Testicular structure and sperm production in flounders from a polluted estuary: a preliminary study

Abstract

Discharges of industrial and domestic waste have been linked with the production of vitellogenin and intersex conditions in wild male flounder from industrialized estuaries. The chemicals act as xenoestrogens or hormone mimics causing feminisation in male fish. This initial study follows seasonal changes, between July and March, in testicular development and spermatogenesis in 17 male flounder. The fish were taken from the lower Tyne estuary in northeast England, a heavily impacted site known to contain high levels of endocrine-disrupting chemicals. Abnormal changes in testicular structure were detected using standard histological techniques. Most notable was hypertrophy of connective tissue. A marked synchrony of testicular development was also recorded. Sperm samples were taken from the testis and from milt. The morphology and dimensions of flounder sperm are described for the first time. ‘Normal’ sperm were identified, and a number of abnormalities in head and tail morphology, e.g. ‘big’ heads and ‘fuzzy’ tails, were also recorded. The incidence of abnormalities ranged from 0 to 43.0% for heads and from 0 to 100% for tails. The levels and type of abnormality were the same in sperm taken from the testis and from milt samples. It is suggested that the incidence of sperm and testicular abnormalities on the scale observed will compromise the reproductive success of the flounder and result from the influence of endocrine-disrupting chemicals.