32 
W.F. Humphreys, M.N. Feinberg 
Table 4 Stygofauna associated with the two sympatric cave fishes on the Cape Range peninsula. V = is known from 
the same sites but not recorded in the guts; + = is known from the same sites and not recorded in the guts; 
- = is not recorded from the same sites. 
O. candidum M. veritas 
Stygiocaris lancifera Holthuis + 1 + 
S. stylifera Holthuis + 1 V 
Halosbaena tulki Poore and Humphreys + V 
Haptolana pholeta Bruce and Humphreys - V 
Remipedia - V 
Melitid amphipod gen. et sp. nov. V V 
Calanoid copepods V V 
Harpacticoid copepods V V 
Ostracoda V V 
1 The species of Stygiocaris in O. candidum from C-26 is not known; immediately to the north of C-26 S. stylifera and S. 
lancifera are sympatric, while to the south only S. lancifera is known. 
DISCUSSION 
The prey identified is consistent with the 
behaviour of the fish. O. candidum inhabits the 
surface of, and burrows into, the faecal ooze 
characteristic of crustacean-rich stygal habitats. All 
the prey items identified are bottom dwellers or, in 
the case of the isopod, would sink to the bottom 
when it fell into the water. In contrast M. veritas 
moves widely through the water column, often 
hovering in mid- to surface waters where prey 
with hygrophobic integuments, such as 
cockroaches, would be encountered when they fell 
into the water. 
The locations sampled for M. veritas include 
flooded sinkholes, small rock pools, shallow open 
caves in the coastal limestones, old wells (hand- 
excavated and lined with wood or cement) deep 
anchialine caves (i.e. inland caves connected at 
depth to the sea) and deep bores. From these 
samples the food of M. veritas comprised 
predominantly terrestrial taxa (79%) that have 
presumably fallen into the water; both the isopods 
and cockroaches are plentiful in some of the 
sampling locations as these cryptic taxa shelter 
there from the hot arid climate. However, there are 
populations of gudgeon known from caves (e.g. C- 
215, C—452) where such accidental food is unlikely 
to occur as the water is reached only at some 
horizontal distance from the entrance, or from 50 
m deep bores. However, both these habitats 
contain rich stygofauna. 
Both species of troglobitic fish are clearly 
opportunistic in their feeding, able to take 
accidental inputs of energy. The eel forages on the 
specialised subterranean inhabitants and the 
gudgeons must have this ability, although rarely 
recorded in these samples, because it inhabits some 
locations, such as C-215 and deep bores, essentially 
closed to accidentals. The gudgeons are capable of 
taking large and energy rich prey such as 
cockroaches, while the eels include prey of minute 
size (Halosbaena tulki is <2 mm in total length; 
Poore and Humphreys 1992). 
There is one area of bias in the data that impinges 
on the interpretation of these findings. From 
necessity the fishes were sampled at the few places 
where the stygal realm opens to the surface - wells 
and rockholes - and hence where epigean prey 
species would be present. Throughout the greatest 
part (>99.99%) of the distribution of this stygal 
community there are no known openings to the 
surface. Extensive sampling down boreholes has 
shown that the stygofauna is present in such areas, 
with the exception of O. candidum which was not 
sampled there, and that there was a general 
absence of epigean species in these areas (W.F. 
Humphreys, unpublished data, 1994). Hence, in 
general, the fish will be dependent on the 
stygofauna for food and not, as suggested by the 
data presented here, on epigean species 
accidentally in the water. 
The stygal community on the Cape Range 
peninsula is unusual in that there are recorded only 
eight instances world wide of two species of 
sympatric cave fish (Thines and Proudlov 1986), 
and because of their occurrence with a rich 
community of Crustacea, many belonging to relict 
groups (Wagele 1992) such as thermosbaenaceans 
and remipedes (Poore and Humphreys 1992; W.F. 
Humphreys, unpublished). Given their Tethyan 
origins (Humphreys 1993a, 1993d; Knott 1993) it is 
not remarkable that the fish and crustaceans should 
be part of the same food web and the broad 
conservation implications are clear - the 
stygofauna is a functional community, changes to 
part of which may effect the remainder. 
ACKNOWLEDGEMENTS 
We thank Julianne Waldock for her continued 
support. Dr G. Allen (WAM) for permission to 
dissect fish from the collections of the Western 
