The Australian Water Mites: A Guide to Families and Genera

By MS Harvey

Water mites are a dominant feature of the fauna of all freshwater ecosystems. Over 400 species in 87 genera and 22 families have been recorded in Australia. This book consists of illustrated keys to each family and genus. There are sections on cladistic analysis and classification, biogeographic affinities of the Australian fauna, general biology and morphology.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Jan 1, 1998
• ISBN: 9780643105881

Book preview

THE AUSTRALIAN WATER MITES

A GUIDE TO FAMILIES AND GENERA

Monographs on Invertebrate Taxonomy

Other books in the series:

Vol. 1. Australian Lauxaniid Flies

Revision of the Australian species of Homoneura van der Wulp,

Trypetisoma Malloch, and allied genera (Diptera: Lauxaniidae)

SP Kim

Vol. 2. Click Beetles

Genera of the Australian Elateridae (Coleoptera)

AA Calder

Vol. 3. Australian Ants

A Guide to the Genera

SO Shattuck

Vol. 5. Mites of Australia

A Checklist and Bibliography

RB Halliday

Vol. 6. Oribatid Mites

A Catalogue of Australian Genera and Species

M Colloff and RB Halliday

THE AUSTRALIAN WATER MITES

A GUIDE TO FAMILIES AND GENERA

MONOGRAPHS ON

INVERTEBRATE TAXONO MY

Vol.  4

MARK S. HARVEY

National Library of Australia Cataloguing-in-Publication entry

Harvey, Mark S.

The Australian Water Mites: A Guide to Families and Genera

Bibliography.

Includes index.

ISBN 0 643 06301 3

1. Water mites – Australia. 2. Water mites – Australia – Identification.

I CSIRO. II Western Australian Museum. III. Title. (Series: Monographs on invertebrate taxonomy; vol. 4).

595.42

© CSIRO Australia and Western Australian Museum 1998

This book is available from:

CSIRO PUBLISHING

PO Box 1139 (150 Oxford Street)

Collingwood, VIC 3066

Australia

Tel: [phone]     Int: +(613) 9662 7666

Fax: [phone]    Int: +(613) 9662 7555

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Publisher: Kevin Jeans

Editor: Marta Veroni

Design: Anita Adams

Typesetting: Linda Kemp

Production: Publishing Solutions Pty Ltd

Printer: Western Australian Museum

This volume is dedicated to David R. Cook in honour of his

exceptional contributions to the study of water mites.

Contents

Abstract

Acknowledgements

Introduction

Materials and Methods

Higher Classification

Biogeography

General Biology

Morphology

Key to Families

Superfamily Hydryphantoidea

Superfamily Hydryphantoidea Piersig

Family Hydrodromidae K. Viets

Family Hydryphantidae Piersig

Family Zelandothyadidae Cook

Superfamily Eylaoidea

Superfamily Eylaoidea Leach

Family Eylaidae Leach

Family Limnocharidae Grube

Family Piersigiidae Oudemans

Superfamily Hydrachnoidea

Superfamily Hydrachnoidea Leach

Family Hydrachnidae Leach

Superfamily Lebertioidea

Superfamily Lebertioidea Thor

Family Anisitsiellidae Koenike

Family Limnesiidae Thor

Family Oxidae K. Viets

Family Torrenticolidae Piersig

Superfamily Hygrobatoidea

Superfamily Hygrobatoidea Koch

Family Astacocrotonidae Thor

Family Aturidae Thor

Family Frontipodopsidae K. Viets

Family Hygrobatidae Koch

Family Omartacaridae Cook

Family Pionidae Thor

Family Pontarachnidae Koenike

Family Unionicolidae Oudemans

Family Wettinidae Cook

Superfamily Arrenuroidea

Superfamily Arrenuroidea Thor

Family Arrenuridae Thor

Family Athienemanniidae K. Viets

Family Mideopsidae Koenike

Family Momoniidae K. Viets

References

Appendix 1 – List of Australian Hydracarina

Appendix 2 – List of Taxonomic Changes

Index

ABSTRACT

The genera and families of Australian water mites (Hydracarina) are documented, and over 400 species, placed in 89 genera and 24 families, are recorded. Illustrated dichotomous keys are provided to allow for the discrimination of aquatic mites, water mite families, and water mite genera within each family.

The following taxonomic changes are made:

The Zelandothyadidae Cook, 1983, is elevated from subfamily status, and found to contain two subfamilies, Australiothyadinae Cook, 1986 and Zelandothyadinae Cook, 1983.

The family Sperchontidae Thor is placed in its own superfamily, Sperchontoidea Thor.

The specific epithet Declinatobates longmorei K.O. Viets, 1984b, is corrected to Declinatobates longmoreae.

The following species are transferred from Corticacarus (Procorticacarus) K.O. Viets, 1978c to Procorticacarus: P. aligenitalis (Cook, 1986), P. aloonus (Cook, 1986), P. angulicoxalis (K.O. Viets, 1978c), P. australicus (K.O. Viets, 1978c), P. cooki (Imamura, 1984), P. cramerae (Cook, 1986), P. gennadus (Cook, 1986), P. gracilipalpis (K.O. Viets, 1978c), P. hirsutus (K.O. Viets, 1978c), P. longipalpis (Cook, 1986), P. nabidus (Cook, 1986), P. pachydermis (Cook, 1986), P. parvus (Cook, 1986), P. prasadi (Cook, 1986), P. tadilopus (Cook, 1986), P. tasmanicus (Cook, 1986), P. togalus (Cook, 1986), and P. victorianus (K.O. Viets, 1978c).

The following species are transferred from Unionicola (Unionicola) Haldeman, 1842 to Unionicola (Hexatax): U. (Hexatax) lindrothi K. Viets, 1981, U. (Hexatax) longiseta Walter, 1915, U. (Hexatax) neoaffinis Cook, 1986.

The following species are transferred from Torrenticola Koch to Monatractides K. Viets, 1926c: M. australica (Cook, 1986) and Monatractides kotooma (Cook, 1986).

ACKNOWLEDGEMENTS

This project was initially funded by the Australian Biological Resources Study, and was instigated by John Blyth to whom I owe a deep debt of gratitude. This work would not have been possible without the enthusiastic support and assistance of David Cook, whose knowledge of the world’s water mite fauna is unsurpassed and whose volume on the Australian fauna provided much of the background material on which the present volume is based. Ian Smith (Biosystematics Research Institute, Agriculture Canada, Ottawa) kindly made available a collection of Australian water mites, and type and other identified reference material was graciously donated or lent by Bruce Halliday (Australian National Insect Collection, CSIRO, Canberra), Torbjörn Kronestedt (Swedish Museum of Natural History, Stockholm), Norman Fashing (College of William and Mary, Williamsburg), David Walter (University of Queensland, St Lucia) and Rhonda Butcher (Monash University, Melbourne). My efforts to personally check numerous older references cited in this volume was only made possible through the generous aid of Bruce Halliday, Mark Judson, Torbjörn Kronestedt, Philip Lawless, Heather Proctor and Harry Smit who supplied many obscure articles, and by the library staff of the Western Australian Museum. John Hawking and Jane Growns very kindly allowed the use of their colour photographs. I am also grateful to Dave Cook, Jane Growns, Heather Proctor, Harry Smit and Andrew Austin for their detailed comments on a draft of the manuscript and for checking the usefulness or otherwise of the keys; naturally, any errors or omissions remain my responsibility. Finally, I am indebted to M ra Blosfelds for her encouragement in ensuring that this guide was completed prior to the turn of the millennium.

INTRODUCTION

Few extant arachnid groups have attained a truly aquatic lifestyle, although several have adapted to temporary immersion or to short forays into water (Roth and Brown, 1976). Indeed, some spiders (e.g. Idioctis, Desis, Paratheuma, Amaurobioides) and pseudoscorpions (e.g. Garypus, Halobisium, Parahya) are truly intertidal and can withstand regular sea-water inundation over their silken retreats. Some spiders (e.g. Argyroneta) are able to occupy freshwater habitats by utilising air transported to an underwater chamber. However, each of these groups must ultimately renew their air source and are unable to fully survive under water.

On the other hand, several groups of Acarina have made the transition to a fully aquatic lifestyle. These include all of the Hydracarina and Halacaroidea, and numerous species of Oribatida (especially Hydrozetoidea), Astigmata and Mesostigmata. The Hydracarina (also referred to as Hydrachnellae, Hydrachnidia and Hydrachnida), or water mites, are the most abundant with over 5000 named species (K.O. Viets, 1987). They occur in almost every known freshwater habitat and their diversity, both taxonomically and ecologically, makes them a dominant part of freshwater ecosystems (Smith and Cook, 1991). Indeed, the abundance of described Australian water mites at all major taxonomic levels (family, genera and species) rivals that of all important aquatic insect and crustacean groups. They are currently exceeded only by the Trichoptera and Coleoptera (Table 1). However, numerous unrecorded and undescribed species of Chironomidae are known to exist in collections and the Australian fauna is at present vastly underestimated (P. Cranston, personal communication).

Despite their abundance in aquatic habitats, the study of Australian water mites has often been a piece-meal affair, with sporadic descriptions of isolated species (K. Viets, 1932). The first described species was Hydrachna odontognatha Canestrini (1884) from Queensland, followed more than 20 years later by Rainbow’s (1906) rudimentary descriptions of Eylais maccullochi Rainbow and Atax cumberlandensis Rainbow from Sydney. Single species were added by Koenike (1914) (the bivalve parasite Unionicola cirrosa Koenike), Lohmann (1909) (the marine Pontarachna denhami Lohmann, now Litarachna denhami), Haswell (1922) (the freshwater crayfish parasite Astacocroton molle Haswell) and Womersley (1937) (the marine Pontarachna halei Womersley, now Litarachna halei). Halík (1940a, 1940b, 1941a) added four species including a new subgenus which was later regarded as a full genus, and Lundblad (1941a, 1941c, 1947, 1952a) described more than 40 species and several new genera. Szalay (1953), K. Viets (1955), Weigmann and Schminke (1970) and Imamura (1984) added new species, while K.O. Viets (1975, 1977, 1978b, 1978c, 1980a, 1980b, 1981, 1984a, 1984b) described numerous species based on collections from many different regions of Australia. Womersley (1954) added Mackerrasiella globus Womersley based upon the larval stage of a mite attributed to the trombidioid family Leeuwenhoekiidae, which was later recognised as a member of the water mite genus Hydryphantes (Vercammen-Grandjean, 1972). Ironically, this remains one of only two water mites in which the larva has been described from Australian material; the other is Hydrachna odontognatha described by Canestrini (1884).

Table 1 NUMBERS OF DESCRIBED TAXA OF SOME MAJOR AQUATIC GROUPS IN AUSTRALIA

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However, the most significant publication was by Cook (1986) who described a vast number of new taxa from eastern Australia, including many new genera. Cook redescribed many of the older species and has provided a firm base for Australian water mite systematics and their routine identification. Since this seminal publication, several species and genera have been added by Harvey (1987, 1988a, 1988c, 1988d, 1989a, 1989b, 1990a, 1990b, 1990c, 1990d, 1996a, 1996b, 1996c, 1998), Harvey and Cook (1988), Smith and Harvey (1989), Southcott (1991) and Smit (1992, 1996b, 1997, 1998a, 1998b, 1998c, 1998d). At present, 413 species in 89 genera and 24 families have been recorded from Australian waters (Appendix 1).

Although there are many water mite species from Australia yet to be named, the number of new or previously unrecorded genera is diminishing. Thus, it seems opportune to consolidate this large body of work into a generic key for the use of ecologists, taxonomists and other interested scientists.

MATERIALS AND METHODS

Material

Apart from the primary type specimens described by Cook (1986), which are now lodged in the Museum of Victoria, Melbourne, I have made an extensive examination of specimens lodged primarily in either the Museum of Victoria or the Western Australian Museum, Perth. The water mite collections of other state or national museums are extremely small, as aquatic mites are normally not taken in standard collecting trips undertaken by museums.

Methods

Several excellent guides to the collection, preservation and slide preparation of water mites have been published, in particular Barr (1973) and Cook (1974). However, a brief survey of the major techniques is presented here.

Collection

As water mites are generally small, it is usually not possible to directly scoop them individually from water bodies. Exceptions include some large red mites (e.g. Eylais, Limnochares) that are occasionally found in shallow waters. By far the best technique is to strain the water, and more importantly, the substrate or submerged vegetation, through a suitably sized mesh. For most purposes 250 μm is sufficient, although smaller mesh sizes are necessary for interstitial mites. Once enough material has been caught in the net, the contents should be placed in a shallow white tray that has already been filled with water. After a short time, most animals caught in the net start to leave the concentrate and are clearly visible against the white background. Water mites tend to swim or crawl in fairly straight lines, but initially may be easily confused with other small invertebrates such as ostracods.

The mites should be removed from the tray with a pipette, and placed in a small water-filled receptacle such as an excavated block or petri dish. They can be later transferred to a vial filled with the preservative GAW (see below).

Alternatively, the contents of the net may be preserved and sorted at a later date with the aid of a dissecting microscope.

Barr (1979) discussed a novel collecting technique which used underwater light traps baited with a chemoluminescent source. These traps are suitable for use in lentic and slow lotic habitats.

Preservation

Undoubtedly, the best water mite preservative is GAW or Koenike’s fluid (50% glycerol, 10% acetic acid, 40% distilled water), as it generally retains any colour pattern and leaves the specimens supple and the appendages flexible. If mites have been initially preserved in ethanol, they should be transferred to GAW as soon as possible. The worst preservative is formalin, which makes the specimens very brittle and virtually useless for identification or taxonomic studies.

Examination and slide mounting

With experience it is possible to recognise genera and even species with the use of a dissecting microscope. However, the small size of most specimens means that a compound microscope is always necessary, and that the specimens must be mounted on a microscope slide. Two different techniques may be employed to prepare specimens for examination with a compound microscope.

The first involves making a permanent slide mount, in which the specimen is cleared and dissected before being mounted. The clearing process is begun by cutting a hole or slit in the side of the idiosoma (with micro-scissors or a micro-scalpel). If the specimen is heavily sclerotised and with a distinct dorsal shield, it is advisable to remove the dorsal shield. Place the specimen in 10% potassium hydroxide until the body contents have dissolved (if heated in a water bath, this process only takes a few minutes). Transfer the specimen to a small watchglass filled with water, and then to another with a small amount of GAW (the acetic acid in the