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Ephippodontamorpha hirsutus

By Jingchun Li

Geographic Range

Currently this species is only known from its type locality: Queensland, Australia. Multiple individuals have been collected from islands and beaches in the Great Barrier Reef area. (Middelfart, 2005)

Habitat

This species has an interesting commensal relationship with mantis shrimp in the genus Lysiosquillina. These shrimps live in mud flats and sand flats and build large U-shaped burrows. The tubes are often of great size, sometimes with internal diameters reach 6.5~10 cm; and could potentially last as long as 20 years (pers. comm. Caldwell, 2011). Clams normally live in the shrimp burrows, attached to the vertical burrow wall just below the entrance, or the upper side of the horizontal wall. Up to 26 individuals of E. hirsutus have been found within one shrimp burrow. (Middelfart, 2005; Popham, 1939)

Physical Description

Many clams in the superfamily Galeommatoidea have unusual physical characters. Unlike typical bivalve shells, the two valves of Ephippodontamorpha hirsutus stay 180° apart from each other and cannot be closed together. The animal crawls with two valves horizontally placed on the dorsal side, superficially resembling the shape of a limpet. The shells are up to 9.9 mm long and 2.6 mm wide and have very small hinge teeth. (Middelfart, 2005)

The mantle structure of this species is also unusual: it extends beyond the shell margins and reflects back on the outside of the shell. When alive, the shell is completely covered by the thin, fused and semitransparent mantle tissue, with two mantle openings, one each on the anterior and posterior ends. The mantle is not retractable and bears various tentacles. The dorsal side of the animal is covered with numerous small round tentacles. The cowl and margins of the mantle are covered with very elongate tentacles, giving the animal a jellyfish-like overall shape. The size and number of the long tentacles seem to be symmetrical from left to right. The foot is muscular and keel-shaped, with an elongate ventral groove and a posterior byssal gland. A flower-like organ (function unknown) is found on the antero-dorsal part of the foot. Interestingly, galeommatoidean clams from different genera that live with mantis shrimps also seem to possess flower-like organs. Middelfart 2011 is a link to a short video clip of a live individual of this species showing how un-clam-like it is in appearance and the unusual way in which it can rotate its body. (Middelfart, 2011; Mikkelsen and Bieler, 1992; Mikkelsen, 1989; Simone, 2001)

  • Range length
    9.9 (high) mm
    0.39 (high) in

Development

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. (Jespersen and Lützen, 2006)

Reproduction

Specific information about the mating system of Ephippodontamorpha hirsutus is currently unknown. Related species have separate sexes or are simultaneous or protandric hermaphrodites. (Ponder, 1998)

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. (Jespersen and Lützen, 2006)

Parental investment in this species is currently unknown. While the majority of bivalve species spawn gametes into the open water column, all the members of Galeommatoidea that have been studied have been found to be brooders. Adults keep fertilized eggs inside their mantle cavity until they develop into either veliger larvae or juveniles. It is likely that this species also broods its young. (Jespersen and Lützen, 2006; Ponder, 1998)

Lifespan/Longevity

The life span of Ephippodontamorpha hirsutus is currently unknown, but it probably lives for multiple years.

Behavior

Unlike other bivalves that use their foot for digging, Ephippodontamorpha hirsutus uses its foot to crawl around like a snail. Interactions between Ephippodontamorpha hirsutus and its shrimp host have not been observed. Observations on other shrimp commensals suggest that the clam might form a slight depression in the mud lining and compress down in it to avoid obstruction to the movements of the shrimp. (Cotton, 1938; Middelfart, 2005; Middelfart, 2011)

Communication and Perception

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 locate its host. The elaborated mantle tentacles seem to be sensitive to touch. (Middelfart, 2011)

  • Other Communication Modes
  • mimicry

Food Habits

Ephippodontamorpha hirsutus is probably a suspension feeder.

Predation

The predators of Ephippodontamorpha hirsutus are unknown.

Ecosystem Roles

This species lives in burrows of mantis shrimp in the genus Lyosquillina. The nature of the relationship between the clam and its host is unknown. (Middelfart, 2005)

Species Used as Host

Economic Importance for Humans: Positive

Ephippodontamorpha hirsutus has no known economic value.

Economic Importance for Humans: Negative

There are no known adverse effects of Ephippodontamorpha hirsutus on humans.

Conservation Status

At the time of this writing, very little was known about the population size of this species. It is not protected by any special conservation regulations.

Contributors

Jingchun Li (author), Special Projects, George Hammond (editor), Animal Diversity Web Staff.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

mimicry

imitates a communication signal or appearance of another kind of organism

native range

the area in which the animal is naturally found, the region in which it is endemic.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Cotton, B. 1938. Ephippodonta-South Australia's most peculiar bivalve shell. Victorian Naturalist, 55: 58–61.

Jespersen, Å., J. Lützen. 2006. Reproduction and sperm structure in Galeommatidae (Bivalvia, Galeommatoidea). Zoomorphology, 125/3: 157-173.

Middelfart, P. 2011. "Ephippodontamorpha hirsutus (Middelfart 2005)" (On-line video). Youtube. Accessed July 30, 2011 at http://www.youtube.com/watch?v=GGC_x4wk0g8.

Middelfart, P. 2005. Review of Ephippodonta sensu lato (Galeommatidae: Bivalvia), with descriptions of new related genera and species from Australia. Molluscan Research, 25/3: 129-144.

Mikkelsen, P. 1989. Biology and comparative anatomy of Divariscintilla yoyo and D. troglodytes, two new species of Galeommatidae (Bivalvia) from stomatopod burrows in eastern Florida. Malacologia, 31: 175-195.

Mikkelsen, P., R. Bieler. 1992. Biology and Comparative Anatomy of 3 New Species of Commensal Galeommatidae, with a Possible Case of Mating-Behavior in Bivalves. Malacologia, 34/1-2: 1-24.

Ponder, W. 1998. Superfamily Galeommatoidea. Pp. 316–318 in R de Keyzer, P Beesley, G Ross, eds. Mollusca : The Southern Synthesis. Melbourne: CSIRO Publishing.

Popham, M. 1939. On Phlyctaenachlamys lysiosquillina gen. and sp. nov., a lamellibranch commensal in the burrows of Lysiosquilla maculata. Great Barrier Reef Expedition 1928–29. Scientific Reports. British Museum (Natural History), 6: 62-84.

Simone, L. 2001. Revision of the genus Parabornia (Bivalvia: Galeommatoidea: Galeommatidae) from the western Atlantic, with description of a new species from Brazil. Journal of Conchology, 37: 159–169.

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Classification

  • This scientific name is not yet recognized in our classification database.