Eulimnadia hansoni, Brian V Timms, 2016

Brian V Timms, 2016, A partial revision of the Australian Eulimnadia Packard, 1874 (Branchiopoda: Spinicaudata: Limnadiidae), Zootaxa 4066 (4), pp. 351-389 : 374-376

Eulimnadia hansoni sp. nov.

( Figs 9 E, 14)

Etymology. This species is named for Sue and Roger Hanson, present owners of Bloodwood Station, Paroo, where the type locality is. This is a reward for their hospitality and assistance over many years to shrimp ecologists and taxonomists and recognition of their wise stewardship of the property which is central in the biodiversity hotspot for large branchiopods.

Type locality. New South Wales, Paroo district, Bloodwood Station, 125 km NW of Bourke, Marsilea Pond, 29o 32’ 13.5”S, 144o 52’ 26.0”E, 12 November, 1999, BVT.

Type material. Holotype. Male deposited in Australian Museum, Sydney, length 5.3 mm, height 3.1 mm, registration number AM P97809.

Allotype. Female deposited in Australian Museum, Sydney, length 5.6 mm, height 3.8 mm, registration number AM P97810.

Paratypes. Five females, 4.7 x 3.1 mm, 4.7 x 3.1 mm, 4.6 x 3.1 mm, 4.2 x 2.6 mm, 4.1 x 2.6 mm, registration number AM P97811.

Other Material. New South Wales: 125 km NW of Bourke, Bloodwood Station, small unnamed pond NW of Monogan’s Pan, 29o 26’ 51.3”S, 144o 48’ 39.4”E, 6 June 2007, BVT, AM P97812; Bloodwood Station, Lower Crescent Pool, 29o 32’ 36.5”S, 144o 51’ 29.4”E, 29 April 1998, BVT, AM P97813; 130 km NW of Bourke, Tredega Station, a blackbox swamp near homestead, 29o 28’ 57.8”S, 144o 52’ 02.8”E, 22 February 2011, MS & BVT, AM P97814; Queensland: Currawinya Nat Pk, creek between Paroo R and Lake Kaponyee, 28o 50’ 00.3”S, 144o 21’ 16.0”E, 17 May 1996, AM P97815; 47 km E of Thargomindah, roadside pool, 28o 05’ 12.4”S, 144o 16’ 40.3”E, 27 February 2011, MS & BVT, AMP85610; via Thargomindah, a coolabah swamp, 28o 50’ 51.9”S, 143o 53’ 54.4”E, 26 February 2011, MS & BVT, AM P85611.

Diagnosis. Egg with about 30 deep polygons, each with a central linear depression and marginally fringed. 18 trunk segments. Clasper with about 8 spines of uniform length at junction of the two palpomeres of the large palp and with a similar spine mediolaterally on basal palpomere. Cercopod setae short, usually not much longer than diameter of cercopod, and numbering about 12–15. Telsonic spines about 15, generally fairly evenly spaced and sized.

Description. Egg ( Fig 9 E) spherical, diameter 185–192 Μm (n = 5), with about 30 deep polygons, each with a central linear depression, marginally fringed, the fringe extruded into weak spines mainly at polygon junctions. These spines about the same length as the depth of each polygon. Tertiary layer spongiform and surface microporous.

Male. Head ( Fig 14 C) with ocular tubercle prominent, the compound eye occupying most (ca 80%) of it. Rostrum subequal in size to ocular tubercle, asymmetrical and most prominent dorsally with a rounded apex and an ocellus basodorsally. Frons-rostrum angle about 110o. Dorsal organ posterior to eye by about its height, pedunculate about height of ocular tubercle.

First antenna distinctly longer than peduncle of second antennae, and with 8 lobes, each with numerous short sensory setae.

Second antenna with a spinose peduncle and each flagella with 8 antennomeres, dorsally with 1–4 spines and ventrally with 1–4 longer setae. Basal and distal antennomeres with minimal spines, though setae maximal on distal antennomeres.

Carapace ( Fig 14 A) elongated oval, pellucid and with hardly any indication of growth lines. Adductor muscle scar at about 30o to the horizontal axis of carapace.

Thoracopods. Eighteen pairs, the first two modified as claspers ( Fig 14 G). Claspers with palm trapezoidal, apical club rounded with thick denticles distomedially and spine apicolaterally, moveable finger of normal curved structure and palps of typical structure. Moveable finger terminating in a suctorial disc distoventrally and with many small pits distodorsally. Long palp subequal in length to the palm in the first clasper and about 1.5x longer in second clasper; both two-segmented with about 8 spines at their junctions. Each with a spine medolaterally on the basal palpomere. All these spines a little longer than palpomere diameter. Other thoracopods of typical structure for Eulimnadia , decreasing in size and complexity after 10th thoracopod.

Trunk. Dorsal surface with 1–2 short spines medially or posteriorly on each of the posterior 12 trunk segments.

Telson ( Fig 14 E) with about 15 pairs of dorsal spines; a little variation in size and spacing. Most spines naked. Caudal filaments originating from a mound a little higher than the dorsal telsonic floor and between the 3rd and 4th spine. This dorsal floor sloping evenly posteriorly to base of cercopod. Cercopod a little longer than telson dorsum, the basal 80% hardly thinning to a small naked spine, then rapidly thinning to an acute apex. About 15 short setae (all a little longer than cercopod diameter) on dorsum of basal 80% and a cirrus of tiny denticles dorsolaterally on apical 20% of cercopod. All setae two-segmented and with more setules on distal segment than on basal. Prominent spiniform projection beneath the cercopods at the ventroposterior corner of the telson.

Hermaphrodite. Head ( Fig 14 D) with ocular tubercle prominent, with compound eye occupying most (ca 80%) of it. Rostrum a smooth bulge at an angle of about 160o to the frons and with the ocellus basodorsal. Ocellus about 40% size of eye. Dorsal organ posterior to eye bya bout its height, pedunculate and asymmetrical and subequal in height to ocular tubercle.

First antenna subequal in length to the peduncle of second antenna, with six small lobes each with many short sensory setae. Second antenna as in male.

Carapace ( Fig 14 B) as in male, though dorsum more vaulted.

Thoracopods. Eighteen of typical Eulimnadia structure.

Trunk dorsum with 3–9 setae terminally, these setae few, short and stout on posterior few segments, numerous and longer on segments 8–15 and hardly any setae on anterior trunk segments 1–7.

Telson ( Fig 14 F) as in male, though with 14 cercopod setae.

Variability. Many meristic structures vary numerically so that telsonic spines can number 12–16, cercopod setae 11–15, first antennal lobes 7–9 in male and 5–7 in females, and clasper palp spines 7–9. Eggs can lack spines (maybe they have worn off in older eggs) and can have about 40 polygons. Only rarely do antennomeres of the second antenna number more than 8, and then only to 9.

Comments. While many features are within the range usually seen in Eulimnadia , the cercopod setae are distinctive as they are short and numerous, whereas in many other species they are long (e.g. E. dahli ) or distinctly fewer in number (e.g. E. centenaria sp. nov.). In having about 15 telsonic spines fairly uniform in size and spacing, this species is distinct from others with fewer spines (e.g. E. uluruensis sp. nov.), irregular spacing and size (e.g. E. centenaria sp. nov.), or with>16 spines (e.g. E. contraria sp. nov.). Many Australian species of Eulimnadia have 5 spines at the palpomere junctions, but E. hansoni has 8 spines plus another midlaterally on the basal palpomere, to make this species unique. The eggs are also distinctive with their frilled polygons, though these can be like those of E. dahli and E. gnammaphila sp. nov. eggs in form, there are differences, with those of E. hansoni with about 30 polygons and with a frothy surface.

Eulimandia hansoni could be any one of four of Schwentner et al ’s (2015) species G, H, K or 0, such was the high syntopy in many Paroo sites.

Few males occur in the collections, suggesting androdiocious mode of reproduction (Weeks et al., 2008).

Distribution. Central and northern Paroo and Bulloo River systems. It may be more widespread as specimens in AM P10145 from Central Australia and AM P91993 from near Aramac, central Qld have some similarities, but there are too few specimens for a detailed study.

Figures

FIGURE 9. Eulimnadia eggs. A, E. contraria sp. nov. (Lake Dunn, Qld); B, E. gnammaphila Kooyoora, Vic); C, E. gnammaphila (Peela, SA); D, E. gnammaphila (Yanneymooning, WA); E. hansoni (Bloodwood, NSW); F, E. pinocchionis (Karratha, WA), G, E. taroomaensis (Taroom, Qld), H, E. uluruensis (Uluru, NT); enlargement of portion of egg of E. uluruensis. Scale bars 1 mm, except I for which the bar = 0.01 mm.

FIGURE 14. Eulimnadia hansoni sp. nov. Bloodwood Station, NSW. A, male carapace; B, female carapace; C, male head and antennae; D, female head; E, male telson; F, female telson; G, male clasper. Scale bars 1 mm.