Diacyclops ballaballaensis Karanovic 2024, sp. nov.

Diacyclops ballaballaensis sp. nov. (Figs. 1C, 13–16) urn:lsid:zoobank.org:act: 22E70096-E81F-4238-9576-FC7E40509A05 Type locality. Western Australia, Pilbara Region, Balla Balla Station, bore BBR052, sample no. FBN111, 20.764256°S 117.750643°E, 5 August 2008, collected by E. Thomas. Holotype. Adult female dissected on 1 microscope slide. Paratypes. One female from type locality dissected on 1 microscope slide; 1 female and 1 copepod from type locality in 1 alcohol vial; 1 male dissected on 1 microscope slide from bore BBWP015, Balla Balla Station, Pilbara Region, Western Australia, 20.805288°S 117.758197°E, sample no. FBN102, 8 June 2008, collected by E. Thomas; 1 male and 1 female from bore BBWP015 (see above) and 1 female from Harding Dam, Pilbara Region, Western Australia, 20.970278°S 117.090278°E, sample no. HD3/00, 3 April 2003, collected by J. Cocking and M. Scanlon, together on 1 SEM stub (row no. 1), together with 5 other species described here; 1 copepodid from bore BBMB007, Balla Balla Station, Pilbara Region, Western Australia, 20.749846°S 117.778707°E, sample no. FBN012, 4 December 2007, collected by E. Thomas, in 1 alcohol vial. Etymology. The species name refers to its type locality, Balla Balla Station, which is a pastoral lease and cattle station about 140 km east of Karratha in Western Australia. It is an adjective for place, made with the Latin suffix “ -ensis ”. Diagnosis. Female. Body length from 520 to 540 µm. Habitus (Fig. 1C) robust, 2.75 times as long as wide, with prosome/urosome ratio of more than 1.6, and cephalothorax nearly 2.5 times as wide as genital double-somite in dorsal view. Integument on all somites (Fig. 16A, B) thin and wrinkled, with light bacterial cover; general distribution of spinules and cuticular pores on somites as in D. leijsi. Hyaline fringes of prosomites (Fig. 16A) and first urosomite (Fig. 16A) smooth, those of genital double-somite and 2 subsequent urosomites (Figs. 13A, 16B) very slightly wavy. Genital double-somite (Figs. 13A, 16A) wider than long in ventral view, widest at first third of its length and gradually tapering posteriorly, widest part about 1.5 times as wide as posterior margin; seminal receptacle smaller than in previous 2 species, anterior part less dome-like, posterior part short and broad; copulatory pore small and located more posteriorly than in previous 2 species; copulatory duct wide, long, and well-sclerotized. Anal somite (Figs. 13A, 16B) more cleft than in previous 2 species, with minute spinules along ventral margin. Caudal rami (Figs. 13A, 16B) long and slender, widely spaced, nearly 4.6 times as long as wide and about 2.7 times as long as anal somite; principal terminal setae without breaking planes, inner one strong and slightly longer than entire urosome, outer one greatly reduced and even shorter than innermost terminal seta; dorsal seta extremely long, about 3 times as long as caudal ramus, nearly 10 times as long as innermost terminal seta, and about 9 times as long as outermost terminal seta. Antennula (Fig. 13B) 12-segmented, slightly shorter than cephalothorax, with single aesthetasc on fifth segment and setae formula 8.4.2.6.3.2.2.3.2.2.2.8; ultimate segment about 1.9 times as long as wide. Antenna (Fig. 13C) 5-segmented, without exopodal seta, with setae formula 0.2.1.5.7; second segment about 1.4 times as long as fifth segment. Labrum (Fig. 13D) with 2 diagonal rows of 12–13 slender spinules each on anterior surface, and short rows of minute spinules in blunt lateral corners; cutting edge nearly straight, with 16 sharp teeth. Mandibula (Fig. 13E) similar to that in D. leijsi, but with 1 less unicuspidate tooth on cutting edge. Maxillula (Fig. 13F) also similar to that in D. leijsi, but without exopodal seta on its palp. Maxilla (Fig. 13G) similar to that in D. leijsi, but basal spine less robust and partly articulated basally. Maxilliped slenderer than in previous 2 species, with setae formula 1.2.1.2. Shape and segmentation of all swimming legs (Fig. 14A, B, C, E) as in D. leijsi, but second and third endopodal segment of first to third leg partly fused towards inner margin, while endopod of fourth leg clearly 3-segmented; basis of first leg with long outer seta and short inner spine, latter slightly shorter that first endopodal segment; basis of second to fourth legs with shorter outer seta and inner distal corner blunt; all first exopodal segments without inner seta; all second exopodal segments, all first endopodal segments, and second endopodal segment of first to third legs with single inner seta; second endopodal segment of fourth leg with 2 inner setae; third exopodal segments spine formula 2.3.3.3 and setae formula 4.4.4.4; third endopodal segments of first to third leg with 2 inner setae, 1 apical seta, 1 apical spine, and 1 outer seta; third endopodal segment of fourth leg about 1.7 times as long as wide, with 2 inner setae, 1 apical spine, and 1 outer seta; its apical spine slightly longer than segment. Fifth leg (Figs. 13A, 14F) shape and segmentation as in D. leijsi; second segment about 1.7 times as long as wide and only half as long as its spine. Sixth leg (Figs. 14G, 16A) minute, with very short outer seta. Male. Body length from 515 to 530 µm. Habitus and urosome (Fig. 15A) slightly slenderer than in female; free genital somite (Fig.15A) about 1.5 times as wide as subsequent urosomite, with relatively large ovoid spermatophores. Ornamentation of cephalothorax, free prosomites, and last 3 urosomites (Fig. 15A) as in female. Caudal rami (Fig. 15A) significantly shorter than in female, only about 3.5 times as long as wide in ventral view; dorsal seta also considerably shorter in female, only about 1.9 times as long as ramus; reduced outer principal terminal seta longer than in female, about 1.9 times about as long as innermost terminal seta. Antennula (Figs. 15B, C, 16C, D) very similar to that in D. leijsi, but shorter, fifth segment reduced in size, and ninth segment almost completely fused with eighth; armature and ornamentation of first 4 and last 7 segments as in D. leijsi, except ultimate segment missing smallest seta in distal cluster; fifth segment unarmed (two setae missing), ninth segment missing one seta, and seta on eighth segment smaller when compared to D. leijsi; penultimate segment about 1.7 times as long as wide. Antenna (Fig. 16C, E), labrum (Fig. 16E), mandibula (Fig. 16E), maxillula (Fig. 16E), maxilla (Fig. 16E), and maxilliped as in female. All swimming legs (Figs. 15D, E, F, G, H, 16F) with completely divided second and third endopodal segments, but armature and ornamentation as in female; third exopodal segments of first (Fig. 15E) to fourth (Fig. 15G) legs, as well as third endopodal segment of fourth leg (Fig. 15H), shorter than in female. Fifth leg as in female. Sixth leg (Fig. 15A) with single short spine. Variability. One third swimming leg of the holotype female showed an aberrant third exopodal segment (Fig. 14D), with 5 spines. The other third leg was normal, with three spines, as in the second swimming leg (Fig. 14B).