Ozestheria pellucida, Brian V Timms, 2018

Brian V Timms, 2018, Three new species of spinicaudatan clam shrimps from Australia, all from gnammas (rock pools), Zootaxa 4418 (2), pp. 136-148 : 143-145

Ozestheria pellucida sp. nov. ( Fig. 5 )

Etymology. The specific epithetic celebrates the colourless carapace (hence pellucid in latin) of this species. All other known Ozestheria have reddish-brown-black carapaces.

Type locality. Rock pool. Western Australia, Kimberley, Gardner Plateau, from, 14o 47’ 25.8”S, 126o 30’ 32.1”E.

Holotype. Male. length 5.2 mm, height 3.2 mm. (WAM C72091). Coll. A. Cross, March 2012.

Paratype. Male. Lengths 5.0 and 3.2 mm from the same locality ( WAM C72092).

Diagnosis. Rostrum long and pointed, dorsal profile humped at the eye and occipital condyle rounded. Carapace pellucid. Telson with ca 5 spines plus a large spiniform projection and cercopod with ca. 10 setae, but no spine at end of setal row.

Description. Male. Head ( Fig 5C ) with a long pointed rostrum, a dorsal profile humped at the compound eye and with occipital condyle rounded and occipital notch area wide and shallow. Anterior third of rostrum flanged on each side with central ridge starting a little posterior to the apex. Ocellus elongated located ventroposteriorly in the rostrum, under its lateral margin.

First antenna ( Fig 5C ) about half the length of the second antenna and with about 8 lobes each with sensory setae.

Second antenna ( Fig 5C ) with a multi segmented peduncle and two flagella each of normally 11 antennomeres. All antennomeres, except the basal and distal antennomeres, with 3–5 short spines dorsally and 3–5 long setae ventrally. Basal antennomere with just one seta.

Carapace ( Fig. 5A ) oval, highest anteriorly, umbo distinct. Pellucid. Surface with about 9 growth lines with area between each granulated ( Fig 5B ).

Trunk of 18 segments. Dorsum of each segment beyond about segment VI with a cluster of short spines on a central mound ( Fig 5D ); about 3–5 on segments VII and VIII, 5–7 on segments IX to XIII, about 3 on segments XIV to XVI and just one on segments XVII to XVIII. First two thoracopods modified as claspers ( Fig. 5F ). Palm cylindrical though expanded a little mid length and terminating medially in an apical bulb with curved stout spines terminally and a short palp laterally. Moveable finger smoothly curving terminating in sharp apex with two clawlike scales and many small scales ventrally near the apex ( Fig 5F ). Large palp originating from the palm behind the moveable finger, its length slightly shorter than the palm in the first clasper and slightly longer in the second clasper. Both palps of one segment and terminating in a curved row of short soft setae.

Telson ( Fig. 5E ) short and cercopod a little longer. One large spine (twice size of others) anteriorly on dorsal surface followed posteriorly by a large mound supporting the paired telsonic filaments. A few denticles on posterior surface of the mound, then an even declivity of the telsonic floor to the cercopod bases. About four small spines posterior to the mound on the lateral edge of the telson. A large spiniform projection, about as long as the telson’s height, on posterior corner of telson.

Cercopod ( Fig 5E ) with a cylindrical basal area 50% of its length and bearing about 10 setae as long as twice the cercopod diameter. Distal 50% narrowing to a sharp apex and bearing a cirrus of denticles. This distal section without a demarking spine from the basal section and similar in size and shape to the large spiniform projection of the telson.

Differential diagnosis. With just two males available and no females this species description is minimal. However from what features are discernible, it is unique among the known species of Ozestheria . Only O. mariae ( Olesen and Timms, 2005) and O. packardi (Brady 1886) are remotely similar, firstly in size and shape (all 3) and also in inhabiting gnammas ( O. packardi only rarely, it is normally eurytopic). Ozestheria pellucida stands apart from both by having many fewer growth lines (for same sized individuals) and lack of any carapace colour. The rostrum in O. mariae is less pointed than in O. pellucida , the first antenna has more lobules (11 vs 9) and the second antenna while having similar numbers of antennomeres, is more spinose and setose than in O. pellucida (up to 8 spines and 9 setae in O. mariae compared with maximal numbers of 5 for both in O. pellucida .). These differences are perhaps minor when variably of clam shrimps is considered, but there are major differences in their telsons and cercopods, generally more reliable characters ( Timms, 2016a, b). These are (i) O. mariae has about 10–12 dorsal spines whereas that in O. pellucida has only about 5, (ii) only O. pellucida has a large mound of insertion for the telsonic filaments, (iii) cercopod setae number about 3 and are short in O. mariae , but number about 10 and are long in O. pellucida .

Differences between O. packardi and O. pellucida are harder to assess as O. packardi is poorly described and particularly variable (Brady, 1886; Spencer and Hall, 1896). Most populations of O. packardi have>20 telsonic setae, and though with a similar number of cercopod setae (10–12) there is a demarking spine terminating this row of setae. Moreover the carapace of O. packardi generally has the space between growth lines sculptured with lines at right angles.

Distribution and ecology. Known only from gnammas on the Gardner Plateau, Kimberley. These pools fill during the wet season, November to April, and the deeper pools (averaging 46 mm) support aquatic plants ( Cross et al., 2015a, 2015b). No information is available on their fauna, except that a few pools support the new species of clam shrimp described here plus Limnadopsis multilineata Timms 2009 .

Figures

FIGURE5. Ozestheria pellucida sp. nov. Male.A, carapace.B,sculpturing between growth lines on the carapace.C, head and antennae. D, dorsum of trunk segments VI to XVIII. E, telson. F, clasper with an enlargement of the apex of the moveable finger.Scale bars 1 mm.