351
10.2.2 Phylogenetic Inference of Appearance and Molecular
Estimations of Early Evolution
Cyamida has been interpreted as the sistergroup to the group of raptorial skeleton
shrimps, Caprellida, ambush predators with large sub-chelate grasping appendages;
alternatively, Cyamida could represent an ingroup of Caprellida (e.g., Ito et al. 2011
and references therein). The latter scenario would indicate that cyamidans evolved
from a caprellidan-like ancestor. Cyamidans might have evolved rather recently, in
dependence on the relatively young geological age of their exclusive hosts (c.
50 mya; e.g., Thewissen and Williams 2002). There are currently no molecular estimations available on the evolution of cyamidans or hyperiidans, but the origin of
Amphipoda lies presumably at least in the Triassic (Copilaş-Ciocianu et al. 2019).
10.2.3 Fossil Representatives
The oldest unequivocal amphipodan fossils are known from Baltic amber (c.
50 mya; e.g., Jażdżewski and Kupryjanowicz 2010; a putative older fossil amphipodan from the Triassic described by McMenamin et al. 2013 has been re-interpreted
as a remain of a decapodan crustacean by Starr et al. 2016). Concerning the oldest
occurrence of other peracaridan ingroups, e.g., Tanaidacea, Amphipoda are likely to
be much older, probably late Palaeozoic (see Vonk and Schram 2007, their Fig. 5).
However, all fossil amphipodans found to date are gammarideans. No fossil hyperiidans or cyamidans have been identified yet, despite the relatively large size of
cyamidans compared to many other parasites, or supposed parasites, reaching into
the centimetre range.
10.3 Isopoda
10.3.1 General Aspects
Isopoda is, like Amphipoda, a group of peracaridan crustaceans, best known by
their terrestrial representatives, the wood lice. Yet, isopods have evolved very different lifestyles and morphologies and show a very wide geographical distribution
(Wägele 1989; Brandt 1992; Dreyer and Wägele 2001; Poore and Bruce 2012).
Cymothoida sensu Wägele (1989) is the only isopodan ingroup with parasitic
representatives and includes various different groups that evolved different strategies. These strategies range from scavengers, predators, “micropredators” (in fact
temporary parasites; see also Robin 2021; Robin et al. 2019 and references therein)
to obligate, permanently attached parasites completely relying on their hosts
10 Evolutionary History of Crustaceans as Parasites
10.2.2 Phylogenetic Inference of Appearance and Molecular
Estimations of Early Evolution
Cyamida has been interpreted as the sistergroup to the group of raptorial skeleton
shrimps, Caprellida, ambush predators with large sub-chelate grasping appendages;
alternatively, Cyamida could represent an ingroup of Caprellida (e.g., Ito et al. 2011
and references therein). The latter scenario would indicate that cyamidans evolved
from a caprellidan-like ancestor. Cyamidans might have evolved rather recently, in
dependence on the relatively young geological age of their exclusive hosts (c.
50 mya; e.g., Thewissen and Williams 2002). There are currently no molecular estimations available on the evolution of cyamidans or hyperiidans, but the origin of
Amphipoda lies presumably at least in the Triassic (Copilaş-Ciocianu et al. 2019).
10.2.3 Fossil Representatives
The oldest unequivocal amphipodan fossils are known from Baltic amber (c.
50 mya; e.g., Jażdżewski and Kupryjanowicz 2010; a putative older fossil amphipodan from the Triassic described by McMenamin et al. 2013 has been re-interpreted
as a remain of a decapodan crustacean by Starr et al. 2016). Concerning the oldest
occurrence of other peracaridan ingroups, e.g., Tanaidacea, Amphipoda are likely to
be much older, probably late Palaeozoic (see Vonk and Schram 2007, their Fig. 5).
However, all fossil amphipodans found to date are gammarideans. No fossil hyperiidans or cyamidans have been identified yet, despite the relatively large size of
cyamidans compared to many other parasites, or supposed parasites, reaching into
the centimetre range.
10.3 Isopoda
10.3.1 General Aspects
Isopoda is, like Amphipoda, a group of peracaridan crustaceans, best known by
their terrestrial representatives, the wood lice. Yet, isopods have evolved very different lifestyles and morphologies and show a very wide geographical distribution
(Wägele 1989; Brandt 1992; Dreyer and Wägele 2001; Poore and Bruce 2012).
Cymothoida sensu Wägele (1989) is the only isopodan ingroup with parasitic
representatives and includes various different groups that evolved different strategies. These strategies range from scavengers, predators, “micropredators” (in fact
temporary parasites; see also Robin 2021; Robin et al. 2019 and references therein)
to obligate, permanently attached parasites completely relying on their hosts
10 Evolutionary History of Crustaceans as Parasites