Mictacea

(Mictaceans)

Phylum Arthropoda

Subphylum Crustacea

Class Malacostraca

Order Mictacea

Number of families 2

Thumbnail description
Very small crustaceans, generally allied with peracarids, that are constructed much like thermosbaenaceans and spelaeogriphaceans, but there is no carapace and only rudimentary appendages on the abdomen

Evolution and systematics

The order Mictacea includes two families, three genera, and five species. This group has been included in the super-order Peracarida on the basis of a posteriorly directed flap on the walking legs that is thought to be homologous to the brood plates of other peracarids.

Physical characteristics

The body is elongate and cylindrical. There is no carapace emanating from the posterior margin of the head. In fact, the side of the head is also without pleurae, so the mandible is quite visible. Eye lobes may be present or absent, but functional eyes are absent. One thoracic somite is fused to the head and its appendage has been modified as a maxilliped. There are seven walking legs, the first six of which have exopods. On the abdomen, the first five somites have minute one-segmented pleopods. Attached to the last abdominal somite is the telson and a pair of biramous uropods.

Distribution

Of the five known species, one was described from the deep sea off the north coast of South America, one from the continental slope off southeastern Australia, and the others from marine caves in Bermuda, Bahamas, and the Cayman Islands. Only the Bermudan species, Mictocaris halope, is known from several specimens.

Habitat

Mictaceans are found in marine caves or rubble.

Behavior

The animals move both by walking and swimming.

Feeding ecology and diet

Because of the design of the mouthparts and the small size of the body, mictaceans are thought to be detritivores.

Reproductive biology

Copulation is presumed but has not been observed. Young hatch as manca, missing the last pair of pereopods.

Conservation status

No species is threatened or listed by the IUCN, but those species confined to cave systems are obviously dependent on the health of the cave waters being maintained.

Significance to humans

They are of intellectual interest only.

Species accounts

List of Species

No common name

Mictocaris halope

family

Mictocariidae

taxonomy

Mictocaris halope Bowman and Iliffe, 1985, Bermuda.

other common names

None known.

physical characteristics

Body elongate and cylindrical; no functional eyes; no carapace. Most appendages are less setose in this species than in the other species. (Illustration shown in chapter introduction.)

distribution

Bermuda.

habitat

Sediments and rock of a marine cave.

behavior

Spends most of its time swimming or crawling on the substratum. When walking, the antennae are held out to the sides and are folded backwards somewhat during swimming events. In many respects, acts like spelaeogriphacean.

feeding ecology and diet

Material in the gut suggests it is a detritivore. Scraping of small food particles from the substratum was observed in aquaria.

reproductive biology

Copulation presumed but has not been observed. Young hatch as manca, missing last pair of pereopods.

conservation status

Not threatened at present, but its conservation status depends on the water quality of the cave systems of Bermuda not being degraded.

significance to humans

None known.

Resources

Periodicals

Bowman, T. E., and T. M. Iliffe. "Mictocaris halope, a New Unusual Peracaridan Crustacean from Marine Caves on Bermuda." Journal of Crustacean Biology 5 (1985): 58–73.

Hessler, R. R. 1999. "Ordre des Mictacés. Traité de Zoologie, Tome VIII, Fasc. 3A." Mémoires de l'Institut Océanographique 19 (1999): 87–91.

Sanders, H. L., R. R. Hessler, and S. P. Garner. "Hirsutia bathyalis, a New Unusual Deep-sea Benthic Peracaridan Crustacean from the Tropical Atlantic." Journal of Crustacean Biology 5 (1985): 30–57.

Les Watling, PhD