Rhadine infernalis
From Wikipedia, the free encyclopedia
| "Rhadine infernalis" No Common Name | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Adephaga |
| Family: | Carabidae |
| Genus: | Rhadine |
| Species: | R. infernalis |
| Binomial name | |
| Rhadine infernalis (Barr & Lawrence, 1960) | |
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Rhadine infernalis is a species of troglobitic beetle of the family Carabidae.[1][2][3] They are endemic to the county of Bexar, Texas.[4] Within this county, R. infernalis has been found in 39 caves.[1] There are 2 named subspecies of R. infernalis: R. infernalis infernalis and R. infernalis ewersi.[3][4] There is a third possible subspecies that has not been officially described.[5] R. infernalis was classified in 2000 as endangered under the IUCN Endangered Species Act of 1973, along with 8 other karst invertebrates in the same region.[4] It has the widest known range of the endangered karst invertebrates.[3]
These two subspecies belong to the species Rhadine infernalis:
- Rhadine infernalis ewersi (Barr, 1960)
- Rhadine infernalis infernalis (Barr & Lawrence, 1960)
Description
Similar to other cave-dwelling invertebrates, R. infernalis has reduced eyes and elongated appendages.[1][2] It is reddish brown and has smooth elytra, with a narrow neck that is less than half the width of its head.[2][3] It ranges in length from about 6.6 (0.26 in) to 8.2 mm (0.32 in).[2][3] It may be distinguished from R. exilis, another karst-dwelling invertebrate that lives in Bexar County, by its thick rather than slender body.[3][5] Its pronotum, a plate that covers the prothorax, is wider and less elongated compared to that of R. exilis.[3] The pronotum also has two pairs of bristle-like structures called setae.[3]
Life history
Little is known about the life history of R. infernalis. It is likely to have evolved life characteristics similar to other cave-dwelling invertebrates, who have adapted to low levels of light and a lack of primary producers for food and nutrients.[5] These types of conditions favor relatively long life spans and lower reproductive rates.[5][6] This would be expected to be accompanied by a low metabolic rate as well.[3][5][6]
Ecology
Diet
Rhadine Infernalis inhabits caves and mesocaverns, which are small caves that are not accessible to humans.[1][5][6] Due to their elusive nature, little is known about their behavior. The troglobite karst invertebrates probably depend on plant or animal matter that is washed into the caves, or on other invertebrates that live in the caves but feed on surface plants.[3][4][6] It is thought that R. infernalis is an opportunistic feeder, eating smaller or dead arthropods that live in the caves.[3][7] Cave crickets from the genus Ceuthophilus are abundant in Texas caves, and may be an important food source for R. infernalis.[3] Karst invertebrates have been found to feed on these crickets, as well as on their nymphs and eggs.[3][6][7]
Behavior
As R. infernalis likely occupies mesocaverns and cavities that cannot be studied without excavation, its behavior is not well understood.[6]
In a study conducted by Veni and Associates (2006), R. infernalis was observed 23 times in 3 caves at Camp Bullis in Bexar County, Texas.[5] It was mostly found under rocks, and was found nearer to cave entrances than R. exilis.[5] Of the 23 observations, almost all were made during the spring and summer, while one sighting occurred in the fall.[5] Due to the small sample size, no conclusions can be made about regular periods of dormancy or activity for R. infernalis.[5] However, it is believed that troglobites such as R. infernalis can go long periods without food.[5] When they do not need to feed, they retreat into very small spaces that cannot be surveyed by humans.[5] This may explain the irregularity of R. infernalis sightings.[5] Observations of R. infernalis suggest that it prefers areas of high organic content.[3] R. infernalis has also been observed on old bat guano in Headquarters Cave.[3]
Habitat
R. infernalis only occurs in the karst terrain specific to Bexar County, Texas.[3][4][6] Karst habitats are formed from the dissolving of bedrock, resulting in sinkholes, caves, and mesocaverns.[3][4][5] The karst habitat has stable temperatures and high humidity owing to the water that flows from the surface down through the cavities and interconnected voids in the limestone.[4][5][6] The movement of water is an important way that nutrients flow through the underground system.[4][5][6]
Range
The karst habitat in Bexar County has been divided into 6 karst fauna regions (KFRs), which are recognized by the U.S. Fish and Wildlife Service (USFWS).[4] These were designated according to geographical barriers that occur within the karst habitat that would potentially prevent interaction between troglobite populations.[4][7] For example, a KFR may be defined by faults or streams that would limit movement by troglobite invertebrates into other KFRs.[4] R. infernalis has been found in 5 of the KFRs, in 39 caves.[1]