 60 on endite 1 + 2 and 15 on endite 3. Endites 4 to 6 asymmetrical (i.e. distal edge shorter than proximal edge) and with 2 anterior + 3 posterior setae, 2 + 2 and 1 + 2 respectively. Anterior setae of unequal lengths, but shorter and stouter than posterior setae, except basal seta of endite 4; this seta subequal in length to adjacent posterior setae. The five anterior setae of endites 4–6 with a double pectin of short setules except near their bases. All endites clothed basally with small spines generally grouped in 3–5 s (not shown in Fig. 1 View FIGURE 1. P ). Endopodite broadly rounded and bearing about 36 posterior setae, all based with a coronet of numerous (> 10) small spines. The first 8 of these setae (essentially those on the medial edge of the thoracopod) stouter and with a one-sided pectin on the distal half of setae, whereas the remaining setae thinner and closely feathered with short setules. Exopodite elongate oval and about twice length of endopod and bearing about 44 posterior setae similar to most on the endopodite. Epipodite oval shaped and praeepipodite elongated oval shaped, both unadorned.

First thoracopod (Fig 3 A) less than half the size of thoracopods 4–10; 2 nd, 3 rd, and 11 th also reduced in size. These four thoracopods essentially similar to thoracopod 5, but 1 st with a stout endite 1 anterior setae and a large endite 5 basal anterior seta as well as the usual enlarged endite 4 basal anterior seta (Fig 3 A). The 1 st endite anterior seta with a double pectin of stout stunted spines (‘teeth’), better developed on one side than the other, and the other two large anterior seta with double pectin of thin spines. Anterior setae reduced in numbers on endopod (8 cf ca 36) and exopod (20 cf ca 45).

Thoracopod 11 lacks an epipodite.

Gonopods ( Fig 1 View FIGURE 1. P C) fused basally. Each free apical tube with a recurved spine basoventrally and a short digitiform process inserted ventrolaterally at about half the length of the tube.

FIGURE 3. P. longicaudata   , some other thoracopods. A, male 1 st thoracopod; B, female 1 st thoracopod; C, female 10 th thoracopod; D, female 11 th thoracopod. Numbers on endites, endopodite and exopodite refer to the usual numbers of posterior setae on that part. Those of endites 4 to 6 almost always are invariable for the thoracopod concerned, but the higher numbers on other endites and the endopodite and exopodite can vary by up to about 10 %. Not to scale, but most thoracopods are 0.5 to 1.5 mm long, with the 10 th shorter than the 1 st and 11 th, if present, <0.5 mm in length.

Abdomen ( Fig 1 View FIGURE 1. P B) with segments increasing in length and decreasing in diameter sequentially 1 to 6, with sixth unusually long being a little more than twice the length (and half the diameter) of first segment. Cercopods about length of fifth abdominal segment and sixth abdominal segment unusually long, about 2.5 times length of first abdominal segment.

Female. Length 11 mm (head plus thorax 5.9 mm, abdomen 5.1 mm).

Head ( Fig 1 View FIGURE 1. P D) with first antenna filiform and a little longer than eye plus peduncle. Second antenna a little longer than twice length of pedunculate eye, somewhat flattened, and narrowing suddenly to a sharp apex. Labrum with a prominent recurved spine.

Thoracic segments ( Figs 1 View FIGURE 1. P E,F) 1–8 typical, but segment 9 with prominent lateral lobes and dorsally a large tumidity. Segment 10, and particularly 11, reduced, sclerotized and dorsum denticulate. Neither with lateral lobes. Anterior edge of genital segment crenulated and in life close to posterior edge of segment 9 ’s lateral lobe. Brood pouch extended laterally and posteriorly terminating in a posteriolateral extension.

Fifth thoracopod as in males (Fig. 2), but with exopodite less prominent and with all anterior setae shorter than posterior setae and tapering uniformally, i.e. no blade like portion on any anterior setae. Ninth thoracopod, although smaller than average, of normal proportions, but with the basal anterior seta of endite 4 longer than adjacent posterior setae. First and tenth thoracopods much smaller than usual and with different component proportions. First thoracopod (Fig. 3 B) similar to that in males but with a few more anterior setae on endopodite and exopodite, and double pecten of stout blunt spines on first endite anterior setae more balanced. Tenth thoracopod (Fig. 3 C) more reduced, with no praeepipodite or epipodite, reduced numbers of anterior setae on exopodite, endopodite and endites 1–6, and no anterior seta particularly enlarged. Eleventh thoracopod represented by a bulbous protrusion with a small spinous projection (Fig. 3 D).

Abdominal segments typical for Parartemia   , i.e. segments increase in length sequentially from segments 1 to 6. Surface coarsely denticulate.

Variability. Absolute size of adult males ranges from 10 mm in Lake Daringdella to 27 mm in a small lake near Lake Yarra Yarra and of adult ovigerous females from 7 mm in Lake Daringdella to 14 mm in the lake near Lake Yarra. In some populations the frontal process is somewhat shorter than the ventral processes are deep, while in others genital segments may not be quite as swollen as the lateral lobe of the 11 th thoracic segment, and in others the 6 th abdominal segment may be 2.5 to 3 times the length of the first. In females the tumidity on segment 9 may be small and hardly noticeable, and in other populations the lateral lobe of segment 9 may be extended backwards, and in still others where females are large, the ventrolateral tumidity between thoracic segments 9 and 11 is large and bears a small projection posteriorly. In the Lake Carmody population, the brood pouch is slightly extended posteriolaterally in the form of an egg-free pocket.

Differential diagnosis. No other species, except Parartemia boomeranga   sp. nov., has a wide area between the ventral processes without a medial process; in P. longicaudata   this area is convexly domed, while in Parartemia boomeranga   sp. nov. it is concave. Further, more subtle differences, between these two closely related species are given under Parartemia boomeranga   sp. nov. The long abdomen and long 6 th abdominal segment are unusual, but not unique as shown below.

Female Parartemia longicaudata   are distinctive from all other Parartemia   , except again Parartemia boomeranga   sp. nov., by having a central dorsal tumidity on thoracomere 9, but the two species are separable by the relative development of thoracomeres 10 and 11; in P. longicaudata   thoracomere 10> 11, but in Parartemia boomeranga   sp. nov. the sizes are reversed. Other differences are given under Parartemia boomeranga   sp. nov.

Remarks. I am confident Linder and I are dealing with the same species as the neotype and topotypes are from the original type locality and the two descriptions are essentially the same, but the present account is more detailed. It differs in the understanding of the 8 th abdominal segment (now 6 th as the genital segments are now regarded as modified thoracic segments ― Walossek, 1993). Linder claims it is ‘very long’ and the ‘boundary between it and the telson obscure.’ Certainly this segment is longer than usual (ratio of length of first abdominal segment to sixth is an average of 2.24 times in 10 specimens compared to somewhat less than 2 times in many other species of Parartemia   , eg, 1.31 in 10 specimens of P. informis   , another large species) Also the whole abdomen is relatively longer than in many other large species ― the ratio abdominal length to head plus thorax length is an average of 1.27 in 10 specimens of P. longicaudata   compared with 1.09 in 10 specimens of P. informis Linder. However   some other species have relatively long abdomens, eg. P. purpurea   sp. nov. the average ratio is 1.78 (see below) and some small species also have relatively long abdomens e.g. the ratio in P. yarleensis Timms and Hudson 2009   , a species <18 mm, is 1.4. However it is true that among the species familiar to Linder, P. longicaudata   has an unusually long abdomen.

The thoracopods of P. longicaudata   are similar to those described for the genus ( Linder, 1941, though with different terminology), and for P. minuta ( Geddes, 1973)   and P. acidiphila ( Timms and Hudson, 2009)   . The greatest differences from many other Parartemia   species include larger numbers of posterior setae on endites 1–3 and exopodite.

Distribution and ecology. P. longicaudata   is common throughout the Western Australian Wheatbelt, particularly in a band through Lake Grace ― Lake King and also northeast of Perth ( Fig. 4 View FIGURE 4 ). It extends easterly to lakes bordering Israelite Bay and northerly to around Morawa; there are no records in the central east e.g. north of Merredin, nor in the Goldfields (Timms et al., 2009). It can withstand high salinities to at least 240 g /L and in the Esperance hinterland lives in higher salinity alkaline lakes while other species live in lower salinity lakes and acid salinas ( Timms, 2009 b).

WAM

Western Australian Museum