315
© The Author(s) 2021
K. De Baets, J. W. Huntley (eds.), The Evolution and Fossil Record of Parasitism,
Topics in Geobiology 49, https://doi.org/10.1007/978-3-030-42484-8_9
Chapter 9
Chelicerates as Parasites
Jason A. Dunlop
Abstract Among Chelicerata, larval instars of sea spiders (Pycnogonida) can be
parasitic. The oldest putative sea spider from the Cambrian ‘Orsten’ is immature
and resembles comparable instars of modern species with a parasitic phase to their
life cycle. All other parasitic chelicerates are mites, with several examples in both
the Acariformes and Parasitiformes clades. Fossils revealing parasitic behaviour, or
belonging to purely parasitic clades, come from various amber sources from the
mid-Cretaceous onwards. From Acariformes there are records of Parasitengona,
Myobiidae, Pterygosomatoidea, Resinacaridae, Acarophenacidae, Pyemotidae and
Apotomelidae. Parasitiformes is represented by several ticks (Ixodida) and potentially Laelapidae from the Mesostigmata. Parasitism appears to have evolved independently within mites on several occasions. Possible transitions to this lifestyle via
nest associations and/or phoresy are discussed. Arachnids as victims of parasites
include amber records of nematode worms (Mermithidae), erythraeid mites
(Erythraeidae), mantid flies (Neuroptera: Mantispidae), ichneumon wasps
(Hymenoptera: Ichneumonidae) and spider flies (Diptera: Acroceridae).
Keywords Chelicerata · Pycnogonida · Arachnida · Acariformes · Parasitiformes ·
Parasitism · Fossil · Amber
9.1 Introduction
Chelicerata are one of the major arthropod clades and encompass the largely terrestrial Arachnida (arachnids), together with their marine relatives Pycnogonida
(sea spiders), Xiphosura (horseshoe crabs), the extinct Eurypterida (sea spiders) and
the little-known extinct group Chasmataspidida. Most living chelicerates are predators and this lifestyle was probably true as well for most of the fossil taxa. The name
Chelicerata refers to the first pair of head appendages, the chelicerae or chelifores,
which are modified into mouthparts. These may be chelate (= pincer-like), as in
J. A. Dunlop ()
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science,
Berlin, Germany
e-mail: Jason.dunlop@mfn.berlin
© The Author(s) 2021
K. De Baets, J. W. Huntley (eds.), The Evolution and Fossil Record of Parasitism,
Topics in Geobiology 49, https://doi.org/10.1007/978-3-030-42484-8_9
Chapter 9
Chelicerates as Parasites
Jason A. Dunlop
Abstract Among Chelicerata, larval instars of sea spiders (Pycnogonida) can be
parasitic. The oldest putative sea spider from the Cambrian ‘Orsten’ is immature
and resembles comparable instars of modern species with a parasitic phase to their
life cycle. All other parasitic chelicerates are mites, with several examples in both
the Acariformes and Parasitiformes clades. Fossils revealing parasitic behaviour, or
belonging to purely parasitic clades, come from various amber sources from the
mid-Cretaceous onwards. From Acariformes there are records of Parasitengona,
Myobiidae, Pterygosomatoidea, Resinacaridae, Acarophenacidae, Pyemotidae and
Apotomelidae. Parasitiformes is represented by several ticks (Ixodida) and potentially Laelapidae from the Mesostigmata. Parasitism appears to have evolved independently within mites on several occasions. Possible transitions to this lifestyle via
nest associations and/or phoresy are discussed. Arachnids as victims of parasites
include amber records of nematode worms (Mermithidae), erythraeid mites
(Erythraeidae), mantid flies (Neuroptera: Mantispidae), ichneumon wasps
(Hymenoptera: Ichneumonidae) and spider flies (Diptera: Acroceridae).
Keywords Chelicerata · Pycnogonida · Arachnida · Acariformes · Parasitiformes ·
Parasitism · Fossil · Amber
9.1 Introduction
Chelicerata are one of the major arthropod clades and encompass the largely terrestrial Arachnida (arachnids), together with their marine relatives Pycnogonida
(sea spiders), Xiphosura (horseshoe crabs), the extinct Eurypterida (sea spiders) and
the little-known extinct group Chasmataspidida. Most living chelicerates are predators and this lifestyle was probably true as well for most of the fossil taxa. The name
Chelicerata refers to the first pair of head appendages, the chelicerae or chelifores,
which are modified into mouthparts. These may be chelate (= pincer-like), as in
J. A. Dunlop ()
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science,
Berlin, Germany
e-mail: Jason.dunlop@mfn.berlin