The evolution of cheating and selfish behavior

Summary We examine the necessary conditions for the spread of genes that determine selfish and cheating behaviors and the rate of spread of these genes through structured populations, in order to address the question of the invadability of altruistic systems by anti-social mutations. We find that, although cheaters always have a higher relative fitness than altruists within groups, population structures which permit the evolution of altruism also preclude invasion by anti-social mutations. These results are related to a discussion by Hamilton (1971) concerning the limits to the evolution of altruistic and selfish behaviors.     

The role of male vs male interactions in maintaining population dialect structure

Summary Nonmigratory populations of Whitecrowned Sparrows in coastal California exhibit dialects in territorial male songs that are stable in space and time. By field playback experiments, we tested a prediction from the hypothesis that male aggressive interactions prohibit mixing of song dialects. Playback of the home dialect Clear song to territorial males singing the Clear dialect resulted in less response than that given to playback of the neighboring Buzzy dialect. Response to both Buzzy and Clear dialect songs by target Clear males, however, was greater than that given to the Bodega dialect recorded 55 km away (Figs. 2 and 3). We conclude that these results are consistent with the hypothesis that male-male aggressive interactions play an important role in reducing dialect mixing.     

13C/12C ratios and the trophic importance of algae in Florida Syringodium filiforme seagrass meadows

Over 380 stable carbon isotope (¹³C) analyses made during 1981–82 showed that Syringodium filiforme Kutz seagrass meadows in the Indian River lagoon of eastern Florida have food webs based on algal rather than seagrass carbon. Seagrasses averaging approximately-8 were isotopically distinct from algae epiphytic on seagrass blades (X=-19.3) and particulate organic matter in the water column X=-21.6. ¹³C values of most fauna ranged between-16 and-22, as would be expected if food web carbon were derived solely from algal sources. These results counter the idea that seagrass detritus is the dominant carbon source in seagrass ecosystems. Two factors that may contribute to the low apparent importance of seagrass in the study area are high algal productivities that equal or exceed S. filiforme productivity and the high rates of seagrass leaf export from meadows.     

Seasonal changes of locomotor activity patterns in ruin lizards Podarcis sicula

Seasonal differences in the locomotor activity pattern of Podarcis sicula held in constant conditions in the laboratory were found to be associated with systematic differences in both the freerunning period of locomotor rhythms () and the circadian activity time (). In order to establish whether the pineal played a role in the control of seasonal changes in circadian parameters, we examined the effects of pinealectomy in constant conditions on the locomotor behavior of lizards displaying the bimodal activity pattern typical of summer. In most lizards pinealectomy lengthened , shortened and abolished the bimodal activity pattern. Pinealectomy induced a sudden transition from the typical locomotor behavior of summer, characterized by a marked bimodal pattern, short and long , to the typical locomotor behavior of autumn, characterized by a unimodal pattern, a long and short . These results demonstrate that the pineal plays a central role in the seasonal reorganization of the circadian system that occurs in P. sicula.     

The structure of plankton communities of the Indian Ocean

Species diversity and trophic structure of plankton communities have been considered as most important biological features. The Fisher () and Simpson () indices and the information index H=- pi log₂ pi (Margalef) were used for evaluation of species diversity. The indices have been calculated within the group of filter feeders by numbers ( and H) and biomass ( and H) of the species; the best results were obtained in the latter case. The index H=- pi log₂ pi is proposed for the quantitative evaluation of trophic structure, where a portion of an individual trophic group is taken as pi. The plankton material was collected by the R.V. Vityaz in the northern Indian Ocean in January through February, 1960. Analysis of characteristics of zooplankton distribution, species and trophic diversity in connection with characteristics of the water regime resulted in the definition of 3 types of the plankton communities: (a) those in intensive divergence zones; (b) those in poor divergence zones; (c) those in regions with stable water stratification or with feebly marked convergence, distiguished by different values of biomass, species diversity, and trophic group ratios.     

Are communal pukeko caught in the prisoner's dilemma?

Summary The prisoner's dilemma of game theory provides a possible explanation for communal breeding in the pukeko (Porphyrio porphyrio, Aves) where group breeding birds are at a reproductive disavantag compared to pairs. Territorial defence is largely the realm of males. A male who defect on neighbours by taking in an extra male defender and so becoming communal stands to gain territorial area and possibly higher reproductive success. Neighbours are forced to follow suit if additional males are available or lose their territory and therefore their breeding opportunities. If neighbours also admit an extra defender, the initial defector loses his advantages and all males end up with the lower breeding success of communal groups. Such defection to a communal habit appears to be the only stable solution.     

Aggregation and foraging behavior of whirligig beetles (Gyrinidae)

Summary Whirligig beetles aggregate in the daytime into dense single-and multispecies groups (rafts) of hundreds or thousands of individuals. On the 22km shoreline of Lake Itasca in northern Minnesota, these aggregations were on the average 0.8 km apart, and they were usually found day after day in the same ocations.Most beetles apparently do not home to the aggregation of their origin after dispersing at night because (a) the species composition of some aggregations changed greatly, and (b) paint-marked beetles (Dineutus horni) moved overnight from one aggregation as far as 4km, joining 11 of the 14 large (>300 beetles) D. horni groups on the lake.Throughout the night, the largest concentrations of beetles remained within 100m of the diurnal aggregation sites. Beetles reconvened into the compact rafts before daybreak, in part by following each other in sometimes long single files or trains. Their forward motion stopped after they joined large number of other beetles. We infer that following behavior enables those individuals that have dispersed from their original aggregations (during their nocturnal foraging) to find and join other aggregations before daylight.Naive fish ate the beetles despite their noxious secretions. However, fish living near rafting sites and feeding on insects on the water surface in daylight should soon learn to avoid the beetles. The rafting sites would then become safe places. We observed fish attacking only those beetles that had been either dispersed from their rafts or released into open water away from raft sites in the daytime. We speculate that the evolutionary significance of the aggregation behavior is related to predator (fish) avoidance.     

Dependence of consumers on macroalgal (Laminaria solidungula) carbon in an arctic kelp community: δ13C evidence

Stable carbon isotope measurements (¹³C) were used to assess the importance of kelp carbon (-13.6 to-16.5) versus phytoplankton carbon (-25.5 to-26.5) to resident fauna of an isolated kelp bed community on Alaska's north arctic coast from 1979 to 1983. The predominant kelp, Laminaria solidungula, showed some seasonal variation in ¹³C which was correlated with changes in the carbon content of the tissue. Animals that showed the greatest assimilation of kelp carbon (>=50%) included macroalgal herbivores (gastropods and chitons,-16.9 to-18.2), a nonselective suspension feeder (an ascidian,-19.0) and a predatory gastropod (-17.6). Animals that showed the least incorporation of kelp carbon into body tissues (<=7%) included selective suspension-feeders (hydroids, soft corals and bryozoans,-22.8 to-25.1). Sponges, and polychaete, gastropod and crustacean omnivores exhibited an intermediate dependence on kelp carbon (15 to 40%). Within some taxonomic groups, species exhibited a broad range in isotopic composition which was related to differences in feeding strategies. In the polychaete group alone, ¹³C values identified four major feeding habits: deposit-feeders (-18.0), omnivores (-20.4), predators (-22.2) and microalgal herbivores (-23.0). Distinct seasonal changes in the ¹³C values of several animals indicated an increased dependence on kelp carbon during the dark winter period when phytoplankton were absent. Up to 50% of the body carbon of mysid crustaceans, which are key prey species for birds, fishes and marine mammals, was composed of carbon derived from kelp detritus during the ice-covered period.     

Descriptions and durations of premolt setal stages in female Dungeness crabs,<Emphasis Type="Italic"> Cancer magister</Emphasis>

For crustaceans with a well-defined annual molting season, such as adult female Dungeness crabs (Cancer magister Dana), setal molt staging can, in principle, be used to predict molting destiny of individual crabs. Size-specific predictions of molting probability could, in turn, be useful for estimating mortalities due to molting. Female Dungeness crabs were collected January–March 1997 at depths of 10–30 m off the California coast, USA (41°N). Intermolt stage A₁–C₄ and premolt stages D₀, D₁, D₁, D₁ and D₂ were described based on features of the branchial epipod. Laboratory experiments suggested that stage D₁ was the earliest stage beyond which eventual molting was inevitable so that molting destiny could be determined. Estimated mean number of days from the beginning of stage D₁ to molting was 85. Estimated individual stage durations, based on laboratory experiments, were 24, 51, –4, 18, and 20 days, respectively, for stages D₀, D₁, D₁, D₁, and >D₂. The estimated –4 days for stage D₁ suggests that this stage must be very brief and raises a question of its utility in designation of molt stages. Molt staging of three field samples, 300–600 crabs in each, collected prior to the 1997 annual molting season, indicated an increase in the size and frequency of crabs staged D₁ or later as the time to molt approached, although crabs of 150 mm carapace width and larger showed few signs of molt preparation. Because the duration of the molting season (approximately 120 days) for adult female C. magister in northern California exceeds the estimated maximum duration of reliable prediction of molting destiny (85 days), it does not appear that molt staging can be used to predict molting destiny in this population. However, the procedures that we have used in this paper for application to female C. magister might be used with success for other crustaceans if the duration of stages D₁ to molting exceeds the duration of the molting season, and furthermore may be used for describing temporal molting trends.Communicated by J.P. Grassle, New Brunswick     

Lead-based paint in dwellings: The potential for contamination of the home environment during renovation

The quantity and particle size characteristics of lead in dust released during three different paint removal techniques was determined under controlled conditions and in situ in a dwelling. Air-lead and deposited dust-lead levels were highest after sanding but burning-off and hot-air removal methods also produced significant contamination. The importance of dust particle-size and lead is discussed in relation to the potential hazard to home renovators via inhalation and to children via the hand-to-mouth route.This paper is also being published in Proceedings of the Conference on Lead in the Home Environment and is one of several selected from SEGH sponsored conferences for simultaneous publication in this journal.     

Autotoxic antibiotic production by a marine Chromobacterium

An antibiotic-producing Chromobacter was isolated from a sea-water sample from the North Pacific Gyre. The bacterium produces 3 bromine-containing metabolites: tetrabromopyrrole, 2-(2-hydroxy-3, 5-dibromophenyl)-3, 4, 5-tribromopyrrole, and hexabromo-2, 2-bipyrrole. It also synthesizes n-propyl 4-hydroxybenzoate and 4-hydroxybenzaldehyde. Some of these compounds were shown to be responsible for autoinhibition of the Chromobacterium itself, as well as for antibiotic action against other kinds of bacteria.     

Circadian rhythmicity of locomotor behavior and oviposition in female Teleogryllus commodus

Summary Locomotor activity of the Teleogryllus commodus is under circadian control, with _LL=25.3 h and _DD=23.4 h. In LD 12:12 h, running occurs either exclusively during darkness (57%), mainly in the dark phase (35%), or with substantial activity peaks in both phases (8%). For oviposition, _LL>24 h and _DD<24 h; in LD 12:12 h, 80% of the studied deposited their eggs mainly during the light phase and 20% primarily during darkness. In the discussion, a temporal correlation between stridulation, spermatophore formation, and locomotion, and oviposition is established, which serves to make an encounter and mating between the sexes as likely as possible.Dedicated to Prof. Dr. M. Gersch on the occasion of his 70th birthday     

Importance of the fatty acids 20:5ω 3 and 22:6ω 3 in the diet of plaice (Pleuronectes platessa) larvae

The requirement of plaice (Pleuronectes platessa L.) larvae for the fatty acids 20:5 3 and 22:6 3 was studied. Larvae were reared from first feeding to beyond metamorphosis on Artemia sp. nauplii (EG brand), whose nutritional content had been manipulated by enrichment. Some larvae were fed Artemia rich in 20:5 3 and 22:6 3, and others were fed nauplii with no 22:6 3 and low levels of 20:5 3 (1.9% of the total fatty acids). The differences in diet had no significant difference on growth or survival of the plaice larvae. The results indicate that the plaice larvae in this study did not require 22:6 3 in their diet, even when the levels of 20:5 3 were low.     

Reproductive effort in relation to maternal social rank in reindeer (<Emphasis Type="Italic">Rangifer tarandus</Emphasis>)

In polygynous mammals, high-quality females may increase their fitness by providing superior care to their offspring. Based on the agonistic interactions of female reindeer in an experimental herd during two consecutive years (1997 and 1998), we tested whether maternal social rank influenced: (1) winter body-mass change of females, (2) preparturition reproductive effort (measured as fecundity, the birth mass and the birth date of their calves), (3) preweaning maternal effort (measured as calves preweaning mortality, early preweaning and late preweaning growth rate and September body mass of calves), and (4) postweaning maternal effort (measured as calves body-mass change during their first winter). In the models, we included September females body mass as a covariate to separate the effects of maternal rank and body mass. We also tested whether the effect of social rank on maternal efforts was dependent on offspring sex. High-ranked females gained body mass whereas low-ranked females lost weight during the winter. Fecundity was higher and date of birth was earlier in high-ranked females than in subordinates, whereas no effect of females rank on birth mass of calves was found. Early preweaning growth rate and September body mass of calves increased with increasing females social rank, whereas late preweaning daily growth rate of calves was not influenced by females rank. Calves preweaning mortality was only influenced by year, which also explained most of the variance in the winter body-mass change of calves. The effects of females rank on the reproductive-efforts parameters studied were not specific to offspring sex. These findings suggest that females rank influences reproductive effort during the preparturition, as well as the preweaning, period, the effect being sex independent.Communicated by R. Gibson     

Effects of light intensity on nitrate and nitrite uptake and excretion by Chaetoceros curvisetus

Michaelis-Menten uptake kinetics were observed at all light intensities. With constant illumination, the V_max and K₁ in nitrate uptake over the natural light intensity range of 0 to 2000 E were 0.343 g-at NO₃–N(g)^-1 at protein-N h^-1 and 26 E, respectively. Nitrate uptake was inhibited at higher light intensities. The K_s for nitrate uptake did not vary as a function of light intensity remaining relatively constant at 0.62 g-at NO₃–N 1^-1. With intermittent illumination, the V_mzx for light intensity in nitrate uptake over a light intensity range of 0 to 5000 E was 0.341 g-at NO₃–N(g)^-1-at protein-N h^-1. No inhibition of nitrate uptake was observed at higher than natural light intensities. Chaetoceros curvisetus will probably never experience light inhibition of nitrate uptake under natural conditions.     

Fouling organisms in the port of Mar del Plata (Argentina). I. Siphonaria lessoni: ecological and biometric aspects

The present paper deals with ecological aspects of the pulmonate gastropod Siphonaria lessoni (Blainville, 1824), a common member of fouling communities in Mar del Plata's port (38°0817 S, 57°3118 W). Populations on colonized panels of an experimental raft were studied during three annual cycles, to determine feeding habits, growth and various factors which restrict their distribution on floating substrata. Although S. lessoni is harmless as a fouling organism, its grazing on the algal belt clears a part of the substratum's surface, which is then quickly colonized by truly aggressive organisms such as Balanus amphitrite.     

Investigation of potential gene flow limitation of behavioral adaptation in an aridlands spider

Summary This study investigates the possibility that gene flow underlies the apparently maladaptive behavior of a riparian woodland population of the desert spider Agelenopsis aperta with respect to territorial, foraging, and antipredatory behaviors. I found that other local populations of A. aperta in the vicinity of the riparian woodland habitat are prey-limited and exhibit an aridlands phenotype (high aggressiveness in competitive interactions over energy-based territories and a lack of discrimination among potential prey types). The riparian woodland population deviates from surrounding populations in the area in that prey are abundant and this population shows a mixture of aridlands and riparian (low aggressiveness towards conspecifics and discrimination of prey profitability) phenotypes. Electrophoretic analyses of population subdivision in the area indicate that significant levels of gene flow have occurred, at least, sometime in the past. Drift fence analyses of spider movement futher indicate that there is marked unidirectional movement of spiders each year from the more arid habitats into the riparian woodland. Experimental manipulation of gene flow and predation pressure demonstrates that gene flow restricts adaptation in this habitat: one generation of predation pressure in the absence of gene flow is sufficient to cause a marked shift in spider behavior towards the expected riparian phenotype.     

Studies on the nutritional requirements of the larval stages of Penaeus japonicus using microencapsulated diets

Fatty acid biosynthesis in the larval stages of Penaeus japonicus Bate was examined by feeding microencapsulated diets containing (1-¹⁴C) palmitic acid, and fat-free diets supplemented with defined fatty acids. Highest larval growth rates were achieved on diets containing Tapes philippinarum lipid and, when defined fatty acids were substituted, on diets containing 20:63 fatty acid. The radioactive tracer experiments indicate that 16:17, 18:0 and 18:19 fatty acids may be synthesised from palmitic acid and that P. japonicus larvae may possess the ability to elongate 18:33 to 20:53 and 22:63, and 18:26 to 20:46. However, the rates of these reactions appear to be too slow to meet the larval requirements for essential fatty acids and the 3 series of polyunsaturated fatty acids must be provided in the diet.     

Metabolism of a nonylphenol isomer by Sphingomonas sp. strain TTNP3

For elucidation of the metabolism of the endocrine disruptor nonylphenol by Sphingomonas sp. strain TTNP3, the degradation of an isomer of nonylphenol, 4(2,6-dimethyl-2-heptyl)-phenol, has been studied. As in the case of 4(3,5-dimethyl-3-heptyl)-phenol, the metabolism of this nonylphenol isomer leads to the formation of the NIH-shifted product 2(2,6-dimethyl-2-heptyl)-1,4-benzenediol (NIH: National Institute of Health), but also to the alkoxy derivative 4(2,6-dimethylheptan-2-yloxy)phenol as additional metabolite. To the best of our knowledge, this is the first report describing the formation of alkoxyphenol as a degradation product of nonylphenol. Additionally, these results provide for the first time evidence for slight differences in the biodegradation of the isomers of nonylphenol.     

Digestive carbohydrases from the hepatopancreas of two Antarctic euphausiid species (Euphausia superba and E. crystallorophias)

The hepatopancreatic extracts of Euphausia superba Dana and E. crystallorophias Holt and Tattersall collected from the Antarctic. Ocean during January 1985, are most effective in hydrolysing substrates containing (13)--glucosidic linkages. Three enzymes appear to be involved in the depolymerization of (13)--D-glucans in the euphausiid diet: (1) an exo-(13)--D-glucanase, (2) an endo-(13)--D-glucanase and (3) a -D-glucosidase. The glucanases have a pH optimum of 5.4, a temperature optimum of 50°C and are optimally extracted in bistripropane buffer, pH 7.2. Levels of (13)-D-glucanase in laboratory-cultured E. superba are inversely affected by food availability, and activities double after starvation for 12 d. The increase is due mainly to higher activities of exo-acting glucanases. -Amylase and endo-(14)--D-glucanase (cellulase) activity are also present in the extracts in addition to glycosidase activity against a range of p-nitrophenyl substrates (-and -D-glocose, - and -D-galactose, -D-xylose, - and -D-mannose). Digestive activity against several acidic polysaccharides, including the acidic mucilage polysaccharide of the ice diatom Stauroneis amphioxys, is minimal and is not induced when the polysaccharide is present in the diet of E. superba. These results indicate that some, but not all, components of the algal material in the euphausiid diet can be hydrolyzed and assimilated.