Freshwater mussel (Bivalvia, Palaeoheterodonta) larvae in natural history collections: an underutilised resource

Natural history collections which store the soft bodies of freshwater mussels can provide information for research and the public in a comparatively simple way that has so far been insufficiently considered. This involves the examination of larval forms, which are often present, unnoticed, in gravid animals. The features of the larvae provide important information about the systematic position of the bivalves and their study in light microscopic or electron microscopic images can illuminate the importance of freshwater mollusc collections. A processing routine and a standard for the presentation of freshwater mussel larvae is proposed. The processing of old samples is challenging, as their condition cannot be predicted, examples of which are discussed. Nevertheless, even samples that are not in optimal condition can provide useful information. In view of the global threat to this group of animals, any additional information is also of great value for applied aspects of species conservation.