169
cyst-forming, but transforms into a subsequent larva stage, rooted in its host tissues
(commonly fins of a cyprinid Barbus altanialis radcliffi) by a fork-like, long (up to
3 mm), nutrient transmitting stalk, a haustorium (Fryer 1959, 1961; Wächtler
et al. 2001).
5.3 Life History, with the Review of the Adaptations
to Attracting the Host
5.3.1 Life History
Unionoid bivalves live in lakes and rivers on all the continents, except Antarctica
(Graf and Cummings 2007; Bogan 2008; Bogan and Roe 2008; Bolotov et al. 2016;
Lopes-Lima et al. 2017). Their lack on this continent is believed as a result of climate limitation (Pugh and Scott 2002), possibly together with host limitation (no
freshwater fish fauna lives in Antarctic freshwater today; Eastman 1993).
Additionally, although most Antarctic lakes are today inhabited by various invertebrates (tardigrades, rotifers, crustaceans; McInnes and Pugh 1998; Pugh and
McInnes 1998; Boxshall and Defaye 2008; Segers 2008), no freshwater mollusk is
currently known from Antarctica (Pugh and Scott 2002). Antarctica has been an
isolated glaciated continent for about the last 34–36 million years (DeConto and
Pollard 2003; Carter et al. 2017), previously it was a part of Gondwana (together
with Africa, Australia and South America), and before that—up to Middle Mesozoic
it was a part of Pangea with all the rest of the continents (e.g. Eastman 1993; Jokat
et al. 2003; Eagles and König 2008; Seton et al. 2012). Before isolation and glaciation freshwater habitats were well developed there, with numerous groups of freshwater fish (the possible hosts) that are preserved as fossils there today (Eastman
1993). However no unionoid fossil has so far been published from Antarctic freshwater fossil sites (to my best knowledge the only published freshwater bivalve fossils are Pliocene sphaeriids; Ashworth and Preece 2003). Even though one may
suppose there is no reason for their absence in Antarctic freshwaters since the middle Mesozoic, until glaciation (Thompson and Stilwell 2010; Graf et al. 2015; Van
Damme et al. 2015).
Unionoids are large (commonly over a dozen cm) and long lived (tens to a hundred years; Bauer 1992, 2001b; Mutvei and Westermark 2001). Juveniles spend the
first years of their life completely burrowed within aerated sediments, feeding on
particles present in interstitial water, until they emerge to the sediment surface at the
size of about 1 cm to live as semi-infaunal burrowing filter feeders (Yeager et al.
1994; Gatenby et al. 1997; Bauer 2001b; Jansen et al. 2001; Reis and Araujo 2016;
Araujo et al. 2018). After they mature (after several years), they were observed to
group for spawning (Amyot and Downing 1998) and males release the spermatozoa
to the water (Fig. 5.5).
5 Evolutionary History of Bivalves as Parasites
cyst-forming, but transforms into a subsequent larva stage, rooted in its host tissues
(commonly fins of a cyprinid Barbus altanialis radcliffi) by a fork-like, long (up to
3 mm), nutrient transmitting stalk, a haustorium (Fryer 1959, 1961; Wächtler
et al. 2001).
5.3 Life History, with the Review of the Adaptations
to Attracting the Host
5.3.1 Life History
Unionoid bivalves live in lakes and rivers on all the continents, except Antarctica
(Graf and Cummings 2007; Bogan 2008; Bogan and Roe 2008; Bolotov et al. 2016;
Lopes-Lima et al. 2017). Their lack on this continent is believed as a result of climate limitation (Pugh and Scott 2002), possibly together with host limitation (no
freshwater fish fauna lives in Antarctic freshwater today; Eastman 1993).
Additionally, although most Antarctic lakes are today inhabited by various invertebrates (tardigrades, rotifers, crustaceans; McInnes and Pugh 1998; Pugh and
McInnes 1998; Boxshall and Defaye 2008; Segers 2008), no freshwater mollusk is
currently known from Antarctica (Pugh and Scott 2002). Antarctica has been an
isolated glaciated continent for about the last 34–36 million years (DeConto and
Pollard 2003; Carter et al. 2017), previously it was a part of Gondwana (together
with Africa, Australia and South America), and before that—up to Middle Mesozoic
it was a part of Pangea with all the rest of the continents (e.g. Eastman 1993; Jokat
et al. 2003; Eagles and König 2008; Seton et al. 2012). Before isolation and glaciation freshwater habitats were well developed there, with numerous groups of freshwater fish (the possible hosts) that are preserved as fossils there today (Eastman
1993). However no unionoid fossil has so far been published from Antarctic freshwater fossil sites (to my best knowledge the only published freshwater bivalve fossils are Pliocene sphaeriids; Ashworth and Preece 2003). Even though one may
suppose there is no reason for their absence in Antarctic freshwaters since the middle Mesozoic, until glaciation (Thompson and Stilwell 2010; Graf et al. 2015; Van
Damme et al. 2015).
Unionoids are large (commonly over a dozen cm) and long lived (tens to a hundred years; Bauer 1992, 2001b; Mutvei and Westermark 2001). Juveniles spend the
first years of their life completely burrowed within aerated sediments, feeding on
particles present in interstitial water, until they emerge to the sediment surface at the
size of about 1 cm to live as semi-infaunal burrowing filter feeders (Yeager et al.
1994; Gatenby et al. 1997; Bauer 2001b; Jansen et al. 2001; Reis and Araujo 2016;
Araujo et al. 2018). After they mature (after several years), they were observed to
group for spawning (Amyot and Downing 1998) and males release the spermatozoa
to the water (Fig. 5.5).
5 Evolutionary History of Bivalves as Parasites