Eulimnadia taroomaensis , Brian V Timms, 2016
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Eulimnadia taroomaensis sp. nov.
( Figs. 9View FIGURE 9 G, 16)
Etymology. The species is named after the major town, Taroom, in the region where it was collected.
Type locality. Queensland, 50 km N of Taroom on Fitzroy Development Rd, an unnamed lagoon, 25 o 13 ’ 58 ”S, 149 o 35 ’ 4 ”E, 13 February 2010, BVT.
Type material. Holotype. Female, deposited in the Australian Museum, Sydney, length 7.0 mm, height, 4.8 mm, registration number AM P 97816View Materials.
Paratypes. Two females, deposited in the Australian Museum, Sydney, 7.2 mm x 5.0 mm and 6.7 mm x 4.6 mm, registration number AM P 97817View Materials.
Other material. Seven females, Queensland, 50 km N of Taroom on Fitzroy Development Rd, an unnamed lagoon, 25 o 13 ’ 58 ”S, 149 o 35 ’ 4 ”E, 13 February 2010, BVT & MS, AM P 97818View Materials, one female, same site and date, noted as Lia 42,H 8 of Schwentner 2015, AMPAbout AMP 91995View Materials.
Diagnosis. The egg is the most distinctive feature, having about 28 steep sided, flatish floored polygons without adornment on their rounded ridges. Tertiary layer spongiform and ridge surface microporous. Sixteen even sized and spaced telsonic spines, except first and last, 14 cercopod setae gradually decreasing in length posteriorly.
Description. Egg ( Fig 10View FIGURE 10 H) spherical, ca 133 Μm in diameter (range 125–142 Μm, (n = 5) with about 28 polygons, each with almost vertical walls and a saucer-shaped floor. Surface of floors smooth but ridge surfaces microporous. Tertiary layer spongiform. No macrosurface adornments.
Hermaphrodite. Head ( Fig 16View FIGURE 16 B) with prominent ocular tubercle with a round compound eye occupying most (ca 80 %) of it. Rostrum an evenly rounded protrusion larger in volume than the ocular tubercle, but not protruding as much. Ocellus centrally placed in rostrum, about size of eye. Dorsal organ posterior to eye by about its height, pedunculate and with a flattened apex at about a 70 o angle to the peduncle and subequal in height to the ocular tubercle.
First antennae subequal in length to the second antenna peduncle, and with about 5 lobes each with numerous tiny sensory setae.
Second antennae with spinose peduncle and each flagella with 9 antennomeres, dorsally with 1–5 spines and ventrally with 2–5 long setae. Spines most numerous on antennomeres 2–5, and setae most numerous on antennomeres 4–9.
Carapace ( Fig 16View FIGURE 16 A) elongate oval, transparent brown and much vaulted dorsally with maximum height about 1 / 3 from the anterior. A few growth lines visible.
Thoracopods. Eighteen pairs of typical structure for Eulimnadia , decreasing in size and complexity posteriorly.
Trunk dorsum with 3–9 setae terminally on most segments; these setae few, short and stout on last few segments, numerous and longer on segments 8–15 and hardly any setae on anterior trunk segments.
Telson with about 16 dorsal spines, the first about 1.5 times the subsequent few, followed by many approximately equal in size and spacing. Most spines clothed in denticles. Caudal filaments originating between 3 rd and 4 th spine from a mound a little higher than dorsal floor. Posterior to the mound dorsal floor sloping evenly to base of cercopods. Cercopods weakly convex, bearing about 14 long setae on basal 75 %, then a small spine and distal 25 % narrowing to an sharp apex and bearing a cirrus of many small denticles dorsolaterally. Basal setae about 2.5 x cercopod diameter decreasing to 1.5 times distally; all setae evenly feathered on both segments. Spiniform projection at ventroposterior corner of telson.
Variability. Based on an examination of just a few specimens, telsonic spines are known to vary between 16 and 18, though in all cases they were evenly spaced and sized, except the first. In some specimens the spines are denticulated, in others naked. Cercopod setae ranged from 14–16, and were always long basally (2.5 cercopod diameter), shortening a little distally. In some specimens (e.g. holotype) the cercopods were convex, but in most specimens they were straight. No variation as noted in the number of antennomeres (always 9) and first antennal lobes (always 5).
Comments. All the females examined looked mature with their vaulted dorsal edge, and filamentous algae growing on the carapace surface. Their older apparent age could have influenced their colouration. This is species M of Schwentner et al. (2015). The lack of males could indicate androdioecy (Weeks et al., 2008) or perhaps even hermaphroditism.
Distribution and ecology. This species occurs in at least one of many lagoons lateral to river systems in the Taroom district. Judged from subsequent visits these are generally much shallower than encountered in 2010, an abnormally wet La Nina year. It is possible their occurrence is episodic associated with these wet years, just like some large branchiopods in seasonal lakes near Esperance, WA, subject to rare extreme weather conditions ( Timms, 2009).
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