Kensakia australis, Harris, 2014

Harris, Vernon A., 2014, Porcellidiidae of Australia (Harpacticoida, Copepoda). II. The Importance of the Male Antennule in Taxonomy, Records of the Australian Museum 66 (2), pp. 111-166 : 130-131

publication ID	https://doi.org/ 10.3853/j.2201-4349.66.2014.1595
persistent identifier	https://treatment.plazi.org/id/03E56619-FFC7-3208-F775-7D8155554B35
treatment provided by	Carolina
scientific name	Kensakia australis
status	sp. nov.

Treatment

Kensakia australis sp. nov.

Figs 13 View Figure 13 , 14 View Figure 14 ; Plate 1D

Type material. HOLOTYPE adult male, length 0.55 mm, P81210 . ALLOTYPE adult female, length 0.62 mm, P81211 . PARATYPE specimens P81212 (10 ♀♀, 5 ♂♂) deposited at AM, Sydney. Additional paratypes deposited at NHM, London. All collected from a brown seaweed, Zonaria sp., sublittoral fringe, Point Vernon, Hervey Bay , Queensland (25°15' S 152°47' E), V. A. Harris 1997 .

Diagnosis. Labrum with medial pad of minute setules plus four or five lateral striations (ridge-plates absent); female rostrum broad (W/R = 4.1); females carry eight eggs; male antennule with transverse tunnel-like thickening of cuticle on ventral side of segment 4 ( Fig. 13E View Figure 13 ), distal coupling denticle very small (3–5 µm), dactylus long (= length of segment 3+4), hooked distally; ventrolateral band on ventral side of cephalosome with net-like markings; very few dorsal sensilla; no setae lateral to female genital opening; male rostrum V-shaped ventrally; α and β setae on male caudal ramus short (1/2 width of ramus); ventral setules on male anal segment; dorsal setae on female P5 not pinnate.

Biometric data. Females (N = 25): maximum length (Lmax) mean 0.615 mm, range 0.58–0.65 mm, body length (Lurs) mean 0.58, range 0.56–0.61 mm; cephalosome width (W) mean 0.37 mm; rostrum (R) width 0.09 mm; genital doublesomite width 0.186 mm, length 0.145 mm; caudal ramus maximum width 0.05 mm, length 0.135 mm,

Ratios: Lurs / W 1.57, Lmax / W 1.66; W/ R 4.1 ; genital double-somite w/l 1.27, arch 55% of length; caudal ramus 22% of Lurs, l/ w 2.6, Hicks’ index for α 88%, for β 76%, apex angle of ramus 42 °.

Males (N = 23): maximum length (Lmax) mean 0.55 mm, range 0.55–0.58 mm, body length (Lurs) mean 0.51, range 0.49–0.64 mm; cephalosome width (W) mean 0.34 mm, range 0.31–0.37 mm, length 0.32 mm; rostrum length 0.045 mm; caudal ramus width 0.04, length 0.05 mm; antennule (fully extended) 0.145 mm; spermatophore 0.078 × 0.02 mm.

Ratios: Lurs / W 1.5, Lmax / W 1.6; cephalosome 58% of Lmax; caudal ramus l/ w 1.25; antennule 26% of body length Lurs, segments 3+4 41%, dactylus 43%, aesthetasc 70% of antennule length; spermatophore 14% of Lurs.

Description. Adult females ( Fig. 13A View Figure 13 ; Plate 1D, p. 163): colour pale yellow or colourless, mid-dorsal area of cephalosome, metasome and genital double-somite dark blue-purple, caudal rami and P5s not coloured. Cephalosome semicircular, rostrum broad, not prominent, dorsal pits on cephalosome, metasome, genital double-somite and P5 exopod small (3–5 µm), very few dorsal sensilla. Hyaline border clear, 6–7 µm wide. Ducts of marginal glands open dorsally. On ventral side of cephalosome there is a broad lateral band of net-like markings about 30 µm wide that narrows posteriorly (ventrolateral band, Fig. 13J View Figure 13 ) and a peripheral band of vacuous cells (seen from ventral side Fig. 13H View Figure 13 ). Some specimens have reticulate markings on ventral surface of the rostrum. Labrum ( Fig. 14J View Figure 14 ) with pad of minute hair-like setules and a group of four or five setules laterally, but no ridge plates. Genital double-somite ( Fig. 14C View Figure 14 ) narrow (50% of cephalosome width), lateral border with fine setules, small notch marks boundary between anterior and posterior lobes, posterior lobe pointed posteriorly, arch deep, no anterolateral ridges (rugosities) present. Sternal sclerite of metasome segment 4 with fimbriate posterior border, genital opening narrow (35 µm), no seta at lateral corner of opening. Caudal ramus ( Figs 13D View Figure 13 ) trapezoid (sides slightly divergent), maximum width 2/3 down ramus, lateral and medial edges without setules, dorsal surface with net-like pattern. α and β setae close, terminal setae T1 and T4 plain, very small, setae T2 and T3 absent, posterior border with very short, fine setules. Structure and setation of mouthparts and ambulatory limbs typical of family. Antenna basis with triangular setules along anterior edge but no setules on lateral surface ( Fig. 14B View Figure 14 ), exopod with five plumulose setae and one plain spinous seta, fine border setules on segment 1 of endopod, segment 2 with three lateral setae, end segment of geniculate setae plain, long thin comb-like claw (> 1/3 length of endopod segment 2). Mandible, maxillule and maxilla as shown in Figs 14G, I and K View Figure 14 respectively, maxilliped ( Fig. 14L View Figure 14 ) basis with fimbriate border but no rows of small lateral setules. P1 ( Fig. 13C View Figure 13 ) with coxal seta, inconspicuous small patch of denticulate pegs at lateral end of fimbriate crescent. Serrulate spinous seta on segment 2 of P3 endopod ( Fig. 14E View Figure 14 ) shorter than endopod (0.8:1), large serrate spinous seta on segment 3 much longer than endopod (1.5:1). P4 endopod with serrulate spinous seta on segment 2 and 3 ( Fig. 14D View Figure 14 ). Exopod of P5 lanceolate, without ventral expansion, dorsal surface pitted, apical end of ventral falciform ridge with concave notch ( Fig. 14A View Figure 14 ), border setules short, two prominent dorsal setae and two apical setae. P5s extend beyond genital double-somite and caudal rami but do not touch posteriorly. Females carry eight eggs.

Adult males ( Fig. 13B View Figure 13 ). Colour similar to female except that the blue-purple dorsal area does not extend beyond metasome segment 2. Cephalosome truncated with sloping, rounded shoulders, lateral angle of antennule socket prominent. Rostrum narrow, keeled and Y-shaped in ventral view, width 2/3 of length ( Fig. 14M View Figure 14 ). Dorsal pits, hyaline border, vacuolated cells, reticulate ventral band and labrum as for female. Caudal rami ( Fig. 14H View Figure 14 ) rectangular, slightly longer than wide (1.2:1), dorsal surface with net-like markings, α and β setae short (<1/2 width of ramus). Setae T1, T2 and T4 very short and small (T2 and T4 lost on many specimens), T3 absent. Posterior border with very short setules. Small group of striations (5 or 6) on ventral side of anal segment at the posterolateral corner ( Fig. 14H View Figure 14 ). Antennule ( Fig. 13F View Figure 13 ) with pinnate seta on segment 1, distal coupling denticle on segment 4 small (3–5 µm) bicuspid, close to brush-pad, aesthetasc almost as long as segment 3+4 + dactylus with two characteristic constrictions, dactylus equals length of segment 3+4, hooked at tip ( Fig. 13F, G View Figure 13 ). A tunnel like indentation of the ventral cuticle is found on the ventral side of segment 4 just proximal to the sensory lobe carrying aesthetasc ( Fig. 13E View Figure 13 , “tunnel”). Limbs as for female except that P2 has only two terminal setae on the endopod. All setae on P4 endopod plumose. P5 exopod trapezoid, lateral seta with row of 12–15 ventral setules and of different shape to terminal setae ( Fig. 14F View Figure 14 ). Spermatophore very small.

Etymology. The first species belonging to Kensakia recorded from Australia.

Remarks. Kensakia australis closely resembles Japanese specimens of K. acuta but is significantly smaller, differs slightly in colour pattern, shape of female rostrum and in the number of eggs carried in each brood.

Distribution. Kensakia australis is common at low water spring tides at Hervey Bay, Queensland on Zonaria sp. Type series (PV3, 7/97, 76 ♀♀ + 65 ♂♂) and Eucheuma sp., (PV6, 60 ♀♀ + 23 ♂♂ + juveniles), V. A. Harris 1997. It has also been recorded from Dilophus sp., and Lobophora sp., in rock pools at Arrawarra, NSW (30°03' S 153°02' E), V. A. Harris, 1982.