184
cells and later their proliferation and differentiation (Quilhac and Sire 1999).
Additionally Rogers-Lowery and Dimock (2006) documented that cells in fish epithelium are in constant motion. It is reasonable, that a combination of these characters might have facilitated quick encapsulation of glochidia once the parasitic
relation was developed. Yet, Rogers-Lowery and Dimock (2006) highlighted that
modern glochidia must additionally stimulate host tissue to form a capsule, because
glochidia of different mussel species and similar morphology are not encapsulated
in the same rate on the same fish species.
5.5.3.3 Suitable Host
The magnitude of fish tissue reactions is amplified in unsuitable or resistant hosts,
compared to naïve suitable hosts, resulting in the shedding the larvae (Waller and
Mitchell 1989; Watters and O’Dee 1996; Dodd et al. 2006). Thus the transformation
success of glochidium depends on if and how often the host suitable fish was
infected before (review by Jansen et al. 2001; Rogers and Dimock 2003; Dodd et al.
2005). Usually smaller (younger) fishes are more heavily infested than larger (Tedla
and Fernando 1969; Hastie and Young 2001), but Rogers and Dimock (2003) found
a positive correlation between the size and the number of attached larvae, during
laboratory infestation experiments (nevertheless smaller fishes were more often
infested by fewer glochidia). Similarly Hastie and Young (2001) described even
greater initial infection load of Margaritifera margaritifera glochidia on older salmonid fish (with larger gill surface areas/greater ventilation rates) but finally young
ones were much more susceptible. The metamorphosis success on older and larger
fish appeared lower than on fish younger and smaller even in the wild (Bauer 1987 in
Strayer 2008). In some cases host infection by one species of mussel may even
result in cross-resistance of fish to the other mussel genera and even subfamilies and
might involve both specific and nonspecific mechanisms, as found by Dodd et al.
(2005). Yet these studies show conflicting results related with the degree of resistance (discussed by Jansen et al. 2001; Strayer 2008). Nevertheless, Dodd et al.
(2006) noticed a progressive loss of immunity to glochidia of Lampsilis reeveiana
in the largemouth bass (Micropterus salmoides) about a half year past developing
the immune response. Little is known about the mechanisms involved in the specificity of the association between mussels and their hosts, however Rogers-Lowery
et al. (2007) identified that fish antibodies recognize glochidial granular structures
located between the larval mantle and shell, together with the mantle cells in relation of bluegill sunfish (Lepomis macrochirus) and Utterbackia imbecillis. Dubansky
et al. (2011) gave insight into a poorly understood physiological mechanism regulating this host-ectoparasite interaction. Cortisol is the main corticosteroid hormone
in vertebrates, influencing a variety of physiological and behavioral actions including stress reactions, during which its concentration in plasma rises (Mommsen et al.
1999; Fürtbauer and Heistermann 2016). Dubansky et al. (2011) showed a wide
range of actions elicited by the cortisol on fish, including its immunosuppressant
properties, enhancing glochidial metamorphosis probably by improving the retention of attached glochidia of U. imbecillis on gills of L. macrochirus. It is also clear
A. Skawina
cells and later their proliferation and differentiation (Quilhac and Sire 1999).
Additionally Rogers-Lowery and Dimock (2006) documented that cells in fish epithelium are in constant motion. It is reasonable, that a combination of these characters might have facilitated quick encapsulation of glochidia once the parasitic
relation was developed. Yet, Rogers-Lowery and Dimock (2006) highlighted that
modern glochidia must additionally stimulate host tissue to form a capsule, because
glochidia of different mussel species and similar morphology are not encapsulated
in the same rate on the same fish species.
5.5.3.3 Suitable Host
The magnitude of fish tissue reactions is amplified in unsuitable or resistant hosts,
compared to naïve suitable hosts, resulting in the shedding the larvae (Waller and
Mitchell 1989; Watters and O’Dee 1996; Dodd et al. 2006). Thus the transformation
success of glochidium depends on if and how often the host suitable fish was
infected before (review by Jansen et al. 2001; Rogers and Dimock 2003; Dodd et al.
2005). Usually smaller (younger) fishes are more heavily infested than larger (Tedla
and Fernando 1969; Hastie and Young 2001), but Rogers and Dimock (2003) found
a positive correlation between the size and the number of attached larvae, during
laboratory infestation experiments (nevertheless smaller fishes were more often
infested by fewer glochidia). Similarly Hastie and Young (2001) described even
greater initial infection load of Margaritifera margaritifera glochidia on older salmonid fish (with larger gill surface areas/greater ventilation rates) but finally young
ones were much more susceptible. The metamorphosis success on older and larger
fish appeared lower than on fish younger and smaller even in the wild (Bauer 1987 in
Strayer 2008). In some cases host infection by one species of mussel may even
result in cross-resistance of fish to the other mussel genera and even subfamilies and
might involve both specific and nonspecific mechanisms, as found by Dodd et al.
(2005). Yet these studies show conflicting results related with the degree of resistance (discussed by Jansen et al. 2001; Strayer 2008). Nevertheless, Dodd et al.
(2006) noticed a progressive loss of immunity to glochidia of Lampsilis reeveiana
in the largemouth bass (Micropterus salmoides) about a half year past developing
the immune response. Little is known about the mechanisms involved in the specificity of the association between mussels and their hosts, however Rogers-Lowery
et al. (2007) identified that fish antibodies recognize glochidial granular structures
located between the larval mantle and shell, together with the mantle cells in relation of bluegill sunfish (Lepomis macrochirus) and Utterbackia imbecillis. Dubansky
et al. (2011) gave insight into a poorly understood physiological mechanism regulating this host-ectoparasite interaction. Cortisol is the main corticosteroid hormone
in vertebrates, influencing a variety of physiological and behavioral actions including stress reactions, during which its concentration in plasma rises (Mommsen et al.
1999; Fürtbauer and Heistermann 2016). Dubansky et al. (2011) showed a wide
range of actions elicited by the cortisol on fish, including its immunosuppressant
properties, enhancing glochidial metamorphosis probably by improving the retention of attached glochidia of U. imbecillis on gills of L. macrochirus. It is also clear
A. Skawina