Cave Organisms
Organisms within caves may occur on the ground, within debris, on the roof and walls, or on any cave formation. Cave organisms are typically divided into troglobites, troglophiles, and trogloxenes (Gunn, 2004).
Tadarida brasiliensis mexicanus – Mexican free-tailed bat. Photo from Pollak (2004).
Troglobites live permanently and exclusively in caves. Troglobites generally show morphological and physiological adaptations for life in caves. Such adaptations include the reduction (or loss) of eyes, pigmentation, egg volume, body size, swim bladder, circadian rhythms, scales, and aggression; some troglobites also exhibit increased lifespan (Gunn, 2004). There are nearly 1000 described species of troglobites within the 48 contiguous states of the US, and most of these species are known only from a single county (Culver et al., 2000). The caves in the region of the Edwards Aquifer in central Texas contain 108 species of troglobites (Culver et al., 2003).
Troglophiles are species that can live completely underground, but also occur in surface ecosystems. These species typically do not have the modifications seen in troglobites.
Trogloxenes are animals that use caves occasionally, but belong to surface ecosystems. This includes bats that sleep and hibernate in caves and carnivores that den in caves.
Aquatic Organisms
Animal species that live exclusively in subterranean waters are called stygobites. Only about 8% of named species of aquatic animals are known to live within groundwater. This number is so limited because of the limited accessibility of habitats, the homogeneity of the environment, and low amounts of food resources (Sket, 1999). The Edwards Aquifer of central Texas contains a total of 55 stygobite species (Culver et al., 2003)
Eurycea sosorum – the Barton Springs salamander. Photo from Mahler (2004); taken by Lisa O’Donnell.
Organisms within caves may occur on the ground, within debris, on the roof and walls, or on any cave formation. Cave organisms are typically divided into troglobites, troglophiles, and trogloxenes (Gunn, 2004).
Tadarida brasiliensis mexicanus – Mexican free-tailed bat. Photo from Pollak (2004).
Troglobites live permanently and exclusively in caves. Troglobites generally show morphological and physiological adaptations for life in caves. Such adaptations include the reduction (or loss) of eyes, pigmentation, egg volume, body size, swim bladder, circadian rhythms, scales, and aggression; some troglobites also exhibit increased lifespan (Gunn, 2004). There are nearly 1000 described species of troglobites within the 48 contiguous states of the US, and most of these species are known only from a single county (Culver et al., 2000). The caves in the region of the Edwards Aquifer in central Texas contain 108 species of troglobites (Culver et al., 2003).
Troglophiles are species that can live completely underground, but also occur in surface ecosystems. These species typically do not have the modifications seen in troglobites.
Trogloxenes are animals that use caves occasionally, but belong to surface ecosystems. This includes bats that sleep and hibernate in caves and carnivores that den in caves.
Aquatic Organisms
Animal species that live exclusively in subterranean waters are called stygobites. Only about 8% of named species of aquatic animals are known to live within groundwater. This number is so limited because of the limited accessibility of habitats, the homogeneity of the environment, and low amounts of food resources (Sket, 1999). The Edwards Aquifer of central Texas contains a total of 55 stygobite species (Culver et al., 2003)
Eurycea sosorum – the Barton Springs salamander. Photo from Mahler (2004); taken by Lisa O’Donnell.
No comments:
Post a Comment