Environment Agency Kingsmeadow House, Reading, Berkshire, U.K. SUMMARY1. Releases of non-native fish into the wild is an increasing problem posing considerable ecological and genetic threats through direct competition and hybridisation. 2. We employed six microsatellite markers to identify first generation hybrids and backcrosses between native crucian carp (Carassius carassius) and introduced goldfish (C. auratus) and common carp (Cyprinus carpio) in the U.K. We also investigated the genetic characteristics of the taxonomically controversial gibel carp (Carassius spp.) from sites across Europe. 3. Natural hybridisation between goldfish and crucian carp occurs frequently, although hybrids between all other species pairs were observed. Only 62% of British crucian carp populations (n ¼ 21) consisted exclusively of pure crucian carp. In some populations hybrids were so frequent, that no pure crucian carp were caught, indicating a high competitive ability of hybrids. 4. Most hybrids belonged to the F1 generation but backcrossing was evident at a low frequency in goldfish · crucian carp hybrids and goldfish · common carp hybrids. Furthermore, some local populations had high frequencies of backcrosses, raising the opportunity for introgression. 5. Gibel carp from Germany and Italy belonged to two triploid clonal lineages that were genetically closely related to goldfish, whereas all individuals identified from British populations proved to be crucian carp · goldfish hybrids. 6. Our study suggests that the release of closely related exotic cyprinids not only poses a threat to the genetic integrity and associated local adaptations of native species, but may also contribute to shifts in community structure through competitive interactions.

Prolific polyembryony is reported in few major taxa, but its occurrence has generated theoretical debate on potential conflict between sexual and asexual reproduction. It is, therefore, important to genetically confirm a widely cited inference, based on microscopy, that polyembryony characterizes marine bryozoans of the order Cyclostomata. Microsatellite genotyping of brooded embryos and maternal colonies conclusively demonstrated polyembryony, while genetic variation among broods within colonies indicated outcrossing via water-borne sperm, in the rocky-shore species Crisia denticulata. The characteristically voluminous brood chamber of cyclostomes is judged to be an adaptation linked to larval cloning and hence an indicator of polyembryony. We speculate that although the almost universal occurrence of polyembryony among crown-group Cyclostomata is probably attributable to phylogenetic constraint, adaptive consequences are likely to be significant.

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Successful mating is essentially a consequence of making the right choices at the correct time. Animals use specific strategies to gain information about a potential mate, which is then applied to decision-making processes. Amongst the many informative signals, odor cues such as sex pheromones play important ecological roles in coordinating mating behavior, enabling mate and kin recognition, qualifying mate choice, and preventing gene exchange among individuals from different populations and species. Despite overwhelming behavioral evidence, the chemical identity of most cues used in aquatic organisms remains unknown and their impact and omnipresence have not been fully recognized. In many crustaceans, including lobsters and shrimps, reproduction happens through a cascade of events ranging from initial attraction to formation of a mating pair eventually leading to mating. We examined the hypothesis that contact pheromones on the female body surface of the hermaphroditic shrimp Lysmata boggessi are of lipophilic nature, and resemble insect cuticular hydrocarbon contact cues. Via chemical analyses and behavioural assays, we show that newly molted euhermaphrodite-phase shrimp contain a bouquet of odor compounds. Of these, (Z)-9-octadecenamide is the key odor with hexadecanamide and methyl linoleate enhancing the bioactivity of the pheromone blend. Our results show that in aquatic systems lipophilic, cuticular hydrocarbon contact sex pheromones exist; this raises questions on how hydrocarbon contact signals evolved and how widespread these are in the marine environment.

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Cyclostomata bryozoa are thought to reproduce via polyembryony, a clonal replication of a fertilized egg. To test this hypothesis and to assess the impact of their reproductive strategy on the structure of populations, we isolated microsatellite markers in Crisia denticulata (Cyclostomata, Stenolemata), using an initial enrichment step with random amplified polymorphic DNA (RAPD) primers. A total of nine microsatellites, one tetra‐ and eight dinucleotides repeats were isolated; seven were found to be polymorphic in a test sample of 30 individuals, with allele numbers/locus varying from 2 to 6. The tetranucleotide locus showed heterozygote deficiency. These primers did not amplify the DNA of Crisia eburnea.

Characterisation of distance sex pheromones in decapods is challenging, although great efforts have been made in this field in the past 50 yr. In a previous study, we identified a component of the distance (soluble) sex pheromone bouquet of the peppermint shrimp Lysmata wurdemanni as being a uridine-5’-di-phosphate (UDP)-like chemical. However, UDP itself does not elicit the full pre-copulatory ‘approach and follow’ behaviour in peppermint shrimp. Here, we tested the hypothesis that the UDP-like chemical is uridine-5’-tri-phosphate (UTP), a metabolic product of chitin synthesis, and that this is the component of the distance sex pheromone of L. wurdemanni. We ran a series of bioassays to examine whether UDP, UTP or mixtures of the 2 compounds elicit male mating behaviour. Our results showed that male L. wurdemanni responded to UTP by displaying stereotyped courtship behaviour—the same behaviour elicited from males when exposed to water that previously contained moulting females. Combining UTP and UDP did not enhance the intensity of this courtship behaviour. The minimum effective concentration of UTP found to elicit courtship behaviour in the male shrimp was between 10-6 and 10-7 M. HPLC analysis showed the presence of UTP in the moulting water of female shrimp and also the partial conversion of UTP to UDP during the sample preparation procedure. Both the bioassay and chemical analysis results presented in this study suggest that UTP is a component of the distance sex pheromone in L. wurdemanni, and that the major peak in the chromatogram of a L. wurdemanni pheromone identified in previous studies might be a breakdown product of UTP.

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