Diacyclops hancocki sp. nov.

(Figs. 1D, 17–21)

urn:lsid:zoobank.org:act: 9413A572-A2CE-41A3-8BAC-DC692D7625B0

Type locality. Australia, New South Wales, Tamworth, bore 30150, sample no. 3T30P0-100, 31.08221°S 150.91257°E, 20 July 2006, collected by P. Hancock.

Holotype. Adult female dissected on 1 microscope slide.

Paratypes. One male and 1 copepodid from type locality dissected on 1 microscope slide each; 2 males and 4 females from type locality on 1 SEM stub (row no. 4), together with 5 other species described here; 3 females and 1 copepodid from type locality in 1 alcohol vial; 2 males, 6 females, and 3 copepodids from type locality in 1 alcohol vial; 2 males from bore 93024, Tamworth, New South Wales, 31.36435°S 151.20272°E, sample no. 7T26P0-100, 17 July 2007, collected by M. Tomlinson; 1 female from bore 93028, Tamworth, New South Wales, 31.30358°S 151.1456°E, sample no. 8T44P200-300, 23 Oct 2007, collected by M. Tomlinson.

Etymology. The species is named after Dr. Peter J. Hancock, Water Resources Group, Adelaide, who collected this species and entrusted it to me for identification. The name is a noun in the genitive singular.

Diagnosis. Female. Body length from 455 to 540 µm. Habitus (Fig. 1D) very robust, 2.2 times as long as wide, with prosome/urosome ratio of about 1.6, and cephalothorax nearly 2.9 times as wide as genital double-somite in dorsal view. Integument on all somites (Fig. 20A, B) thin and smooth, without bacterial cover; general distribution of spinules and cuticular pores on somites as in D. leijsi. Hyaline fringes of prosomites (Fig. 20A) and first urosomite (Fig. 20A) smooth, those of genital double-somite and 2 subsequent urosomites (Figs. 17A, 20B) very slightly serrated. Genital double-somite (Figs. 17A, 20A) only slightly wider than long in ventral view, widest at first third of its length, abruptly tapering towards midlength, and nearly cylindrical in posterior half, widest part about 1.4 times as wide as posterior margin; seminal receptacle narrower than in previous 3 species, anterior part ovoid, about 2.3 times as wide as long, and about 1.3 times as wide as posterior heart-shaped part; copulatory pore very small and located at about 2/5 of somite length; copulatory duct shorter and narrower than in D. ballaballaensis, also less sclerotized, but with similarly inflated first half. Anal somite (Figs. 17A, 20) with long and slender spinules along ventral margin; anal operculum shortest of all species described here. Caudal rami (Figs. 17A) short and stout, widely spaced but not as much as in D. ballaballaensis, about twice as long as wide and less than 1.5 times as long as anal somite; principal terminal setae with breaking planes, inner one about 1.3 times as long as entire urosome and 1.6 times as long as outer one; dorsal seta about 2.3 times as long as caudal ramus, only slightly longer than innermost terminal seta, and about 3.2 times as long as outermost terminal seta. Antennula (Fig. 17B) 11-segmented, somewhat shorter than cephalothorax, with 1 aesthetasc on fourth, eighth, and tenth segments each, and setae formula 8.4.8.3.2.2.2.2.2.2.8; ultimate segment about 1.8 times as long as wide. Antenna (Fig. 17C) 5-segmented, slenderer than in previous 3 species, with well-developed exopodal seta, total setae formula 0.3.1.7.7; second segment about 1.4 times as long as fifth segment. Labrum (Fig. 20C) with 2 diagonal rows of 12–13 slender spinules each on anterior surface; cutting edge slightly concave, with 17–19 sharp teeth between blunt and smooth lateral corners. Mandibula (Figs. 17D, 20C) similar to that in Diacyclops leijsi sp. nov., but with 7 slender spinules on anterior surface. Maxillula (Figs. 17E, 20D) also similar to that in D. leijsi, but apical spine fused basally to inner margin of coxobasis. Maxilla (Figs. 17F) similar to that in D. leijsi, but basal claw with several additional spinules and endopod visibly 2-segmented. Maxilliped (Figs. 17G, 20F) similar to that in D. ballaballaensis, but second segment with fewer spinules and setae formula 2.1.1.2. Segmentation of all swimming legs (Fig. 18A, B, C, D, E) as in D. leijsi, but they are slightly wider, and intercoxal sclerite of first leg with two short arched rows of minute spinules on anterior surface; basis of first leg with short outer seta and very strong inner spine, latter slightly longer that first 2 endopodal segments combined; basis of fourth legs with less sharp inner distal corner than those of second and third legs; first exopodal segment of first and fourth legs without inner seta, while that segment of second and third leg with 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 3.4.4.3 and setae formula 5.5.5.5; third endopodal segment of first leg with 2 inner setae, 1 apical seta, 1 apical spine, and 1 outer seta; third endopodal segment of second and third legs with 3 inner setae, 1 apical seta, 1 apical spine, and 1 outer seta, but apical spine on second leg much longer than that on third leg; third endopodal segment of fourth leg 1.6 times as long as wide, with 2 inner setae, 2 apical spines, and 1 outer seta; its outer spine very slightly shorter than inner spine and only about half as long as segment. Fifth leg (Fig. 17A) shape, segmentation, and proportions of segments and armature as in D. leijsi, except inner margin of second segment somewhat convex. Sixth leg (Figs. 18F) not larger than in D. leijsi, but with much larger spines than in any other species described here; outer seta less than half as long as plate width.

Male. Body length from 450 to 490 µm. Habitus (Fig. 21A) and urosome (Fig. 19A) slightly slenderer than in female; free genital somite (Fig. 19A) less than 1.4 times as wide as subsequent urosomite, with relatively large ovoid spermatophores. Ornamentation of cephalothorax, free prosomites, and last 3 urosomites (Figs. 19A, 21B) as in female. Caudal rami (Figs. 19A, 21B) also as in female. Antennula (Figs. 19B, 21C) very similar to that in D. ballaballaensis, except that third and fourth segments are fused completely on anterior surface, as well as fifth and sixth segments, although remnants of their original segmentation remain visible on posterior margin; all armature and ornamentation as in D. ballaballaensis; penultimate segment also about 1.7 times as long as wide. Antenna (Fig. 21C), labrum (Fig. 21C), mandibula, maxillula, maxilla, maxilliped, all swimming legs (Figs. 19C, 21E), and fifth leg (19A, 21F) as in female. Sixth leg (Figs. 19A, 21F) as in D. leijsi, with 1 spine and 2 setae, but all 3 elements of similar length.