Invertebrate Cave Fauna 
101 
is usually measured by the level of regressive evolution (Poulson 1963). 
Third, cavernicoles in different cave habitats have been compared 
(Dickson and Holsinger 1981, Estes 1978). 
Selection for delayed reproduction, increased longevity, and the 
like is frequently called K-selection. Recent models (reviewed by 
Charlesworth 1980) show that there is no simple dichotomy between 
r-selection and K-selection, but the following characteristics are likely to 
„ be selected for in at least some cavernicoles: 
1. Delayed maturity 
2. Increased longevity 
3. Fewer clutches 
4. Smaller clutch size 
5. Larger eggs 
6. Low percentage of mature females ovigerous 
7. Sex ratio skewed toward females 
Examples of each of these characteristics will be discussed, but their 
generality will not. 
Ginet’s (1960) study of the amphipod Niphargus orcinus virei 
Chevreux illustrates the first three characteristics (Fig. 34). Compared 
with Gammarus duebeni Lilljeborg, N. orcinus virei takes four times 
longer to mature, lives five times longer, and has only two broods (as 
opposed to seven). The most striking example of increased longevity is 
the crayfish Orconectes australis australis (Rhoades), which lives a 
minimum of 40 years (Cooper 1975). The amphipod Crangonyx 
antennatus, which is common in many Virginia and Tennessee caves, 
i 
lives at least 6 years in the laboratory. Life spans of terrestrial animals 
are apparently shorter. Peck (1975c) found that the leiodid beetle 
Ptomaphagus hirtus Tellkampf lived an average of 2 years. 
Rouch (1968), in a comprehensive study of cave harpacticoid 
copepods in France, found that cavernicolous species had fewer eggs per 
unit size of female and that egg diameters were larger than was the case 
for low-altitude epigean species. High-altitude epigean harpacticoids, 
like cavernicolus species, also had fewer eggs with larger diameters when 
compared with low-altitude epigean species. 
Many populations of cavernicoles have low percentages of ovigerous 
females and mature females. One very clear case is Dickson’s data 
(Dickson and Holsinger 1981) on Crangonyx antennatus from two 
caves in Lee County, Va. (Fig. 35). These data raise some interesting 
evolutionary questions. If ovigerous females are genetically different 
from non-ovigerous females, then those genotypes should increase, 
resulting in higher frequencies of ovigery. Low ovigery may be 
maintained by strong intraspecific competition, with little genetic basis, 
which allows only an occasional female to take in enough food to 
