New Zealand Journal of Marine and Freshwater Research abstracts
Comparison of the ectosymbionts and parasites of an introduced crab, Charybdis
japonica, with sympatric and allopatric populations of a native New Zealand
crab, Ovalipes catharus (Brachyura: Portunidae)
Aroha Miller1,2
Graeme J. Inglis1
Robert Poulin2
1 National Centre for Aquatic Biodiversity and
Biosecurity
National Institute of Water and Atmospheric
Research Limited
P.O. Box 8602
Christchurch, New Zealand
email: a.miller@niwa.co.nz
2 Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
Abstract The success of biological invaders is often attributed
to escape from specialist enemies in their natural range, such as predators
and parasites. For enemy escape to have direct consequences in competitive
interactions, invaders need to be less vulnerable to enemies than native competitors
in the region they invade, but first the presence of these enemies must be
established. We investigated the macroparasite and ectosymbiont fauna of the
recently introduced portunid crab Charybdis japonica, and compared it
with sympatric and allopatric populations of the native New Zealand portunid, Ovalipes catharus.
A total of 468 crabs (350 O. catharus and 118 C. japonica) were
collected from six harbours throughout New Zealand (Whangarei, Waitemata, Nelson,
Lyttelton, Dunedin, and Bluff) and the identity, incidence and prevalence of
ectosymbionts and parasites were compared among the different populations. Charybdis japonica and O.
catharus harboured different ectosymbionts. Serpulid polychaete tubes
occurred on the exoskeleton of 85.4% of C. japonica examined, but
were absent from O.
catharus. The bryozoan, Triticella capsularis occurred on 97.4%
of O.
catharus but was not found on C. japonica. Few endoparasites
were present in either species. An unidentified juvenile ascaridoid nematode
occurred in the hindgut of 5.9% of C. japonica, but was not found
in sympatric populations of O. catharus. A second, unidentified
species of ascaridoid nematode occurred in 7.1% of O. catharus from
Nelson, but was not present in specimens from the five other harbours sampled.
Melanised lesions were observed in the muscle tissue of almost half (46.6%)
of the C. japonica examined. Histological
examination showed these to be of two types: (1) spherical bodies resembling
melanised trematode metacercariae; and (2) lesions consistent with wound repair.
Lesions were not observed in O. catharus. Although the identity of parasites
and epibionts carried by each species differed, both C. japonica and O.
catharus had relatively low parasite species richness. We could not test
whether the introduced portunid, C. japonica,is any less vulnerable
to parasite enemies than the New Zealand portunid, O. catharus.
Keywords Charybdis japonica; Ovalipes catharus;
parasites; ectosymbionts; introduced species; Portunidae
New Zealand Journal of Marine and Freshwater Research, 2006, Vol. 40:
369–378
0028–8330/06/4002–0369 © The Royal Society
of New Zealand 2006
M05074; Online publication date 12 May 2006. Received 28 November 2005;
accepted 20 April 2006
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