Branchinella anatinorhyncha, Timms, Brian V, 2012

Timms, Brian V, 2012, Further studies on the fairy shrimp genus Branchinella (Crustacea: Anostraca: Thamnocephalidae) in Australia, with descriptions of five new species, Zootaxa 3595, pp. 35-60 : 38-41

Branchinella anatinorhyncha sp. nov.

Figs. 1 C, 2, 3

Etymology. The name is an amalgam based on latin ‘anatin’ meaning ‘duck’ and greek ‘rhynchus’ meaning ‘nose’ and refers to the frontal appendage having the form of a duck bill. Should this shrimp ever become known enough to have a common name, it would be the duckbilled fairy shrimp and hence analogous in the broadest sense to the duck-billed platypus, Ornithorhyncus anatinus .

Type locality. Australia, Queensland, Sumana Station 74 km N of Aramac, an unnamed claypan 2 km E of homestead, 22o 18’ 38”S, 145o 23’ 08”E, 2 April 2009, collector M. Schwentner & BVT

Holotype. Male deposited in Australian Museum (Sydney). Total length 11.9 mm. Accession number AM P88368.

Allotype. Female deposited in Australian Museum (Sydney). Total length 14 mm. Accession number, AM P88369.

Paratypes. Males and females deposited in Australian Museum (Sydney). Accession number, AM P88370.

Other material. 3 males, Australia, Queensland, Sumana Station 74 km N of Aramac, unnamed claypan 5 km NW of homestead, 22o 16’ 40”S, 145o 20’ 15”E, 28 February 2008, deposited in the collection BVT and in Australian Museum (Sydney); accession number AM P88371.

Diagnosis. Male with unbranched paddle like frontal appendage. Only frontal appendage adornment a minutely frilled edge on basal third of the wider portion. Second antenna with proximal antennomere’s distomedial corner with a small lobe bearing a few short setae.

Description. Male. Eyes almost sphaerical, freely projecting on peduncles about the same diameter as the eye.

First antennae filiform, about a third longer than second antenna proximal antennomere, terminating in 3–5 long sensory setae.

Second antennae. Proximal and distal antennomeres subequal in length. Proximal antennomere cylindrical and with a small tumidity mediodistally bearing many small setae. Proximal antennomeres fused medially. Distal antennomeres evenly curved, narrowing distally and forming the claspers; apical half of claspers with distinct transverse ridges medially.

Frontal appendage unbranched with a thick roundish pseudosegmented trunk supporting a long paddle-like blade, twice length of the trunk. Two vesicles lying adjacent in the trunk but divergent in the blade. Basal third of blade with a minutely frilled edge, otherwise edge and both surfaces of blade smooth. Blade apex squarish. Blade generally carried coiled in life, particularly lengthwise, but also across its width.

Fifth thoracopod with endite 1+2 and 3 evenly curved, the former about three times the size of the later. Anterior setae of endite 1 smooth, a little more than half the length of adjacent posterior setae. Anterior setae of endite 2 half the length of endite 1, bearing a one-sided pecten of spines and attended at its base by a small smooth spine. Endite 3 with an anterior setae bearing one-sided pecten of spines and three times longer than anterior setae of endite 2. Endites 4–6 asymmetrical and covered with small spines. Endites 4 and 5 with two anterior setae and endite 6 with one anterior seta, each about twice the length of the anterior setae of endite 2. These setae of two types. Each endite with a seta of two equal length parts, a wide base with a few long strong spines on each side on proximal half of base and a thin apical part with thinner shorter spines on each side. The second type, on endites 4 and 5 only, of uniform tapering with a bare basal half and a distal half similar to distal half of the first setal type. Posterior setae of all endites long and numbering about 60 on endites 1+2, 18 on endite 3, then 3, 2, 2 respectively on endites 4–6. Endopod broadly rounded and bearing about 32 spaced posterior feathered setae, those on the medial margin shorter (about same length as anterior setae of endites 4–6) than those on the remainder of the endopod. Exopod oval bearing about 40 posterior setae closely spaced and long and generally bent apically like those on the most of the endopod. Epipodite lanceolate and unadorned. Praeepipodite large and broad, about one and a half the size of endite 1+2, and with a smooth unadorned margin.

Genital segments similar, gonopods short, about two-fifths the length of first abdominal segment and with a small lateral tumidity. Everted gonopod with a short row of about four triangular spines medially and a narrow field of longer thin spines on opposite side.

Cercopods typical for the genus.

Female. Eye plus peduncle elongated to be about two thirds second antenna length.

First antenna filiform and subequal to second antenna length.

Second antenna broad terminating to a symmetrical apex and a little longer than labrum.

Fifth thoracopod and cercopods as in male.

Genital segments larger than abdominal segments and with brood pouch bulbous anteriorly but tubular posteriorly and terminating between second and third abdominal segments.

Egg diameter 169.5 µm and with about 50 irregularly shaped distinct depressions. Walls of depressions wide and rounded and floors flat and moderately dimpled (Timms and Lindsay, 2011).

Size. Males range in size from 11.9–14.1 mm (n=5) and females from 14.0– 14.1 mm (n=2) so males and females about the same size.

Variability. In the five males examined, the frilled edge on the base of the distal portion of the frontal appendage varied by about 10% in the extent and size, with the holotype about average. The two proximal antennomeres sometimes appear fused at about 60o instead of the more usual 80–90o.

Differential diagnosis. Branchinella anatinorhyncha sp. nov. differs from other species of Branchinella in its 16SmtDNA by 4.6% ( Pinceel et al. 2012). Morphologically it is unlike any other species of Branchinella with its frontal appendage unbranched and paddle like. Moreover it has almost no adornments in the form of papillae or setae on its frontal appendage, thus further distinguishing from many species including B. macraeae Timms , B. affinis and those with ramified frontal appendages such as B. frondosa Henry and B. arborea Geddes. It is not unusual for species of Branchinella to have some kind of sensory apparatus on or near the mediodistal corner of the proximal segment of the first antenna (e.g. B. affinis , B, arborea , B. kadjikadji Timms, B. insularis Timms , B. macraeae , B. pinderi Timms), but the lobes bearing setae of B. anatinorhyncha sp. nov. are unique. Perhaps B. anatinorhyncha sp. nov. can be thought as related to B. affinis and associated species in which the frontal appendage instead of branching apically is undivided.

Like many species of Branchinella , females lack unique characteristics.

Distribution. So far this species is known only from claypans on Sumana Station, but it could well occur in claypans over a wider area north of Aramac/Muttaburra to south of Prairie in inland north Queensland. Resting eggs similar to those known to be B. anatinorhyncha sp. nov. have been found in claypans at Kooroorinya on the Muttaburra to Prairie Road (21o 20’S, 144o 40’E).

Figures

FIGURE 1. Resting eggs of selected species of Branchinella. A, B. affinis; B, B. clandestina n. syn.; C, B. anatinorhyncha; D, B. compacta; E, B. erosa sp. nov.; D, B. compacta; F, B. hearnii sp. nov.; G, B. herrodi sp. nov.; H, B. simplex; J, B. wellardi. Scale bars 50 µm. Images modified from Timms and Lindsay, 2011.