Kauai Cave Amphipod
Kauai Cave Amphipod
|Listed||January 14, 2000|
|Description||A cave-dwelling crustacean.|
|Habitat||Caves in limestone and calcareous rocks, and in lava tubes.|
|Food||Dead organic matter, especially plant biomass.|
|Reproduction||Lays externally fertilized eggs.|
|Threats||Destruction of the cave ecosystem by the influences of above-ground land use for various development activities, as well as poisoning by pesticides, and effects of predation and competition by introduced invertebrates.|
The Kauai cave amphipod was first "discovered" in 1971. This unusual animal is placed within its own, unique genus (Spelaeorchestia ). Among its unusual characteristics is a highly reduced, pincer-like condition of the first gnathopod appendage, while the second gnathopod is mitten-like in both sexes (these are attached to the cephalothorax, or the fused head and thorax in the middle region of the animal). This amphipod is also unusual because it lacks eye facets (lens-like divisions of a compound eye), is non-pigmented, and has extremely long and spiny post-cephalic appendages (located behind the head). Adult Kauai cave amphipods are 0.25-0.40 in (7-10 mm) long and slender-bodied, with a hyaline exoskeleton (a translucent outer cuticle). Its antenna is slender and elongate, with the flagellum (a thread-like structure used for movement) only slightly longer than the peduncle (a stalk-like structure). Its peraeopods (the abdominal walking legs) are very elongate, and tipped with slender, attenuated claws. All of the pleopods (swimming legs) are reduced, and their branches are vestigial (i.e., they are small and rudimentary, and probably non-functional) or lacking. The first and second uropods (tail-like appendages) have well-developed prepeduncles, and the brood plates are vestigial or absent in mature females.
The Kauai cave amphipod is a detritivore, meaning it feeds on dead organic matter of decomposing plants, animals, and fecal material. Much of its food washes into its cave habitat, or is dead roots from trees growing above. It is not particularly gregarious. When disturbed, individuals typically move slowly away rather than jumping like most amphipods. Nothing is known of the reproductive biology of the Kauai cave amphipod, but the vestigial brood plates of the female suggest that they give birth to a small brood of relatively large offspring.
The Kauai cave amphipod inhabits underground caves formed in limestone and calcareous sandstone, as well as lava tubes. It occurs in microhabitats that are dark and moist, and have organic debris of various kinds, including dead and living tree roots.
The Kauai cave amphipod is a locally evolved (or endemic) species that is only known from five sites on the Hawaiian island of Kauai. Its populations occur in an area of only about 4 sq mi (10.5 sq km), in a coastal section of the Koloa lava flows that have not filled with erosional sediment.
The local area where the Kauai cave amphipod occurs is rapidly being developed, resulting in degradation or destruction of the cave habitat. The dominant land-uses are for agriculture, residential and tourism development, and golf courses; there is little natural habitat left. In fact, the Koloa cave systems are considered to among the ten most-endangered cave ecosystems in the world. The rare amphipods are also at risk from predation by and competition with introduced invertebrates, and the contamination of groundwater with pesticides and nutrients used in nearby residential areas and golf courses. Because of the small number of populations, each containing few individuals, the species is also at risk from such unpredictable catastrophes as hurricanes.
Conservation and Recovery
All of the known habitats of the Kauai cave amphipod are on privately owned land. The deliberate killing or collecting of the rare amphipod is illegal, but its critical habitat has not been conserved effectively. However, from the mid-1990s significant progress was made in the planning and implementation of conservation measures around three of the Koloa caves. In 1995, the U. S. Fish and Wildlife Service negotiated a cooperative agreement with a local development company to implement conservation measures for two caves. The measures included gating of the cave entrances to restrict human access and reduce air-flow (to increase ambient humidity), and the planting of native trees over the caves to develop a root system that will serve as a food base for the cave animals. The private landowner also agreed to set aside an area above the two caves as either a limited-use park or reserve, and to not use any pesticides or dump refuse in this special-management zone. Negotiations are being undertaken with another landowner to conserve a third cave ecosystem beneath a golf course.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
U. S. Fish and Wildlife Service, Pacific Islands
300 Ala Moana Boulevard, Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-3441
Fax: (808) 541-3470
U. S. Fish and Wildlife Service. January 14, 2000. "Endangered and Threatened Wildlife and Plants; Final Rule To List Two Cave Animals From Kauai, Hawaii, as Endangered." Federal Register 65 (10): 2348-2357.