Ephippodonta lunata (Tate 1887)

Detailed studies on the communication and perception of Ephippodontamorpha hirsutus have not been done so far. But it is possible that this species uses chemical cues to communicate with conspecifics and to find the host shrimp.

Communication Channels: chemical

Other Communication Modes: pheromones

Perception Channels: chemical

Very little is known about the population status of this species. It does not receive any special conservation effort at the time of this writing.

US Federal List: no special status

CITES: no special status

The fertilized eggs are brooded in mantle cavities of females, then released as veliger larvae. No detailed studies have been done on the development of this species. However, studies on species from the same superfamily show that early cleavage to larval release may take 12-29 days, or even up to 2 months. the veligers feed on the plankton and metamorphosis into juveniles.

Development - Life Cycle: metamorphosis

There are no known adverse effects of Ephippodonta lunata on humans.

There are no known positive effects of Ephippodonta lunata on humans.

Ephippodonta lunata is not the only commensal in the shrimp burrow. The burrow of the shrimp host Axius plectorhynchus may harbor other commensals as well, including a sponge and other galeommatoidean bivalves.

Species Used as Host:

• Axius plectorhynchus

Ephippodonta lunata is probably a suspension feeder.

Animal Foods: zooplankton

Plant Foods: phytoplankton

Other Foods: detritus

Foraging Behavior: filter-feeding

Primary Diet: planktivore

Ephippodonta lunata is endemic to the southern coast of Australia. The type locality is Long Beach, South Australia. It is possible that the distribution of this species ranges from Western Australia to Victoria.

Biogeographic Regions: australian (Native )

This species has a non-obligate commensal relationship with the slow shrimp Axius plectorhynchus. The shrimp burrows in the sediment, forming a usually horizontal tube with diameters from 0.5~1.5 inches (1-3 cm); and the clam just locates in the burrow without apparently obstructing the shrimp’s movements. However, Ephippodonta lunata can also be found crawling in rock crevices in the shallow intertidal and subtidal.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: benthic ; coastal

The life span of Ephippodonta lunata is currently unknown, but most galeommatoidean species live for multiple years.

Ephippodonta lunata is one of the peculiar clams with gaping valves that belong to the superfamily Galeommatoidea. When alive, the two semicircular valves are held fully open at 180°C from each other; together they form a moon-like shape, hence the common name of this animal - moon cockle. The shells are up to 10 mm long and 4.5 mm wide. The shell surface has rough sculpturing composed of different types of pustules, ranging from minute rounded granulae about 10 μm in diameter to pedunculate articulating pustules around 300 μm long. The pustules may easily fall off when dried. The degree of pustule development could be different for different specimens. Also, some shells appear to have radial color patterns on them and some do not. The above characters make the shells polymorphic among individuals.

In large individuals, the mantle extends and reflects to cover the shells, it is non-retractable but generally does not cover the prodissoconch. Small individuals don’t have mantle reflections. The mantle edge of the animal is thickened and posses pustules. There also present four anterior as well as six posterior tentacles. The mantle forms an anterior cowl and a posterior exhalant siphon. The foot is large and can protrude through the cowl. Middelfart 2011 is a link to a short video showing the bizzare appearance and movement of this clam.

Range length: 10 (high) mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Known predators of Ephippodonta lunata have not been documented so far. However the commensal bivalve could potentially be predated by a spectrum of benthic predators if they can get access to it.

Species in the superfamily Galeommatoidea either have separate sexes or are protandric or simultaneous hermaphrodites. Specific information about the reproductive mode of Ephippodonta lunata is currently unknown. However studies of other species in the genus Ephippodonta have revealed the existence of dwarf males (miniature mature males that live inside adult female individuals).

Mating System: polygynandrous (promiscuous)

Reproductive behaviors of this species has not been closely observed or documented so far. Based on its commensal living style, it is possible that the males may exhibit bulk sperm transfer/storage mechanisms such as dimorphic sperm, spermatophores, seminal receptacles or dwarf males, etc.

Key Reproductive Features: sexual ; fertilization (Internal ); ovoviviparous

We have no information on parental investment in this species. However, all species in the Galeommatoidea studied to-date brood their young.

Parental Investment: female parental care ; pre-hatching/birth (Protecting: Female)