Serripes

Abstract: A long sequence of open-coast tidal flat deposits with a restricted, mainly boreal fauna, comprises the Tapes and Mactra Zones. Characteristic species are Venerupis aurea, Spisula arcuata, Arctic islandica and Lentidium complanatum. This stage is provisionally correlated with the Upper Pliocene of the North Sea Basin. During the time of deposition of the Serripes Zone the basin apparently deepened and the fauna greatly diversified with immigration of arctic elements. It went back finally to beach-deposit conditions. The characteristic species —Serripes groenlandicus, Macoma praetenius, and Beta borealis — are also characteristic of the Early Pleistocene of the North Sea Basin with which the Serripes Zone is provisionally correlated. The climate is interpreted as having been colder than that of the Tapes and Mactra zones. A preliminary list of the Mollusca is given.

Abstract: Caged Davis soybean plants were infested with Nezara viridula (L.) and Riptortus serripes (F.) (4.4 adults/m) at 3 stages of pod development in 3 experiments in 1987, 1988 and 1989. Bug feeding reduced seed yield and oil content during pod fill, but not during pod elongation or pod ripening. N. viridula reduced yields significantly in 1987 and 1988, (183 and 494 kg/ha) but R. serripes reduced yields significantly only in 1988 (353 kg/ha). Both species damaged more seeds during pod fill than during any other pod stage, but N. viridula damaged more seeds than R. serripes. Mean seed weight was reduced only during pod fill. In contrast, the mean weight of undamaged seeds increased during pod fill. This indicated partial compensation by Davis soybeans for damage caused by the above bug species at a density of 4.4 adults/m. Seed oil content, recorded only in 1988, was reduced significantly by N. viridula, but not by R. serripes.

Abstract: We studied distribution and growth of Serripes groenlandicus and Macoma calcarea in the southeastern part of the Pechora Sea. The hypothesis was tested that trends in the site-to-site variability of population characteristics of these two bivalve species were driven by their feeding types (suspension-feeder and deposit-feeder, respectively). However, such a trend was found only in the abundance distribution of these species and site-to-site variability in growth rates of S. groenlandicus. M. calcarea density on silty sediments was almost twice as high as on sandy sediments, while Serripes biomass was almost 1.5 times higher on sandy sediments than on silty sediments. The slowest-growing Serripes were found at the deepest stations and in habitats with the largest content of fine fractions (silt) in sediments. Differences in the growth of S. groenlandicus could reflect variability of feeding conditions of this suspension-feeder (e.g., hydrodynamic conditions). Thus, the growth rate of S. groenlandicus was sensitive to environmental conditions, which means it can be used as an indicator of their changes. In general, S. groenlandicus in the Pechora Sea is very slow-growing compared to other areas (maximum life span and shell length are 28 years and 70 mm, respectively). Their growth rate was closest to that in Arctic-influenced locations. On the contrary, the maximum life span and shell length of M. calcarea in the Pechora Sea (15 years and 30 mm, respectively) were similar to those in other parts of the distribution area. No significant differences were found in the group growth of M. calcarea from different studied localities.

Abstract: Mesocarp removal in A. chambira fruits had a significant effect on oviposition by Caryoborus serripes females. When given the choice between unpee- led and peeled freshly fallen fruits, females laid preferentially their eggs on peeled fruits. Once the mesocarp of control fruits had been removed through the action of microorganisms, insects or rodents (after 45 to 62 days), no more difference was observed with peeled fruits. No sign of the existence of an intraspecific competi- tion avoidance mechanism in ovipositing females was detected. Resulting larval mortality was high.