Remipedia

(Remipedes)

Phylum Arthropoda

Subphylum Crustacea

Class Remipedia

Number of families 2

Thumbnail description
Small, marine, cave-dwelling crustaceans characterized by a short head and a long trunk bearing setose swimming appendages.

Evolution and systematics

The class Remipedia has two families, six genera, and 12 described species. At least three more species are undescribed. A single extinct species from a Carboniferous fossil has been placed in the class Remipedia.

Physical characteristics

Remipedes are troglobitic (cave-dwelling) crustaceans, lacking pigmentation and eyes. They are free-swimming and characterized by a short head and an elongate, segmented trunk. The head is covered with a cephalic shield. With the exception of the posterior-most segment(s), each trunk segment bears biramous, paddle-like, setose swimming appendages. Trunk segment number differs in each species. For example, the smallest species has no more than 16 segments as an adult; the largest has 29. Head appendages consist of a pair of small frontal filaments, long first antennae, and small paddle-like second antennae. The base of antenna 1 bears clusters of long aesthetascs for chemosensation. The setae of antenna 2 are long and plumose. The mandibles have a broad molar surface and cusped incisor processes. The first maxillae bear a terminal fang. The second maxillae and maxillipeds are nearly identical, and bear a terminal claw complex. These three feeding appendages are robust and prehensile. The largest species, Godzillius robustus, is about 1.8 in (45 mm) and the smallest, Godzilliognomus frondosus, is about 0.35 in (9 mm) in length.

Distribution

Remipedes are currently known from anchialine caves in most of the major islands of the Bahamas, several islands of the Turks and Caicos, the island of Cozumel, Mexico, Holguin and Matanzas Provinces, Cuba, and the island of Lanzarote in the Canary Islands. They are also known from continental coastal caves in the state of Quintana Roo, Mexico, and in Western Australia.

Habitat

Remipedes live exclusively in submerged caves (anchialine caves) found near the sea on islands or along the coast. Anchialine caves are caves that have surface openings on land and subsurface connections to the sea. This habitat is accessible only by trained cave divers using special scuba techniques and equipment. Anchialine caves typically have a fresh or brackish layer of water overlying deeper marine water. The density interface or halocline also delineates differences in temperature, pH, and dissolved oxygen. Remipedes live in the dark, beneath the density interface in waters that are low in dissolved oxygen. They live in an ecosystem that includes other troglobitic crustaceans, most commonly thermosbaenaceans, cirolanid isopods, caridean shrimp, and amphipods. Blind cave fish are occasionally found in the cave systems where remipedes live. With the exception of one Mexican cave system, all known locations of remipedes contain very few individuals. Most species are quite rare, and fewer than 10 individuals can be observed during a typical cave dive.

Behavior

Remipedes are typically observed swimming in the water column in most caves. However, in one cave in Mexico the remipedes are more frequently swimming along the surface of the sediment. Some of these remipedes have been observed

resting motionless on the sediment and sometimes grooming. Several types of grooming behavior have been observed. The first antenna is flicked posteriorly and run along the setae of the swimming appendages. Circle grooming involves a remipede curling into a circle and cleaning trunk appendages with the feeding appendages.

Feeding ecology and diet

In their natural habitat remipedes have been observed feeding on cave shrimp and on blind cave fish. In laboratory experiments they will capture, subdue, and eat cave shrimp. Additionally they will eat non-native food items such as brine shrimp and bloodworms. They use the fang of the first maxilla to inject a secretory product into their prey that immobilizes and kills it. The fang is connected by a duct to a large secretory gland. The secretory product remains unanalyzed. Remipedes have a close association with the sediment in some caves. In captivity they have been observed to gather sediment into a small bolus, hold it over their mouth, and ingest material. Some scientists believe that they are using bacteria found in the sediment as either a food source or for some physiological purpose.

Reproductive biology

Remipedes are simultaneous hermaphrodites. The ovary originates in the head, and the oviducts extend to the base of the seventh swimming appendage where the female gonopore is found. The testes originate in the segment of the seventh swimming appendage, and the vas deferens extends to the fourteenth swimming appendage where the male gonopore is located. Sperm is flagellated and packaged into spermatophores. To date, nothing is known about remipede development. Tiny juveniles have been collected. Resembling adults, they are about one-third the length of adults and have at least 14 swimming appendages.

Conservation status

No remipedes are listed by the IUCN. One species, Speleonectes lucayensis, is protected by Lucayan National Park on Grand Bahama Island. Worldwide, anchialine caves are threatened ecosystems. Dangers include deforestation and development above or near the cave systems, use of biocides, improper sewage disposal, and destruction of nearby mangroves. The many caves along the coast of Quintana Roo, Mexico, are in imminent danger due to rapid development of tourist hotels, expansion of cities, and lack of enforcement of environmental laws. Most caves are formed in limestone, which is porous. Any kind of pollutant on the surface can eventually end up in the aquifer. One cave in Quintana Roo is home to thousands of remipedes, a number never recorded anywhere else in the world. This cave is in the path of development.

Significance to humans

Remipedes have no known commercial significance.

Species accounts

List of Species

No common name

Lasionectes entrichoma

order

Nectiopoda

family

Speleonectidae

taxonomy

Lasionectes entrichoma

other common names

None known.

physical characteristics

Maximum length is 1.26 in (32 mm); maximum number of trunk segments is 32. The second maxillae and maxillipeds are robust and have thick rows of uniform short setae along the medial margins.

distribution

Anchialine caves of the Turks and Caicos Islands.

habitat

Found beneath the halocline from 16 ft (5 m) to deeper depths.

behavior

Lasionectids swim in the water column.

feeding ecology and diet

Main diet is the caridean shrimp Typhlatya garciai Chace.

reproductive biology

Hermaphroditic. Nothing is known about reproductive behavior.

conservation status

Not listed by the IUCN.

significance to humans

None known.

No common name

Speleonectes gironensis

order

Nectiopoda

family

Speleonectidae

taxonomy

Speleonectes gironensis

other common names

None known.

physical characteristics

Maximum length is 0.55 in (14 mm). Maximum number of trunk segments is 25. First maxillae are robust. The caudal rami are at least two times the length of the anal segment.

distribution

Anchialine caves of Matanzas and Holguin Provinces, Cuba.

habitat

Found beneath the halocline from 39 ft (12 m) to deeper depths.

behavior

Speleonectids swim in the water column.

feeding ecology and diet

Their main diet consists of small cave crustaceans.

reproductive biology

Hermaphroditic. Nothing is known about reproductive behavior.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Resources

Book

Yager, Jill. "The Reproductive Biology of Two Species of Remipedes." In Crustacean Sexual Biology, edited by R. T. Bauer and J. W. Martin. New York: Columbia University Press, 1991.

Periodicals

Yager, Jill. "Cryptocorynetes haptodiscus, New Genus, New Species, and Speleonectes benjamini, New Species, of Remipede Crustaceans from Anchialine Caves in the Bahamas, with Remarks on Distribution and Ecology." Proceedings of the Biological Society of Washington 100, no. 2 (1987): 302–320.

——. "Pleomothra apletocheles and Godzillignomus frondosus, Two New Genera of Remipede Crustaceans (Godzilliidae) from Anchialine Caves in the Bahamas." Bulletin of Marine Science 44 (1989): 1195–1206.

——. "Remipedia, a New Class of Crustacea from a Marine Cave in the Bahamas." Journal of Crustacean Biology 1 (1981): 328–333.

——. "Speleonectes gironensis, New Species (Remipedia: Speleonectidae), from Anchialine Caves in Cuba, with Remarks on Biogeography and Ecology." Journal of Crustacean Biology 14, no. 4 (1994): 752–762.

Yager, Jill, and Frederick R. Schram. "Lasionectes entrichoma, New Genus, New Species, (Crustacea: Remipedia) from Anchialine Caves in the Turks and Caicos, British West Indies." Proceedings of the Biological Society of Washington 99, no. 1 (1986): 65–70.

Jill Yager, PhD