Key to Families of Australian Aquatic Molluscs


This large phylum is divided into several classes of which only the Bivalvia (bivalved molluscs) and Gastropoda (snails and slugs) are found in inland waters.


Bivalved molluscs occur commonly in marine and estuarine environments.  Four families are known from Australian inland waters.  Identification to Bivalvia is relatively easy based on the bi-valved shell which covers the whole body, but care should be taken, especially with small specimens, to check the animal is not a crustacean of class Conchostraca (clam shrimp) Ostracoda (mussel-shrimp or seed-shrimp), or Cladocera (water flea).  These animals have a bi-valved carapace and may superficially resemble bivalved molluscs, but within the carapace is a shrimp-like body with several pairs of jointed legs.

The four freshwater bivalve families are:

1 Hyriidae (Freshwater mussels)

A family restricted to South America and Australasia.  Found throughout mainland Australia and central-north Tasmania, absent from southern Tasmania.  Some species are endemic to particular catchments whilst others are cosmopolitan.  The first larval stage is the minute, bivalved glochidium, ectoparasitic on the gills, fins, or general body surface of various fish.

2 Corbiculidae (Orb-shell mussels)

Found in Asia, Australia and Oceania, with isolated introductions in other parts of the world.  A tropical to subtropical group.  There are two distinct species groups in Australia.  The first (genera Batissa and Polymesoda) inhabit fresh and estuarine coastal streams of northern Australia, and are closely related to forms found in south-east Asia.  The second (genus Corbicula, endemic subgenus Corbiculina) are found throughout Australia except for Tasmania and the southern part of Western Australia.

3 Sphaeriidae (Pea shell mussels, pea shells, fingernail clams)

A little studied but cosmopolitan family of small bivalves.  Previously, many names were based on minute differences in the shell and on geographic distribution.  Some species are widespread throughout Australia but others are confined to small regions or in some cases to a single body of water.

4 Mytilidae (Mussels)

The cosmopolitan family which includes the marine mussels.  Several species are estuarine and some may be found in near-fresh water, but never entirely away from marine influence.

Identification to family can be based on the shell.  The Hydriidae and Mytilidae are elongate mussels with the beak of the shell at one end.  Corbiculidae and Sphaeriidae are sub-circular.  Hydriid larvae (glochidium larvae), parasitic on freshwater fish, are keyed separately in this key.


The aquatic gastropod families divide into two subclasses, the gill-breathing Prosobranchia are related to marine snails, the lung-breathing (or secondarily gilled) Pulmonata are related to land snails.  Eleven prosobranch families and nine pulmonate families are recorded from Australian inland waters.

Almost all species are shelled and recognisably snail-like, but one family (Onchidiidae) of marine, air-breathing slugs extends into estuaries and damp terrestrial situations near the sea.

Identification to class Gastropoda is relatively easy based on the snail-like shell and/or the presence of a pulmonate lung in the mantle cavity.  Larvae of Helicopsychidae, a family of caddis-fly (Insecta: Trichoptera) construct a helical case which resembles a snail shell, and could be mistaken for molluscs.  The trichopteran case is composed of sand grains and the animal inside is a typical insect larva with segmented body and three pairs of legs.

The identification of gastropods to family level can be difficult because the families are defined on internal anatomical structures.  There are few readily observable characters, other than those of the shell, but shells vary as much within as between families.  Adult whole animals can be identified using a combination of shell (and operculum) plus external body characters, but juveniles and shells alone are not always identifiable to the family level.

Character systems useful for identifying gastropod families include:

1   Shell coiling (dextral, sinistral, flat, or not-coiled)

2   Operculum presence/absence

3   Shell shape (spired, globose, turbinate, etc.) and spire height

4   Shell patterning (ridges, striations, colour patterns, etc.)

5   Tentacle and eye position

Some species will key easily to family level, but others may be difficult.

Posted By: Site Admin Last Updated: Aug 8, 2012 Views: 9144
Key Author(s): CSIRO Entomology Key Version: 1.1
Queensland Pasture Selection Tool

A pasture selection tool.

Posted By: Site Admin Last Updated: Nov 10, 2008 Views: 9144
Key Author(s): Stuart Brown Key Publisher: CSIRO Key Version: 1.0
Key to Families of Australian Aquatic Coleoptera, Megaloptera and Mecoptera Larvae


The Coleoptera (beetles) is the most speciose of all the insect orders with over 5,000 aquatic species.  The majority of the approximately 120 families known from Australia are terrestrial but around 10 families are exclusively aquatic as larva and adult, an additional few are predominantly aquatic as larvae and terrestrial as adults or vice versa, and several more have sporadic aquatic representation.  This key identifies 19 families but may not distinguish members of the aquatic or semi-aquatic set from all other, terrestrial, beetles.

Coleoptera undergo holometabolous development, meaning there is an abrupt change of body form at the final moult.  It is convenient to deal with adults and larvae in separate keys.

Larvae are very variable, all with distinct sclerotised head, strongly developed mandibles, 2-3 segmented antenna; 3 pairs of jointed thoracic legs, lacking abdominal prolegs; open peripneustic (9 pairs of spiracles) tracheal system, but variably reduced spiracle number in most aquatic larvae, some with lateral and/or ventral abdominal gills, sometimes hidden beneath terminal sternite.  Pupation terrestrial (except some Psephenidae); pupa lacking functional mandibles.

Identification to family level can be partly achieved on gross features such as size and shape, but in many cases requires a careful examination of external morphology.  There is much variation of body form within many families and large-scale characters can readily be misleading.  On the other hand it is never necessary to examine internal characters in order to identify a specimen to family level.

The Australian aquatic and semi-aquatic beetles fall into three suborders: Myxophaga (1 family: Microsporidae), Adephaga (6 families: Carabidae through Gyrinidae in the key), and Polyphaga (12 families: Hydrophilidae through Brentidae in the key).

A few families are instantly recognisable on the basis of unique characters.  Most specimens, however, will fall readily into one of several not necessarily closely related families and then may require close examination for final placement.


The Mecoptera is comprised of nine families of which five families are known to occur in Australia.  Of these five families, only the Nannochoristidae are aquatic.  Nannochoristidae occur in Tasmania and the highlands of south-eastern Australia.  The larvae can be found in accumulations of  silt  in shallow, slow-flowing streams.  The larvae are carnivorous, feeding on larval chironomids and other dipteran larvae.

Posted By: Site Admin Last Updated: Aug 9, 2012 Views: 9142
Key Author(s): CSIRO Entomology Key Version: 1.1
Key to Families of Freshwater Arachnids (Spiders & Mites) in Australia

The Arachnida belongs to the Phylum Arthropoda, Subphylum Chelicerata, and is typically placed at the level of Class.  Arachnids are characterised by having 4 pairs of legs as adults and lacking antennae.  Their mouthparts are chelicerae; however, only some arachnids retain the ancestral chelate (pincer-like) form of the chelicerae, while other groups have hook-like or styletiform mouthparts.

There are two major groups of arachnids that have aquatic representatives: the spiders (Order Araneae) and the mites (Subclass Acari).  Species from four families of spiders may be encountered in Australian fresh waters.  Despite being able to survive for some time under water, none of these spiders is truly subaquatic.

The vast majority of aquatic arachnids are mites.  Larval mites are 6-legged and are often morphologically very different from the 8-legged nymphal and adult mites.  This key is designed for identification of post-larval stages; however, it may work for larvae of some groups of mites.  Representatives of four major suborders of mites occurs in fresh water: Mesostigmata, Oribatida, Astigmata and Prostigmata (Walter & Proctor 1999).  The greatest radiation of freshwater mites has been in the prostigmatan group Hydracarina (also called Hydrachnellae, Hydrachnidia, Hydrachnida).  The Hydracarina, commonly called 'water mites', includes more than 5000 named species worldwide.  In Australia there are 413 described species in 89 genera, representing 22 families (Harvey 1998). 

Posted By: Site Admin Last Updated: Aug 8, 2012 Views: 9142
Key Author(s): CSIRO Entomology Key Version: 1.1
Western Australia Pasture selection tool

Pasture selection tool for Western Australia

Posted By: Site Admin Last Updated: Oct 22, 2008 Views: 9141
The Key to Pythium species

The key is presented as a guide to identifying Pythium to the species level. It is a modification of that created by Anna van der Plaats-Niterink (Van der Plaats-Niterink, A. J. 1981. Monograph of the genus Pythium. Studies in Mycology. Baarn, Centraalbureau voor Schimmelcultures. Monograph No. 21:242). Some but not all species of Pythium are included. This key is only a guide and diagnostic tool to assist in the identification of Pythium species. To learn more about identifying Pythium species, culturing Pythium, and Pythium in general visit and work through the Module set. 

Be flexible in your interpretation of what you observe and observe cultures over time. As you gain experience through looking at many different Pythium cultures, you will begin to be able to differentiate sporangia from oogonia, slightly inflated filamentous sporangia from hyphae, and recognize proliferating sporangia. At first, just reading descriptions is confusing, but the more cultures you observe the process will become much easier.

The key was built using the Lucid Builder program. When you open the key, the window is divided into four sections: features available, features chosen, entities remaining and entities discarded. The culture characteristics are present in the Lucid key as “features”. Pythium species are present as “entities”.

As you look at Pythium cultures, check off the characters you observe on the character checklist. Check off characters by expanding the options beneath each main heading of the “features available” section and click on the empty box next to the character you have observed in your culture. When a character is selected, a check mark will be placed next to that character in the “features available” section. These selected characters will also be copied into the “features chosen” section. In order remove a feature chosen, simply click the checked box next to the unwanted character, and it will become unchecked again.  Lastly, as you select the characters you are observing, Pythium species are discarded into the “entities discarded” section, leaving fewer and fewer “entities remaining,” or possible Pythium species.

To help you identify Pythium species, images of the characters are available in the Lucid key. To view these images, make sure that “image thumbnails” is selected under the view tab. Simply expand the contents of the “features available” section and click on the thumbnails to enlarge the images. 

Be flexible in using the key. If you are not certain of a characteristic, select one option for that characteristic and see where the key takes you. When you have eliminated most species, examine the description of the species to which you are led and see if it fits. If the descriptions do not match what you have observed, go back and select a different option for that characteristic and other questionable characters and examine the description of the species to which you come.


Gary W. Moorman, Ph.D.
Department of Plant Pathology and Environmental Microbiology
The Pennsylvania State University
111 Buckhout Laboratory
University Park, PA 16802
Phone: 814-863-7401
Email: [email protected]

Sara May
Department of Plant Pathology and Environmental Microbiology
The Pennsylvania State University
220 Buckhout Laboratory
University Park, PA 16802
Phone: 814-865-2204
Email: [email protected]

Kathleen M. Ayers
Department of Plant Pathology and Environmental Microbiology
The Pennsylvania State University
220 Buckhout Laboratory
University Park, PA 16802
Email: [email protected]

Posted By: Site Admin Last Updated: May 21, 2014 Views: 9133
Key Author(s): Gary W. Moorman, Ph.D., Sara May, Kathleen M. Ayers Key Version: 1.0
Antarctic Marine Dinoflagellates

Antarctic Marine Dinoflagellates

Posted By: Site Admin Last Updated: Aug 24, 2016 Views: 9114
Key Author(s): Australian Antarctic Division
Campbell Island Larval Chironomidae Key

Campbell Island/Motu Ihupuku lies 700 km south of New Zealand’s mainland, the most Campbell Island/Motu Ihupuku lies 700 km south of New Zealand’s mainland, the most southerly of the five New Zealand Subantarctic groups.

There are two identification keys to the freshwater invertebrate taxa of Campbell Island. This key is for identifying the freshwater Chironomidae larvae of Campbell Island to genus or species level.

The key is suitable for users that have basic knowledge in invertebrate identification or animal biology.

The keys were made possible by funding from the Terrestrial and Freshwater Biodiversity Information System (TFBIS) Programme.

How to cite the key:  McMurtrie, S.A.; Sinton, A.M.R.; & Winterbourn, M.J.; 2014. Lucid identification key to the freshwater Chironomidae of Campbell Island. EOS Ecology, Christchurch.

Go to the website:

Key Author(s): McMurtrie, S.A.; Sinton, A.M.R.; & Winterbourn, M.J. Key Version: 1.0

Posted By: Site Admin Last Updated: Jul 9, 2014 Views: 9114
Key Author(s): McMurtrie, S.A.; Sinton, A.M.R.; & Winterbourn, M.J. Key Version: 1.0
South Australian Pasture Selection key

Key for South Australia

Posted By: Site Admin Last Updated: Oct 22, 2008 Views: 9106
Key Author(s): Stuart Brown Key Publisher: CSIRO Key Version: 1.0
Dung Beetles of eastern NSW - Amphistomus subkey

How to identify the Scarabaeinae of eastern New South Wales

A subkey to the Key to the Dung Beetles of eastern New South Wales

Australian Museum

Posted By: Site Admin Last Updated: Apr 21, 2016 Views: 9074
Key Author(s): Rebecca Harris and Dr Chris Reid Key Publisher: Australian Museum Key Version: 1.0
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