Development and maturation in the nereidid polychaetes Platynereis dumerilii and Nereis succinea exposed to xenoestrogens.

Few studies link biochemical, cellular and whole animal effects of toxic compounds with growth and reproductive output on invertebrate model organisms. Thus, we explore the effects of xenoestrogens on nereid worms. Larvae of Platynereis dumerilii exposed to estradiol (E(2)) ethynylestradiol (EE(2)) and nonyplhenol (NP) observing the effects on growth, primordial germ cell (PGC) proliferation and maturation. In addition, a single exposure study was performed with a 50 days latency period on adult worms of Nereis succinea. Since reduced glutathione (GSH) is required in detoxification of NP and is the precursor of the spawning pheromone nereithione (CSSG) in N. succinea, we analysed how the estrogenic chemical NP affects GSH concentrations. PGC were not affected by exposure to E(2) and EE(2) from 24hpf to 6 days. Chronic exposure of P. dumerilii with NP over the full life cycle did not influence segment proliferation. Mature females that developed, even at high concentrations, were able to spawn and successful fertilization occurred. However, at high NP levels no P. dumerilii males matured. A significant decline of GSH can be seen in N. succinea males upon treatment with NP, but not in females, indicating that females stabilize GSH levels even in stress situations. This study shows some results that link the foundation to causally integrate toxic exposure to xenoestrogens with development, growth and reproductive outputs in nereidid polychaetes.

Biological responses to contaminants in the Humber Estuary: disentangling complex relationships.

Due to the ecological importance of estuaries, it is necessary to understand the biological effects that potentially toxic contaminants induce in bioindicator species. A key aspect is whether effects at lower levels of biological organisation transfer through the system to higher levels. In understanding such processes, characterising multivariate relationships between contaminants, sediment toxicities and detoxification processes are important. Worms (Hediste diversicolor) and sediments were collected along the Humber Estuary, England, and inorganic and organic contaminants were quantified. Sediment toxicities and glutathione-S-transferases (GSTs) activity in the ragworm were analysed. Concentrations of metals were highest near urban and industrial areas, whereas organic contaminants appeared at upstream locations. GST activity correlated with heavy metals. The genotoxicity, oestrogenicity, dioxin and dioxin-like activity were higher at upstream locations. Oestrogenicity correlated with alkylphenols and some organochlorines, whilst genotoxicity correlated with organochlorines and heavy metals. Despite this, higher level biological responses could not be predicted, indicating that homeostasis is operating.

Chemical signal mediated premating reproductive isolation in a marine polychaete, Neanthes acuminata (arenaceodentata).

Neanthes acuminata Ehlers (1868) is a monogamous coastal polychaete with male parental care and a high level of sexual selection. We measured the level of prezygotic isolation among allopatric populations of N. acuminata; from the East and West Coast of the USA, a population from Hawaii, and a laboratory culture originating from Los Angeles, CA. All populations were found to preferably mate with members of their own population. Individuals from populations from Atlantic vs. Pacific Ocean failed to pair and to mate, either during the 10 min or 48 hr experiments. Instead, individuals showed high levels of aggressive behavior. Experiments measuring the levels of interpopulation aggression, established that individuals can recognize and discriminate among different populations of N. acuminata on the basis of olfactory cues. Aggressive behavior was induced by exposure of animals to seawater "conditioned" by individuals from the other populations, thus demonstrating the role of olfaction in the detection of "home" populations. The aggressive display was stronger upon exposure to seawater conditioned with "unrelated" populations and especially between Pacific and Atlantic populations.

The spawning pheromone cysteine-glutathione disulfide ('nereithione') arouses a multicomponent nuptial behavior and electrophysiological activity in Nereis succinea males.

The pheromone nereithione (cysteine-glutathione disulfide), which is released by swimming females of the polychaete Nereis succinea to activate spawning behavior of N. succinea males, has recently been identified and synthesized. Nereithione activates sperm release at less than 10(-6) M, one to two orders of magnitude less than oxidized glutathione or any other glutathione derivative tested. The glutathione fragment gamma-glu-cys inhibited sperm release. Nereithione aroused three components of the male nuptial behavior: circling, sperm release, and accelerated swimming. Electrophysiological activity elicited by nereithione near the sperm release site consisted of initial large spikes, cyclic bursting activity, and small spikes lasting up to a minute and was dose dependent, rapid, reversible, and repeatable. This preparation is an excellent model system for characterizing the receptors and functions of a marine pheromone.

Tricyclic antidepressants suppress spawning and fertilization in the zebra mussel, Dreissena polymorpha.

Tricyclic antidepressants (TCAs), which are psychotropic drugs that work in vertebrates by interfering with serotonergic mechanisms, were tested for their effects on the serotonin-elicited spawning behavior of the zebra mussel, Dreissena polymorpha. Exposure of mussels to 10(-4) M imipramine or desipramine for 2 hr prior to serotonin treatment inhibited spawning in male, but not female, zebra mussels (p < 0.05). Clomipramine (10(-4) M) inhibited spawning of both sexes (p < 0.01). Inhibition of spawning was more effective with 2 hr preexposure time than with shorter times (p < 0.0001). Oocytes released in the presence of TCAs had a normal appearance, with no germinal vesicle present; however, fertilization and embryonic development were adversely affected in oocytes released into TCA concentrations as low as 10(-6) M. Oocytes fertilized after TCA treatment rarely developed normally. This is the first report of an inhibitory effect of TCAs on spawning, fertilization, and early embryonic development in any animal. The concentrations that affect embryonic development in zebra mussels are in the same range as therapeutic plasma concentrations in humans.

In vivo and in vitro induction of germinal vesicle breakdown in a freshwater bivalve, the zebra mussel Dreissena polymorpha (Pallas).

Oocyte maturation and germinal vesicle breakdown (GVBD) was induced in zebra mussel (Dreissena polymorpha) oocytes by in vivo and in vitro application of serotonin (5-hydroxytryptamine, 5-HT), and in vitro application of 8-hydroxydipropylaminotetralin hydrobromide (8-OH-DPAT, a 5-HT1A receptor agonist). Oocytes initiated GVBD approximately 30 minutes after exposure to 5-HT (10(-3) M) at 23 degrees C, and by 40-50 minutes after exposure, most oocytes lacked a germinal vesicle. An exposure time to 5-HT as brief as five to ten minutes was required to trigger the maturation process, which terminates in spawning of fertilizable oocytes in nearly all mussels. But, with an exposure time of less than five minutes, spawning was reduced by application of 10(-4) M methiothepin (a potent blocker of 5-HT-induced spawning in zebra mussels). Thus, the sequence of oocyte maturation events in zebra mussels was determined. Oocytes are arrested at the germinal vesicle stage (prophase I) within the ovary. 5-HT reinitiates the maturation process, including GVBD and spawning of metaphase I oocytes, which are further arrested until fertilization. To our knowledge this is the first demonstration of oocyte maturation induction by serotonergic ligands in a freshwater bivalve.

Sex pheromones in marine polychaetes: steroids from ripe Nereis succinea.

A number of neutral marine steroids such as desmosterol, campesterol, brassicasterol, gorgosterol, and other trace steroids were isolated from the coelomic fluid of ripe Nereis succinea and checked for biological activity as sex pheromones on swarming specimens of Platynereis dumerilii and Nereis succinea. No significant influence of synthetic gorgosterol or a natural extract of gorgosterol or the other identified steroids on the swarming behavior was observed.