PORT PHILLIP BAY


Ramshorn Crab 

Naxia aries (Guérin-Méneville, 1834)

View scientific description and taxonomy

Scientific Details

Carapace pear-shaped, strongly narrowing anteriorly, with mesogastric tubercle; surface smooth between groups of strong curled setae. Rostral spines slender, strongly curved outwards, hepatic spine sharp. Anterolateral angle of basal antennal article unarmed. Preorbital and antorbital angles not produced; intercalated spine well separated from supraorbital eave; postorbital and hepatic spines close at base. Walking legs with propodi having expanded lower distal margin.

Source: Poore, G.C.B. (2004) Marine decapod Crustacea of southern Australia. A guide to identification (with chapter on Stomatopoda by Shane Ahyong). CSIRO Publishing, Melbourne, 574 pp.

Taxonomy

Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Malacostraca
Subclass:
Eumalacostraca
Superorder:
Eucarida
Order:
Decapoda
Suborder:
Pleocyemata
Infraorder:
Brachyura
Family:
Majidae
Subfamily:
Majinae
Genus:
Naxia
Species:
aries

General Description

Carapace pear-shaped, covered with bumps, with 5 strong spines protruding from each side. Rostral spines slender, strongly curved outwards. Walking legs long, spindly and slightly flattened with second last segment (propodi) expanded. Up to 3.7 mm long.

Biology

Decorative sponges, seaweeds and sea mosses are attached to stiff curved hairs on the carapace and legs. The two rostral spines can be seen to diverge and curve outwards once the camouflage has been removed. This camouflage, and moving very slowly, makes them hard to see in their natural habitat. Males have stronger claws than females.

Habitat

Low intertidal reef to 85 m depth.

Soft substrates

Reefs

Coastal shores

Distribution guide

Southern temperate oceans, including south-eastern Australia.

Species Group

Crabs and allies Crabs

Depth

Shore (0-1 m)
Shallow (1-30 m)
Deep ( > 30 m)

Water Column

On or near sea floor

Max Size

4 mm

Diet

Organic matter

Harmful

Not harmful but a nip from large claws could be painful.

Commercial Species

No

Global Dispersal

Native to Australia

Species Code

MoV 743

Conservation Status

  • DSE Advisory List : Not listed
  • EPBC Act 1999 : Not listed
  • IUCN Red List : Not listed

Author

article author Taylor, J.

Dr. Jo Taylor is the Sciences Collections Online Coordinator at Museum Victoria.

Author

article author Poore, G.C.B.

Dr. Gary Poore is Principal Curator Emeritus at Museum Victoria.

citation

Cite this page as:
Taylor, J. & Poore, G.C.B., 2011, Ramshorn Crab, Naxia aries, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 18 Oct 2017, http://portphillipmarinelife.net.au:8098/species/5484

Text: creative commons cc by licence