Genotype data not consistent with clonal transmission of sea turtle fibropapillomatosis or goldfish schwannoma

Abstract

Recent discoveries of transmissible cancers in multiple bivalve species suggest that direct transmission of cancer cells within species may be more common than previously thought, particularly in aquatic environments. Fibropapillomatosis occurs with high prevalence in green sea turtles ( Chelonia mydas) and the geographic range of disease has increased since fibropapillomatosis was first reported in this species. Widespread incidence of schwannomas, benign tumours of Schwann cell origin, reported in aquarium-bred goldfish (Carassius auratus), suggest an infectious aetiology. We investigated the hypothesis that cancers in these species arise by clonal transmission of cancer cells. Through analysis of polymorphic microsatellite alleles, we demonstrate concordance of host and tumour genotypes in diseased animals. These results imply that the tumours examined arose from independent oncogenic transformation of host tissue and were not clonally transmitted. Further, failure to experimentally transmit goldfish schwannoma via water exposure or inoculation suggest that this disease is unlikely to have an infectious aetiology.

Keywords: fibropapillomatosis; goldfish schwannoma; sea turtle fibropapillomatosis; transmissible cancer; wildlife cancer.

Figure 1.. Gross appearance of sea turtle fibropapillomatosis and goldfish schwannoma.

( A) Gross appearance of sea turtle fibropapillomatosis (FP) in C. mydas individuals collected for this study at the Whitney Sea Turtle Hospital, University of Florida. Upper panel, Patient 1 (GT1): dorsal image (left) and established tumour on left rear flipper (right). Lower panel, Patient 3 (GT3) showing multiple established lesions around ventral tail, inguinal regions, plastron, axillary regions, neck and front flippers (left), and Patient 4 (GT4) showing new-growth tumours on the inguinal regions (right). ( B) Left, gross appearance of goldfish schwannoma in an individual collected for this study. Tail fin tumour indicated with an arrow. Right, representative tumour histology from a haematoxylin and eosin stained section. Nuclear palisading, which is diagnostic for goldfish schwannoma can be observed (arrows) (right).