Scorpions - introduction

The first scorpions were aquatic and descendants of the now extinct giant water scorpions. Soon, scorpions radiated into many families of which only a few survived. Scorpions today are of course descendants of those that survived on land – and one can say that the scorpions today once escaped extinction in the sea.

Currently scorpions inhabit some of the hottest area in the world where they actually constitute a great part of the biomass (Brownell & Polis, 2001). Scorpions are arachnids and distantly related to other arthropods such as crustaceans (lobsters, crabs, crayfish and shrimps) and insects.

Appearance

Scorpions are highly segmented animals with some of the segments having fused into discrete body segments. The most anterior segment (the prosoma, the head section) has six pairs of appendages: the chelicerae, the chelate pedipals, and four pairs of legs. The remaining part of the scorpion can be divided into two sections, the abdomen, which has seven segments and the tail with five segments. The figure below illustrates the division of a scorpion into the prosoma, abdomen and tail section.

The tail sections terminates in the anus and the sting, while the abdomen contains four pair of book lungs, genitals and some appendages. Book lungs evolved from the gills, and book lungs are essentially modified gills. Specifically, book lungs is an organ containing multiple hemolymph (blood in arthropods) filled plates that are surrounded by air. The oxygen is transferred from the air into the hemolymph. The book lungs are connected to the surroundings by a small opening in the scorpions abdomen.

References

Brownell, P & Polis, G. Scorpion Biology and Research, Oxford University Press 2001.

References

Acknowledgements