323
major clades which are now usually treated as separate orders: Acariformes (or
Actinotrichida) and Parasitiformes (or Anactinotrichida). The two mite clades differ
from each other in several important characters (summarised by Dunlop and Alberti
2008) thus Acari in its traditional sense may not be monophyletic; see e.g. Pepato
et al. (2010) and Pepato and Klimov (2015), but see also Lozano-Fernandez et al.
(2019) for a recent defence of mite monophyly. A time-calibrated summary of the
major mite groups, also indicating lineages in which parasitism has been recorded
is presented in Fig. 9.3. At least ten major lineages (five acariforms, five parasitiforms) include taxa with parasitic behaviour, although some of these clades appear
to show multiple acquisitions of this lifestyle and there may be at least 21 independent evolutionary shifts to these ecologies (Table 9.1).
9.4.1 Acariform Mites
Acariform mites are the more diverse of the two main clades with more than 42,000
species described so far and presumably many more undiscovered. They can be
broadly divided into two main lineages: Trombidiformes and Sarcoptiformes. The
following survey follows the higher systematics and superfamily classification recognised in the Manual of Acarology (Lindquist et al. 2009); see also Fig. 9.3 and
Table 9.1.
9.4.1.1 Trombidiform Mites
Trombidiform mites are the most diverse assemblage (ca. 25,800 species) and
exhibit a correspondingly diverse range of ecologies; summarised by Krantz (2009).
Two main divisions can be recognised. Sphaerolichida is a small clade of poorlyknown mites which may be fungal feeders and/or predators. None are considered
parasites. Most trombidiforms belong to the Prostigmata, a group which as a whole
can potentially be traced back to the Early Devonian (ca. 407 Ma) based on material
first described by Hirst (1923), although Sidorchuk (2018) cautioned that the precise affinities of these fossils are unclear. Prostigmatids include free-living predators, such as snout mites or rake-legged mites, as well as plant pests such as spider
mites. A number of prostigmatan superfamily lineages are parasitic, or at least contain parasitic species, as summarised below:
1. Halacaroidea within the cohort Eupodides are a group of mites inhabiting
marine or freshwater environments (Bartsch 1989); they should not to be confused with water mites (see below). While most halacaroid mites are believed
to be predators, or to feed on algae, several taxa are known or suspected parasites (e.g. Bartsch 1987) of other aquatic invertebrates. There is no fossil record.
2. Tydeoidea, also in Eupodides, is a diverse assemblage of mites which includes
predatory and omnivorous species. Some members of the tydeoid family
9 Chelicerates as Parasites
major clades which are now usually treated as separate orders: Acariformes (or
Actinotrichida) and Parasitiformes (or Anactinotrichida). The two mite clades differ
from each other in several important characters (summarised by Dunlop and Alberti
2008) thus Acari in its traditional sense may not be monophyletic; see e.g. Pepato
et al. (2010) and Pepato and Klimov (2015), but see also Lozano-Fernandez et al.
(2019) for a recent defence of mite monophyly. A time-calibrated summary of the
major mite groups, also indicating lineages in which parasitism has been recorded
is presented in Fig. 9.3. At least ten major lineages (five acariforms, five parasitiforms) include taxa with parasitic behaviour, although some of these clades appear
to show multiple acquisitions of this lifestyle and there may be at least 21 independent evolutionary shifts to these ecologies (Table 9.1).
9.4.1 Acariform Mites
Acariform mites are the more diverse of the two main clades with more than 42,000
species described so far and presumably many more undiscovered. They can be
broadly divided into two main lineages: Trombidiformes and Sarcoptiformes. The
following survey follows the higher systematics and superfamily classification recognised in the Manual of Acarology (Lindquist et al. 2009); see also Fig. 9.3 and
Table 9.1.
9.4.1.1 Trombidiform Mites
Trombidiform mites are the most diverse assemblage (ca. 25,800 species) and
exhibit a correspondingly diverse range of ecologies; summarised by Krantz (2009).
Two main divisions can be recognised. Sphaerolichida is a small clade of poorlyknown mites which may be fungal feeders and/or predators. None are considered
parasites. Most trombidiforms belong to the Prostigmata, a group which as a whole
can potentially be traced back to the Early Devonian (ca. 407 Ma) based on material
first described by Hirst (1923), although Sidorchuk (2018) cautioned that the precise affinities of these fossils are unclear. Prostigmatids include free-living predators, such as snout mites or rake-legged mites, as well as plant pests such as spider
mites. A number of prostigmatan superfamily lineages are parasitic, or at least contain parasitic species, as summarised below:
1. Halacaroidea within the cohort Eupodides are a group of mites inhabiting
marine or freshwater environments (Bartsch 1989); they should not to be confused with water mites (see below). While most halacaroid mites are believed
to be predators, or to feed on algae, several taxa are known or suspected parasites (e.g. Bartsch 1987) of other aquatic invertebrates. There is no fossil record.
2. Tydeoidea, also in Eupodides, is a diverse assemblage of mites which includes
predatory and omnivorous species. Some members of the tydeoid family
9 Chelicerates as Parasites