Hydrodroma cooki Pesic & Smit, 2007, sp. nov.
Creators: name: Pesic, Vladimir
name: Smit, Harry
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Hydrodromidae
Hydrodroma
Hydrodroma cooki

description: Hydrodroma cooki sp. nov.
(Figs. 7 – 13, 16; Tables 3 – 4)
Type series: Holotype: male, dissected and slide mounted in Hoyer's fluid, NORTHERN TERITORY: Jabiru, Jabiru NP, 20.viii.1994, 12° 40.264 S 132° 50.436 E (NTM). Paratypes: 13 males, 2 juvenile females same data as holotype (NTM, ZMAN, MNHP), one female of these were dissected and slide mounted on Hoyer's fluid.
Other material: VICTORIA: swamp at junction of Victoria Valley Road and Bundol Road, 30.ix.1997, 4 males, 20 females. NEW SOUTH WALES: MacDonald River, upstream of Upper MacDonald River, 33° 12.312 S 150° 53.613 E, 02.xii.2003, 3 males, 1 female, 1 deutonymph; Water Gardens, Batemans Bay, 16.xii.2003, 35° 42.733 S 150° 10.688 E, 1 male, 1 female; Pools N of Lake Hiawatha, Yuragir NP, Character MALE FEMALE
holotype mean (r) n paratype mean (r) n genital acetabula, n 144 126.8 6 139 155.6 3
(111–155) (141–165)
number of genital setae 38 37.5 6 37 36 3
(29–46) (32–40)
genital plate length, Μm 288 252.4 5 270 250.5 2
(244–261) (242–259)
ejaculatory complex 228 214 5 – – – length Μm (203–219)
P1 64 62.8 5 73 63.5 2
(59–68) (59–68)
P2 89 86.6 5 102 94 2
(80–95) (91–97)
P3 56 57. 3 5 67 55 2
(53–61) (49–61)
P4 245 228.2 5 259 238.5 2
(209–241) (230–247)
P5 91 90.8 5 100 97 2
(76–100) (92–102)
Palp, total L 545 525.4 5 601 548 2
(494–534) (521–575)
%P1 11.7 12 5 12.1 11.6 2
(10.9–13.8) (11.3–11.8) %P2 16.3 16.5 5 17 17.2 2
(15.0–17.7) (16.9–17.5) %P3 10.3 11 5 11.1 10 2
(10.2–12.4) (9.4–10.6)
%P4 45 43.4 5 43.1 43.6 2
(42.3–44.4) (43.0–44.1) %P5 16.7 17.3 5 16.6 17.7 2
(15.4–18.7) (17.7)
W P-4 45 44 5 48 44.5 2
(40–47) (43–46) 10.xi.2003, 29° 47.315 S 153° 15.171 E, 2 males, 4 females. WESTERN AUSTRALIA: Pond Snake Creek, Millstream-Chichester NP, 17.viii.1994, 5 males, 10 females; Palm Pool, Millstream-Chichester NP, 15.viii.1994, 1 male; Pond Kalamina Gorge near falls, Hamersley Range NP, 13.viii.1994, 14 males, 9 females; Cockatoo Creek at crossing with Northern Highway, 08.ix.1998, 5 males, 1 female, 1 deutonymph. QUEENSLAND: Emu Creek at Clanly’s Camping Area, Benarkin State Forest, 03.xi.2005 26° 58.334 S 152° 0 9.916 E 12 males, 21 females; Lake Emma, Lakefield NP, 15° 17’47.43’’ S 144° 38’48.05’’ E, 3.ix.2000, 1 male, 8 females; Small lake Hawkwood Road, 13 km S of Munduberra, 31.x.2005, 25° 39.910 S 151° 13.941 E, 1 male; Small lake S of Biggenden (along road Biggenden-Maryborough), 01.xi.2005, 25° 33.583 S 152° 0 7.345 E, 12 males, 4 females; Mt Carbine Dam, Mt Carbine, 14.x.2005, 16° 32.019 S 145° 0 7.525 E, 2 males, 6 females; Cattle pond, Upper Daintree Road, Daintree, 09.viii.1989, 14 specimens. TASMANIA: Big Waterhouse Lake, Waterhouse Protected Area, 21.x.1997, 40° 53 S 147° 36 E, 1 male, 7 females; Little Waterhouse Lake, Waterhouse Protected Area, 21.x.1997, 40° 52 S 147° 36 E, 6 males, 5 females. NORTHERN TERRITORY: Manton Dam, 01.viii.1994, 12° 51.726 S 131° 0 7.148 E, 1 male; Lake Jabiru, Jabiru, 20.ix.2005, 12° 40.264 S 132° 50.436 E, 1 male; Small Billabong, Gunlon, Kakadu NP, 25.vii.1994, 4 males, 5 females; Caranbirini Waterhole, 06.x.2005, 16° 16.279 S 136° 0 4.837 E 15 males, 7 females; Billabong at Douglas Hot Springs, 01.viii.1994, 5 males, 6 females.
Females probably belonging to this species: WESTERN AUSTRALIA: McKenzie Spring, Millstream- Chichester NP, 17.viii.1994, 5 females; QUEENSLAND: Oxbow pond, Carnarvon NP, 29.x.2005, 25° 0 2.608 S 48° 11.750 E, 2 females; Nankin Creek, Rockhampton, 26.vi.1982, leg. A.P. Mackay 1 female; ibid., 24.ix.1982 leg. A.P. Mackay 1 juvenile female; Fitzroy River, Yaamba, 27.vi.1984 leg. A.P. Mackay 1 female; Moore’s Creek, Rockhampton, 9.iv.1983, leg. A.P. Mackay 3 females; ibid., 19.iii.1983 1 juvenile female.
H. cooki
Male holotype female paratype (n = 17) (n = 6) II-L-5 posterior 1 (1) 1 (1)
III-L-4 posterior 11 (10–13) 14–15 (11–13) III-L-5 posterior 10 (7–10) 13 (7–11) IV-L-4 anterior 13–15 (8–12) 12–13 (8–14) IV-L-4 posterior 13 (10–16) 15–16 (11–14) IV-L-5 anterior 0 0
IV-L-5 posterior 8–11 (6–10) 10–11 (8–11) Diagnosis: Characters of the genus Hydrodroma; the basic shape and setation of coxae, genital field and palps are similar to that found in H. despiciens; genital plates with 63–161 acetabulae in 5–9 rows; the palpal segments are narrower; ejaculatory complex L 194 – 231.
Description: Males (holotype, in parentheses range of variability based on specimens from Caranbirini Waterhole, n = 5): Length of idiosoma 1700 (1170 – 1440), width 1460 (1000 – 1370). Total number of coxal setae varies between 14 – 15 (13 – 18, =15.2) on coxae 1, 14 (11 – 17, =14.6) on coxae 2, 11 (8 – 12, =10.6) on coxae 3, 20 (13 – 20, =16.8) on coxae 4. Further details of genital plate morphology (Fig. 8) are given in Table 3. Gnathosoma: capitulum (Fig. 10) length 153 (250 – 266, =255.6); chelicerae total length 397 (359 – 375, = 368), claw 75 (69 – 71, = 70) in length. Palp chaetotaxy see figures 12 – 13 (measurements in Table 3).
Female (paratype, in parentheses range of variability based on specimens from Caranbirini Waterhole, n = 2): Length of idiosoma 1056 (1230 – 1300), width 981 (1120 – 1300).
Number of coxal setae varies between 19 (14 – 15) on coxae 1, 16 (14 – 17) on coxae 2, 10 (9 – 12) on coxae 3, 18 (16 – 22) on coxae 4. Gnathosoma: capitulum 281 (259 – 271) in length; chelicerae total length 425 (384 – 406), claw 78 (69 – 75) in length. Further details of genital plate morphology (Fig. 9) are given in Table 3.
Remarks: Hydrodroma cooki sp. nov. is most similar to H. despiciens (Müller) in the number and distribution of swimming setae on legs and in morphology of the genital field; legs with a relative small claw (Fig. 11). The main difference between the two species lies in the proportions of the palp. Hydrodroma cooki sp. nov. possesses much narrower palpal segments. In H. despiciens the palpal segments are much stockier, especially P-4 (compare Figs. 12 – 13 with Figs. 14 – 15). Furthermore, H. despiciens (in parentheses data taken from Wiles 1986) is distinguished by its relatively fewer acetabula (49–79 in generally 4 – 5 rows vs. 60–165 in 5–9 rows in H. cooki sp. nov.), while the ejaculatory complex is longer (e.g. 288 in male from Montenegro vs. 194 – 228 in H. cooki sp. nov.).
From H. monticola (Piersig) (in parentheses data taken from Wiles 1986), a species similar in the number and distribution of swimming setae on legs and in legs with relatively small claws, H. cooki sp. nov. can be easily distinguished by its relatively higher number of acetabula (64 – 83 in males, 70 – 90 in females). Males of H. monticola have twice as many setae present on the genital plate as females (mean number of genital plate seta: 78 – 92 in males, 38 – 48 in females).
Variability: We found considerable variability in number of acetabula between populations from different parts of Australia (eg. Western Australia [Pond Katherine Gorge]: male 63, female 82; New Southern Wales [MacDonald River; pool N of Lake Hiawatha]: male 76 – 97, female 72 – 96; Tasmania [Big Waterhouse Lake]: male 71; Queensland [Small lake S of Biggenden; Emu Creek]) male 89 – 96; Victoria: female 90 – 98; Northern Territory [Caranbirini Waterhole]: in both sexes 111 – 165). However, with regard to number and distribution of swimming setae on legs, narrower palpal segments (especially P-4) and length of ejaculatory complex (L 194 – 219, n = 12 from various localities), no differences could be found.
Malformations: In one male (from Lake Jabiru) and one female (from Victoria), deformations in shape of the genital field were observed (Fig. 16), accompanied by reduced number of acetabula and deformation in shape of the ejaculatory complex in the male.
Etymology: The species is named after Dr David Cook (USA) in appreciation of his studies of Australian water mites.
Distribution: Widespread in Australia (Victoria, New Southern Wales, Western Australia, Queensland, Northern Territory, Tasmania).
Habitat: Stagnant waters.
description: Published as part of Pesic, Vladimir & Smit, Harry, 2007, Water mite species of the genus Hydrodroma Koch (Acari: Hydrachnidia, Hydrodromidae) from Australia. Part II, pp. 41-50 in Zootaxa 1509 on pages 43-49, DOI: 10.5281/zenodo.177223