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Two new water mite species of the genus Hydrodroma Koch, 1837 from New Caledonia (Acari, Hydrachnidia: Hydrodromidae)

Pešić, Vladimir1; Smit, Harry2 and Mary, Nathalie J.3

1✉ Department of Biology, University of Montenegro, Cetinjski put b.b., 81000 Podgorica, Montenegro.
2Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, the Netherlands.
3Etude des Hydrosystèmes Continentaux tropicaux (ETHYC’O), B.P. 13 821, Nouméa Cedex 98 803, New Caledonia.

2021 - Volume: 61 Issue: 3 pages: 581-590

https://doi.org/10.24349/aGHX-uIU1
ZooBank LSID: 505D641C-5C48-44A4-8B98-8FE2304A4090

Original research

Keywords

Acari new species New Caledonia taxonomy Australia

Abstract

Two new water mite species of the genus Hydrodroma Koch (Acari: Hydrachnidia, Hydrodromidae) are reported from New Caledonia, i.e. Hydrodroma novacaledonica sp. nov. and H. pacifica sp. nov. An updated key for the Australasian species of Hydrodroma is provided.


Introduction

The family Hydrodromidae K. Viets, 1936 comprises of two genera, the widely distributed Hydrodroma Koch, 1837 and the doubtful Oxopsis Nordenskiöld, 1905, known from a single specimen collected in Sudan (see Cook 1974). The genus Hydrodroma has been found in all biogeographic regions except Antarctica. Species of this genus are often abundant in standing waters or pool areas of streams, but can be found also in stream riffles and cascades (Di Sabatino et al. 2010; Gerecke 2017). In general, adults have a uniform appearance, with idiosoma lacking muscle attachment sclerites, genital flaps bearing numerous small acetabula arranged in several rows along the medial edge, P-4 with a long and pointed dorsodistal extension reaching the tip of the slender and elongated P-5, and legs bearing swimming setae (Di Sabatino et al. 2010; Gerecke 2017).

More than 28 species of the family Hydrodromidae are known worldwide to date (Zhi-Qiang et al. 2010). Currently, six species have been described from the Australasian region (Australia and New Caledonia), i.e. Hydrodroma kununurra Pešić & Smit, 2007, H. australis Pešić & Smit, 2007, H. kakadu Pešić & Smit, 2007, H. wilesi Pešić & Smit, 2007, H. cooki Pešić & Smit, 2007 and H. meridionalis Pešić & Smit, 2007 (Pešić and Smit 2007a, b, 2011).

This paper gives the description of two new species of the genus Hydrodroma from New Caledonia.

Material and methods

Water mites were collected by hand netting, sorted live in the field, and immediately preserved in Koenike-fluid. In the lab, selected specimens were dissected, and slide mounted in Faure's medium. Holotypes and paratypes of the new species will be deposited in Muséum National d'Histoire Naturelle, Paris (MNHN), paratypes and non-type-material in Naturalis Biodiversity Center in Leiden (RMNH).

All measurements are in µm. The photographs of ejaculatory complexes were made using a camera on Samsung Galaxy smartphone. The following abbreviations are used: Ac = acetabula; Cx-I = first coxae; dL = dorsal length; H = height; I-L-4-6 = fourth-sixth segments of first leg; L = length; lL = lateral length; mL = medial length; NP = National Park; P-1-P-5 = palp segment 1-5; RMNH = Naturalis Biodiversity Center, Leiden; W = width.

Mentioning author(s) and year of publication in taxon names in this paper is for nomenclatural completeness only, and therefore no citation of the original papers is given in the references.

Systematics

Family Hydrodromidae K. Viets, 1936

Genus Hydrodroma Koch, 1837

Hydrodroma novacaledonica Pešić & Smit sp. nov.

ZOOBANK: C2A308F0-C3CB-4A75-AE55-D113163B5A91

Figs. 1A-C, E-G

Figure 1. A-C, E-G: Hydrodroma novacaledonica sp. nov. (A, E, G holotype ♂, Creek des Japonais; B-C, ♀, Creek des Japonais; F, ♀, Rivière Thio): A-B – genital field; C – integument papillae; E – palp, lateral view; F – palp, medial view; G – IV-L-6. D: H. kakadu, ♀, Plunge Pool Edith Falls, Northern Territory: integument papillae. Scale bars = 100 μm.

SynonymHydrodroma kakadu Pešić & Smit 2007a: 38 [in part].

Material examined — Holotype ♂ (MNHN), New Caledonia, Creek des Japonais at crossing with road Thio-Boulouparis, 27 Sept. 2000, leg. Smit, dissected and slide mounted. Paratypes: 2♂, 3♀, same place and data as holotype, 1♀ dissected and slide mounted (MNHN, RMNH); 8♀, 1 deutonymph, New Caledonia, Hienghène Rivière, 19 km from mouth, 29 Sept. 2000, leg. Smit (RMNH).

Other material — New Caledonia: Rivière Amoa tributary RG, 20°58'47.857 S, 165°09'32.126 E, 25 Oct. 2005 leg. Flouhr, 1♂, 1♀; Rivière Nodéla, 20°26'42.600 S, 165°19'52.345 E, 13 May 2005 leg. Flouhr, 1♀; Rivière Nodéla, 20°26'42.600 S, 165°19'52.345 E, 13 May 2005 leg. Flouhr, 1♀; Dothio Rivière at crossing with road Thio-Nakéty, 28.ix.2000, leg. Smit, 4♀; Oua Mendiou Rivière 30 km from mouth, 01 Oct. 2000, leg. Smit, 3♀; Thio Rivière at crossing with road to Kouaré, 27.Sept. 2000 leg. Smit, 1♂; Rivière Coulée, 22°10'24.327'' S, 166°37'18.119'' E, 21 Oct. 2005 leg. Smit, 1♂, 2♀; Rivière Coulée, 22°60'25.876'' S, 166°37'22.857'' E, 20 Sept. 2001 leg. Mary, 1♀ [damaged; gnathosoma and palps lacking]; Rivière Thio, 21°38'13.4736'' S, 166°11'56.935'' E, 29 Oct. 1997 leg. Mary, 1♀, dissected and slide mounted (RMNH); Thio 7, 02.viii.2000 leg. Mary, 2♀; Néaoua, 27 Oct. 1999, leg. Mary, 1♀; Thiiem, 02 Nov. 1999 leg. Mary, 5♀; Boghen 1, 30 Oct. 1999, leg. Mary, 1♀; Thio 7 (Dothio I), 12 Jan. 2000 leg. Mary, 2♀.

Diagnosis — Idiosoma and gnathosoma large in size (idiosoma L ˃ 1000, genital plates L ˃ 200, P-4 ˃ 190 µm); integument papillae rounded. Genital plates with 47–51 pairs of Ac in at most 4 longitudinal rows. Leg setae numbers: II-L-posterior 3-4; III-L-4 posterior 9-14; III-L-5 posterior 7-11; IV-L-4 anterior 8-12, posterior 9-14; IV-L-5 anterior 0, posterior 6-8.

Figure 2. Hydrodroma pacifica sp. nov. (A holotype ♂, Rivière Ouénaoué; B ♀, La Coulée Rivière): A – coxal and genital field; B – genital field. Scale bar = 100 μm.

Description — Integument with reticulation in deeper layers (Fig. 4B). Cx-I+II medially separated by a fine membranous line, with a row of long fine setae at medial margins of Cx-I, and posterior margins of Cx-II, -III, and -IV. Genital flaps with rounded lateral and concave medial margins. Excretory pore sclerotized. Leg claws without claw blade, with a dorsal clawlet.

Male (holotype): Idiosoma L 1300, W 1050. Coxal field L 588; Cx-III W 659, L Cx-I+II 253, Cx-III+IV 322; coxal setae numbers: Cx-I, 17; Cx-II, 19; Cx-III, 13; Cx-IV 18. Genital plate L 208, on each plate Ac number 49, with 23-26 setae, all hollow. Ejaculatory complex L 194.

Gnathosoma vL 244; chelicera total L 277, L basal segment 211, claw 63, L ratio basal segment/claw 3.3. Palp (Fig. 1E) total L 452, dL/H, dL/H ratio: P-1, 56/37, 1.53; P-2, 77/56, 1.38; P-3, 50/58, 0.87; P-4, 191/45, 4.3; P-5, 78/19, 4.2; L ratio P-2/P-4, 0.4. dL IV-L: 94, 169, 191, 297, 313, 275.

Female (paratype from Creek des Japonais, n = 1; in parentheses some measurements of the specimen from Rivière Thio, n = 1): Idiosoma L 1420 (1350), W 1160. Coxal field L 623 (622); Cx-III W 669 (644); L Cx-I+II 291 (283), Cx-III+IV 363 (338); coxal setae numbers: Cx-I, 19 (16); Cx-II, 28 (19); Cx-III, 20 (15); Cx-IV 16 (17). Genital plate large, L 228 (219), on each plate Ac number 51 (47), with 26 (22) setae.

Gnathosoma vL 255 (259); chelicera total L 309 (305), L basal segment 242 (231), claw 66 (67), L ratio basal segment/claw 3.7 (3.5). Palp (Fig. 1F) total L 463 (464), dL/H, dL/H ratio: P-1, 56/39, 1.44 (60/42, 1.4); P-2, 77/62, 1.25 (83/63, 1.32); P-3, 52/59, 0.87 (48/55, 0.88); P-4, 198/47, 4.2 (195/45, 4.3); P-5, 80/19, 4.1 (78/20, 3.9); L ratio P-2/P-4, 0.39 (0.42). dL IV-L: 111 (113), 184 (172), 209 (198), 325 (316), 338 (347), 292 (291).

Etymology — Named after the island where the new species was collected.

Discussion — The new species from New Caledonia closely resembles Hydrodroma kakadu Pešić & Smit, 2007, a species similar in the presence of 3-4 swimming setae on II-L-5 and in the absence of swimming setae from anterior IV-L-5. It was originally described from Kakadu National Park, Australia, and reported also from New Caledonia (Pešić & Smit 2007a). The latter authors mentioned that specimens of H. kakadu from Australia differ from specimens from New Caledonia, in this study assigned to the new species H. novacaledonica sp. nov., in smaller dimensions of the idiosoma and gnathosoma (e.g., idiosoma L: ˂ 800 in ♂, ˂ 1000 in ♀; L genital plates ˂ 180 in ♂, ˂ 190 µm in ♀; in both sexes L gnathosoma ˂ 190, chelicera ˂ 250, P-4 ˂ 150 µm) and in a reduced number of swimming setae on III/IV-L (less than 10 on both posterior III-L-4 and anterior IV-L-4) (Pešić & Smit 2007a). These differences are confirmed by the examination of new material from New Caledonia. Moreover, the new species from New Caledonia differs in the shape of integument papillae (rounded vs. pointed in specimens of H. kakadu from Australia; compare Fig. 1C and Fig. 1D).

Distribution — New Caledonia.

Table 1. Number of swimming setae for Hydrodroma novacaledonica sp. nov..

Hydrodroma pacifica Pešić & Smit sp. nov.

ZOOBANK: 7F836BF0-9B10-4686-B013-A469D331C630

Figs. 2, 3A-C, E-G

Figure 3. A-C, E-G: Hydrodroma pacifica sp. nov. (A, C-E holotype ♂, Rivière Ouénaoué; F-G ♀, La Coulée Rivière): A – integument papillae; C – palp, lateral view; D, F – palp, medial view; E – IV-L-6; G – chelicera. B: H. cooki, ♀, Caranbirini Waterhole, Northern Territory: integument papillae. Scale bars = 100 μm.

Figure 4. Photographs of selected parts. A-G: Hydrodroma novacaledonica sp. nov. (A, D, F, holotype ♂, Creek des Japonais; B-C, E, G, ♀, Creek des Japonais): A, C – coxal and genital field; B – dorsal integument papillae; D-E – genital field; F = ejaculatory complex; G – gnathosoma, lateral view; H-K: Hydrodroma pacifica sp. nov. (H holotype ♂, Rivière Ouénaoué; K-I ♀, La Coulée Rivière): H – ejaculatory complex; I – genital field; K – coxal and genital field. Scale bars = 100 μm.

Material examined — Holotype ♂ (MNHN), New Caledonia, Rivière Ouénaoué at crossing with Mt Koghi road, 22°10.856 S, 166°29.532 E, 13 Nov. 2005 leg. Smit, dissected and slide mounted. Paratypes: 1♀, same place and data as the holotype, leg. Smit, dissected and slide mounted, (MNHN); 2♀, 1 deutonymph, La Coulée Rivière downstream of barrage, 22°10.404 S, 166°37.291 E, 16 Nov. 2005 leg. Smit, 1♀ dissected and slide mounted (RMNH).

Other material — New Caledonia: Rivière Voh, 20°56'13.241'' S, 164°43'29.427'' E, 6 Nov. 2001 leg. Mary, 1♂; Unnamed Creek E of Pont Pérignon, Parc de la Rivière Bleue, 24 Sept. 2000 Smit, 1 ♀ (partly damaged); Coco amont, 5 Oct. 2000 leg. Mary; Rivière Confiance, leg. Mary, 1♂.

Diagnosis — Integument papillae rounded. Genital plates with 38–43 pairs of Ac in at most 3 longitudinal rows. Leg setae numbers: II-L-posterior 1 (short); III-L-4 posterior 4-6; III-L-5 posterior 3-6; IV-L-4 anterior 4, posterior 7; IV-L-5 anterior 0, posterior 3-4.

DescriptionGeneral features —Integument with reticulation in deeper layers. Cx-I+II medially separated by a fine membranous line, with a row of long fine setae at medial margins of Cx-I, and posterior margins of Cx-II, -III, and -IV. Genital flaps with rounded lateral and strongly concave medial margins. Excretory pore sclerotized. Legs claws without claw blade, with a dorsal clawlet.

Males (holotype): Idiosoma L 910. Coxal field L 464; Cx-III W 456; L Cx-I+II 219, Cx-III+IV 256; coxal setae numbers: Cx-I, 22; Cx-II, 25; Cx-III, 19; Cx-IV 16. Genital plate slender, L 197, on each plate Ac number 38, with 23 setae, all hollow. Ejaculatory complex L 156.

Gnathosoma vL 194; chelicera total L 266, L basal segment 205, claw 63, L ratio basal segment/claw 3.3. Palp (Figs. 3C-D) total L 376, dL/H, dL/H ratio: P-1, 44/34, 1.27; P-2, 66/55, 1.2; P-3, 41/47, 0.87; P-4, 158/39, 4.0; P-5, 67/17, 3.9; L ratio P-2/P-4, 0.42. dL IV-L: 84, 141, 166, 250, 266, 244.

Female (paratype from Rivière Ouénaoué, n =1; in parentheses specimen from La Coulée Rivière, n =1): Idiosoma L 1050, W 1000. Coxal field L 484 (450); Cx-III W (516); L Cx-I+II 209 (216), Cx-III+IV 247 (256); coxal setae numbers: Cx-I, 19 (20); Cx-II, 23 (26); Cx-III, 24 (20); Cx-IV, 17 (15). Genital plate L 181 (183), on each plate Ac number 43 (44), with 21 (31) setae. Egg maximum diameter (n =2) 116-122.

Gnathosoma vL 197; chelicera total L 266 (256), L basal segment 198 (203), claw 65 (61), L ratio basal segment/claw 3.1 (3.3). Palp (Fig. 3F) total L 375 (382), dL/H, dL/H ratio: P-1, 47/35, 1.35 (47/32, 1.47); P-2, 63/56, 1.12 (66/48, 1.37); P-3, 38/50, 0.75 (39/47, 0.83); P-4, 158/39, 4.0 (163/38, 4.27); P-5, 69/17, 4.1 (67/15, 4.5); L ratio P-2/P-4, 0.40 (0.41). dL IV-L: 86 (100), 147 (150), 166 (172), 256 (263), 275 (272), 238 (241).

Etymology — Named after the Pacific region.

Discussion — The new species resembles Hydrodroma cooki Pešić & Smit, 2007, a species widely distributed in lentic waters in Australia (Pešić & Smit, 2007b). It shares the presence of only one short swimming setae on II-L-5 and the absence of swimming setae from anterior IV-L-5. From the new species, H. cooki is distinguished by an increased number of genital acetabula (on each plate 63–161 Ac in 5–9 longitudinal rows) and swimming setae on III/IV-L (more than 10 on both posterior III-L-4 and anterior IV-L-4), legs with a relatively small-sized claw and by the shape of the integument papillae (pointed vs. rounded in H. pacifica sp. nov.). Hydrodroma wilesi Pešić & Smit, 2007, reported from a helocrene spring and stream in the Northern Territory, Australia (Pešić & Smit, 2007b), is similar in legs with a relatively large-sized claw and genital plate with < 60 Ac in 4–5 rows. It differs from the new species in a reduced number of swimming setae on III/IV-L (III-L-4 posterior 12, III-L-5 posterior 1–3 rather short, IV-L-4 anterior 2–3, posterior 2–4, IV-L-5 posterior 1).

Distribution — New Caledonia.

Key to the Australasian species of Hydrodroma Koch, 1837

1. II-L-5 with more than four swimming setae
...... 2

— II-L-5 with one or without swimming setae
...... 5

2. IV-L-5 anteriorly without swimming setae
...... 3

— IV-L-5 anteriorly with 2–5 swimming setae
...... 4

3. Idiosoma and gnathosoma small in size (idiosoma L: ˂ 800 in ♂, ˂ 1000 in ♀; L genital plates ˂ 180 in ♂, ˂ 190 µm in ♀; in both sexes L gnathosoma ˂ 190, chelicera ˂ 250, P-4 ˂ 150 µm); III-L-4 at most with ten swimming setae, IV-L-5 anteriorly with 7-9 swimming setae; integument papillae distally pointed
...... Hydrodroma kakadu Pešić & Smit, 2007 (Australia)

— Idiosoma and gnathosoma large in size (Idiosoma L ˃ 1000; L genital plates ˃ 200, L gnathosoma ˃ 200, chelicera ˃ 270, P-4 ˃ 180 µm); III-L-4 with more than ten swimming setae, IV-L-5 anteriorly with 9-14 swimming setae; integument papillae distally rounded
...... Hydrodroma novacaledonica Pešić & Smit, sp. nov. (New Caledonia)

4. Genital plate with less than 50 pairs of acetabula in 3–4 rows
...... Hydrodroma australis Pešić & Smit, 2007 (Australia)

— Genital plate with more than 70 pairs of acetabula in 5–6 rows
...... Hydrodroma kununurra Pešić & Smit, 2007 (Australia)

5. IV-L-5 anteriorly with 2–4 swimming setae (usually with 2, occasionally with 1)
...... Hydrodroma meridionalis Pešić & Smit, 2011

— IV-L-5 anteriorly without swimming setae
...... 6

6. Genital plate with fewer than 60 pairs of acetabula in 4–5 rows; legs with a relatively large-sized claw
...... 7

— Genital plate with more than 60 pairs of acetabula in 5–9 rows; legs with a relatively small-sized claw
...... Hydrodroma cooki Pešić & Smit, 2007

7. III-L-4 with 1-2 swimming setae, III-L-5 with 1-2 rather short swimming setae, IV-L-5 posteriorly with one swimming seta
...... Hydrodroma wilesi Pešić & Smit, 2007 (Australia)

— III-L-4 with 4-6 swimming setae, III-L-5 with 3-4 long swimming setae, IV-L-5 posteriorly with 3-4 swimming setae
...... Hydrodroma pacifica Pešić & Smit, sp. nov. (New Caledonia)

Table 2. Number of swimming setae for Hydrodroma pacifica sp. nov..

Acknowledgements

HS is indebted to the Direction des Resources Naturelles de la province Sud and to the Direction du Développement Rural et de la Pêche de la province Nord for permission to collect water mites. Truus van der Pal (Alkmaar) assisted HS with the collecting. We are indebted to Petr Tuzovskij (Borok), Joanna Mąkol (Wrocław), and one anonymous referee whose constructive comments improved this work.



References

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  3. Gerecke R. 2017. The water mites of the genus Hydrodroma (Acari, Hydrachnidia, Hydrodromidae) in Europe and Africa. Ecol. Monten., 13: 1-24. https://doi.org/10.37828/em.2017.13.1
  4. Pešić V., Smit H. 2007a. Water mite species of the genus Hydrodroma Koch (Acari: Hydrachnidia, Hydrodromidae) from Australasia. Part I. Zootaxa, 1389: 31-44. https://doi.org/10.11646/zootaxa.1389.1.2
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  6. Pešić V., Smit H 2011. A new species of the genus Hydrodroma Koch, 1837 (Acari, Hydrachnidia, Hydrodromidae), with a key to the hitherto known six species of the genus in Australia. ZooKeys, 143: 13-22. https://doi.org/10.3897/zookeys.143.2115
  7. Zhang Z.-Q., Fan Q.-H., Pešić V., Smit H., Bochkov A.V., Khaustov A.A., Baker A., Wohltmann A., Wen T.H., Amrine J.W., Beron P., Lin J., Gabrys G., Husband R. 2011. Trombidiformes. In: Z.-Q. Zhang (ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa, 3148: 129-138. https://doi.org/10.11646/zootaxa.3148.1.24


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Article editorial history

Date received:
2021-05-23
Date accepted:
2021-06-21
Date published:
2021-07-21

Edited by:
Mąkol, Joanna

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This work is licensed under a Creative Commons Attribution 4.0 International License
2021 Pešić, Vladimir; Smit, Harry and Mary, Nathalie J.

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