Population dynamics ofGlaux maritima (L.) along a distributional cline

Population fluctuations ofGlaux maritima, along a transect on a Baltle sea shore meadow, were recorded between 1979 and 1983. A bimodal distribution in numbers along the transect reflects the variation in factors regulating numbers: The two maintenance systems of the species, vegetative propagation and sexual reproduction play different roles. Vegetative propagation is fast and responds quickly to variations in the environment. The seeds germinate in strongly fluctuating temperatures which are triggered by disturbances such as flooding, damaging the vegetation.     

A note on the feeding ofAmphichaeta leydigii (Oligochaeta,Naididae) in lacustrine sandy shores

The analysis of gut contents ofAmphichaeta leydigii, found for the first time in Italy in sandy shores of Lake Vico (Central Italy), proved grazing of the species on diatoms (Centrales and Pennales). Detritus and organic particles, abundant in the substratum, were observed only in small amounts.     

Diet composition influences the fitness of the herbivorous crab Grapsus albolineatus

The tropical rocky shore crab Grapsus albolineatus feeds primarily on filamentous algae but eats animal matter whenever it is available. During the summer the crab's diet switches to encrusting algae due to a die-off of filamentous algae. As a result of the switch the nutrients in the diet of the crab vary seasonally and may influence the fitness of the crab. Maintenance, growth, reproductive performance and nutrient storage of crabs were examined under four dietary regimes of increasing nutritional value ranging from low organic to high protein content. The nutritional quality of these diets significantly affected crab survival and moulting. Crabs fed on the nutritionally superior diet of algae and meat exhibited enhanced growth, higher levels of energy in the reproductive organs and stored more energy in the hepatopancreas than did individuals on the shore and crabs fed only on algal diets in the laboratory. Filamentous algae were a better food source than other algae, resulting in fewer deaths and superior levels of maintenance and growth. Growth and maintenance can occur on a pure algal diet, but reproductive performance and nutrient storage require some degree of added nutrients in the form of animal matter in the diet. Crabs fed coralline or foliose algae had higher mortality and fewer successful moults than crabs fed the other two diets. The fitness of G. albolineatus appears to be limited by the amount of extra nutrients obtained from animal matter. The opportunistic consumption of animal material in the form of carrion, or of animals associated with dietary algae, could be a key factor in the reproductive success of this crab.     

根据孢粉资料推论长江三角洲地区1200年以来的环境变迁

根据长江三角洲地区全新世９个具代表性钻孔的孢粉分析结果讨论了本区约自１２０００年以来的环境变迁。孢粉序列表明：本区约在距今１２０００年前就已发育了亚热带性质的落叶常绿阔叶林,约在９０００—５０００ａＢ．Ｐ．常绿阔叶林获得大发展。孢粉序列良好地记录了古季风盛衰的历史,表现在：１２０００—１０８００ａＢ．Ｐ．较温湿,东南季风强度加强;１０８００（或１１０００－１００００（或１０３００）ａＢ．Ｐ．偏闵干,东南季风强度减弱,对应于新仙女木期;约自１００００ａ．Ｐ．起,气候好转,气温明显上升,东南季风强度再次增强,约在９０００—５０００ａＢ．Ｐ．温暖湿润,为东南季风强盛期。此外．还讨论了约在距今１１０００年前的海侵,全新世下限和哥德堡事件的年代问题,并确定哥德堡事件的年限为１１０００—１０００ａＢ。Ｐ。     

Gelidiaceae (Rhodophyta) in Bahía de Banderas,Western Pacific,México

We present the results of a floristic study of intertidal species of Gelidiaceae collected in ten localities in the Bahía de Banderas region. The study area is within an extensive overlapping transitional zone between the tropical and subtropical regions of the Mexican Pacific coast. Species of the genera Gelidium and Pterocladia were found, G. microdentatum and G. pusillum being the most abundant and widely distributed in the Bay. The local and Mexican Pacific distribution for each species is given. The number of species found in this study is compared with the numbers reported in the literature for the Mexican Pacific.     

Seasonal migration promoting assortative mating in Littorina brevicula on a boulder shore in Japan

Littorina brevicula Philippi is one of the most common snails found in the upper intertidal zone of Japan. In Amakusa, some of the population of L. brevicula migrate to the lower zone in the winter, while the rest stay in the upper zone. Thus, during the winter, which is its reproductive season, the population of L. brevicula divides into two sub-populations. This leads to a hypothesis that the migration pattern in winter is genetically controlled and this behavioural dimorphism is maintained by reproductive isolation between the two sub-populations. In order to test this hypothesis, the following three points were investigated: (1) whether the same snails migrate in a similar way every winter, (2) whether there is a significant tidal level preference in snails, and (3) whether reproductive isolation occurs between the two sub-populations. The results showed (1) the migration behaviour of each snail was consistent over two successive winters, i.e. the same group of snails migrated downward every winter and the same group of snails stayed in the upper zone every winter, (2) transplanted snails moved toward the original zones where they were caught, suggesting that the snails actively selected their tidal zone in winter, and (3) most of the snails copulated within each sub-population. Therefore, reproductive isolation between the two sub-populations was considered to be established to some extent by the dimorphic migration behaviour. In conclusion, the migratory behaviour of L. brevicula is determined separately for each individual and might be genetically controlled, and the behavioural dimorphism may be maintained by partial reproductive isolation between the two sub-populations.     

External factors determining seasonal breeding in a subtropical population of the shore crab Pachygrapsus transversus (Gibbes, 1850) (Brachyura,Grapsidae)

Summary

Monthly samples of the shore crab Pachygrapsus transversus from two distinct annual periods showed that ovigerous females are present throughout the year in the population. However, the relative ovigerous abundance of specimens among sexually mature changes from less than 10% during the winter months to almost 80% in summer. Linear correlations for each year revealed that both temperature and photoperiod were positively associated with relative abundance of ovigerous females. Multiple regression analyses suggested that photoperiod was the main factor affecting breeding in this species. Timing of observed reproductive pattern may enhance larval survival because of particular oceanographic conditions in the study region and favor early juvenile development due to certain species-specific growth features.     

Isolation and distribution of iridescent Cellulophaga and other iridescent marine bacteria from the Charente-Maritime coast,French Atlantic

An intense colored marine bacterium, identified as Cellulophaga lytica, was isolated previously from a sea anemone surface on the Charente-Maritime rocky shore (Atlantic Coast, France), and iridescence of its colonies under direct light was recently described. In addition, iridescence intensities were found to differ strongly between C. lytica strains from different culture collections. However, importantly, the occurrence and distribution of iridescent bacteria in the marine environment were still unknown. Therefore, in this study, a search was undertaken for marine iridescent bacterial strains in different biotopes of the Charente-Maritime coast. Various marine samples (water, sediment, macroalgae, other macroorganisms and detritus) were collected from seven biotopes using a direct plate inoculation method. As a result, 34 iridescent strains related to the genus Cellulophaga, as well as 63 iridescent strains affiliated to the genera Tenacibaculum and Aquimarina, were isolated. Iridescent colors were different according to the genera but iridescent marine bacteria were widely distributed. However, a majority of strains were isolated from rocky shores and, in particular, red seaweed surfaces and mollusks. The data from the study suggested that isolates with iridescent properties were well conserved in stressful environments such as the coastal shoreline. This origin may provide an insight into the ecological and biological functions of iridescence.     

When time is of the essence: choosing a currency for prey-handling costs

1.  Heartbeat rate was measured in shore crabs Carcinus maenas (L.) feeding on mussels Mytilus edulis L. in order to estimate the energetic cost of handling prey and to assess the relative importance of energy and time as costing currencies.
2.  Energetic handling costs represented approximately 2% of corresponding gains.
3.  The tendency of profitability (gain per unit handling time) to increase with prey size was weakened by including energetic handling costs.
4.  Time was judged to be a more appropriate currency than energy for costing prey-handling behaviour.
5.  The importance of time as a costing currency, either through the principle of lost opportunity or through exposure to mortality risk, may extend to other behavioural systems, including aggression.