Paralimnadia flavia, 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 : 477-480

Paralimnadia flavia n. sp.

( Figs. 4 , 11 , 14 , 15 )

Etymology. The epipodites of the types of this species are yellow and hence the Latin word ‘flavus’ meaning ‘blonde’ or ‘golden’ is the source for its specific name. Other collections of this species are not similarly coloured, but the epipodites have many chromatophores that may have been coloured before preservation.

Type material. Holotype: AM P98899, male, length 8.8 mm, height 5.7 mm, Northern Territory, 12 km SE of Jabiluka, N tributary of Radom Springs , 12°44’43”S, 132°55’27”E, 8 November 1998, C. Humphries . Allotype: AM P98911, female, length 9.5 mm, height 6.0 mm, from type locality, 8 November 1998, C. Humphries.

Other material examined. Northern Territory: 12 km SE of Jabiluka, N tributary of Radom Springs, 12°44’43”S, 132°55’27”E, 8 November 1998, C. Humphries, one male, one female, AM P55645 ; Larrimah , ca 15°35’S, 137° 11’E, 15 December 1980, M.J. Tyler, 5 females, AM P98999 . Western Australia: 34 km W of Kununurra, Yearling Creek , 5 February 1982, M.J. Tyler and M. Davis, 20 males and 15 females, WAM C61749 .

Diagnosis. Egg of two bands of parallel ridge-groove systems in line to form a basal cylindrical structure with inflated ridge separating cylinder from conical upper part (i.e., like a cupcake). Telsonic spines 17–20 pairs. Cercopod setae long (2.5–3.5 × cercopod diameter) and numerous (> 20). Clasper usually with 3 palpomeres, first palp inerm, second palp with three spines at basal junction.

Description. Male: Head ( Fig. 14 B) with ocular tubercle prominent, the compound eye occupying about 80%. Rostrum protruding subequally as ocular tubercle and at 110° from frons, triangular, apex sharp.Triangular ocellus slightly smaller than compound eye and lying at base of rostrum. Dorsal organ posterior to eye by about two-thirds its height, pedunculate and asymmetrical and two-thirds as high as ocular tubercle.

First antennae ( Fig. 14 B) about 1.75 × length of peduncle of second antennae, with 8 lobes, each with numerous short sensory setae.

Second antennae with spinose peduncle; dorsal flagellum with 12 antennomeres; ventral flagellum with 13 antennomeres; each antennomere dorsally with 1–3 short spines and ventrally with 1–5 longer setae, usually 2 spines and 3 or 4 setae. Distal antennomeres with minimal spines and maximal setae.

Carapace ( Fig. 14 A) elongated oval, highest at 40% of its length, pellucid, with many growth lines. Adductor muscle scar at about 45° to carapace long axis, only visible when animal removed from carapace.

Thoracopods. Eighteen pairs of thoracopods. Claspers ( Fig. 14 D) with palm trapezoidal with triangular projection distomedially, projection about 0.2 of distal palm width. Apical club spherical with many stout spines pointing medially.Small palp with many short, thin spines apically on gripping area. Finger arcuate with blunt apex bearing many rounded pits ventrally. Both long palps of clasper inserted on apical edge of palm, both with 3 palpomeres and many thin, limp setae on flattened palaform apical area. Only longer palp with 3 spines at the basal junction of palpomeres. Long palp of 1st clasper about 1.5× length of palm and 2.25× length in 2nd clasper.

Thoracopods. Other thoracopods of typical structure for Paralimnadia , decreasing is size and complexity posteriorly. Last 10 segments dorsally with short spine medially.

Telson ( Fig. 14 C) with about 17 pairs of posterior row spines, anteriormost spine little larger than next few; penultimate spines little longer than most spines. Spines with spinulae. Telsonic filaments originating from mound little higher than floor of telson positioned near fourth spine. Floor of telson posterior to mound sloping with marked declivity followed by slightly convex surface to base of cercopod. Cercopods subequal in length to telson, basal 60% hardly narrowing and bearing about 24 long setae of variable length (2.5–3.5 × diameter of basal cercopod) and distal 40% narrowing to acute apex and with many tiny denticles dorsolaterally. No spine demarcating the two areas. Ventroposterior corner of telson rounded and hardly protruding.

Female. Head ( Fig. 14 F) with ocular tubercle prominent, compound eye occupying about 80%. Rostrum an asymmetrically rounded bulge, little less prominent than ocular tubercle; ocellus about half as large as compound dorsobasally. Dorsal organ posterior to eye by about three quarters height, pedunculate and asymmetrical and not about three quarters as high as the ocular tubercle.

First antennae ( Fig. 14 F) little shorter than peduncle of second antennae, with 4 lobes each with many short sensory setae. Second antennae as in male.

Carapace ( Fig. 14 E) as in male, though marginally more vaulted dorsally.

Thoracopods. Eighteen thoracopods of typical Paralimnadia structure. Trunk dorsum with segments 1–9 naked, segments 10–14 with 3–5 spines medioterminally and segments 15–18 with 1 spine medioterminally. Thoracopods 9 and 10 with long flabellum dorsally.

Telson as in male, though with 20 pairs of posterior row spines of various sizes. Cercopod similar but with about 30 setae and spine at demarcation between basal and distal sections.

Egg ( Figs. 11 D–F). Average diameters 169–192 µm for the three sites, range 162–200 µm (n =15). Two bands of parallel ridge-groove systems, generally one band vertical and other sloping, but with ridge-groove systems of two bands usually linear. Vernacularly, the egg looks like a cupcake. Both bands sloping or not, always smoothly adjacent so that ridge-groove systems of two bands not linear.

Variability. With only four specimens available from the type locality, little variation was noted, but there are considerable differences between the three known sites in its distribution. The Larrimah collection has only a few females, but the Kununurra one has many individuals of both sexes ( Fig. 15 ). Its males have a triangular rostrum with its apex somewhat rounded and with a 9 or 10 lobed first antennae (cf 8 in Radom sample) and the second antenna with 12 or 13 antennomeres on each flagellum. The claspers are different too, with a less developed projection at the mediodistal corner of the hand and the longer palp has just two palpomeres instead of three. There are 16 telsonic spines but only about 16 cercopod setae (cf 17 and 24 in the Radom sample), but there is a midlength spine and the setae are long (2.5× cercopod diameter). The female also has fewer cercopod setae (ca. 15) that are long and a mid-length spine is present. However, there are 8 first antennal lobes (4 in other populations) and the female rostral bulge is less than in the Radom material and is symmetrical. The Larrimah females have an asymmetrical rostrum like that in the Radom sample and numerous (ca. 26) long cercopod setae as in the Radom sample.

Given the above variability between these three collections, it is possible three species rather than one, are represented. The indecision is aided by variation in egg morphology ( Figs. 11 D–F), though in these cases there is variation within each population and indeed eggs from each individual, so that many of the variations noted can occur in the one individual’s eggs. For simplicity and expediency the view is taken that there is one variable species, perhaps influenced by poor gene flow between these isolated populations (320 km Radom-Larrimah, 560 km Radom-Kununurra; 490 km Larrimah-Kununurra). Given cercopod characters are generally the more reliable than other body features and egg morphology is more valuable taxonomically than all body features (see Discussion), it is proposed that the numerous long cercopod setae, and the double bands of parallel groove-ridge systems in line of the eggs unite these populations into one entity.

Differental diagnosis. Morphologically P. f l a v i a n. sp. is most similar to P. queenslandicus n. sp. This is by reason of their numerous long cercopod setae, similar rostrums and claspers. However, the long palps of P. queenslandicus n. sp. are inerm, whereas the longest palp of P. f l a v i a n. sp. has spines at the basal palpomere junction. The eggs of the two species are very different—spherical with about 36 depression-groove systems arranged randomly in P. queenslandicus n. sp. as against having two rows of groove-ridges arranged in line in P. flavia n. sp. and the whole egg being shaped like a cupcake.

Distribution. Paralimnadia flavia n. sp. is sparsely distributed across the ‘Top End’ (i.e., northern quarter) of the Northern Territory and adjacent eastern Kimberleys in Western Australia ( Fig. 4 ). If these remote areas and environs were collected more intensely, P. f l a v i a may well prove to have a wider distribution and be considered more common.

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 11. Scanning electron micrographs of eggs. A-B, Paralimnadia ammolophos n. sp., C, P. bishopi n. sp., D-F, P. flavia n. sp., G-H, P. hyposalina n. sp., I-J, P. monaro n. sp., K-L, P. montana n. sp. A from Brooms Head, NSW, AM P 99008; B from Shelly Beach, NSW, AM P 99007; C from Cape Bedford, Qld, AM P 99359; D from Radom Springs, NT, AM P 98911; E from Larrimah, NT, AM P 98999; F from near Kununurra, WA, WAM C 61749; G from Coomberdale, WA, WAM C 61751; H from Watheroo, WA, WAM C 61753; I from near Berridale, NSW, AM P 99011; J from Manderley Pool, NSW, AM P 47129; K from Glencoe Lagoon, NSW, AMP 99014; L from Emu Rk Tarn, NSW, AM P 47132. Scale bars 0.1 mm.

FIGURE 14. Paralimnadia flavia n. sp., A – D male from AM P 98899 near Kakadu, NT; A – D male; A, carapace; B, head; C, telson; D, 1 st clasper with long palp of 2 nd clasper beside it; E – F female from AM P 98911; E, head; F, telson. Scale bars 0.1 mm.

FIGURE 15. Paralimnadia flavia n. sp., WAM C 61749 near Kununurra, WA. A – D male; A, carapace; B, head; C, telson; D, 1 st clasper with long palp of 2 nd clasper beside it; E – F female; E, head; F, telson. Scale bars 0.1 mm.