The reproduction of the anemone Sagartia troglodytes (PRICE): no influence of tidal manipulation

The reproductive cycle and the glycogen content were monitored in the subtidal anemone Sagartia troglodytes (PRICE). Moreover, these parameters were followed for periods of 3 to 30 days over the course of 1 year in anemones previously submerged in stagnant water and thus subjected to a reduced food supply. The anemones showed an annual reproductive cycle with, in contrast to previous studies. 2 spawning cycles. The glycogen content varied between 5 and 8% of the dry weight. Submersion in stagnant water did not alter the reproductive cycle or the glycogen content

The effect of polluted sediment on the gonadal development and embryogenesis of bivalves

Cockles (Cerastoderma edule) and Baltic clams (Macoma balthica) were kept on polluted sediment from the harbour of Rotterdam, and on clean sediment from the Wadden Sea (control). Their gametogenesis was then followed. In vitro fertilisation (IVF) experiments were carried out and larvae were cultured until the D-stage (veliger-stage). At the end of the experiment, in animals from the Rotterdam harbour sediment, the condition- index (CI) and gonad-index (GI) were significantly lower, whereas the proportion of parasitised animals was higher than in the controls. Spawning- and fertilisation percentages were also lower in animals kept on harbour sediment. Larval development did not show significant differences. [KEYWORDS: Cerastoderma edule; Macoma balthica; polluted sediment; gametogenesis; IVF; embryogenesis; veliger-larvae; parasites Mytilus-edulis; larvae; exposure; stress; growth; adult; eggs]

Effects of tidal zonation on size and genetic traits of Mytilus edulis (L.) and Macoma balthica (L.)

Genetic and some ecophysiological traits of mussels collected in the European Arctic, up to their northeastern distribution limit in the Barents Sea, were studied and compared with traits of mussels from the Mediterranean, Atlantic and Baltic. The genetic traits of these populations we-re analysed by isoenzyme electrophoresis on seven loci in order to assess the Mytilus complex to which populations in the Arctic region belong. Ecophysiological variables, the weight-index and glycogen were analysed to assess the physiological fitness of the populations. Three distinct groups were recognised: (1) Mytilus (edulis) galloprovincialis in the Mediterranean and Spain, (2) M. (edulis) edulis along the Atlantic coast from the Netherlands northwards into Russia, and (3) the Baltic Mytilus (edulis) trossulus. The mussels from populations in the Russian Arctic all belong to the Atlantic Mytilus (edulis) edulis group. The genetic variability and ecophysiological measures indicated that the sub-Arctic White Sea mussel populations have a relatively lower performance capacity, whereas those in the Arctic at the edge of their northern distribution showed a surprisingly strong performance.

Effects of tidal zonation on size and genetic traits of Mytilus edulis (L.) and Macoma balthica (L.)

Genetic and some ecophysiological traits of mussels collected in the European Arctic, up to their northeastern distribution limit in the Barents Sea, were studied and compared with traits of mussels from the Mediterranean, Atlantic and Baltic. The genetic traits of these populations we-re analysed by isoenzyme electrophoresis on seven loci in order to assess the Mytilus complex to which populations in the Arctic region belong. Ecophysiological variables, the weight-index and glycogen were analysed to assess the physiological fitness of the populations. Three distinct groups were recognised: (1) Mytilus (edulis) galloprovincialis in the Mediterranean and Spain, (2) M. (edulis) edulis along the Atlantic coast from the Netherlands northwards into Russia, and (3) the Baltic Mytilus (edulis) trossulus. The mussels from populations in the Russian Arctic all belong to the Atlantic Mytilus (edulis) edulis group. The genetic variability and ecophysiological measures indicated that the sub-Arctic White Sea mussel populations have a relatively lower performance capacity, whereas those in the Arctic at the edge of their northern distribution showed a surprisingly strong performance

Variation in genetic traits of the Baltic clam Macoma balthica from a tidal gradient in the subarctic

In a subarctic tidal gradient, strong heterogeneity in genetic traits of the Baltic clam Macoma balthica was found. The heterogeneity was stronger within the intertidal gradient, over a distance of only about GO mi than along a horizontal gradient over a distance of 1200 km in clams from the west European coast. For the locus Idh1 and the average heterozygosity, a tidal dine was found. The frequency of allele Idh1-B decreased with tidal level, whereas the frequency of allele Idh1-C, as well as the average heterozygosity, increased. The possibility is discussed that the strong genetic heterogeneity and tidal dines are caused by differential selection related to the (subarctic) temperatures to which the higher tidal zones are more exposed. [KEYWORDS: Allele frequency cline; mytilus-edulis; population-genetics wadden sea; electrophoretic data; allozyme variation; systematics; settlement; pollution; selection]