Tick in amber

Our fossil tick has three superlatives: It is the only known adult tick in amber, probably the geologically oldest fossil tick at all and finally one of the few fossil records of this group of animals throughout Earth’s history. The tick is embedded in a rectangular piece of amber, about 12 x 11 mm, that is grinded and polished completely. It was collected in Königsberg (its former German name), Kaliningrad in modern usage. It was a part of the allowance of Dr. Weiss, a former professor for physiology, bought by Dr. T. Kruckow for the Überseemuseum in 1955.
This purchase from Kaliningrad is now part of the Geosciences Collection. It was not until 1964 that the importance of this unique specimen was recognised and it has been described scientifically. Recently there are about 800 different species of ticks on Earth, differing from the 50 million year old fossil only in some details. There are records from beds of the same age or somewhat younger in Wyoming, United States, however, these can only doubtfully be assigned to this group of animals in contrast to the Bremen specimen.

Anatomy and comparison with recent animals
The ticks belong to the mites that are grouped with other categories, for example the scorpions, to the arachnids. Herbert Weidner (1964) described the first fully grown mite preserved in amber as Ixodes succineus in a former periodical of the Überseemuseum (Veröffentlichungen aus dem Übersee-Museum in Bremen). This new species is distingushed from recent species only by a few details from modern relatives. Adult ticks have four, the larvae only three pairs of legs. The most conspicuous feature for the identification of modern species of the tick genus Ixodes is the first limb (coxa) of the first pair of legs. The tick in amber is very similar to the recent and widely distributed European Castor Bean Tick, Ixodes ricinus, concerning its appearance and habit. Merely the coxal spines (coxes of the first pair of legs) are broader and differently shaped. The number of similarities in anatomic details makes it likely that the life habits are similar. The mouth anatomy shows adaptions to blood sucking, like that of the European Castor Bean Tick. It surely lived on the blood of small lizards and mammals. Typical habitats of ticks are high grass, woods with widely spaced trees and bushes where they sit on leaves and branches. The larvae a of tick climbs up to a height of 25 cm, the juvenile nymphs up to 50 cm and the adult ticks up to a height of 150 cm. The ticks clamp themselve with their hind legs and wait until a host is passing by. A host can be an animal as well as a human being. The tick needs physical contact to reach its host, sometimes only a fraction of a second. In this short period of time the tick accesses the host by leaving the vegetation and searching for the humid parts of the body. Ticks are transmitters of different pathogens, however, they do not posses poison.

References:

• Lehmann, J. (2007): Fossile Zecke im baltischen Bernstein. – Fossilien 24 : 226-228.
• Weidner, H. (1964): Eine Zecke, Ixodes succineus sp. n., im baltischen Bernstein. – Veröffentlichungen aus dem Übersee-Museum in Bremen 3: 143-151.
• Weitschat, W. (2004): Zecken im Bernsteinwald – wahre Raritäten. – ImpfDialog 4 : 11-12.