Biology Reference
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Figure 5.2. Monogeneans infecting the gills of marine fish may use identical
microhabitats on the gills when they differ in the shape (and/or size) of their copulatory
organs; they are always segregated when they have identical copulatory organs,
suggesting that not interspecific competition but reproductive segregation is the
primary reason for species segregation. The following examples illustrate this: they
show copulatory sclerites of monopisthocotylean monogeneans infecting the gills of
A. Lethrinus miniatus,B.Haliotrema lethrini,C.H. fleti,D.H. chrysostomi,E.Calydiscoides
gussevi,F.Protolamellodiscus sp., G. Calydiscoides difficilis, C. autralis, and of
polyopisthocotytleran monogeneans on the gills of Scomber spp., H. four species with
copulatory organ, and I one with copulatory organ. All species on L.miniatus except for
E inhabit identical or overlapping microhabitats, the four species H on Scomber spp. are
segregated in different microhabitats or hosts, species I overlaps with some of the
others. Arrow points to anterior end. Reprinted from Rohde, Hayward, Heap, and
Gosper (
1994
), with permission of Elsevier.
that interspecific competition has been an important evolutionary force
leading to niche segregation, but that there is much support for the view
that mechanisms leading to reproductive isolation have been important.
Evidence for reinforcement of reproductive barriers as an agent of
niche segregation in parasites was discussed by Rohde and Hobbs
(
1986
) and Rohde (
1989
,
1991
). Rohde and Hobbs (
1986
) compared
niche overlap in 35 parasite species on the gills and in the mouth cavity of
six species of marine fish. Nineteen species occurred in congeneric pairs
or triplets. They found, using a newly proposed asymmetric percent
