Paralimnadia multispinosa, Timms, Brian V., 2016

Timms, Brian V., 2016, A review of the Australian endemic clam shrimp, Paralimnadia Sars 1896 (Crustacea: Branchiopoda: Spinicaudata), Zootaxa 4161 (4), pp. 451-508 : 487-490

Paralimnadia multispinosa n. sp.

( Figs. 4 , 19 , 20 )

Etymology. This species has more than 24 spines on the telson, making it unusual among Paralimnadia , hence the specific epithet of ‘ multispinosa ’

Type material. Holotype: WAM C61754, male, length 7.1 mm, height 4.3 mm, Western Australia, Paynes Find , 12 km E on Great Northern Highway, a roadside burrow pit, 29°17’12”S, 117°33’52”E, 21 August 2011 , BVT. Allotype: WAM C61755, female, length 6.9 mm, height 4.0 mm, collected with holotype. Paratypes: male, 7.3 × 4.5 mm, female, 6.3 × 3.9 mm, from Western Australia, Paynes Find , 12 km E on Great Northern Highway, a roadside burrow pit, 29°17’12”S, 117°33’ 52”E, 21 August 2011, BVT, AM P99019.

Other material examined. Western Australia, Paynes Find , 12 km E on Great Northern Highway, a roadside burrow pit, 29°17’12”S, 117°33’52”E, 21 August 2011, BVT, 7 males, 4 females, WAM C61756 .

Diagnosis. Egg spherical with about 80 elongated polygons with irregular walls and on smooth surface. Telson with about 26 pairs of closely spaced spines and telsonic setae inserted at 6th–8th spine. Cercopod with about 6 setae about as long as basal diameter of cercopod and confined to basal quarter leaving next quarter inerm until single spine at 50% length.

Description. Male: Head ( Fig. 19 B) with ocular tubercle prominent; spherical compound eye occupying about 80%. Rostrum protruding little more than ocular tubercle and at an angle of 115° from base, triangular, apex blunt. Ocellus about two thirds size of compound eye and lying at base of rostrum. Dorsal organ posterior to eye by about its height, pedunculate and asymmetrical and about half as high as ocular tubercle.

First antennae ( Fig. 19 B) about 1.5 × the length of peduncle of second antennae, and with 8 lobes. Second antennae with spinose peduncle; both dorsal and ventral flagella with 12 antennomeres, each armed with 2–4 short spines dorsally and 2–8 setae ventrally. Distal antennomeres with minimal spines and maximal setae, though most common arrangement 3 spines and 5 or 6 setae.

Carapace ( Fig. 19 A) elongated oval, pellucid, hardly any indication of growth lines externally, though few visible internally. Adductor muscle scar at about 45° to carapace long axis, only visible when animal removed from carapace.

Thoracopods. Eighteen pairs of thoracopods. C laspers ( Fig. 19 D) with palm trapezoidal with distinct rounded endite III distomedially. Apical club spherical with many stout denticles apically, few long spines medially. Small palp with many short aciculate spines apically. Finger arcuate with blunt apex bearing many rounded pits ventrally. Both long palps of claspers inserted on apical edge of palm, palp of 1st clasper with 2 palpomeres and about twice as long as the palm; palp of 2nd clapser with 3 palpomeres and about 2.3 × palm length. Both palps inerm at palpomere junctions but with many limp filiform spines on flattened palaform apical area. Other thoracopods of typical structure for Paralimnadia , decreasing is size and complexity posteriorly. Last three segments dorsally with 1–3 short spines medially; next 5 segments with 3–9 longer spines/setae medially.

Telson ( Fig. 19 C) spine ridges with about 26 pairs of spines; anteriormost spine not much larger than the next few; penultimate spines little longer than most spines. All spines crowded, with spinules. Telsonic filaments originating from mound little higher than dorsal floor of telson positioned after sixth spine. Floor of telson posterior to mound with declivity, followed by distinctly convex telsonic floor. Cercopods almost as long as dorsum of telson, basal 50% narrowing to small spine then tapering to acute apex. About 6 short setae, each little longer than basal diameter of cercopod. These setae confined to basal quarter of cercopod, next quarter inerm, small spine dorsally at half-length, many tiny denticles dorsolaterally on apical half. Setae geniculate and plumose on upper two-thirds. Posteroventral corner of telson rounded and hardly protruding.

Female. Head ( Fig. 19 F) with ocular tubercle prominent, with compound eye occupying about 80%. Rostrum a rounded asymmetrical bulge, protruding about same as ocular tubercle. Ocellus large, about half size of compound eye, located in basodorsal area of rostrum. Dorsal organ posterior to eye by about its height, pedunculate and asymmetrical and about half height of ocular tubercle.

First antennae ( Fig. 19 F) little shorter than peduncle of second antennae, with about 4 small lobes. Second antennae largely as in male, but with ventral flagellum with 13 antennomeres; dorsal spines 1–5 and ventral setae 1–6, with typical number of 3 spines and 4 or 5 setae.

Carapace ( Fig. 19 E) virtually identical to that of male.

Thoracopods. Eighteen thoracopods of typical Paralimnadia structure. Trunk dorsum with segments 1–9 naked, segments 10–15; with 3–9 long spines/setae distomedially; segments 16–18 with 1–3 short spines medioterminally. Thoracopods 9 and 10 with long flabellum dorsally.

Telson ( Fig. 19 G) as in male, though telsonic setae inserted between 7th and 8th spine.

Egg ( Fig. 20 A) diameter 276 µm, range 253–282 µm, n = 5. Spherical with about 80 elongated polygons, sometimes in rows of 3–5 but generally randomly arranged, each with uneven discrete walls and flat floors. Slight elevations where walls meet. (In the vernacular, the walls look like amateur strings of icing added to a smooth ball) Variability. This species is known only from one locality, so its full morphological variability is unknown. Little departure in numbers of meristic features was noted, i.e., always 8 or 9 first antennae lobes in male and 3 or 4 in females, 11–13 antennomeres, 26 or 27 pairs of telsonic spines, and 6 cercopod setae. One specimen had only two palpomeres in the long palp of the 2nd clasper, instead of three.

Differential diagnosis. No other species has a spherical egg with superficial elongated polygons (ca. 80) demarcated by irregular ropey walls and inner surface flat. The large number (ca. 26) of telsonic spines and an inerm partial section of the cercopod is shared by only P. westraliensis n. sp., from which it is distinguished by its shorter and less numerous cercopod setae.

Distribution and ecology. This species is known only from the Paynes Find area in Western Australia ( Fig. 4 ). The habitat was semiturbid water of a roadside burrow pit. Its natural habitat is unknown.

Figures

FIGURE 4. Map of Australia showing distributions of all species with insert of details of Sydney region, especially for sites of P. stanyleyana.

FIGURE 19. Paralimnadia multispinosa n. sp.: A – D, male, WAM C 61754; E – G, female, WAM C 61755. A, carapace; B, head; C, telson; D, 1 st claspers and long palp of 2 nd clasper; E, carapace; F, head; G, telson. Scale bars 1 mm.

FIGURE 20. Scanning electron micrographs of eggs. A, Paralimnadia multispinosa n. sp.; B – F, P. queenslandicus n sp.; G – H, P. saxitalis n. sp.; I – L, P. westraliensis n. sp. A, near Paynes Find, WA, WAM C 61755; B, near Lake Buchanan, Qld AM P 99026; C, near Lake Buchanan, Qld showing details of the paired pits; D, Craven Peak Station, Qld, AM P 99030; E, near Emerald, Qld, AM P 99031; F, Bloodwood Station, Paroo, NSW, AM P 99036; G, Mt Kaputar, NSW, AM P 99021; H, Uluru NT, AM P 98561; I, Sieda Farm, near Grass Patch, WA, WAM C 61758; J, Guest Rd Lake, near Grass Patch, WA, WAM C 61762; K, Wanarra Station, near Perenjori, WA, WAM C 61763; L, Austin Downs Station, near Cue, WA, WAM C 61764. Scale bars: A, B, D – I 0.1 mm; C 0.01 mm.