Carbon-14 net incorporation does not accurately estimate the weight-specific growth rate of the polychaete Capitella capitata

Tracer techniques to measure carbon-14 incorporation from labeled food can seriously overestimate the growth of an organism. The degree of overestimation can change with varying food supply and correlates with changes in the tracer activity in lipid and protein pools of the organism. These changes may be associated with differential metabolic partitioning of newly assimilated food.     

A non-motorized dye ejector for visualization of flow in situ and its use with coral reef crinoids

We describe a portable, non-motorized device for delivering a tracer dye into seawater under field conditions. Dye is ejected at a constant flow rate over a period of tens of minutes. The ejector works in a wide range of ambient pressures without external energy requirements. The flow rate is adjusted simply by varying the length of the delivery tube. The dye streams permitted observations of the upcurrent and downcurrent flow regimes for a filter-feeding crinoid (Comanthus bennetti) living at a depth of 8 m on a coral reef. The results indicate that the crinoid may enhance the rate of particle capture by changing the scale of turbulence in the water passing through the mesh of the filtration fan.     

Oxygen consumption of pelagic juveniles and demersal adults of the deep-sea fish Sebastolobus altivelis,measured at depth

Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O₂ consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O₂ consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O₂ consumption regression equation) was 11.01 μl O₂ m^-2 h^-1, which is two orders of magnitude less than the O₂ consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O₂ consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day.     

Allopaternal care in the fathead minnow,Pimephales promelas: females prefer males with eggs

Summary Some species of fishes with exclusive male parental care exhibit the phenomenon of allopaternal care; that is, some males acquire and care for other males' eggs. We conducted a series of experiments to investigate the dynamics and evolution of allopaternal care in one such species, the fathead minnow (Pimephales promelas). In choosing a nest site, a newly reproductive male tended to take over the nest site of a parental male by evicting the resident male, rather than occupy a physically identical empty nest site. The new male generally cared for the old male's eggs, and in most cases, daily egg survival improved under the new male's care. When males were given a choice among unguarded nest sites, they preferred to occupy nest sites already containing eggs. When eggs were randomly assigned to nesting males, females preferred to spawn with males who had eggs in their nest sites. Thus, it appears that female preference for males with eggs led to the evolution of allopaternal care in the fathead minnow.     

Swimming performance and endurance of the Norway lobster Nephrops norvegicus

The swimming behaviour of the Norway lobster, Nephrops norvegicus (L.), was studied in the laboratory. The lobsters were stimulated to swim repeatedly until they failed to respond to a single tactile stimulus. The position of the initiating stimulus on the body determined the height of the escape path above the bottom of the tank. A stimulus to the rostrum resulted in a low swimming trajectory, rarely exceeding a height of 0.1 m. A similar tactile stimulus to the abdomen produced higher mean swimming trajectories up to 0.5 m. Several parameters of swimming performance and endurance were measured for each swimming sequence, including distance, duration, mean and maximum velocities and the frequency and number of tail beats. Results showed no significant differences in the average swimming performance and endurance of males and females, but there was a sex difference in the relationship between swimming performance and N. norvegicus size.     

Fertilization and early developmental stages of eggs of Clupea harengus pallasi n. maris-albi under fresh-water conditions

Eggs of the White Sea herring Clupea harengus pallasi Val. are laid in the intertidal zone, where they are liable to come under the influence of fresh water. The present paper deals with the effect of fresh-water influence on the egg of the White Sea herring, under experimental conditions. In fresh water, egg and sperm are in an unactivated state and, after transfer into sea water, are capable of re-activation, even after 212/ h exposure. The treated eggs develop until the hatching of normal and viable larvae. The number of eggs which are able to complete development depends upon the period of freshwater exposure, although the correlation between the length of that period and survival rates is not very close. Apparently, this is due both to the ability of C. harengus pallasi eggs to develop parthenogenetically and different qualities of eggs (which were obtained from different females). The morphological features of White Sea herring eggs, induced by experimental fresh-water influence, are very similar to those typical for herring eggs of the genus Ilisha, obtained from natural brackish waters. However, such changes are not characteristic of the eggs of forms from natural fresh and brackish-waters.     

Standing crop and leaf area index of the sublittoral Laminaria species near Helgoland

Standing crop values of Laminaria species sampled between 0 to 2 m depth in the sublittoral of Helgoland, a small rocky island in the southern North Sea, are similar to those reported by other workers from Norwegian or Scottish coasts. Below 2 m water depth, however, standing crop values are found to be reduced to a far greater extent with increasing depth than in the Norwegian or Scottish areas studied. Maximum standing crop values are not found in Laminaria digitata and L. saccharina growing just below the low water mark of spring tides, but in the upper L. hyperborea forest at 2 m depth. Population density and leaf area index (LAI) decrease with increasing depth (but not the average weight of individuals constituting the L. hyperborea forest). It is suggested that the depth at which LAI becomes 1 represents an important ecological threshold, since growth rates of L. hyperborea specimens appear to decrease at greater depths but not to increase above the threshold. Self-shading might equalize, to a certain extent, the quantity of underwater irradiance available to an individual phylloid at all depths at which a close vegetation of Laminaria species occurs.     

Sex-specific energy requirements in nestlings of an extremely sexually size dimorphic bird, the European sparrowhawk (Accipiter nisus)

Allocation of parental investment is predicted to be equal at the population level between both sexes of offspring, and should lead to sex ratio biases in species that exhibit a sex-difference in parental care. Sex-differences in parental care are rarely quantified. We measured daily energy expenditure in free-living nestlings of the extremely sexually size dimorphic European sparrowhawk (Accipiter nisus), using the doubly labelled water method. These data were combined with measured growth characteristics to estimate daily and total metabolised energy intake of male and female young during the nestling stage. Females reached an asymptotic body mass 1.6 times higher than males. This resulted in a total metabolised energy an estimated 1.4 times higher for the nestling stage. Furthermore, we observed a decline in daily metabolised energy with an increase in brood size, which was significantly stronger for females than for males. These results are discussed in the context of Fishers equal allocation theory. Empirical evidence of a sex ratio bias at the end of parental care, with an overall excess of males, is lacking in this species. Consequently, our data do not support the idea of equal allocation between the sexes. The observed sex difference in daily metabolised energy in response to brood size may give scope for sex ratio bias at the level of the individual brood.     

Effects of Widespread Fish Introductions on Paedomorphic Newts in Europe

Abstract:  As a result of factors such as global warming, habitat destruction, and species introduction, amphibians are declining worldwide. No one, however, has analyzed the status of polymorphic amphibian species at a national or continental scale, although some local reports exist. Our aim was to report on the loss of intraspecific heterochrony as a loss to diversity in determining the consequences of fish stocking on European populations of paedomorphic newts. Paedomorphosis is a polymorphism in which larval traits are retained in the adult stage. We surveyed 39 paedomorphic populations of the alpine (  Triturus alpestris ) and palmate ( T. helveticus ) newts, all but one of which initially occupied fishless ponds and lakes in France, Italy, Slovenia, Bosnia, Montenegro, and Greece. Exotic fishes were found in 44% of the studied aquatic habitats, with a 100% presence in Montenegro. At all sites paedomorphs disappeared and metamorphs declined. Only fish explained these population changes because alternative factors such as drying were not significant. More catastrophically, fish introductions occurred in habitats known to support the largest populations of newts and even some endemic subspecies. If management and legislative measures are not taken to stop fish stocking, protect paedomorphs as conservation units at national and international levels, and restore natural habitats, all the largest paedomorphic populations may disappear in the near future. Their disappearance would represent a loss of one of the rare, fascinating examples of intraspecific heterochrony.