Biology Reference
In-Depth Information
Britain observed over 17 years never exceeded four species, and that of
1276 eels at 64 other localities in England and Ireland observed over
shorter periods never exceeded three. The maximum component com-
munity richness was nine species in the long-term study, and eight in the
others. Between 45% and 62% of the fish were free from parasites
altogether. Infracommunities were composed of different species at dif-
ferent localities. The total number of intestinal species was 19.
The infracommunity richness of intestinal parasites of Anguilla anguilla
in four Italian lagoons was similar to that in British eels, although the
composition of the parasite fauna was quite different. Most eels were not
infected or had a single parasite species; the maximum infracommunity
richness was three, and the component community richness was eight,
four, four, and three respectively (Kennedy et al.
1997
). Except for one
lagoon, where some freshwater parasites were found, all parasites were
marine or euryhaline, and digeneans - very rare in Britain - dominated
the communities, although few digeneans appeared to be eel specialists.
The most prevalent and abundant species were usually specialists.
In all British and Italian localities, the relationship between maximum
and mean infracommunity richness and component community richness
of parasites was ''curvilinear,'' best described by a power or polynomial
function. Kennedy and Gu´gan (
1996
) and Kennedy et al.(
1997
) inter-
preted this as meaning that infracommunity richness became increasingly
independent of component community richness, concluding that these
findings cannot be explained by ''supply side ecology'' (i.e., pool exhaus-
tion or transmission rates), but only by processes acting within infracom-
munities that limit species numbers.
Anguilla rostrata from Atlantic North America (Nova Scotia) also have
depauperate parasite faunas, as shown by Marcogliese and Cone (
1993
,
1996
,
1998
), who examined a total of 1041 eels from 28 sites in Nova
Scotia and recorded a total of 12 metazoan parasite species, including 8
from the digestive tract. Differences between total component community
richness, intestinal component community and infracommunity richness
between British and Nova Scotian eels were not significant, and eels from
both regions were infected with nearly identical suites of eel specialists.
Kennedy (
1995
; see also Gosper
1992
) examined 82 Anguilla reinhardti
from 10 localities in Queensland (Australia) and recovered 27 species of
parasites, 15 of them specific to eels: 17 of the species occurred in the
digestive tract, and there were 12 nematode and 8 digenean species.
All fish were infected, although 8% were not infected with intestinal
helminths. At least 55.5% of the parasite species were eel specialists. It is
