168
between 60–400 μm in diameter (Wächtler et al. 2001; Pimpão et al. 2012). Pfeiffer
and Graf (2015) listed five primary types of glochidia: unhooked; hooked with basal
spines; S-shaped hooked; axe-head shaped; and bilaterally asymmetrical, while
Wächtler et al. (2001) described them as “triangular, spherical or hatch-shaped”.
Hooked glochidia are usually larger and easily attach to both the gills and the skin
(or fins; Davis and Fuller 1981) of a broad spectrum of fish, for a shorter time, while
hookless glochidia are usually small and found on the gills of the host fish, where
they encapsulate for a longer period of time (Bauer 1994, 2001b; Jansen et al. 2001;
Barnhart et al. 2008). The valves of a glochidium are closed due to contraction of a
single larval adductor (Lefevre and Curtis 1910b). On the soft body of a glochidium, sensory tufts/hairs are present (possible chemo and mechanoreceptors) and
ciliary fields (possibly for respiration). Cells of larval mantle have microvilli, which
are believed to gather nutrition from the host tissue after encapsulation (Nezlin et al.
1994; Wächtler et al. 2001).
Lasidium, the second type of larvae, is found in Mycetopodidae, Iridinidae and
Etheriidae (Bogan and Hoeh 2000; Wächtler et al. 2001; Graf and Cummings 2006;
Fig. 5.3). According to Wächtler et al. (2001), a lasidium is characterized by the lack
of a calcified shell. Their size is about 85–330 μm in diameter (Fryer 1961; Wächtler
et al. 2001; Graf and Cummings 2006). They attach to the host by anterior ciliated
lobes and posterior adhesive structures, with hooks and sensory hairs (Fryer 1961;
Wächtler et al. 2001; Barnhart et al. 2008; Silva-Souza et al. 2011). In most cases
it forms a cyst in the fish epithelium. Depending on the species, it may parasitize a
variety of fish or have a narrow host spectrum. The lasidium of Mutela however is not
Fig. 5.4 Hooked glochidium morphology
A. Skawina
between 60–400 μm in diameter (Wächtler et al. 2001; Pimpão et al. 2012). Pfeiffer
and Graf (2015) listed five primary types of glochidia: unhooked; hooked with basal
spines; S-shaped hooked; axe-head shaped; and bilaterally asymmetrical, while
Wächtler et al. (2001) described them as “triangular, spherical or hatch-shaped”.
Hooked glochidia are usually larger and easily attach to both the gills and the skin
(or fins; Davis and Fuller 1981) of a broad spectrum of fish, for a shorter time, while
hookless glochidia are usually small and found on the gills of the host fish, where
they encapsulate for a longer period of time (Bauer 1994, 2001b; Jansen et al. 2001;
Barnhart et al. 2008). The valves of a glochidium are closed due to contraction of a
single larval adductor (Lefevre and Curtis 1910b). On the soft body of a glochidium, sensory tufts/hairs are present (possible chemo and mechanoreceptors) and
ciliary fields (possibly for respiration). Cells of larval mantle have microvilli, which
are believed to gather nutrition from the host tissue after encapsulation (Nezlin et al.
1994; Wächtler et al. 2001).
Lasidium, the second type of larvae, is found in Mycetopodidae, Iridinidae and
Etheriidae (Bogan and Hoeh 2000; Wächtler et al. 2001; Graf and Cummings 2006;
Fig. 5.3). According to Wächtler et al. (2001), a lasidium is characterized by the lack
of a calcified shell. Their size is about 85–330 μm in diameter (Fryer 1961; Wächtler
et al. 2001; Graf and Cummings 2006). They attach to the host by anterior ciliated
lobes and posterior adhesive structures, with hooks and sensory hairs (Fryer 1961;
Wächtler et al. 2001; Barnhart et al. 2008; Silva-Souza et al. 2011). In most cases
it forms a cyst in the fish epithelium. Depending on the species, it may parasitize a
variety of fish or have a narrow host spectrum. The lasidium of Mutela however is not
Fig. 5.4 Hooked glochidium morphology
A. Skawina