Effects on the sexual maturation of the sediment-living amphipod Monoporeia affinis

The objective was to investigate whether sediment-living amphipods, i.e., M onoporeia affinis, were affected by endocrine disrupters in the same way as perch (Perca fluviatilis) and pike (Esox lucius) were observed to be affec ted in an earlier study. Surface sediments were collected at a reference si te in Lake Malaren (Station 1), in a remote lake contaminated with an unide ntified leakage water from a refuse dump (Station 2). The latter was compar ed to a sediment contaminated with heavy metals and PHOCs (polycyclic aroma tic hydrocarbons and polychlorobiphenyls) from a sampling site located in t he urban area of the city of Stockholm (Station 3). Amphipods were exposed to the contaminated sediments in soft-bottom microcosms in the laboratory d uring the periods for sexual maturation, mating, and embryogenesis. Three s amplings were included; one at the start of the experiment, another after o ne month (to examine effects on gonad maturation), and a third after 3 mont hs to investigate effects on fertilization success and embryogenesis. No ef fects were observed on organisms exposed to sediments from Station 1 and St ation 3, while effects on sexual maturation on females and males of M, affi nis were detected in sediment from Station 2. Females were more seriously a ffected. Nearly 50% of the females showed a delayed sexual development and 28% of these were immature, showing that the sexual maturation was interrup ted due to contaminants in the sediment. In addition to the interrupted sex ual maturation, other reproduction variables such as fertilization success and fecundity, were insignificantly (p = 0.383) lower in Station 2 sediment and thus enforce the possibility of endocrine effect. Similar effects were observed on males in terms of a delayed sexual maturation and a lower numb er of secondary sexual characteristics, i.e., antennule segments, and chemi cal sensory organs, i.e., aesthetascs. Since effects were recorded on proce sses before mating we suggest that the contaminant(s) in the leakage water act as an endocrine disrupter by inhibiting the release of neural hormones controlling the normal sexual maturation in both female and male amphipods. (C) 2000 by John Wiley & Sons, Inc.