FOSSIL AND EXTANT PARASITIC ARTHROPODS AND HOW THEY ENLIGHTEN EACH OTHER

Parasites are ubiquitous abundant in all ecosystems and in all groups of life. They influence food webs and are ecologically and evolutionary significant, as parasitism drives co-evolution of host and parasite. Parasitism is also found within arthropods (insects, crustaceans, spiders and alike) where several lineages independently evolved a parasitic lifestyle.

The fossil record can report such parasitic behavior in extinct forms, for example by:

1) direct indications (parasite associated with its host); 2) indirect phylogenetic indications (ingroup of extant parasite group); 3) indirect functional morphological indication (isolated parasite) or 4) indirect pathological changes (of the host).

Unfortunately, often parasitic arthropods would not be recognized due to their size or may be removed during the preparation process, often because they were not recognized as parasites. Yet, in deposits with exceptional preservation, particularly Mesozoic limestones and Eocene amber, a wide diversity of parasitic arthropods occurs.

For a comprehensive view, we combine several methods, including phylogenetic systematics, functional morphology, and a direct comparison of fossil and extant species together with up-to-date imaging methods. In this way, we are able to answer questions on aspects of functional morphology, ecology, environmental impact, evolution, radiations and extinctions, as well as changes of their lifestyle from free living to parasites or vectors.

We will present examples, e.g. of our recent studies on fossil and extant parasitic isopods, which nowadays represent an important factor in fisheries and aquaculture.

We show the first direct evidence for parasitism of fossil isopods on fishes supporting their minimum age of 150 million years. We reconstructed the functional morphology of the modern counterparts, with appendages strongly modified for parasitism and mouth parts showing strong modifications to facilitate sucking.