Hydrodroma kakadu, Pesic, Vladimir & Smit, Harry, 2007

Pesic, Vladimir & Smit, Harry, 2007, Water mite species of the genus Hydrodroma Koch (Acari: Hydrachnidia, Hydrodromidae) from Australasia. Part I, Zootaxa 1389, pp. 31-44 : 38-42

Hydrodroma kakadu sp. nov.

( Figs. 14–17 , 20 ; Tables 5–7 )

Type series: Holotype: male, dissected and slide mounted in Hoyer's fluid, Plunge Pool Gunlom Falls, Kakadu NP, Northern Territory, Australia, 30.ix.2005, 13° 25.17 S 132° 24.989 E ( NTM). Paratypes: 9 males, 11 females same data as holotype ( NTM, ZMAN, MNHP), four males and two females of these were dissected and slide mounted on Hoyer's fluid, same data as holotype.

Further records: AUSTRALIA: NORTHERN TERITORY: Pond Jim Jim Creek near Jim Jim Campground, Kakadu NP, 23.vii.1994, 13°16 S 132°48 E, 3 males, 4 females; Pond in Jim Jim Creek at Jim Jim Crossing, Kakadu NP, 12°16 S 132°40 E, 22.vii.1994, 3 females; Mardugal Billabong, Kakadu NP, 12°16 S 132°40 E, 21.vii.1994, 12 males, 19 females, 2 deutonymphs; Plunge Pool, Gunlom Falls, Kakadu NP, 13° 25.917 S 132° 24.989 E, 25.vii.1994, 3 males, 1 female; Plunge Pool Edith Falls, Nitmiluk (= Katherine Gorge) NP, 14°19 S 132°34 E, 14° 10.899 S 182° 11.342 E, 30.vii.1994, 14 males, 26 females; same location, 02.x.2005, 17 males, 11 females; Pool Twin Falls, Kakadu NP, 12°16 S 132°40 E, 23.vii.1994, 3 maleS, 1 female; Lily Ponds Falls, Katherine Gorge NP, 14°19 S 132°34 E, 27.vii.1994, 1 female; Roper River, 06.x.2005, 14° 57.111 S 133° 13.401 E, 3 males, 6 females.

NEW CALEDONIA: Oua Mendiou Rivière 30 km from mouth, 01.x.2000, 3 females; Dothio Rivière at crossing with road Thio­Nakety, 28.ix.2000, 4 females; Rivière de Pirogues at crossing with road Nouméa­ Yaté, 11.xi.2005, 22° 11.257 S 166° 43.397 E, 1 female; Hienghène Rivière, 19 km from mouth, 29.ix.2000, 2 males, 10 females, 1 deutonymph.

Diagnosis: Characters of the genus Hydrodroma ; the shape and setation of coxae, genital field and palps are similar to those found in H. pilosa ; genital plates with 28–47 acetabula in 3–4 rows; swimming setae are absent on the anterior surface of IV­L­5.

Description: Males (n = 5, Plunge Pool Gunlom Falls): Length of idiosoma 738–775, width 606–656. Total number of coxal setae varies between 13–17 (=15.4) on coxae 1, 12–16 (= 13.6) on coxae 2, 11–13 (=12) on coxae 3, 11–14 (= 12.4) on coxae 4. Further details of genital plate morphology are given in Table 5 . Gnathosoma: capitulum length 153–172 (= 160); chelicerae total length 216–228 (= 222), claw 48–51 length (= 50). Palps without diagnostic features, for chaetotaxy of the palp see Figure 16 (measurements in Table 5 ). Number of swimming setae on legs are presented in Table 6.

Female (n = 2, Plunge Pool Gunlom Falls): Length of idiosoma 688–1000, width 569–888. Number of coxal setae varies between 15–16 on coxae 1, 15–18 on coxae 2, 13–14 on coxae 3, 15 on coxae 4. Gnathosoma: capitulum L 172–185; chelicerae total length 241–245, claw 53–54 in length.

Characters MALE FEMALE

H. kakadu

male (n = 9) female (n = 3) II­L­5 posterior 3–4 4–8

III­L­4 posterior 8–10 8–10

III­L­5 posterior 5–7 6–9

IV­L­4 anterior 7–8 8–9

IV­L­4 posterior 7–8 8–9

IV­L­5 anterior 0 0

IV­L­5 posterior 3–4 4–6

H. kakadu

male (n = 2) female (n = 4)

II­L­5 posterior 3–4 3–4

III­L­4 posterior 13–14 10–12 III­L­5 posterior 8–11 7–11 IV­L­4 anterior 11 10–11 IV­L­4 posterior 12–13 11–13 IV­L­5 anterior ­ ­

IV­L­5 posterior 6–7 6–7

Remarks: Hydrodroma kakadu sp. nov is most similar to H. kununurra sp. nov., and H. australis sp. nov. which both have more than one swimming setae on II­L­5. Hydrodroma kakadu can be easily distinguished from both species by the absence of swimming setae on the anterior side of IV­L­5. Furthermore, H. kakadu sp. nov., is distinguished by its relatively fewer acetabula, 28–47 (70–93 in 5–6 rows in H. kununurra sp. nov) and the ejaculatory complex is shorter, L 166–182 (188–209 in H. australis sp. nov., 216–236 in H. kununurra sp. nov).

From H. americanus Marshall (in parentheses data taken from Wiles 1986) a species similar in the absence of swimming setae on the anterior side of IV­L­5, H. kakadu sp. nov. can be easily distinguished by its relatively fewer acetabula (69± 10 in both sexes) and males of H. americanus have twice as many setae present on the genital plate as females (mean number of genital plate seta: 94± 14 in males, 41± 6 in females).

Due to the morphology of the genital field and the absence of swimming setae on the anterior side of IV­ L­5, specimens from New Caledonia show a general conformity with H. kakadu sp. nov. The New Caledonian specimens can be distinguished from the type­material of H. kakadu sp. nov. in its larger idiosoma and gnathosoma dimensions (e.g. idiosoma L males 831–1000, females 1100–1200; L genital plates 173–198 in male 192–203 in female; L capitulum in both sexes 219–244, L chelicera in both sexes 275–303; palp total L males 387–408, females 432–438) and in a higher number of swimming setae on III­IV­L (III­L­4p> 10, IV­ L­4a> 10, IV­L­5p> 6, see Table 7). Furthermore, the ejaculatory complex is longer, L 193–197. However, many of these characters are known to be variable and these specimens probably represent a New Caledonian race of H. kakadu sp. nov. The degree of variability of additional specimens is necessary before we can assess the taxonomic status of the New Caledonian specimens

Etymology: The species is named after the Kakadu National Park.

Distribution: Australia (Northern Teritory); New Caledonia.

Habitat: Most specimens were taken from (plunge) pools in running waters. Like H. australis , the new species is obviously rheophilous.

Figures

FIGURES 14 – 17. Hydrodroma kakadu sp. nov., male holotype (Northern Teritory, Plunge Poool Gunlom): 14, coxal and genital field; 15, genital field; 16, palp, mediel view; 17, capitulum. Scale Bars = 100 µm.

FIGURES 18 – 20. Genital field: 18, H. kununurra sp. nov.; 19, H. australis sp. nov.; 20, H. kakadu sp. nov. Scale Bar = 100 µm.

Tables

TABLE 5. Morphometric data for the genital plate and palp for H. kakadu sp. nov. (abbreviations: r = range, n = number of mites examined).

mean	r	n	mean	r	n
genital acetabula, n 34	28–38	5	46.5	46–47	2
genital setae, n 23	21–26	5	22	21–23	2
genital plate length, m 164	152–174	5	182.5	180–185	2
ejaculatory complex length, m 172.8	166–182	5	–	–	2
P1 34	31–39	5	37	36–38	2
P2 57.8	49–62	5	62	62	2
P3 33.3	32–34	5	33.5	33–34	2
P4 138	132–144	5	147	146–148	2
P5 58.2	53–62	5	65.5	63–66	2
Palp, total L 321.8	298–338	5	344	342–346	2
%P1 10.6	9.8–11.5	5	10.8	10.5–11.1	2
%P2 17.9	16.4–18.5	5	18	17.9–18.1	2
%P3 10.4	10.1–10.7	5	975	9.7–9.8	2
%P4 42.9	41.7–44.3	5	42.75	42.7–42.8	2
%P5 18.3	17.8–18.7	5	18.75	18.4–19.1	2
W P­4 27.1	26–29	5	27.5	27–28	2