180
the freshwater fish Dastilbe is commonly found (sometimes with mineralized soft
tissues; Davis and Martill 1999), as well as other freshwater fish (e.g. amiiforms,
semionotiforms; Brito et al. 2008). Bruno and Hessel (2006) list Pseudohyria, in
freshwater layers (however they do not picture it)—a representative of
Trigonioidoidea (Unionida or Trigoniida member, according to Carter et al. 2011).
Recently a possible member of Unionida was also discovered in deposits of this
Formation (da Silva et al. 2020).
5.5.3 Origin and Evolution of Unionoid Parasitism
5.5.3.1 Phoresis
The great advantage of dispersal and upstream transport using the fish might have
been an important selective force during the early evolution of unionoids (e.g. Graf
1997; Watters 2001; Barnhart et al. 2008; Strayer 2008). Although all the extant
members of this order possess both parasitic larvae and the eulamellibranch gills
(Wächtler et al. 2001; Graf and Cummings 2006, Fig. 5.3), one may expect these
characters already existed in their last common ancestor. So probably after the origin of the Unionida but before the Middle Jurassic, when advanced unionoids
already existed (based on their characteristic, double-looped or V/W shaped
[according to Zieritz et al. 2015] umbonal sculpture; Watters 2001; Skawina and
Dzik 2011; Bolotov et al. 2016, Fig. 5.6). The material from the early Late Triassic
(specimen ZPAL AbIII/2210, Fig. 2a in Skawina and Dzik 2011) preserve juvenile
shell morphology which indicates an early postlarval development similar to extant
unionoids, but unfortunately the preservation of the area of larval shell does not
allow discussion about the presence of glochidium (Skawina and Dzik 2011).
According to Malchus and Sartori (2013), the early ontogenetic shells (prodissoconch = glochidia) from fossil unionoids are currently unknown, also because juvenile part of the shell frequently suffers from abrasion (e.g. McMichael 1957;
McMichael and Hiscock 1958).
According to Nagler and Haug (2015), who discussed direct and indirect evidence which allow parasitism to be inferred in the fossil record, among others,
that phylogenetic inference may give some indications. Following this rationale, the
genera of unionoids, which live today, possibly had a parasitic larvae at their origin.
Thus estimations on the basis of molecular clock, or direct fossil evidences of the
origin of Recent genera might cautiously set the minimum time constraints (e.g.
Margaritifera [Margaritiferidae] about 70 Ma; Parreysia [Unionidae]—45 Ma;
Diplodon [Hyriidae] about 130 Ma; Etheria [Etheriidae]—150 Ma; Graf et al. 2015;
Bolotov et al. 2016; Santos-Neto et al. 2016; Bolotov et al. 2017b; Huang et al.
2018). The maximum age assessment could possibly be related to the origin of
Recent families of the crown unionoid group (Table 5.2), as all the glochidia-bearing and lasidia- bearing unionoids were recently confirmed to be reciprocally monophyletic by mitogenomic phylogenetic reconstructions (Guerra et al. 2017; Huang
A. Skawina
the freshwater fish Dastilbe is commonly found (sometimes with mineralized soft
tissues; Davis and Martill 1999), as well as other freshwater fish (e.g. amiiforms,
semionotiforms; Brito et al. 2008). Bruno and Hessel (2006) list Pseudohyria, in
freshwater layers (however they do not picture it)—a representative of
Trigonioidoidea (Unionida or Trigoniida member, according to Carter et al. 2011).
Recently a possible member of Unionida was also discovered in deposits of this
Formation (da Silva et al. 2020).
5.5.3 Origin and Evolution of Unionoid Parasitism
5.5.3.1 Phoresis
The great advantage of dispersal and upstream transport using the fish might have
been an important selective force during the early evolution of unionoids (e.g. Graf
1997; Watters 2001; Barnhart et al. 2008; Strayer 2008). Although all the extant
members of this order possess both parasitic larvae and the eulamellibranch gills
(Wächtler et al. 2001; Graf and Cummings 2006, Fig. 5.3), one may expect these
characters already existed in their last common ancestor. So probably after the origin of the Unionida but before the Middle Jurassic, when advanced unionoids
already existed (based on their characteristic, double-looped or V/W shaped
[according to Zieritz et al. 2015] umbonal sculpture; Watters 2001; Skawina and
Dzik 2011; Bolotov et al. 2016, Fig. 5.6). The material from the early Late Triassic
(specimen ZPAL AbIII/2210, Fig. 2a in Skawina and Dzik 2011) preserve juvenile
shell morphology which indicates an early postlarval development similar to extant
unionoids, but unfortunately the preservation of the area of larval shell does not
allow discussion about the presence of glochidium (Skawina and Dzik 2011).
According to Malchus and Sartori (2013), the early ontogenetic shells (prodissoconch = glochidia) from fossil unionoids are currently unknown, also because juvenile part of the shell frequently suffers from abrasion (e.g. McMichael 1957;
McMichael and Hiscock 1958).
According to Nagler and Haug (2015), who discussed direct and indirect evidence which allow parasitism to be inferred in the fossil record, among others,
that phylogenetic inference may give some indications. Following this rationale, the
genera of unionoids, which live today, possibly had a parasitic larvae at their origin.
Thus estimations on the basis of molecular clock, or direct fossil evidences of the
origin of Recent genera might cautiously set the minimum time constraints (e.g.
Margaritifera [Margaritiferidae] about 70 Ma; Parreysia [Unionidae]—45 Ma;
Diplodon [Hyriidae] about 130 Ma; Etheria [Etheriidae]—150 Ma; Graf et al. 2015;
Bolotov et al. 2016; Santos-Neto et al. 2016; Bolotov et al. 2017b; Huang et al.
2018). The maximum age assessment could possibly be related to the origin of
Recent families of the crown unionoid group (Table 5.2), as all the glochidia-bearing and lasidia- bearing unionoids were recently confirmed to be reciprocally monophyletic by mitogenomic phylogenetic reconstructions (Guerra et al. 2017; Huang
A. Skawina