Records of the Westem Australian Museum 17: 29-33 (1995). Food of the blind cave fishes of northwestern Australia W.F. Humphreysl and M.N. Feinberg2 I Department of Terrestrial Invertebrate Zoology, Western Australian Museum, Francis Street, Perth, Western Australia 6000 2Department of Herpetology and Icthyology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA. Abstract - Cape Range peninsula, in the arid northwest of Western Australia, contains the only cavernicolous fishes in Australasia, both of which are considered as vulnerable or endangered. They are associated with a stygofauna considered to be of Tethyan origin. Opllistemon candidum (Mees, 1962) (Synbranchiformes: Synbranchidae) and Milyeringa veritas Whitley, 1945 (Perciformes: Eleotrididae) occur widely in underground waters and are endemic to the peninsula. The gut contents of existing collections were examined to elucidate their prey. Both species of troglobitic fish are opportunistic in their feeding, able to utilize occasional packets of energy entering the stygal realm. Opllistemon candidum eats the specialised stygofauna of the region, including Halosbaena tulki (Poore and Humphreys, 1992) (Thermosbaenacea) and atyid shrimps (Stygiocaris spp.) and also feeds opportunistically on aquatic larvae living in the more open part of the subterranean system. The biogeographic affinities of O. candidum is in accord with that of its main prey. The gut contents constitute the only records of Stygiocaris and Halosbaena from Tantabiddy Well (C-26), the type locality of O. candidum. M. veritas primarily feeds opportunistically on invertebrates accidentally introduced into the aquatic system (mostly terrestrial isopods and cockroaches) but also feeds on the stygofauna. INTRODUCTION The genus Ophisternon has a disjunct distribution, The Cape Range peninsula in the arid northwest being found in Australasia, Indo-Malaya, west of Australia is noted for its subterranean animals, Africa and some island and mainland areas of the both a terrestrial fauna with wet forest affinities Caribbean. While the diet of O. candidum has been (Humphreys 1993a, 1993b, 1993c, 1993d), and an unrecorded previously, synbranchids are aquatic fauna with Tethyan affinities (Humphreys recognized as nocturnal predators (Moyle and 1993a, 1993d; Knott 1993). Amongst the latter are Cech 1982). Cavernicolous species, showing two species of blind cave fish, the Blind or Cave considerable atrophy of the eye tissue, occur on the Gudgeon, Milyeringa veritas Whitley, 1945 Yucatan peninsula, Mexico (0. infernale) (Rosen (Perciforrnes: Eleotrididae) and the Blind Cave Eel, and Greenwood 1976) and in Australia (0. Ophisternon candidum (Mees, 1962) candidum). (Synbranchiformes: Synbranchidae). These two The Eleotrididae are widespread in tropical and species of fish comprise the entire vertebrate subtropical shallow marine to fresh waters mainly troglobite fauna of Australasia. While other in the Indo-Pacific region (Nelson 1984). The stygobiontic fish have been extensively researched monotypic genus Milyeringa is endemic to the Cape (e.g. Wilkens 1988), nothing is known of the Range peninsula but the phylogenetic relationships ecology of those inhabiting the Cape Range between members of the family Eleotrididae have peninsula. not been established (see discussion in Knott 1993). The Synbranchidae, or swamp eels, are widely M. veritas is cavernicolous, eyeless and translucent. distributed in tropical and sub-tropical regions. This species has been considered to feed They exhibit marked habitat plasticity, being opportunistically upon detritus, algae and predominantly freshwater inhabitants but whatever animals, including insects, accidentally extending into brackish and estuarine waters; the fall into the water (AlIen 1989). same species may occupy a range of epigean Their subterranean habitat restricts observation habitats from streams and lakes to swamps and in life and hence very little is known about the marshes. Swamp and marsh dwellers often show biology of these fishes. Nonetheless, they have amphibious or burrowing habits and many are respectively been classified as rare and capable of aerial respiration (Rosen and recommended for total protection, and vulnerable Greenwood 1976). (Michaelis 1985); both fish species as well as two of 30 W.F. Humphreys, M.N. Feinberg the prey species (Stygiocaris spp.) have been listed RESULTS AND DISCUSSION under Schedule One of the Wildlife Protection Act of Western Australia oWing to their small Ophisternon candidum geographic distribution, low populations and Members of the stygofauna were found in the vulnerability of their habitat. midgut of P5813, namely thermosbaenaceans To establish basic biological data required for (Halosbaena tulki Poore and Humphreys, 1992) and conservation purposes the gut contents of existing atyid shrimps (Stygiocaris sp.); sand grains to 1.2 collections have been examined to elucidate their mm diameter were also recovered. The hindgut of prey. the same individual yielded only terrestrial taxa or taxa terrestrial as adults namely, slaters (Isopoda: Philosciidae) and dragonfly (Odonata) and METHODS dipteran larvae (Table 1). No gut contents were found in P4918 or P7716. The intestines were either dissected out and later The gut contents and the habitat characteristics examined by flushing the contents, or the flushing of the taxa would suggest that two feeding was conducted in situ on intestines longitudinally episodes had occurred in the first (hindgut) of incised. The contents were identified to whatever which the eel foraged in an open cave habitat on a level practicable depending on the state of non-cave aquatic fauna (Odonata and Diptera digestion. As no details are available of the larvae) as well as cryptic species accidentally in the treatment of the specimens prior to preservation, water (philosciid isopod). During the subsequent no attempt is made to quantify feeding rates. feeding episode the eel foraged solely on the With the exception of the holotype the gut specialised subterranean aquatic (stygo-) fauna contents were examined of all available specimens comprising sediment foraging species (Halosbaena of Ophisternon candidum namely, Paratype P4918 and Stygiocaris). Tantabiddy Well (C-26), Yardie Creek Station, No shrimps were taken from Tantabiddy Well collected A.M. Douglas and G.F. Mees, 17/5/1960; (C-26) in the original collections (Mees 1962) or P5813; Tantabiddy Well (C-26), Yardie Creek subsequently (Humphreys and Adams 1991; W.F. Station, collected A.M. Douglas, 22/7/1963; P7716; Humphreys, unpublished) although both S. North West Cape area, collected R. Gredling, 1963­ lancifera and S. stylifera occur in an adjacent well 4. (C-25, Kudamurra Well; Mees 1962; W.F. The stomach contents of a large series of Humphreys and M. Adams, unpublished 1991). Milyeringa veritas in the collection of the American Halosbaena has not been collected from C-26 (Poore Museum of Natural History were extracted by and Humphreys 1992; W.F. Humphreys, MNF and examined in Perth. Material came from: unpublished). Hence, these gut contents constitute AMNH 45497 (N=30) which included specimens the only records of Stygiocaris and Halosbaena from collected by Nelson, Butler and Rosen from the C-26. west side of the Cape Range peninsula between The distribution of the genus Ophisternon has Yardie Station and Yardie Creek on the afternoon been described as Gondwanan (Rosen and of 2 April 1969; AMNH 48568 (N=20) which Greenwood 1976) but a recent interpretation included specimens collected by Nelson, Butler considered both the genus Ophisternon and the and Rosen from the east side of Cape Range family Synbranchidae to have a Tethyan peninsula from Neds Well to Mowbowra Creek on distribution (Banarescu 1990: 203). The latter the morning of 5 April 1969. interpretation would accord with the stygofauna of Table 1 The gut contents of Ophisternon candidum in the collections of the Western Australian Museum. Location Identification Reg. No. Midgut Thermosbaenacea, Halosbaena tulki BES: 820 Midgut Atyidae: Stygiocaris sp. BES:821 Midgut Atyidae: Stygiocaris sp. BES: 822 Midgut Thermosbaenacea, Halosbaena tulki BES: 823 Midgut Thermosbaenacea, Halosbaena tulki BES: 824 Midgut Thermosbaenacea, Halosbaena tulki BES: 825 Midgut Sand to 1.2 mm diameter and residue BES: 826 Hindgut Isopoda: Philosciidae BES:817 Hindgut Odonata, larva BES: 818 Hindgut Unidentified BES: 819 Hindgut Diptera, larva BES:856 Food of cave fishes 31 Table 2 The gut contents of Milyeringa veritas from the American Museum of Natural History collections. 'Fish N' and 'Prey N' denotes the number of fish containing that prey item. Side of peninsula West East AMNH number (N) 45497 (N=23) 48568 (N=16) Contents Prey N(%) Fish N(%) Prey N(%) Fish N(%) No contents 8 (31) 4 (21) Cockroaches 1 (5) 1 (4) 9 (53) 7 (37) lsopods (Armadillidae) 14 (64) 12 (46) 2 (12) 2 (11) 5tygiocaris (shrimps) 1 (5) 1 (4) 1 (6) 1 (5) Crustacea (probably Stygiocaris) 1 (5) 1 (4) 1 (6) 1 (5) Trichopteran larvae 1 (5) 1 (4) 2 (12) 2 (11) Ants 4 (18) 1 (4) 0(0) 0(0) Unidentified insect parts 1 (4) 0(0) 0(0) Worms? 0(0) 0(0) 1 (6) 2 (11) Total 22 26 16 19 the Cape Range peninsula and that of the prey = 28.75, P<O.OOl) on the west coast (38.5±3.99 mm, items (Humphreys 1993a, 1993d; Knott 1993). n=26) than on the east coast (30.6±5.47 mm, n=19), Indeed, an undescribed species of syncarid as were those (F 1,31 = 17.5, P<O.OOl) in which crustacean of the genus Atopobathynella (H.K. prey