Limnadopsis parvispinus Henry, 1924

Timms, Brian V., 2009, A Revision of the Australian Endemic Clam Shrimp Genus Limnadopsis Spencer & Hall (Crustacea: Branchiopoda: Spinicaudata: Limnadiidae), Records of the Australian Museum 61 (1), pp. 49-72 : 58-60

Limnadopsis parvispinus Henry, 1924

Figs. 2C , 4C , 5G,H , 8 , 9

Limnadopsis parvispinus Henry, 1924: 121 (list), 132 (key), 132–133, pl. 32, figs. 1–7; Brtek, 1997: 58 (list); Richter & Timms, 2005: 349.

Types. Syntypes (3 3, 9 ♀) in AM G5524 and G5226 .

Comment on types. The syntypes are from two different localities about 305 km apart. The inaccurate (see below) original description seems to be based on all specimens, and given the variability in this species (see below), it was decided not to choose a lectotype from a particular locality because this may jeopardize future detailed work on this species/species complex.

Material. New South Wales: 103, 10♀, 180 km NW of Bourke, Brindingabba-Willara Crossing Road , 29.3°S 144.7°E, 9.iii.1995, B. V . Timms , AM P47126 ; 63, 3♀, NW of Bourke, Bloodwood Station, Lower Crescent pool on Bell Ck , 29°32'S 144°52'E, 10.vi.1998; B. V . Timms , AM P76804 ; 13, 4♀, NW of Bourke, Bloodwood Station, Marsilea Pool , 29°33'S 144°52'E, 7.xii.1999, B. V . Timms , AM P76805 ; 103, 15♀, NW of Bourke, Tredega Station, Johnsons Tank , 29.5°S 144.9°E, 26.i.1995, B. V . Timms , AM P47124 ; 33, 9♀, NW of Bourke, Tredega Station, Johnsons Tank , 29.5°S 144.9°E, 10.iii.1995, B. V . Timms , AM P47125 ; 23, 4♀, NW of Bourke, Muella Station , vegetated pool no. 3 near homestead, 29°31'S 144°56'E, 7.xii.1999; B. V . Timms , AM P76806 ; 1♀, near Trangie, Old Cathundral , 31°55'S 147°50'E, 12.ii.1941, W. R . G. Officer; 13, 6♀, Griffith District, Rice Bay , 34.3°S 146.0°E, 15.xi.1979, E.L. Jones, AM P53290 ; 133, 8♀, no data, P6788; 6♀, SW of Ivanhoe, Mossgiel , 33°12'S 144°36'E, no date, H.K. Bennett, AM G 5224 ; 33, 3♀, NW of Cootamundra, Bland district , 34°18'S 147°48'E, no date or collector, AM G5226 ; 42 individuals, W of Cooma, Coolringdon Station, Fat Hen Lake , 36°16'S 148°56'E, 19.iv.1992. B. V . Timms , AM P76807 . Queensland: 12 individuals, S of Bollon, Bendee Station , a clearwater lake, 28°12'10"S 146°43'35"E, 23.iv.2004, S. Peck, QM W28373 ; 11 individuals, SW of Cunnamulla, Rockwell Station, Buster Black Box Swamp , 28°48'S 145°02'E, 9.xii.1999; B. V . Timms , QM W28374 .

Distribution. Inland NSW and southern inland QLD, but could be further north, west, and south of this area.

Comments. Henry’s (1924) account is sufficient to identify the species, but is inadequate on details and contains some significant inaccuracies. One of these is the claim that there are about 30 pairs of thoracopods whereas there are 25–26, and another is a supposed series of spines on the basal three-quarters of the caudal claw, whereas there is actually a mixture of a few spines apically and many setae basally. Furthermore, Henry (1924) wrote that the “the end claws are not so strongly armed” in females, whereas little difference from the situation in males, or the opposite, was observed in the syntypes. The species is redescribed below, on the basis of the syntypes.

Redescription. Male: Carapace ( Fig. 8A ) oval, generally about 15 mm long and 9 mm, L:D ratio of 1.66. Dorsal margin weakly convex and with slight depression anterior to weakly developed umbo. Both dorsoanterior and dorsoposterior angles indistinct, and anterior carapace, and particularly the posterior carapace, protruding and strongly but unevenly convex. Ventral edge weakly and evenly convex. Dorsal margin almost smooth, though with some slight serrations at posterior growth lines. Growth lines 11–12, typically weakly developed. Carapace weakly granulated within, but with smooth, somewhat lustrous, surface.

Head ( Fig. 8B ) with pyriform frontal organ situated posteriorly and about as high as eye mound Anterior side of eye mound and rostrum meeting at about 120°, junction evenly curved. Rostrum triangular, about 1.5 times longer than its basal width, with apex narrowly rounded and naupliar eye situated basally with its axis tipped about 45° ventrally to that of rostrum. First antenna subequal in length to peduncle of second antenna and with about 9 lobules. Second antenna with peduncle of about 12 apparent segments and flagella with 16–18 flagellomeres. Spination of middle flagellomeres variable, ranging from 4–7 spines and sometimes with two grouped apically.

Trunk segments usually 25, occasionally 26, each bearing pair of thoracopods, these decreasing in size posteriorly with anterior two modified as claspers. Posterodorsal armature with 1–3 spines on small protuberances on each of last 6–7 segments and a few setae on 4–6 segments anterior to these. Claspers of normal Limnadopsis structure, but with 1–3 spines apically on movable finger and prominent protrusion clasper. Scale bars 1 mm. midway on the anterior edge of hand. Third thoracopod ( Fig. 4C ) similar in structure to that of L. birchii . Proportions of endites, endopod, exopod and epipodite slightly different, and significantly palp of fifth endite slightly shorter than fifth endite and epipodite proportionally larger. Other thoracopods of same basic structure, but without palp and with even larger epipodite.

Telson ( Fig. 8C ) with 18 dorsal spines in each row. Most anterior spine about 1.25 times larger than next few. Most spines subequal in size and evenly spaced, though most posterior ones smaller and crowded on fixed telsonic claw. Two telsonic setae inserted on protuberance situated about one quarter of way along dorsal margin of telson. Caudal claws about 8–10 times longer than wide, with long, almost straight basal section of fairly even width and much shorter, curved apical part narrowing to sharp apex. Basally each caudal claw bearing about 15 setae mediodorsally, most slightly longer than width of claw, followed by about 6 short spines almost dorsally, last of these being largest. First few spines sometimes arising from between last few setae. Curved apical part beyond last spine bearing many short denticles dorsally.

Female. Carapace ( Fig. 8D ) similar to that of male, but more compact (length 13–14 mm, height 9–9.5 mm) and with more convex dorsal and ventral margins. Depression anterior to umbo hardly present or not at all. Growth lines 10–11, weakly expressed.

Rostrum ( Fig. 8E ) a shorter isosceles triangle than in males, with basal width just greater than length. Apex rounded. First and second antennae as in male, but some of syntypes with one fewer lobe on first antennae.

Remainder of animal similar to male, except for tendency to have more spines (up to 10) on cercopods, with many of these spines mixed with last few setae.

Eggs variable ( Figs. 5G,H ). Most populations with eggs shaped like subconical cylinders (i.e. cupcake- or muffinshaped) about 170 µm in diameter and height (range 168–174 µm, n = 6). Sloping sides with 16–20 parallel grooves, with narrow ridge within each groove, and low, wide ridges between, all generally sloping at about 30° from vertical axis of egg. Outer cortex with more included bubbles than in other species of Limnadopsis . Base generally with 2–4 parallel grooves on overall flat surface, but sometimes grooves crescent-shaped and not parallel. Dome of egg with many (4–8) grooves in parallel and grouped; highest point often off centre of vertical axis of egg. Occasionally (as in specimens from Fat Hen Lake), ridges between grooves possessing many included bubbles and dome lacking, thus egg is more cylindrical, and number of grooves on sides reduced to 10–12.

Variability. Limnadopsis parvispinus is a particularly variable species (cf. Figs. 8 , 9 ). The carapace shape is reasonably standard, except for the difference in shape between males and females, but the number of growth lines in apparently mature specimens and their expression is quite variable. Generally there are about 12–15 growth lines, which are scarcely visible except near the dorsal margin. Populations with 10–12 lines occur in the Paroo, and there are 15–18 readily visible lines in individuals from Bollon. Henry (1924) gave the range as 12–14 lines, and all “well marked.” Individual specimens are generally transparent and yellowish green ( Henry, 1924), although those from Bollon are brown, especially near the dorsal margin.

While there is a consistent distinct difference in rostrum shape between males and females, in both sexes it is variable. In males, it may be rectangular or pointed, longer (length 2 twice depth) or shorter (length = depth), and the apex is sometimes curved ventrally. In females, it is always short and shaped like an isosceles triangle, but the height of the triangle is variable. The naupliar eye is always positioned near the base of the rostrum, but its orientation is variable, two common positions being aligned with the axis of the rostrum or with the base at a 45–60° angle to the rostrum axis. The population from Buster’s Black Box Swamp, Queensland, had intersex “males” with a short rostrum and small claspers and no ordinary males.

The length of the first antenna is generally subequal to that of the peduncle of the second antenna, but in males it is slightly longer and has more lobes than in females. In males the lobes number 7–10, typically about 9, while in females the range is 7–9, with a mean of about 8. The peduncle of the second antenna typically has 12 apparent segments, while the number of flagellomeres varies from 14–21, often about 18.

Trunk segments generally number 25, but occasional specimens have 26. Posterodorsal thoracic armature in both sexes involves about the 6–7 most posterior segments each with 1–3 dorsal spines on a small protuberance, preceded by 6–7 segments with long hair-setae on similar protuberances, these decreasing in number and size anteriorly from many long setae per segment to 1–2 short setae per segment. The claspers are of standard structure for Limnadopsis , with the only variability noted in the spines tipping the movable finger; they are relatively small (cf. the spine in L. tatei ) and number 1–3.

On the telson the most anterior dorsal spine in each row ranges from 1.25 times the size of the next few spines (in the syntypes) to otherwise about 1.5 times the size of the next few spines (in most specimens). Telsonic spines vary between 16 and 22 in number and are usually subequal in size and spacing, but uncommonly may be variable in both features. Almost always a few are placed on the ascending limb of the large, posterior, fixed telsonic claw. Although the caudal claws are generally long and thin (8–10 times longer than wide) with a long, straight, proximal section bearing the setae and spines, other proportions occur. The setae on the basal half of the caudal claws vary between 8 and 15 in number and generally are relatively short, particularly the last few, which often overlap with dorsal spines, situated at half to two-thirds the length of the caudal claws. These spines number 4–10 (often c. 6), with the most posterior the thickest, but not necessarily the longest. There are always many fine denticles on the dorsal surface of the curved, tapering apical part of the claw.

Figures

Fig. 2. Photographs of whole specimens of species of Limnadopsis. (A) L. birchii; (B) L. tatei; (C) L. parvispinus; (D) L. minuta; (E) L. multilineata; (F) L. occidentalis; (G) L. paradoxa; (H) L. pilbarensis. Scale bars 5 mm.

Fig. 4. Third thoracopods of males of (A) L. birchii; (B) L. tatei; (C) L. parvispinus; and (D) L. paradoxa n.sp. A few of the numerous setae (see text), and details of the major types of setae are shown only for L. birchii. Scale bars 1 mm.

Fig. 5. SEMs of eggs. (A) Limnadopsis birchii, Twin Pans, Currawinya National Park, Qld; (B) L. birchii, Bluebush Bore Swamp, via Carnarvon, WA; (C) L. multilineata, Mitchell River Falls, Kimberley, WA; (D) L. tatei, Bloodwood Station, Paroo; (E) L. tatei, near Laverton, WA; (F) L. pilbarensis, Chichester Range, WA; (G) L. parvispinus, Bloodwood Station, via Bourke, NSW; (H) L. parvispinus, Coolringdon Station, via Cooma, NSW; (J) L. occidentalis, Boolathana Station, via Carnarvon, WA; (K) L. paradoxa, Sieda Farm, Grass Patch, WA; (L) L. paradoxa, East Lake Bryde, via Newdegate, WA; (M) L. minuta, Keep River National Park, NT. Scale bars 50 µm.

Fig. 8. Limnadopsis parvispinus Henry, syntypes, Mossgiel, NSW. (A) male carapace; (B) male head; (C) male telson;

Fig. 9. Limnadopsis parvispinus Henry, Bollon, Qld. Male: (A) carapace; (B) head; (C) telson; (D) cercopod; (E)