104 
John R. Holsinger and David C. Culver 
Interspecific Interactions — General 
Compared with other ecological problems, interspecific interactions 
among cavernicoles have received considerable attention. Cave 
communities offer several advantages to the student of species 
interactions. First, cave environments and population sizes are relatively 
stable compared with most epigean populations. Thus cave communities 
correspond more closely to the assumptions of ecological models than 
do most communities. Second, the number of species is so small that all 
interactions can be studied. Third, because there are many caves with 
very similar environmental conditions, there are many replicates as well 
as many “natural experiments” where species composition is different. 
The main disadvantage of cave communities is the long generation time 
of species, which makes the study of long-term dynamics difficult. 
Mutualism 
No free-living mutualists have been reported from caves. Mutual- 
istic gut endosymbionts may be important, but they have not been 
studied. Two ectosymbionts on crayfish are known, branchiodbellid 
worms and entocytherid ostracods, both of which occur in the study area. 
Hobbs (1975) has studied ostracod symbionts in Iqdiana caves, and his 
work shows that cave crayfish may be convenient systems for the study 
of symbiosis. The ecosymbiotic entocytherids attach to the exoskeleton 
of crayfish and feed on microorganisms and detritus that accumulate on 
the host exoskeleton. 
The troglobitic crayfish Orconectes inermis Cope has several 
advantages for further study. First, more than 90% of the ostracods on 
Orconectes inermis inermis belonged to one species, Sagittocythere barri 
(Hart and Hobbs), which in turn was rarely found on other crayfish in 
Hobbs’ study area. Thus it is essentially a two-species system. Second, 
the ectosymbionts are common. More than half of the O. inermis popu- 
lations had ostracods. The average number of S. barri per crayfish was 
17.2 (Hobbs 1975). One of Hobbs’ most interesting findings was that 
there was a significant increase in the number of ostracods with increas- 
ing length of the crayfish carapace. Thus the crayfish are like islands 
that are colonized by ostracods. 
Predation 
While predation appears to be more frequent in the terrestrial 
fauna than in the aquatic fauna, there have been no ecological or behav- 
ioral studies of terrestrial predators in the study area. One aquatic pred- 
ator, larval Gyrinophilus porphyriticus, has been extensively studied 
(Culver 1973b, 1975, 1985). This work is summarized below. 
Gyrinophilus porphyriticus larvae form significant populations in 
stream pools in several caves in the Powell Valley of Claiborne and Lee 
counties. Their prey are amphipods and isopods. None of the larvae 
