Branchinella herrodi, 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 : 49-52

Branchinella herrodi sp. nov.

Figs. 1 G, 8, 9A.

Etymology. This species is named for the Herrod family longtime proprietors of Yarromere Station, via Pentland, North Queensland, in particular patriarch Kevin Herrod for his assistance and concern for my well being as I collected shrimp in remote parts of the property.

Type locality. Queensland, Lake Buchanan northwest beaches, pool 1.3 km sw of Lake Constant southern shore, 21o 34’ 31”S, 145o 47’ 32”E, 24 February, 2008, BVT

Holotype Male deposited in Australian Museum. Total length 9.5 mm. Accession number: AM P88354.

Allotype Female deposited in Australian Museum. Total length 11.2 mm. Accession number: AM P88353.

Paratypes. Queensland, Lake Buchanan northwest beaches, pool 1.3 km NE of Lake Constant northern shore, 21o 32’ 38”S, 145o 48’ 29”E, 26 February, 2008, BVT, AM P88355, 4 males, 3 females.

Other Material. Queensland, Lake Buchanan northwest beaches, pool 1.3 km w of Lake Buchanan northwest shore, 21o 32’ 00”S, 145o 48’ 13”E, 26 February, 2008, BVT, AM P88356, 5 males, 3 females.

Diagnosis. Frontal appendage branched, each branch with ca 10 lateral subbranches and 5 lateral medial branches plus a larger one basomedially. Branches terminate in a mixture of small spines and epidermal outgrowths. Male fifth thoracopods distinct with various anterior setae and endopod lack basal knob-like extensions (as in B. wellardi ) but with 6–8 spinules on their base. Females unremarkable. Description. Male. Eyes freely projecting on peduncles about the same length as eye diameter. First antennae filiform, slightly longer than second antenna proximal antennomere, and terminating in 3–5 long sensory setae.

Second antennae with proximal antennomere subequal in length to distal antennomere. Proximal antennomeres well separated on each side, being fused basally at 90o and medially with a long shallow swelling covered in very small denticles. Distal antennomeres of uniform diameter and with transverse ridges medially.

Frontal appendage larger than the second antennae, consisting of short trunk and two ramified branches almost three times trunk length. Each branch with 9–10 subbranches laterally and 4–5 medially, but with one larger branch of different structure basomedially. These subbranches about the same size medially and laterally and decreasing in length towards the branch apex. Each branch terminating in a short spine apically attended by 2–4 smaller spines subapically. Narrow conical outgrowths randomly distributed ventrally along each branch, mainly posteriorly to the larger medial subbranch. Similar outgrowths but smaller along the subbranch generally in pairs. Largest medial branches smooth, each consisting of a short thick trunk and an oval plate at about 60o to the trunk, so overall the axis of the plate and branch trunk similar.

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, and about half the length of adjacent posterior setae. Anterior setae of endite 2 about half the length of anterior seta and bearing a strong pecten of spines and attended at its base by a small smooth spine. Endite 3 with an anterior setae similar on length to the first anterior seta, and bearing a strong pecten of spines and attended at its base by a short smooth spine. 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 with a fine pecten most of their length and a few spines basally; the seta on endites 6 a little longer than the other two. The second seta type on endites 4 and 5 only, comparatively short (half length of adjacent anterior seta) and naked. Posterior setae of all endites long and numbering about 60 on endites 1+2, near 18 endite 3, then 3,2,2 respectively on endites 4–6. Endopod squarish with a shallow wide notch apically. It bears 10 spaced feathered setae medially to the notch and 18 closer together apically and laterally. Setae larger on the apex than proximal sides. The ca 40 feathered setae on the exopod each about 50% longer than endopod setae. Basal attachment of endopod setae with 6–8 spinules compared with 3–4 on the exopod setae base. Epipod broadly oval and naked. Praeepipodite large (about equivalent to exopod + endopod) and with smooth edges.

Genital segments about same width as nearby thoracic and abdominal segments. Bases of gonopods about half the length of the first abdominal segment. No specimens with gonopod everted.

Cercopods typical for Branchinella .

Female. Eye plus peduncle on each side about head width.

First antenna filiform, almost as eye plus peduncle.

Second antenna with a wide base and narrowing to an asymmetrical sharp apex and longer than the labrum.

Genital segments subequal to posterior thoracic and adjacent abdominal segments. No tumidities.

Brood pouch expanded ventrally and tubular posteriorly and terminating at about the second abdominal segment.

Fifth thoracopod and cercopods as in male.

Egg diameter 175 µm. Depressions average number 35 and irregularly polygonal to constricted and linear, inter-depression walls wide and ridge crests rounded and with minute pores (Timms and Lindsay, 2011).

Variability. There is some variability in the number of subbranches of the frontal appendage, but only one either way from the number in the holotype. The larger basomedial branch can be of various sizes, perhaps associated with the developmental stage of the specimen. As indicated for this holotype the placement of the narrow epidermal outgrowths is quite variable in other frontal appendages examined, but always they are ventral and lateral and most common in the apical half of each subbranch.

Differential diagnosis. Branchinella herrodi sp. nov. is most similar to B. multidigitata Timms 2008 , B. campbelli Timms 2001 and B. wellardi . Branchinella multidigitata has frontal appendage branches with subbranches reminiscent of those in B. herrodi sp. nov., but with 6 laterals, 3 terminals, 3–5 very small medials and no larger basomedial in B. multidigitata compared to 9–10 laterals, 0 terminals, 4–5 fully developed medials and a large basomedial subbranch in B. herrodi sp.nov. The basomedial subbranch in B. herrodi sp.nov. is similar to that in B. campbelli , but that is the only feature of resemblance. Given that there is <4% variation in 16SmtDNA ( Pinceel et al., 2012) between B. herrodi sp.nov. and B. wellardi , this is the species it is most likely similar too, or indeed conspecific. While their frontal appendages are superficially similar, there are many morphological differences between the two: (a) B. wellardi has a bilobed lamellar outgrowth between the two branches, B. herrodi sp.nov. does not ( Figs. 8 A, 12A); (b) B. wellardi has 9–10 pairs of lateral and medial subbranches to the branches, whereas B. herrodi sp.nov. has 9–10 laterals and 4–5 medials ( Figs. 8 B, 12B); (c) the branches of B. wellardi are usually pseudosegmented but not in B. herrodi sp.nov. ( Figs. 8 B, 12B); (d) the subbranches have paired thickenings each terminating in a chitinous epidermal outgrowth in B. wellardi , while in B. herrodi sp.nov. the branches are of more uniform thickness, terminate in a spine attended subapically by 2–4 smaller spines and the epidermal outgrowths are scattered ( Figs. 8 B, 12B); and (e) only B. herrodi sp.nov. has a larger basomedial branch ( Fig. 8 B). The second antennae of both species are very similar, though that in B. herrodi sp.nov. has a shallow tumidity covered in minute denticles medioapically, whereas the medial surface in B. wellardi lacks denticles and spinules ( Figs. 8 A, 12A). The thoracopods are also very similar, as they are in many of the smaller species of Branchinella , but four medial endopod setae are inserted on knob-like protrusions in B. wellardi compared to 6–7 medial setae inserted normally in B. herrodi sp.nov. Their bases have 6–8 spinules whereas those in B. wellardi are smooth ( Figs. 9 A, B). Resting eggs of B. herrodi sp.nov. are like the undistinctive eggs of B. affinis , B.

anatinorhyncha sp. nov., etc, whereas eggs of B. wellardi have markedly concave and regular polygonal depressions ( Figs. 1 G, J). Thus the conclusion is inescapable that despite the being similar molecularly (in the 16Smt segment), B. herrodi sp.nov. is distinct from B. wellardi .

Distribution and Ecology. B. herrodi sp.nov. is common in many of the clear freshwater pools in old swales between the fossil high beaches of Lake Buchanan. They have not been found in hyposaline/mesosaline pools associated with Lake Buchanan and its inflowing streams, nor in the saline lake itself (the domain of Parartemia minuta Geddes 1973 and Branchinella buchananensis Geddes 1981 ) ( Timms, 1987), nor in claypans in the greater region. Most of the pools only contain water after heavy summer rains.

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.

FIGURE 8. Branchinella herrodi sp. nov. A, male second antenna, dorsal view; B, head and upper thorax, lateral view; C, male gonopods; D, female head anterior view; E, female genital segments and brood pouch. Scale bars 1 mm.

FIGURE 9. Male fifth thoracopods. A, B. herrodi sp. nov.; B, B. wellardi Milner. Scale bars 1 mm.