The life cycle of Anisakis simplex in the Norwegian Deep (northern North Sea)

Autor: Klimpel, S.; Palm, H.W.; Rückert, S.; Piatkowski, U.
In:

Parasitology Research

ISBN: DOI 10.1007/s00436-004-1154-0
Seite: 1 - 9
Jahr: 2004

Einordung:
Institut: Professur Aquakultur und Sea-Ranching

Abstract:
Copepoda (Calanus finmarchicus n=1,722,
Paraeuchaeta norvegica n=1,955), Hyperiidae
(n=3,019), Euphausiacea (Meganyctiphanes norvegica
n=4,780), and the fishes Maurolicus muelleri (n=500)
and Pollachius virens (n=33) were collected in the
Norwegian Deep (northern North Sea) during summer
2001 to examine the importance of pelagic invertebrates
and vertebrates as hosts of Anisakis simplex and their
roles in the transfer of this nematode to its final hosts
(Cetaceans). Third stage larvae (L3) of A. simplex were
found in P. norvegica, M. muelleri and P. virens. The
prevalence of A. simplex in dissected P. norvegica was
0.26%, with an intensity of 1. Prevalences in M. muelleri
and P. virens were 49.6% and 100.0%, with mean
intensities of 1.1–2.6 (total fish length ‡6.0–7.2) and
193.6, respectively. All specimens of C. finmarchicus and
M. norvegica examined were free of anisakid nematode
species and no other parasites were detected. P. norvegica,
which harboured the third stage larvae, is the
obligatory first intermediate host of A. simplex in the
investigated area. Though there was no apparent
development of larvae in M. muelleri, this fish can be
considered as the obligatory second intermediate host of
A. simplex in the Norwegian Deep. However, it is unlikely
that the larva from P. norvegica can be successfully
transmitted into the cetacean or pinniped final hosts,
where they reach the adult stage. An additional growth
phase and a second intermediate host is the next phase in
the life cycle. Larger predators such as P. virens serve as
paratenic hosts, accumulating the already infective stage
from M. muelleri. The oceanic life cycle of A. simplex in
the Norwegian Deep is very different in terms of hosts
and proposed life cycle patterns of A. simplex from other
regions, involving only a few intermediate hosts. In
contrast to earlier suggestions, euphausiids have no
importance at all for the successful transmission of
A. simplex in the Norwegian Deep. This demonstrates
that this nematode is able to select definite host species
depending on the locality, apparently having a very low
level of host specificity. This could explain the wide
range of different hosts that have been recorded for this
species, and can be seen as the reason for the success of
this parasite in reaching its marine mammal final hosts
in an oceanic environment.

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