Records of the Western Australian Museum 18: 77-85 (1996). 
Copepods from ground waters of Western Australia, II. The genus 
Halicyclops (Crustacea: Copepoda: Cyclopidae) 
G.L. Pesce 1 , P. De Laurentiis 1 and W.F. Humphreys 2 
1 Dipartimento di Scienze Ambientali, University of L'Aquila, Via Vetoio, 
1-67100 L'Aquila, Italy 
2 Western Australian Museum, Francis Street, Perth, Western Australia 6000, Australia 
Abstract - Halicyclops longifurcatus n.sp. is described from groundwaters of 
the Cape Range karst area, north-western Australia. Halicyclops spinifer Kiefer 
1935, from the same region, is for the first time recorded from Australia. 
These findings increase to three the number of congeners from Australia, the 
other being H. ambiguus Kiefer, 1967, reported from the southeastern part of 
the continent. 
INTRODUCTION 
Cyclopoid copepods have recently been collected 
from a variety of different groundwater habitats 
(sinkholes, anchialine caves, wells) on the Cape 
Range peninsula, northwestern Australia. The 
material included several interesting stygobitic and 
stygophilic species, amongst them an undescribed 
species of the genus Halicyclops Norman and the 
species Halicyclops spinifer Kiefer, 1935. 
Halicyclops is a cosmopolitan genus, with 72 
named species and subspecies, widely distributed 
in coastal brackish waters, ponds, marshes and 
sandy beaches; nineteen species, the new species 
included, are stygophilic inhabitants of ground 
water habitats, such as anchialine caves, sinkholes 
and different interstitial media. 
The present finding increases to three the number 
of Halicyclops species from Australia, the other 
being H. ambiguus Kiefer, 1967, described from 
southeastern Australia. 
Habitat and associated fauna 
North-western Australia is arid and on the Cape 
Range peninsula the available water is mostly 
groundwater accessible in a few caves within the 
Cape Range karst as well as in the general water 
table of the surrounding foothills and coastal plain 
where a freshwater lens overlies salt water 
(Humphreys 1993a, 1993c, 1993d). 
Halicyclops longifurcatus is known only from an 
anchialine flooded sinkhole (cenote), 1.6 km from 
the ocean (Figure 24). The specimens were collected 
by hauling a plankton net (125 pm mesh) through 
the water above the marked thermo-halocline 
which occurs at a depth of ca. 6 m. A number of 
taxa have been recorded from the sinkhole above 
the thermo-halocline: foraminiferida, Iravadia sp. 
(Mollusca: Irvadiidae), ostracods, Stygiocaris 
stylifera Holthuis (Malacostraca: Decapoda: 
Natantia: Atyidae), gerrids (Hemiptera), 
chironomids (Diptera), Milyeringa veritas Whitely 
(Perciformes: Eleotridae) and the algae 
Rhizoclonium ?tortuosum (Dillw.) Kuetz. 
(Chlorophyta: Cladophoraceae) and 
Lamprothamnium papulosum (Walk.) J. Gr. 
(Charophyta: Characeae). Below the halocline 
occurs a strictly anchialine fauna (Yager and 
Humphreys 1996) with tethyan affinities 
(Humphreys 1993b; Humphreys and Feinberg 
1994; Knott 1993). This fauna includes Lasionectes 
exleyi (Remepedia: Speleonectidae- Yager and 
Humphreys 1996), Liagoceradocus sp. nov. 
(Amphipoda: Hadziidae- Bradbury and Williams 
1995) and Danielopolina sp. nov. (Ostracoda: 
Thaumatocyprididae - Baltanas and Danielopol 
1995). 
At the surface the salinity was 20,000 mg L 1 and 
below the thermo-halocline tire salinity gradually 
increased with depth to 32,000 mg LA The surface 
temperature was 28.5°C and dropped to 25.0°C at 
the thermocline, increasing with depth to 26.3°C. 
Halicyclops spinifer occurred in a hand-dug 
pastoral well (C-361) near the coast with a salinity 
of 1,400 mg LA and at 200 m above sea level in a 
deep cave (C-18) in central Cape Range where the 
salinity was 500 mg LA The fauna associated with 
C-361, but not at the time of sampling for H. 
spinifer includes Milyeringa veritas and 
Ophislemon candidum (Mees) (Synbranchi- 
formes: Synbranchidae), Stygiocaris stylifera, 
dipteran larvae and harpacticoid copepods. The 
water in C-18 contains Microcyclops varicans 
(Copepoda: Cyclopidae) (Pesce et al. 1996), a 
melitid amphipod (undescribed genus: W. D. 
Williams, per. comm.), and the aquatic insect 
Copelatus irregularis Macl. (Coleoptera: Dytiscidae) 
(further details in Pesce et al., 1996). 
