Halacarines from Rottnest Island 
17 
distinctly differing from the Australian species, is 
recorded from South Africa (Bartsch 1986). 
ECOLOGY 
The two species Agauopsis australiensis and 
Halacaropsis capuzina were commonly taken in 
shallow water substrata, from intertidal to some 
few metres depth. 
Juveniles of Halacaropsis capuzina were found in 
a wide range of habitats, regularly and in large 
numbers in samples with the seagrass Amphibolis 
as well as with coralline algae, whereas the adults 
were registered in seagrass washings. H. capuzina 
is thought to prefer the dense thicket of epifauna 
and flora on the seagrass. With the enlarged 
median claw and the slightly bent posterior tarsi, 
H. capuzina resembles representatives of the genus 
Bradyagaue which live on stolonaceous colonies. H. 
Warringa and H. hirsuta are mostly recorded from 
samples with coralline algae (Chapman 1955; Otto 
1993). 
A remarkable feature of H. capuzina, as also of H. 
warringa, is the presence of long and very stout 
setae on the dorsum. These erect spines may both 
prevent its bearer from being swallowed by small 
fishes nibbling on the epifauna, and they may help 
to trap debris which serve as an optical and 
chemical camouflage. 
Agauopsis elaborata, too, has conspicuously 
enlarged dorsal setae, but these setae are not erect 
but curved. Similar setae and an ornamentation 
resembling that of A. elaborata is described for 
Thalassophthirius auster Bartsch, Copidognathus 
neptuneus Bartsch and C. nasutus Bartsch (Bartsch 
1988, 1992a, 1994). The single specimen of A. 
elaborata and C. nasutus were found within 
corallines, C. neptuneus was extracted from a dead 
coral block dredged in the Tolo Channel, Hong 
Kong; T. auster was taken from 13-34 m depth, 
Staten Island, South America, the substratum 
inhabited is not known. 
A. australiensis, adults as well as nymphs and 
larvae, was taken from various substrata, from 
scrubs of corallines and calcareous tubes of 
polychaetes and together with H. capuzina from the 
epifauna and flora on Amphibolis. 
In the collections gathered in January Halacaropsis 
capuzina was represented with rather large 
numbers of larvae, protonymphs and deuto- 
nymphs (only few of them were examined 
microscopically) whereas adults were sparse. In 
contrast to the juveniles, the four adult specimens 
available were intensely fouled with small algae 
and they lacked the claws on one or more legs. 
According to present knowledge, the majority of 
halacarines have a univoltine life cycle with either 
short or prolonged periods of reproduction 
(Bartsch 1989). H. capuzina obviously belongs to the 
former category, with egg deposition within few 
weeks in early spring, larvae hatching in the 
spring, juveniles predominating in the summer 
months, and adults being present in autumn, 
winter and spring. The heavily fouled adults found 
in January obviously belong to the parental 
generation. Agauopsis australiensis has a less 
distinctive period of reproduction, adults are 
abundant also in summer months. 
The larvae of both H. capuzina and A. australiensis 
have a slender, pointed frontal spine. These frontal 
spines may help the hatching larvae to rupture the 
egg membrane. The anterior spinelet of larvae of 
Halacarellus psammophilus (Krantz) and H. 
suberispus Bartsch is thought to be such an egg 
bursting mechanism (Krantz 1976; Bartsch 1978). 
BIOGEOGRAPHICAL REMARKS 
According to present records, five 
representatives of Agauopsis and two of 
Halacaropsis live in Western Australian shallow 
waters, these are A. aequilivestita, A. australiensis, A. 
elaborata, A. ornatella, a representative of the 
Agauopsis furcata group (Bartsch 1993), Halacaropsis 
capuzina and Halacaropsis sp. (Lohmann 1909). 
A. australiensis, A. ornatella and A. elaborata are 
members of the microrhyncha, omata and pugio 
groups respectively. The microrhyncha group is 
wide-spread, present in warm as well as polar 
waters; most species are known from the southern 
hemisphere. Members of the omata group are 
found in warm waters all around the globe. 
Records of representatives of tire pugio group are 
from the southern hemisphere only, from South 
Africa, South America, and now also from 
Australia. A. aequilivestita is most similar to the 
African A. punctata. The furcata group includes 
psammobiont species; most records are from the 
Indo-Pacific region, but members of this group are 
also known from the Black Sea and northeastern 
Atlantic (Bartsch 1992b). 
In the samples from Rottnest Island, there is no 
representative of the otherwise very common 
brevipalpus group. The lack of records may be due 
to the small size of Rottnest Island, many habitats 
are missing (Wells and Walker 1993), and being an 
area with rather constant environmental 
parameters such as high salinity and temperature. 
Records of the genus Agauopsis from 
southeastern Australia are A. mokari and Agauopsis 
sp. (Otto 1994; Bartsch 1985b), both members of 
the microrhyncha group, and A. collaris Otto, a 
representative of the brevipalpus group (Otto 1994). 
The 'Agaue brevipalpus’ mentioned in Lohmann 
(1893) is certainly not conspecific with the northern 
Atlantic and Mediterranean A. brevipalpus. The 
records of ’Agaue microrhyncha’ and 'Agaue hirsuta’, 
listed by Lohmann (1893) from off Sydney, is 
