between their hosts (salmon) (Hullet al., 1998), which may explain the
involvement of long-range chemical stimuli. But, overall, little is known
about the role of chemoreception in mating sea lice (Hullet al., 1998).The Morphological Basis of Mating and Microhabitat Finding
(Copulatory Organs and Sensory Receptors)
Many Monogenea, a group for which niche restriction and segregation
have been particularly well studied, have an amazing variety of complex
male (and sometimes female) copulatory organs (some examples in Fig.
9.6). This alone points to the importance of mating, even in hermaphro-
ditic species. In this group, numerous electron-microscopic studies have
been made, which have shown the presence of several types of sensory
receptors (Figs 9.3–9.5) possibly involved in mating, as well as perhaps in
feeding and microhabitat finding. However, the functions of the receptors
are not known. Comparison of Figs 9.4 and 9.5 shows certain similarities
in the receptors of two monogenean species infecting the gills of different
fish species and belonging to different families (Microcotylidae and180 K. Rohde
Fig. 9.3. Diagram of sagittal section through anterior end ofPricea multae(a) and of ‘taste
organ’ (b). br, brain; bs, buccal sucker; cs, copulatory spicules; int, intestine; me, metraterm;
ph, pharynx; pp, prepharynx; sv, seminal vesicle; to, taste organ; vs, vaginal spine. (From
Rohde and Watson, 1996.)