Eulimnadia australiensis, 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 : 357-361

publication ID 10.11646/zootaxa.4066.4.1

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scientific name

Eulimnadia australiensis

sp. nov.

Eulimnadia australiensis View in CoL sp. nov.

( Figs 3 View FIGURE 3 C,D; 4,5)

Etymology. The species is named for the country in which it occurs.

Type locality. New South Wales, Moonbi Ranges, prominent rounded peak known locally as ‘Flynns Rock,’ 5.4 km NNE of Moonbi township, 30o 58’ 36.8”S; 151o 05’ 10.8”E; 11 March 2014, BVT guided by W. and M. Schofield and B. Moritz, a small southerly pan gnamma 225 cm by 160 cm by 10 cm deep when full, but only 2 cm deep on 11 March.

Type material. Holotype. Male deposited in Australian Museum, Sydney, length 4.6 mm, height 3.0 mm, registration number AM P97795.

Allotype. Female deposited in Australian Museum, Sydney, length 4.2 mm, height 3.0 mm, registration number AM P97796.

Paratypes. Five males, 4.9 x 3.1 mm, 4.9 x 3.1 mm, 4.8 x 3.0 mm, 4.6 x 3.1 mm, 4.4 x 2.6 mm; 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 P97797.

Other material. New South Wales: A few males, many females, Moonbi Ranges, prominent rounded peak known locally as ‘Flynns Rock’, 5.4 km NNE of Moonbi township, 30o 58’ 36.2”S, 151o 05’ 10.6”E, 14 April 2014, BVT, AM P97798; Queensland: Aramac district, vicinity of Lake Dunn, excavation on south side of lake, 22o 36’ 12”S, 145o 40’ 26”E, 15 February 2010, MS and BVT, AM P91973; Brisbane, Nudgee, 8 March 1945, J.S. Hynd, AM P56359; near Longreach, Thompson R., Yellow Lily Lagoon, 23o 22’ 53”S, 144o 14’ 40”E, 27 November 2000, ARIDFLO, SAM C8460.

Diagnosis. Egg cylindrical with near vertical ridges and expanded ends, these with 1 to a few ridges. 18 trunk segments. Cercopod with 5–7 short (about diameter of cercopod), spaced setae on basal 80%; telson with 15–22 dorsal spines somewhat variable in size, and usually with a single spine anterior to the double telsonic row; male rostrum triangular; clasper palp with 5 spines at the palpomere junctions.

Description. Egg ( Figs. 3 View FIGURE 3 C,D) cylindrical, diameter 136–145 Μm, height 176–185 Μm with 12–15 vertical grooves/ rounded ridges and ends slightly-moderately expanded to a diameter of 154–196 ìm (n=10). Discoid ends with 1 ridge across one diameter or 2–4 shorter ridges on radii. Surface microporous.

Male. Head ( Fig 4 View FIGURE 4 D) with ocular tubercle prominent, the compound eye occupying most (ca. 90%) of it. Rostrum protruding similarly to the ocular tubercle, triangular in shape, with an acute apex and largely occupied by the ocellus, about 50% the size of the compound eye. Frons-rostrum angle about 120o. Dorsal organ posterior to eye by about half its height, pedunculate and asymmetrical and not quite as high as the ocular tubercle.

First antennae ( Fig 4 View FIGURE 4 D) slightly longer than peduncle of second antennae, and with six lobes, each with numerous short sensory setae.

Second antennae with a spinose peduncle and each flagella with 8 antennomeres, dorsally with 1–3 short spines and ventrally with 1–4 longer setae. Basal and distal antennomeres with minimal spines, while setae maximal distally.

Carapace ( Fig 4 View FIGURE 4 A) elongated oval, pellucid and with hardly any indication of growth lines. Adductor muscle scar at about 45o to carapace long axis, almost invisible.

Thoracopods. Eighteen pairs, the first two modified as claspers ( Fig 4 View FIGURE 4 H). Palm trapezoidal with a rounded expansion distomedially. Apical bulb spherical with many denticles mediodistally and with many stout spines pointing medially, also laterally bearing a small palp with many short thin spines apically. Finger arcuate with a blunt apex bearing a suctorial disc apicoventrally and many rounded pits ventrally. Long palp inserted on apical edge of palm; two segmented and with 5 stout setae at the segmental junction and many thin limp setae terminally.

Palp of first clasper about 1.5x length of palm and 2x length in second clasper. Basal palpomere a little longer than distal palpomere in both claspers.

Other thoracopods of typical structure for Eulimnadia , decreasing is size and complexity posteriorly. Dorsal surface of trunk with 1–2 short spines medially or posteriorly on each of the posterior 12 trunk segments.

Telson with about 16 pairs of dorsal spines, with a single spine anterior to the larger first pair. Spines tend to vary in size a little, and increase in length posteriorly. Most spines with spinules. Caudal filaments originating from a mound a little higher than the dorsal floor of the telson and between the 3rd and 4th spine after the largest anterior spine. Dorsal floor of telson posterior to the mound slopes evenly to base of the cercopod. Cercopods a little longer than dorsum of the telson, the basal 80% hardly thinning to a small spine with spinules, then a rapid thinning to an acute apex. About five short (a little longer than diameter of cercopod) setae on basal half and many tiny denticles dorsolaterally on apical quarter. Setae two segmented and feathered. Prominent spiniform projection beneath the cercopods at the ventroposterior corner of the telson.

Hermaphrodite. Head ( Fig 4 View FIGURE 4 F) 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 anteroventral part occupied by large ocellus, about 60% the size of the compound eye. Dorsal organ posterior to eye by about its height, pedunculate and asymmetrical and subequal in height to ocular tubercle.

First antennae ( Fig 4 View FIGURE 4 F) a little shorter than the peduncle of the second antennae, with five small lobes each with many short sensory hairs.

Second antennae as in the male.

Carapace ( Fig 4 View FIGURE 4 B) as in the male.

Thoracopods. Eighteen of typical Eulimnadia structure. Trunk dorsum with 3–9 setae terminally, 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 1–7.

Telson ( Fig 4 View FIGURE 4 E) as in male, though with 17 pairs of dorsal spines, also a single spine anterior to the paired spines, and six setae on each cercopod.

Variability. The position of the dorsal organ in the male from the type locality varies from half height to its total height from the ocular tubercle. One specimen had 6 spines at the junction of the palpomeres. Telsonic spines vary in number from 15–17, the small spine anterior to the long anterior spine is not always present in both sexes. Cercopod setae vary from 5–8 in both sexes.

Material from the larger northern pan of Flynns Rock collected after the next rainy period was much larger, males about 7 mm long and females 8 mm. Notably, putative hermaphrodites outnumbered males 72:6, implying an androdioecious mode of reproduction as in E. texana (Packard 1871) (Weeks et al., 2006) . They were similar morphologically to the type material, but tended to have an extra lobe in the first antennae, an extra antennomere, 17–20 telsonic spines and up to 7 short cercopod setae ( Fig. 4 View FIGURE 4 G).

Specimens ( Figs. 3 View FIGURE 3 E, 5A, B) in the Nudgee collection (AM P56359) were very similar to the type material, but the telsonic spines were more denticulate and there were even denticles on the large last telsonic spine (=anal spine). They had 8 cercopod setae, most up to 2x cercopod diameter.

While the eggs are typical in the Thompson River collection, telsonic spines number only 12 and there are 9 cercopod setae about 1.5 to 2 x times longer than the cercopod diameter ( Fig 5 View FIGURE 5 C, D). This material is included in E. australiensis sp. nov. based on its egg structure.

Comments. This species is distinct by reason of its cylindrical eggs with ridges aligned to the vertical axis and the few spaced short setae of the cercopod, two characters not shared with other Australian species. There are, however, other collections in the museums with cylindrical eggs similar to those of E. australiensis sp. nov., but with the ridges quite twisted and the ends more elaborate (e.g. Fig 3 View FIGURE 3 E). Most have many (16–18) long cercopod setae, eg AM P55693 Rabaul, PNG; AM P82488 Central Qld; AM P85563 Bloodwood Station, NSW; AM P85570 Carrols Swamp, Muella Station, NSW; AM P 82467 & AM P91995 near Taroom, Qld; AM P85563 & AM P96480 Titanic Dam, Bloodwood; SAM C8458, Gibb R Homestead, WA. These look more like some of the overseas species discussed below.

Eulimnadia australiensis View in CoL sp. nov. shares many features with the widespread American species E. texana Packard View in CoL and its relatives, E. belki Martin View in CoL , E. colombiensis Roessler View in CoL , E. cylindrova Belk View in CoL , E. ovisimilis Martin & Belk View in CoL and also E. tauluoensis Hu in China and E. indocylindrova Durga Prasad and Simhachalam View in CoL in India ( Hu 1986; Belk 1989; Martin & Belk 1989; Roessler 1989; Brendonck et al. 1990; Pereira & García 2001; Durga Prasad and Simhachalam 2004; Padhye et al. 2015). The most important similarity, given the specific nature of egg morphology in Eulimnadia View in CoL (Belk 1989; Martin & Belk 1989; Rabet 2010), is the almost identical egg structure in E. australiensis View in CoL sp. nov. and E. texana View in CoL , and also to a lesser extent in other members of the E. texana View in CoL group. All these Eulimnadia View in CoL are those with cylindrical eggs, with just minor variations between them. The eggs of E. australiensis View in CoL sp. nov. are distinctive with grooves and ridges always vertical (i.e. not twisted) numbering about 12– 15 and expanded discoid ends with 1–3 ridges. Eggs of other E. texana View in CoL species group often have twisted ridges/ grooves, fewer of them and ends not expanded as much or more ( Hu 1986; Belk 1989; Martin & Belk 1989; Roessler 1989; Brendonck et al. 1990; Pereira & Garcia 2001). It is not known if there is a phylogenetic link between these types of cylindrical eggs, or whether the similar eggs are due to convergent evolution. The later possibility is suggested by E. australiensis View in CoL sp. nov., for although its egg is similar to that of members of the E. texana View in CoL group, its body morphology is distinctive. Most significant is the few (<7) short weak setae on its cercopods compared with many (>10) long strong setae in the members of the E. texana View in CoL group and the nine odd collections mentioned above. Specimens with twisted cylindrical eggs were designated as species C and F in Schwentner et al. (2015), while specimens with vertical ridges from the type locality were later tested by Schwentner (pers.comm.) and found to be different again. Though the characteristics of E. australiensis View in CoL sp. nov. are distinctive, those of other Australian forms with cylindrical eggs are not and they remain unidentified and undescribed. It would help if the validity of the above mentioned overseas species was resolved.

Distribution and ecology. Northern half of NSW and throughout Qld. It has a very short life cycle in the Moonbi sites (Timms, in prep); from hatching to adults with eggs takes 8 days and after two weeks many individuals die. No living individuals could be found after four weeks in cultures or in situ after six weeks post filling.


South African Museum

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