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

Abstract

The objective was to investigate whether sediment-living amphipods, i.e., Monoporeia affinis, were affected by endocrine disrupters in the same way as perch (Perca fluviatilis) and pike (Esox lucius) were observed to be affected in an earlier study. Surface sediments were collected at a reference site in Lake Mälaren (Station 1), in a remote lake contaminated with an unidentified leakage water from a refuse dump (Station 2). The latter was compared to a sediment contaminated with heavy metals and PHOCs (polycyclic aromatic hydrocarbons and polychlorobiphenyls) from a sampling site located in the urban area of the city of Stockholm (Station 3). Amphipods were exposed to the contaminated sediments in soft-bottom microcosms in the laboratory during the periods for sexual maturation, mating, and embryogenesis. Three samplings were included; one at the start of the experiment, another after one month (to examine effects on gonad maturation), and a third after 3 months to investigate effects on fertilization success and embryogenesis. No effects were observed on organisms exposed to sediments from Station 1 and Station 3, while effects on sexual maturation on females and males of M. affinis were detected in sediment from Station 2. Females were more seriously affected. Nearly 50% of the females showed a delayed sexual development and 28% of these were immature, showing that the sexual maturation was interrupted due to contaminants in the sediment. In addition to the interrupted sexual 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 number of secondary sexual characteristics, i.e., antennule segments, and chemical sensory organs, i.e., aesthetascs. Since effects were recorded on processes 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. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 518–526, 2000