Eulimnadia dahli Sars 1896
Creators: name: Brian V Timms
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Branchiopoda
Diplostraca
Limnadiidae
Eulimnadia
Eulimnadia dahli

description: Eulimnadia dahli Sars 1896.
(Figs. 1,2,3A,B)
Eulimnadia dahli Sars, 1896: 14 –30, pl. 2–6; Sayce, 1903: 244 (text), 247–248 (synopsis), pl. 34, fig. 1,a–c; Wolf, 1911: 254 (list), 270 (Text); Dakin, 1914: 295 (list); Henry, 1924: 122 (list); Daday, 1926: 4 (key), 16–20, figs. 128–129; Richter & Timms, 2005: 348.
Limnadia dahli Brtek, 1997: 57 (list).
Type locality. Mt Showbridge, near Darwin, Northern Territory, collector K. Dahl and date 3 November 1894.
Type material. Series of specimens noted as syntypes in the Oslo Museum. These specimens were not consulted, as the diagrams and description by Sars are excellent, though with SEM technology the egg can be described in more detail.
Material studied. Northern Territory. 27 females, Delamere Highway, 113 km S of junction with Victoria Highway, 16o 11’S, 131o 59’E, M.J. Tyler, SAM C8450; 52 specimens, Charlotte Waters, pre 1912, unknown collector, NMV J53350. Queensland. 4 females, Walkamin Research Station near Atherton, fish rearing pond 6, 22 Oct 1997, B. Herbert AM P97799. Western Australia. Stonewall Ck, via Kununurra, 2 Feb 1978, Coll JEB, SAM C8453; 7 males, Kimberleys, Phillips Gorge, 28.7 km from Barnett River Crossing, 3 Feb 1986, M.J. Tyler, SAM C8454; numerous females, Kimberleys, Phillips Gorge, 28.7 km from Barnett River Crossing, 3 Feb 1986, M.J. Tyler, SAM C8455 1 male, 12 females, Kimberleys, Phillips Gorge, 28.7 km from R Crossing, 3 Feb 1986, M.J. Tyler, SAM C8456; 36 females, Kimberleys, 87 km N of Halls Ck on Northern Highway, 6 Feb 1982, M.J. Tyler & M. Davies, SAM C8457.
Diagnosis. Egg spherical averaging 22 polygons, often as uneven pentagons or hexagons, with central groove and either lacking any frills on the polygon boundaries, or with minor frill. Adults with twenty trunk segments (all other Australian Eulimnadia have 18), numerous (mean 18) long (2.5 x or more cercopod diameter) cercopod setae, about 17 telsonic spines, and 8–9 antennomeres. Also the male typically has a distinctly triangular rostrum.
Short description. Male and Hermaphrodite (Figs.1,2). This species is described in detail by Sars (1896). In essence (from original description plus present observations), the male has a triangular rostrum, first antenna with about eight lobes, and second antenna with eight antennomeres on each ramus; carapace with four growth lines; 20 trunk segments; both claspers have a two segmented long palp with ca. five spines at the palpomere junction, and a telson with ca. 15 dorsal spines, the cercopod with about 18 long setae. The hermaphrodite is similar, but with a short rounded rostrum, and a similar telson as the male. The egg has about 24 polygons each with a central depression and unadorned edges.
Egg (Fig 3). Spherical with about 22 polygons each an uneven pentagon or hexagon with a central groove and even slopes to a sharp marginal ridge. Polygon boundaries with a minor frill or none at all, and often with a spiniform protrusion at ridge junctions.
Comments. I have seen 8 collections containing this species (Figs.1,2). In all except two (Phillips Gorge, SAM C8456; Charlotte Waters, NMV 14427) individuals have 20 trunk segments, thus distinguishing species from all other Australian Eulimnadia. It is possible these exceptions may consist of juveniles. The egg is its other most distinguishing feature. Typically these have ca 22 polygons (range 20–28) often distinctly hexagonal (though sometimes pentagonal) and an overall size of 196 Μm (range 162–212 Μm). The edge of the polygons may be smooth (old eggs?) or with a minor frill extending a little to a short spiniform protrusion at edge junctions (Fig 4 A,B). Interestingly, Sars 1896 noted the hexagonal facets and his figure is remarkably accurate.
Other distinguishing features of lesser value include the male rostrum which is distinctly triangular and symmetrical. The telson has about 17 telsonic spines (range 14–18), and about 18 cercopod setae (range 16–23). Generally the setae are long (2.5 to 3 x cercopod diameter and almost reaching the posterior apex of the telson). The clasper often has a small rounded bulge mediodistally just basal to the apical knob and typically 5 (range 3–6) spines at the palp segmental junction. The number of antennal lobes varies from 8–12 in males and 5–8 in females and 8–9 antennomeres on the rami of the second antenna. In many populations the numbers of spines and setae on each antennomere do not vary much from proximal to distal antennomeres and the ventral setae are unusually long (3– 5 x diameter of antennomeres) (Fig 1 C). Some specimens have a supernumerary spine anterior to the first large telsonic spine (as in SAM C8455 Phillips Gorge population, Fig. 1 G; interestingly Sars’ illustration shows one such spine too. Finally the moveable finger rarely has 3 spines dorsally, a condition occasionally seen in other species (e.g. E. gnammaphila sp. nov., see below) and when numerous and always present, sometimes an identifying feature (eg. E. feriensis, see Timms 2015).
FIGURE 2. Eulimnadia dahli Sars, 1896. Charlotte Waters, NT. A, female head; B, female telson, C, male 2nd clasper; all Charlotte Waters NMV14427; D, female head; E, female telson; both Atherton, AM P97799; F, female telson, Stonewall Ck, SAM C8453; G, female telson, Halls Ck. SAM C8457.
Further south, in a band across the continent, there is a species clearly allied to E. dahli, but they generally have more polygons in the egg and fewer cercopod setae. There were insufficient specimens, or they were too variable for meaningful study.
Weeks et al. 2006 reported E. dahli from four sites in WA and one in SA, but these are most probably misidentifications (Table 1). In material I collected from his Pygery Rocks site, SA (AM P97824) all specimens have 18 trunk segments, ca 10 telsonic spines, <18 cercopod setae and eggs with numerous (>50) polygons each with central depressions and with frilled polygon boundaries (Fig 9 B,C,D) suggesting E. gnammaphila sp.nov. (see later) and certainly not E. dahli. I have also seen their Green Rock material and it has similar characters to that from Pygery Rock. Their material from Bunjil Rocks, The Humps and Kadji Kadji is lost, and the sites need to be recollected to determine their identity. Reed et al (2015), in a molecular analysis of various world Eulimnadia, note that what they identify as E. dahli and E. feriensis are synonymous (Table 1); again I believe this is because they were dealing with E. gnammaphila sp. nov. rather than E. dahli or E. feriensis.
Timms (2006) lists E. dahli as a gnammaphile in SA and WA, but this identification was based on eggs which look like those described by Sars (1896), but when their other characters are now taken into account, they are more likely E. gnammaphila sp. nov.
Few males occur in the collections, probably indicating the androdioecious mode of reproduction and the apparent females being putative hermaphrodites (Weeks et al., 2008), but there is no histological proof of this. Distribution. Eulimnadia dahli occurs in northern Australia, including the Kimberleys, Darwin area, Nicholson River in NW Qld (based only on eggs) and Atherton Tableland in NE Qld.
description: Published as part of Brian V Timms, 2016, A partial revision of the Australian Eulimnadia Packard, 1874 (Branchiopoda: Spinicaudata: Limnadiidae), pp. 351-389 in Zootaxa 4066 (4) on pages 353-357, DOI: 10.11646/zootaxa.4066.4.1, http://zenodo.org/record/264233