Branchinella minmina, 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 : 52-54

Branchinella minmina sp. nov.

Figs. 5 D, 10.

Etymology. The species name commemorates the Min Min Lights, a mysterious phenomenon sometimes occurring in various places in inland eastern Australia ( Pettigrew, 2003; Silcock, 2003) but particularly east of Boulia along the Min Min Way between Boulia and Winton in northwest Queensland, where this species was found. The lights were also known to local aborigines and formed part of their folk lore.

Type locality. Queensland, 8 km E of Boulia, roadside burrow pit, 22o 55’ 44.6”E, 139o 58’ 23.7”E, 4 March 2011, collectors M. Schwentner & BVT

Holotype. Male deposited in Australian Museum. Total length 14.4 mm. Accession number: AM P88365.

Allotype. Female deposited in Australian Museum. Total length 15 mm. Accession number: AM P88364.

Paratypes 4 males, 1 female. Accession number: AM P88366.

Diagnosis. Male frontal appendage unusually long, reaching to end of thorax when extended. More importantly it consists of an unadorned trunk and two triangular branches each with an extended apex, both edges of the branches with small papillae. Gonopods without lateral swellings.

Description. Male. Eyes oval, freely projecting on peduncles about the same length as eye diameter.

First antennae filiform, almost twice as long as second antenna proximal segment, and terminating in 3–5 long sensory setae.

Second antennae with proximal and distal antennomeres subequal in length. Each proximal antennomere cylindrical, with a few small setae on its mediodistal corner and fused medially at their bases. Distal antennomeres evenly curved, narrowing distally and forming the claspers; apical third of claspers with distinct transverse ridges.

Frontal appendage long, almost reaching full length of thorax when extended. Consists of a flattened trunk becoming explanate distally about two-thirds its length followed by a branched apex, each branch an evenly narrowing triangle but with a narrow extended apex. Its two vesicles lie adjacent in the trunk but diverge apically into each branch. The two branches frilled on each side with bulbous papillae tending to be longer and thinner laterally and medially squatter with an apical bulb. These papillae completely lacking at the apical junction of the two branches, but a few present under the narrower oblong apical extension of each branch. Basal half of trunk tends to be pseudosegmented at least immediately above the vessels.

Fifth thoracopod with endite 1+2 and 3 evenly curved, the former about three times the size of the later. Anterior seta of endite 1 naked, a little less than half the length of adjacent posterior setae. Anterior seta of endite 2 half the length of endite 1’s anterior seta, bearing a one-sided pecten of spines and attended at its base by a small smooth spine. Endite 3 with an anterior seta bearing one-sided pecten of spines and about two and a half times longer than anterior seta of endite 2. This anterior seta also attended by a small spine at its base. Endites 4–6 asymmetrical and covered with small spines. Endites 4 and 5 with two anterior setae and endite 6 with one anterior seta, representing two types. The first on all three endites about twice the length of endite 2 anterior seta and strongly setose almost its whole length, and the second type on endites 4 and 5 only a little longer than endite 2 anterior seta and weakly setose almost its whole length. Posterior setae of all endites long and numbering about 35 on endites 1+2, 16 on endite 3, then 3, 2, 2 respectively on endites 4–6. Endopod broadly rounded and bearing about 50 spaced posterior setae, generally only about one third the length of posterior setae of the endites. Exopod oval bearing about 50 posterior setae closely spaced, generally bent apically and about twice as long as the endopodal setae. Epipodite a bent oval 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, significantly wider than abdominal segments. Gonopods short, similar in length to first abdominal segment and no lateral swellings to gonopods. Everted gonopod with a short row of about 5 triangular spines medially and a narrow row of longer thin spines on opposite side.

Cercopods typical for Branchinella .

Female. Compound eye mounted on a similarly sized peduncle and whole structure about two-thirds length of second antenna.

First antenna filiform and a little longer than second antenna.

Second antenna elongated oval shape with rounded apex and about twice length of labrum.

Fifth thoracopod and cercopods as in male.

Genital segments larger than abdominal segments and with brood pouch bulbous anteriorly but tubular posteriorly and about two abdominal segments long.

Egg unstudied.

Size. Males studied vary in length 13.5–14.8 mm and females 14–15 mm.

Variability. The six males and two females were each uniform in structure.

Differential diagnosis. The simple bifurcated frontal appendage variously edged with small papillae of B. minmina sp.nov. clearly affiliates it with the B. affinis group (eg B. affinis , B. apophysata , B. mcraeae , B. denticulata , B. insularis , B. longirostris , B.latzi ). Of these species, it most closely resembles B. mcraeae in having a frontal appendage terminating in long triangular branches edged with papillae. However the two are differentiated by: (a) the papillae being absent on the medial edges of the branches in B. mcraeae but present in B. minmina sp. nov.; (b–d) the papillae tending to be in rows and extending ventrally on the distal half of the frontal appendage in B. mcraeae , but strictly lateral and only on the branches in B. minmina sp. nov.; (e) the lateral branches terminating in sharply pointed apex in B. mcraeae but in an obtuse narrow oblong extension in B. minmina sp. nov.; (f) the frontal appendage being half the thorax length in B. mcareae but almost full length in B. minmina sp. nov.; (g) an elongated patch of minute denticles medially on the proximal segment of the second antenna in B. mcraeae compared to a smooth medial surface and a few setae medodistally in B. minmina sp. nov.; and finally (h) the gonopods have lateral swellings in B. mcraeae but not in B. minmina sp. nov. Even females can be distinguished apart as (i) the second antennae have a sharp apex in B. mcraeae but a rounded apex in B. minmina sp. nov. The brood chamber is longer in B. mcraeae than in B. minmina sp. nov., but the studied females of B. minmina sp. nov. may not be quite mature. Further, the two species differ markedly in size, with B. minmina sp. nov. being almost twice as large as B. mcraeae , but this difference may be environmentally induced.

Distribution. So far known only from its type locality near Boulia.

Figures

FIGURE 5. Male fifth thoracopods. A, Branchinella compacta, B, B. hearnii sp. nov., C, B. erosa sp. nov.; D, B. minmina sp. nov. Scale bars 1 mm.