Provisioning of nestlings by dunnocks,Prunella modularis,in pairs and trios compensation reactions by males and females

Summary The mating systems in a population of dunnocks included monogamy, polygyny, polyandry and polygynandry. Broods were provisioned by lone females, by females with the part-time help of one male, by females with the full-time help of one male (pairs) or by females with the part-time or full-time help of two males (trios). We compared provisioning of nestlings in these different systems and used the results of natural and experimental removals to examine how individuals reacted to the provisioning by others. In pairs, males and females provisioned at similar rates (Fig. 2a). In trios, females and alpha males fed chicks at the same rate, and at a higher rate than beta males (Fig. 2b). Females attained maximum male help when two males shared provisioning equally (Fig. 6). Females were more likely to achieve this when they were able to escape alpha male guarding during the mating period and exercise some control over mating access by the two males (Fig. 7). Female provisioning did not increase when their help was reduced from two males to one (Fig. 4 a), but it did increase when male help was further reduced to either one male's part-time help (Fig. 5 a) or no male help (Fig. 3 a). Beta males increased their provisioning rate when alpha males were removed from a trio (Fig. 4b). Alpha males may have increased their rate when beta males were removed but any reaction was small. When one male was removed from a trio, the remaining male's provisioning rate was as expected for a male in a monogamous pair. When reactions occurred, they were not sufficient to compensate for the loss of the removed adult and nestling weight was reduced. We discuss the relevance of these results to the maintenance of parental care by pairs and trios.     

Reproductive energetics,endocrinology and population dynamics of Nephtys caeca and N. hombergi

An investigation of gametogenetic cycles and spawning success in populations of Nephtys caeca and N. hombergi from the River Tyne estuary, North Shields, England, in relation to production of gonadotrophic (GH) and spawning hormones (SH) has been made, based on data collected from 1978–1984. The data show that a consistent pattern of gametogenesis and efficient spawning occurs in populations of N. caeca in north-east England, but that the reproductive cycle of N. hombergi is erratic. Premature oosorption and gametogenic failure in this latter species is associated with a low level of GH production. Following high levels of GH production, gravid females sometimes fail to spawn owing to the non-release of SH. The reproductive energetics and reproductive success of N. caeca and N. hombergi are described in relation to the observed patterns of endocrine activity and the consequent changes in population structure.     

Development of the ability to take up L-lysine by the diatom Phaeodactylum tricornutum

Freshly harvested cells of Phaeodactylum tricornutum Bohlin grown with nitrate, ammonium or lysine as a sole nitrogen source had a low ability to take up lysine or arginine, but this ability increased when cells were deprived, over 48 h, of either nitrogen or carbon. The effects of nitrogen and carbon deprivation were additive, and the uptake ability was greatest in cells incubated in darkness in nitrogen-free medium. Uptake ability increased in cells illuminated in the presence of 10^-5 M 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) an inhibitor of photosynthetic electron transport. An inverse relationship between rate of development of the uptake system and rate of photosynthesis was also established. Development of the uptake system was prevented by cycloheximide or by anaerobiosis. Following transfer to a normal nitrate medium, illuminated cells lost the lysineuptake system by dilution as the cells grew. There was a linear and positive correlation between the initial rate of uptake of lysine and the maximum concentration which was maintained in the cells when equilibrium was reached, indicating that transinhibition of lysine uptake may occur and that the extent of this inhibition is related to the size of the internal amino acid pool. The relevance of the findings to the growth of phytoplankton in natural waters is discussed.     

Mound building in Ilyoplax pingi (Crustacea: Brachyura: Ocypodidae)

The ocypodid crab Ilyoplax pingi, observed in Kanghwa I., Korea in 1992, builds a mound at the burrow entrance, by piling mud dug out from the burrow. The mounds were made by both waving and non-waving males, and by both ovigerous and non-ovigerous females. The burrow diameter at the widest part tended to be larger in crabs with mounds than in crabs without mounds, whereas the burrow depth was not different between them. The mound density increased in the late exposure period, when the crabs' surface activities declined. Mound removal and rebuilding experiments revealed that the presence of the mounds has the effect of keeping neighboring crabs away.     

Molt cycle alterations in behavior,feeding and diel rhythms of a decapod crustacean,the spiny lobster Panulirus argus

The crustacean molt cycle manifests extensive behavioral changes in addition to physiological and integumentary modifications. The paucity of quantitative studies led us to characterize molt stage dependent alterations in rhythmic locomotor, feeding, and agonistic behavior of subadult spiny lobster Panulirus argus held grouped and solitarily in simulated natural conditions. Non-disruptively determined molt stages were defined as proportions of intermolt duration. Significant nocturnal rhythmicity persisted through the full molt cycle, though daily form varied as a function of activity level and molt stage. A distinct early evening peak signaled initiation of foraging and walking behavior. Thereafter, rhythm amplitude either declined progressively (low activity: unimodal pattern), remained high (high activity: nocturnal plateau), or exhibited a secondary early morning peak (intermediate activity: bimodal and polymodal patterns). Activity ceased at or immediately prior to sunrise. Ecdysis was predominantly nocturnal, probably reflecting species specific spatiotemporal movement patterns and social behavior. A selective advantage of nocturnal ecdysis was postulated concerning avoidance of cannibalism and diurnal predators. Locomotor activity and feeding rates were not equivalent through the molt cycle, though both peaked in stages B₂-C₁. Locomotor activity remained high in metecdysis, decreased sharply at proecdysis initiation (D₀), reaching lowest levels in D₁-D₃, then increased in D₃ through B₁. Activity dropped steeply at ecdysis, though lobsters were capable of intense and coordinated activity. Feeding decreased slowly through metecdysis after the B₂-C₁ maximum, then increased temporarily in C₄ and D₀, indicating heightened feeding motivation. This contrasts with the locomotor activity decrease at proecdysis. Food consumption declined rapidly in D₁ and D₂ and ceased at the D₂-D₃ transition. Feeding resumed in B₁ or B₂, intensifying to maximum in late B₂. Feeding remained relatively constant within stages, whereas locomotor activity varied greatly, though both correlated with metabolic needs. Grouped and solitary lobsters displayed similar patterns of foraging and walking, equivalent to those of locomotor activity and feeding of solitary individuals. Frequency of agonistic interactions (not aggression per se) remained relatively constant through the cycle, peaking in metecdysis, though the highest relative proportion occurred near ecdysis. Lobsters then were submissive and avoided physical contact with conspecifics. Clearly, locomotor activity, feeding, and social behavior of P. argus are not simply determined. Indeed, behavior is distinctly phase coordinated with varying metabolic requirements dependent on the proximity to ecdysis and ecological pressures.     

Effect of phytohormones on the growth dynamics and macromolecular contents of two extreme halophilic Cyanobacteria (Phormidium sps)

Two non-heterocystous, filamentous solar saltern extreme halophilic cyanobacteria viz., Phormidium tenue and Phormidium fragile were allowed to grow in different concentrations of phytohormones. Among the phytohormones, Indole-3 acetic acid and Indole-3-butyric acid at 0. l ppm concentration enhanced the growth, pigments and carbohydrate content in P. fragile. The phycobiliprotein production was found higher at 0. l ppm concentration of Indole-3-acetic acid in P. tenue, whereas Indole-3-butyric acid at 50 ppm and 0. 1 ppm concentrations proved to be inhibitory in the protein and carbohydrate contents in P. tenue.     

Vertical migrations in the tree crab Sesarma leptosoma (Decapoda,Grapsidae)

Sesarma leptosoma, somewhat similar to the Atlantic related species, Aratus pisonii, is an East-African mangrove crab which spends its entire life on the roots and branches of mangrove trees (mostly Rhizophora mucronata, Bruguiera gymnorhiza and Ceriops tagal). S. leptosoma never enters the water, nor does it ever venture onto the free mud surface at low tide. Part of the day and night it remains on the lower parts of the mangrove aerial roots, which are often encrusted with a wet algal mat of Bostrichia spp., searching for food and water. Twice a day, from ca. 06:00 to 08:00 hrs in the morning and 16:00 to 18:00 hrs in the afternoon, many of the crabs migrate as far as the leaves at the top of the tree on which they feed. However, they only spend a brief period among the leaves, from ca. 07:00 to 10:00 and 17:00 to 19:00 hrs, after which time they make their way back towards the roots again in two downward migrations. In the morning, the downward migration brings all the crabs back to the roots, but in the evening not all the crabs take part in the downwards migration and some of them pass the whole night in the tree tops. A comparison of the migration time patterns for two different periods of the year (June–July and November) shows that the number of crabs migrating along the tree trunk is modulated by the spring-neap tidal cycle, while the onset of daily migration seems to be controlled mostly by the light level and/or other climatological cues. The adaptive significance of this migratory behaviour is discussed. Observations reported in our study were made in Mida Creek, Dabaso, Kenya in 1991 and 1992.     

Genetic Structure and Migration in Native and Reintroduced Rocky Mountain Wolf Populations

Gray wolf (Canis lupus) recovery in the Rocky Mountains of the U.S. is proceeding by both natural recolonization and managed reintroduction. We used DNA microsatellite analysis of wolves transplanted from Canada to two reintroduction sites in the U.S. to study population structure in native and reintroduced wolf populations. Gene flow due to migration between regions in Canada is substantial, and all three recovery populations in the U.S. had high genetic variation. The reintroduced founders were moderately genetically divergent from the naturally colonizing U.S. population. These findings corroborate that the reintroduction more than meets generally accepted genetic guidelines. Maintaining this variation, however, will depend on ample reproduction in the first few generations. In the long term genetic variation will best be retained if migration occurs among the recolonizing and the two transplanted populations. Evidence from field observation and genetic studies shows extensive dispersal by wolves, and we conclude that exchange among these groups due to natural dispersal is likely if public tolerance and legal protection are adequate outside lands designated for wolf recovery.     

Incidence,occurrence and distribution of the nematode Echinomermella matsi in its echinoid host,Strongylocentrotus droebachiensis,in northern Norway

The incidence, occurrence and distribution of the nematode Echinomermella matsi (Jones and Hagen) in its host, the echinoid Strongylocentrotus droebachiensis Müller, were examined in Norwegian waters from Nordmre (63° N) to the Russian border (70° N) in a range of habitats (e.g. kelp cover and community type) from 1982 to 1992. The results are used to examine the likely influence of the parasite on fitness (individual growth and gonad production) and its potential in regulating the population size of its echinoid host. The nematode infections are restricted to areas between Vikna (Vega) and middle Troms, with the highest prevalence (40 to 88% infected) in the Bodø area, the focus of the distribution. The prevalence rates are similar on kelp beds and barren grounds. No difference in growth rates between infected and noninfected sea urchins was found. Nematode-infected sea urchins in kelp bed populations had gonads weighing about one-sixth of those of equivalent uninfected individuals. This indicates that nematodes are really parasites causing reduced reproductive capacity. Areas with high prevalence (>40% infected) of nematodes had low sea urchin densities. High nematode intensities were found in the areas with high prevalence. The mean abundance in high prevalence areas was highest (eight nematodes) in the 4-to 7-yr-old age group and decreased to zero among the oldest age groups. The ratio of variance/mean abundance was also highest among 5-to 8-yr-old sea urchins. At highly and slightly infected locations, the relationships between the log of the variance and the log of the mean abundance of parasites were 1.35 and 1.69, respectively. Measurements of the frequency distribution of nematodes in sea urchins and the corresponding estimates of the negative binomial distribution showed significantly higher counts in estimated than observed subpopulations exceeding 20 nematodes per sea urchin. These results may explain nematode-induced sea urchin mortality. The low density of the host in the Bodø area, which had high prevalence, may be a result of increased host mortality caused by nematodes, by lower recruitment because of reduced gonad production, or by other factors. Low prevalence among older sea urchins may be caused by nematodeinduced host mortality or by cycles in infection. However, studies on the life cycle of the nematode and long term investigations of host density and nematode intensity/prevalence will be needed before any true conclusions can can be drawn.     

A simple model for complex waste recycling scenarios in developing economies

Future uncertainties involved in the current waste management activities in the developing nations have been addressed through determining plastic waste recovery, recycling and landfilling scenarios in two case study countries — Bangladesh and India. In order to discern and comprehend the material in-flow and out-flow of such complex successive plastics recoveries and recyclings, within the closed-loop recycling systems present in these two countries, a simple mathematical model is developed. The model is based on limited published information, on extensive fieldwork in Dhaka, Calcutta and Delhi, and on experimental data. An environmental legislative factor has been included in the model which will allow balancing of the quality of recycled products and the amount of landfilling non-recyclable plastics. The model has the potential to create and predict a sound waste database for these countries. Bangladesh has been chosen as a model developing country for this study. The mathematical model can be used in future decision making processes within the plastics recycling arena of the countries concerned to achieve an environmentally sound and cost effective waste management option.