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Modern crustaceans are extremely diverse, not only in their morphologies, but also in their life styles. It is therefore not surprising that parasitism evolved in various lineages of Eucrustacea independently, in groups such as amphipodan, isopodan and copepodan crustaceans, but also barnacles and fish lice. Parasitic crustaceans have become specialized to many different host species and show a wide variety of attachment and feeding specializations. Among the parasitic crustaceans, different groups are especially interesting to study for reconstructing the evolution of parasitism within this group. This chapter summarizes the modern aspects, evolutionary history and fossil record of parasitic crustacean groups. By reviewing the parasitic crustaceans with emphasis on their fossil record, this chapter aims to improve our understanding of parasitism in general.

Holometabolous insects represent a mega-diverse group of organisms that are dominant in most terrestrial faunas. All holometabolous insects develop via a specific transitory stage between the last larval stage and the adult, called the pupa. While insects in general have a comparably good fossil record, fossils of pupae of holometabolous insects are relatively rare. We report here four pupal specimens preserved in a single piece of amber. These represent pupa stages of assassin flies, Asilidae, and are most likely representatives of Laphriinae. While dipterans are quite common in the fossil record, especially in amber, representatives of Asilidae are comparably rare. Combining the rarity of the systematic group and the rarity of the specific life stage, these fossil remains of assassin fly pupae are extremely unusual;to date only a single specimen has been depicted in the literature. We discuss the importance of our new finding and possible interpretations regarding behavioural aspects of the group enclosed in amber.

In this study we describe a unique fossil comprising 13 intact specimens of a pedunculate cirripede attached to a sponge (Codites serpentinus). The fossil comes from the Upper Jurassic lithographic limestones of southern Germany. Based on the shape and distinctive sculpture of the plates, a new genus and species Litholepas klausreschi gen. et sp. nov. (Eolepadidae: Neolepadinae) is introduced. Although lateral plates are indistinct and the rostrum is unknown, plate disposition and strong external sculpture indicate a position within Neolepadinae tough the exact relationships are still uncertain. Representatives of L.klausreschi gen. et sp. nov. are considered to have lived either in a parasitic or commensal relationship partially buried within the sponge.

Parasites are found in all habitats and within all groups of animals, and their influence on food webs, ecosystems and evolutionary development is significant. However, the fossil record of direct parasitism is very scarce. We present here probable examples of parasitic isopods on fishes from the Upper Jurassic Solnhofen Lithographic Limestones (150 million years old, southern Germany). Individual fishes appear to be infested with one to three isopods each. All specimens were documented with up-to-date imaging methods (macrophotography, stereo-photography, composite imaging). Position, orientation and other aspects clearly indicate that the isopods were already attached to the fishes before they died and hence do not represent scavengers but (more or less permanently) attached parasites. While the morphology of the specimens is somewhat uninformative about the systematic position of the isopods, their specific type of parasitism is an indicator for a position in the early lineage towards Cymothoidae. This would represent the first fossil record of this group of obligate fish parasites.

Rhizocephala, a group of parasitic castrators of other crustaceans, shows remarkable morphological adaptations to their lifestyle. The adult female parasite consists of a body that can be differentiated into two distinct regions: a sac-like structure containing the reproductive organs (the externa), and a trophic, root like system situated inside the hosts body (the interna). Parasitism results in the castration of their hosts, achieved by absorbing the entire reproductive energy of the host. Thus, the ratio of the host and parasite sizes is crucial for the understanding of the parasite’s energetic cost. Using advanced imaging methods (micro-CT in conjunction with 3D modeling), we measured the volume of parasitic structures (externa, interna, egg mass, egg number, visceral mass) and the volume of the entire host. Our results show positive correlations between the volume of (1) entire rhizocephalan (externa + interna) and host body, (2) rhizocephalan externa and host body, (3) rhizocephalan visceral mass and rhizocephalan body, (4) egg mass and rhizocephalan externa, (5) rhizocephalan egg mass and their egg number. Comparing the rhizocephalan Sylon hippolytes, a parasite of caridean shrimps, and representatives of Peltogaster, parasites of hermit crabs, we could match their different traits on a reconstructed relationship. With this study we add new and significant information to our global understanding of the evolution of parasitic castrators, of interactions between a parasitic castrator and its host and of different parasitic strategies within parasitic castrators exemplified by rhizocephalans. publishedVersion

The larval phase of metazoans can be interpreted as a discrete post-embryonic period. Larvae have been usually considered to be small, yet some metazoans possess unusually large larvae, or giant larvae. Here, we report a possible case of such a giant larva from the Upper Jurassic Solnhofen Lithographic limestones (150 million years old, southern Germany), most likely representing an immature cirripede crustacean (barnacles and their relatives). The single specimen was documented with up-to-date imaging methods (macro-photography, stereo-photography, fluorescence photography, composite imaging) and compared with modern cirripede larvae. The identification is based on two conspicuous spine-like extensions in the anterior region of the specimen strongly resembling the so-called fronto-lateral horns, structures exclusively known from cirripede nauplius larvae. Notably, at 5 mm in length the specimen is unusually large for a cirripede nauplius. We therefore consider it to be a giant larva and discuss possible ecological and physiological mechanisms leading to the appearance of giant larvae in other lineages. Further findings of fossil larvae and especially nauplii might give new insights into larval evolution and plankton composition in the past.

During an ostracod sampling campaign in the city of Munich (Germany) samples were taken from containers in a greenhouse of the Munich Botanical Garden. Beside the ubiquitous speciesCypridopsis vidua(O. F. Müller, 1776), the samples contained four alien species, i.e.,Chlamydotheca arcuata(Sars, 1901),Strandesia bicuspis(Claus, 1892),Tanycypris centaChang, Lee & Smith, 2012, andTanycypris alfonsiNagler, Geist & Matzke-Karasz, 2014. While sorting the livingTanycyprisspecimens, a yet undescribed usage of the caudal rami was observed. Freshwater ostracods usually move on or in the sediment by using their first and second antennae, walking legs and — if not reduced — their caudal rami. During (non-swimming) locomotion of most freshwater ostracods with well-developed caudal rami, they help pushing the body forward by being used as a lever. This movement can be fast, but has never been reported to include sudden jumps. In contrast, both investigatedTanycyprisspecies show an extraordinarily fast movement, especially when disturbed. Recordings with a high-speed camera were made, shooting horizontally into a 1.5-mm-thick micro-aquarium. The fast movement could be identified as a powerful jump, much resembling the movement of a catapult, propelled by a very rapid repulsion of the caudal rami from the ground. Although sized only around 1 mm, the observed specimens reached top speeds of up to 0.75 ms−1. Anatomically, this speed is obtained by the exceptional length of the caudal rami inTanycypris, combined with a well-developed musculature, which stretches from a broadened posterior end of soft body along the so-called ‘caudal rami attachment’. The jump itself resembles that of springtails or fleas, where the jump is powered by the energy previously stored in an elastic proteinaceous material; however, inTanycyprisno such mechanism could be detected and thus the energy for the catapult-like jump must be considered muscular, possibly aided by tendon-like structures and/or a mechanism involving a muscular pre-tension by a click-joint as recorded for Squillids.

Fossil parasites represent rarities. In many cases, only trace fossils are preserved while body fossils are often lacking. We report here the first find of larval stages of parasitic isopods, identified as cryptoniscus larvae, from Chiapas Amber, Mexico (Lower Miocene). Different crustacean groups, including free-living isopods, have already been reported from the estuarine fauna presented in this type of amber. The seven specimens described here are interpreted as cryptoniscus larvae due to the following characters: 1) The general body organisation in combination with the appendage morphology. 2) A body length between 450 mu m and 695 mu m, which is known from larval stages of Bopyroidea and Cryptoniscoidea (Epicaridea). 3) The morphology of the uropods and the elongated and thin dactyli of the posterior thoracopods (pereiopods) are very similar to the condition in extant cryptoniscus larvae. Although parasitic behaviour can only rarely be directly identified in the fossil record, we can here clearly identify a specialised life stage, the cryptoniscus, which occurs only in a specific monophyletic group, of which all extant representatives are parasitic. These fossils not only represent rare cases of fossil parasites but also the first case of fossil peracarid larvae and the first body fossils of epicarid isopods.

Within Metazoa, it has been proposed that as many as two-thirds of all species are parasitic. This propensity towards parasitism is also reflected within insects, where several lineages independently evolved a parasitic lifestyle. Parasitic behaviour ranges from parasitic habits in the strict sense, but also includes parasitoid, phoretic or kleptoparasitic behaviour. Numerous insects are also the host for other parasitic insects or metazoans. Insects can also serve as vectors for numerous metazoan, protistan, bacterial and viral diseases. The fossil record can report this behaviour with direct (parasite associated with its host) or indirect evidence (insect with parasitic larva, isolated parasitic insect, pathological changes of host). The high abundance of parasitism in the fossil record of insects can reveal important aspects of parasitic lifestyles in various evolutionary lineages. For a comprehensive view on fossil parasitic insects, we discuss here different aspects, including phylogenetic systematics, functional morphology and a direct comparison of fossil and extant species.

Within Metazoa, it has been proposed that as many as two-thirds of all species are parasitic. This propensity towards parasitism is also reflected within insects, where several lineages independently evolved a parasitic lifestyle. Parasitic behaviour ranges from parasitic habits in the strict sense, but also includes parasitoid, phoretic or kleptoparasitic behaviour. Numerous insects are also the host for other parasitic insects or metazoans. Insects can also serve as vectors for numerous metazoan, protistan, bacterial and viral diseases. The fossil record can report this behaviour with direct (parasite associated with its host) or indirect evidence (insect with parasitic larva, isolated parasitic insect, pathological changes of host). The high abundance of parasitism in the fossil record of insects can reveal important aspects of parasitic lifestyles in various evolutionary lineages. For a comprehensive view on fossil parasitic insects, we discuss here different aspects, including phylogenetic systematics, functional morphology and a direct comparison of fossil and extant species.

Specimens of a new species of the non-marine ostracod genus, Tanycypris Triebel, 1959 were found in samples from water plant containers, displayed in a greenhouse of the botanical garden in Munich, Germany. Beside the ubiquitous species Cypridopsis vidua O.F. Müller, 1776, the samples contained four alien species of the subfamily Cypricercinae, namely Chlamydotheca arcuata Sars, 1901, Strandesia bicuspis Claus, 1892, Tanycypris centa Chang et al., 2012, and Tanycypris alfonsi n. sp.. The genus Tanycypris has mainly been reported (native) from Asia, and (invasive) from Italian rice fields. The Cypricercinae unite all species possessing a Triebel loop, a character of the caudal rami attachment. The subfamily is split into the tribes Cypricercini McKenzie, 1971, Bradleystrandesiini SavatenalintonMartens, 2009 and Nealecypridini SavatenalintonMartens, 2009, the latter of which comprises the genera Tanycypris Triebel, 1959, Astenocypris G.W. Müller, 1912, Diaphanocypris WürdigPinto, 1990 and Nealecypris SavatenalintonMartens, 2009. During the process of describing the new species, a number of taxonomic uncertainties were detected within the genus Tanycypris, leading to a revision of the nine species currently ascribed to it: Tanycypris camaguinensis (Tressler, 1937), Tanycypris centa Chang et al., 2012 Tanycypris clavigera (G.W. Müller, 1898) (now: Nealecypris clavigera nov. comb.), Tanycypris madagascarensis (G.W. Müller, 1898), Tanycypris marina (Hartmann, 1965) (now: Dolerocypris marina nov. comb.), Tanycypris pedroensis (Tressler, 1950) (now: Diaphanocypris pedroensis nov. comb.), Tanycypris pellucida (Klie, 1932), Tanycypris siamensis SavatenalintonMartens, 2009a, and Tanycypris telavivensis (Krampner, 1928) (now: Herpetocypris telavivensis). An identification key has been developed to the species of the genus Tanycypris.