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.     

Laboratory simulation of light-focusing by water-surface waves

A laboratory system has been developed to simulate wave-induced irradiance fluctuations that occur in the top few metres of the sea under sunny surface conditions. A principle of operation is that the fluctuations are produced after refraction of light by water waves generated in the tank. Simulated irradiance consists of repetitive high-amplitude flashes resulting from a lens-effect of the waves. Statistical properties of flashes are similar to those recorded at sea. In our laboratory simulation, the flashes that exceed an amplitude level of 1.5 (where is the time-averaged irradiance) have a mean frequency of about 230 min^-1, and a typical duration of 5 to 20 ms. The frequency of the flashes decreases exponentially with increasing amplitude level. The system simulates timeaveraged irradiance comparable to full sunlight at shallow depths (800 mol quanta m^-2 s^-1 over the visible spectral region), and provides light with a reasonable spectral composition. The simulation method was designed for studying responses of phytoplankton, but applications involving optical aspects can also be foreseen.     

Environmental influence on the locomotor activity rhythm of the sand-shore amphipod Talorchestia deshayesi

The precision and persistence of the nocturnal, surface locomotor activity rhythm of the sand-beach amphipod Talorchestia deshayesi is described. The rhythm is expressed as a circadian activity period with no evidence of a circa-tidal component associated with the time of high tide. The rhythm is light-sensitive and entrainment occurs in response to changes in the time of an experimentally simulated dusk transition. Locomotor activity is initiated at the end of the dusk transition with cessation always occurring prior to dawn. The point of activity initiation is taken to be the position of a synchronizing cue controlling entrainment. The cue appears to be an absolute irradiance level of approximately 1.0 to 2.0×10^-4 W m^-2     

Habitat and age of the giant squid (<Emphasis Type="Italic">Architeuthis sanctipauli</Emphasis>) inferred from isotopic analyses

The age and habitat of the giant squid, Architeuthis sanctipauli Velain, 1877, were determined based on isotopic analyses of the statoliths of three female specimens captured off Tasmania, Australia, between January and March 1996. Assuming that the aragonite of the statoliths formed in equilibrium with seawater, ¹⁸O analyses indicated that the squid lived at temperatures of 10.5–12.9°C, corresponding to average depths of 125–250 m and maximum depths of 500 m. The capture records indicated that these squid may have occasionally ranged still deeper, to as much as 1000 m. All the statoliths were labeled with bomb ¹⁴C (¹⁴C=+22.9 to +44.6), consistent with the depths inferred from ¹⁸O. A thin section through one of the statoliths revealed 351 growth increments grouped into check-ring structures every 10–16 increments. A model for statolith growth and the pattern of temporal change in ¹⁴C in the water column was used to estimate the ages of the three specimens. These estimates were very sensitive to the choice of depth range over which ¹⁴C values were integrated. Assuming that the capture depths represented the maximum habitat depths of these individuals, the calculations suggested an age of 14 years or less. More refined age estimates require a better understanding of the variation of ¹⁴C and temperature with depth in the areas in which the squids live.Communicated by J.P. Grassle, New Brunswick     

Triterpenoid and caffeic acid derivatives in the leaves of ragweed, <Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> L. (Asterales: Asteraceae), as feeding stimulants of <Emphasis Type="Italic">Ophraella communa</Emphasis> LeSage (Coleoptera: Chrysomelidae)

Summary. The leaf beetle Ophraella communa infests almost exclusively Ambrosia artemisiifolia in the fields of Japan, even though it normally feeds on several Asteraceous plants. A filter paper bioassay showed that the feeding of O. communa is strongly stimulated by methanolic extracts of A. artemisiifolia. The feeding stimulants for O. communa have been isolated from methanolic extracts of A. artemisiifolia. -Amyrin acetate, -amyrin acetate, 5-caffeoylquinic acid (chlorogenic acid) and 3,5-dicaffeoylquinic acid from A. artemisiifolia have been identified as feeding stimulants for O. communa. Triterpenoid derivatives (-amyrin acetate or -amyrin acetate) and caffeic acid derivatives (3, 5-dicaffoylquinic acid or 5-caffeoylquinic acid) showed feeding stimulant activity when mixed together.     

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.     

Precision and accuracy of stable isotope signals in otoliths of pen-reared cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) when sampled with a high-resolution micromill

A high-resolution sampling technique for stable-isotope measurements in otoliths is now available, but little is known about the precision and accuracy of the results when using this technique. Otolith samples of pen-reared cod (Gadus morhua L.) with well-defined temperature history were obtained using this high-resolution sampling technique. Samples from different-aged cod otoliths were collected in two yearly increments corresponding to the calendar years 1994 and 1995, and the stable-oxygen (¹⁸O) and -carbon (¹³C) isotope compositions of the samples were measured. Otolith ¹⁸O values had a clear seasonal pattern in response to the seasonal water temperature. Otolith material deposited in the same calendar years of different-aged fish showed similar ¹⁸O values. High precision of the temperature estimate using otolith ¹⁸O values was obtained when comparing results from different otoliths. The accuracy of the temperature estimates, relative to measured mean monthly water temperature, was also high, but reduced sampling resolution in the otoliths significantly reduced the accuracy due to attenuation of the ¹⁸O signals. We found that the otolith ¹³C values had a cyclic pattern, roughly in phase with the ¹⁸O values. This was most likely caused by temperature-increased metabolism. Indications of age-specific otolith ¹³C values are also presented.Communicated by M. Kühl, Helsingør     

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.     

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.     

Carbon fixation in marine phytoplankton: carboxylase activities and stable carbon-isotope ratios; physiological and paleoclimatological aspects

We measured the activity of three carboxylases: RuBP carboxylase, PEP carboxylase and PEP carboxykinase of marine phytoplankton species in culture and in natural communities. Activities of the three carboxylases were measured simultaneously with stable carbon-isotope ratios. The enzymatic activities have been used to estimate the importance of carboxylation and its impact on the ¹³C:¹²C ratio (expressed as ¹³C). The marine phytoplankton species in culture were Fragilariopsis kerguelensis, Nitzschia turgiduloides, Skeletonema costatum, Phaeodactylum tricornutum, Isochrysis galbana, Dunaliella marina, and Prorocentrum micans, and the field samples were collected from different depths off the coast of Portugal (August/September, 1981). Our results indicate that, as in terrestrial plants, the ¹³C value is a good indicator of the extent of carboxylation. RuBP carboxylase activity was always predominant, whereas the ¹³C value never reached values typical of the C₄ pathway. The carboxylases could be PEP carboxylase (in dinoflagellates) or PEP carboxykinase (in diatoms). carboxylation increased at the end of the exponential growth phase in a diatom culture and with increased biomass in natural samples. We interpret these increases as an adaptative response mechanism to poor environmental conditions, especially to low light intensity.     

Stable isotope and biochemical fractionation in the marine pelagic food chain: the jellyfish Pelagia noctiluca and net zooplankton

In our field study we analyzed the C and H isotopic and biochemical (C, N, P, protein, lipid, carbohydrate) composition of the jellyfish Pelagia noctiluca (collected from the Gulf of Trieste in 1985 to 1986) and its presumed diet-net zooplankton. The mean ¹³C (-18.8) and D (-58.4) ratios of P. noctiluca showed enrichment in heavy isotopes relative to net zooplankton (2 for carbon and 30 for hydrogen). Both the jellyfish and net zooplankton were characterized by a linear correlation between ¹³C and D. C. N, P, protein, lipid, and carbohydrate contents of P. noctiluca were low on a dry weight basis as compared to net zooplankton. Significantly lower C:N and C:P ratios were found in jellyfish indicating a greater loss of carbon relative to nitrogen and phosphorus along the passage to a higher trophic level. Isotopic and biochemical evidence indicate that, though collected in nearshore waters, P. noctiluca depended on autochthonous marine organic matter.     

Song as an attractant for male and female European starlings,and the influence of song complexity on their response

Summary We tested the hypothesis that song attracts females and repels males in the European starling. We broadcast recorded song from speakers attached to nestboxes, while paired boxes with silent speakers served as controls. As predicted, females were attracted to the song boxes. Contrary to prediction, males were also attracted to the `song' boxes. Singing by male starlings may be costly because it attracts competitors for limited nesting sites, but the cost cannot be avoided due to the need to attract a mate. In a second experiment simple song (composed of 20 different phrase types) and complex song (40 phrase types) were played simultaneously. More males were captured at boxes where simple song was played. Song complexity may function as an indicator of male quality and be used by male starlings to assess potential competitors.     

Le système assimilation-régénération des sels nutritifs dans les eaux superficielles de l'océan Austral

Low primary-productivity levels in high-nutrient environments of the Southern Ocean are not yet well understood. An accurate knowledge of nutrient assimilation by phytoplankton, at the base of the pelagic food-web, therefore appears to be essential. A study of the mesoscale hydrological structure and chemical observations in the upper layers of the Indian sector of the Antarctic Ocean (Cruise MD-25 FIBEX of M.S. Marion Dufresne, January–February 1981) permitted us to develop a method for estimating nutrient consumption by phytoplankton. After strong vertical mixing in winter, the homogeneous Antarctic Surface Water (ASW) is, in summer, divided into two parts by a well-formed pycnocline. In the upper layer, corresponding approximately to the photic zone, we observed nutrient depletion resulting from photosynthetic activity, while the underlaying thermal minimum layer displayed unaltered winter characteristics, including nutrient concentrations typical of winter surface-water conditions. Taking into account the nutrient depletion in summer, we calculated the assimilation ratios for Antarctic phytoplankton as follows: ([NO ₃ ^- lower]-[NO ₃ ^- upper]):([PO ₄ upper])=N:P=11.2±2.4 and N:Si=0.27±0.05. These ratios are lower than the classical Redfield ratios (N:P=16 and N:Si=1), but are in good agreement with the elementary composition of phytoplankton samples collected during the same cruise. Moreover, they agree with previously published data on stoechiometric determinations of particulate matter in surface-water samples. Besides, in the transition layer between the lower layer and Warm Deep Water (WDW), the calculated mineralization ratios were slightly higher than the assimilation ratios: N:P=14.6 and N:Si=0.37. From these ratios, it would appear that, in these surface layers of the Southern Ocean (down to 250 m), assimilation-regeneration mechanisms operate in such a way that phosphate and silicate contents decrease much more than nitrate content during the northward drift of the surface waters. The determination of assimilation ratios taking into account the nutrient depletion of the upper layer allowed us to evaluate the carbon net-production which integrates time-space variations in the photic layer over the whole early summer period. We estimated a production rate (0.4 g C m^-2 d^-1) of the same order of magnitude as the mean value obtained by the ¹⁴C method (0.2 g C m^-2 d^-1). The theoretic silicium consumption by phytoplankton along a meridian transect, calculated using an estimated assimilation ratio of C:Si=1,85, indicates that the marked south-north decrease in silicate concentration in the Antarctic Surface Water would mainly result from biological activity. The silicate concentrations thus calculated were in good agreement with concentrations measured along a previous transect across the Southern Ocean.

---

Le système assimilation-régénération des sels nutritifs dans les eaux superficielles de l'océan Austral

     

Bleaching in<Emphasis Type="Italic"> Amphistegina gibbosa</Emphasis> d’Orbigny (Class Foraminifera): observations from laboratory experiments using visible and ultraviolet light

Bleaching (visible loss of symbiont color) in populations of the diatom-bearing foraminifer Amphistegina has been recorded from reefs worldwide since 1991. Field studies and previous laboratory experiments have strongly implicated solar radiation as a factor in bleaching stress. The influence of spectral quality and quantity of photosynthetically active radiation (PAR) and ultraviolet radiation (UV) on growth rates and bleaching in Amphistegina gibbosa was investigated in the laboratory using fluorescent sources of PAR (blue with a spectral peak at 450 nm and white with a 600-nm spectral peak) and biologically effective ultraviolet radiation [UVB (280–320 nm)]. Growth rate, as indicated by increase in maximum shell diameter, saturated at a PAR of 6–8 mol photon m^–2 s^–1, increased in blue light, and was not influenced by UVB0.0162 W m^–2. Frequency of bleaching increased with increasing PAR photon flux density and with exposure to shorter wavelengths, with or without an increase in total energy. Growth was significantly inhibited by UVB at 0.105 W m^–2. Specimens in treatments exposed to UVB to PAR ratios >0.003 became dark in color, rather than bleaching, which previous cytological studies indicate is a photo-protective response. Implications of these experiments are that environmental factors that affect either the spectral quality or quantity of solar radiation can influence bleaching in Amphistegina.Communicated by P.W. Sammarco, Chauvin

---

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.     

Effect of daylight variations on the energy budgets of shallow-water corals

Energy budgets were determined for small pieces (nubbins) of the coralsPocillopora damicornis, Montipora verrucosa andPorites lobata living at a water depth of 3 m on the fringing reef of Coconut Island, Kaneohe, Hawaii. The budgets were determined for three different types of day: an ideal day with no cloud and an in situ daily integrated irradiance at 3 m of 14.385 E m^–2 d^–1; a normal day with sporadic cloud cover and daily irradiance of 11.915 E m^–2 d^–1; and an overcast day with daily irradiance of 6.128 E m^–2 d^–1. On the ideal day, the energy fixed in photosynthesis was more than that required for respiration and growth of both zooxanthellae and animal components of the association, and there was a predicted loss of between 19.3 and 32.4% of the energy fixed. On a normal day, the total photosynthetic energy fixation was lower and the excess was between 12.1 and 27.9% of the energy fixed. On the overcast day, however, in bothPocillopora damicornis andPorites lobata energy expenditure exceeded photosynthetic energy fixation and the budget was in deficit. Estimates of rate of mucus secretion on an overcast day were derived and, when incorporated into the energy budget, it was predicted that all three species would have a deficit budget, necessitating the catabolism of lipid reserves. From published values for lipid storage in these species it was calculated that the reserves would last from 28 d inPocillopora damicornis to 114 d inM. verrucosa. A model is suggested in which corals draw upon their extensive lipid stores on days of sub-optimal light, replenishing the reserves again when daily light levels are high, and finally excreting the excess energy fixed, as mucus-lipid when the lipid stores are replete.     

Trunk trails and the searching strategy of a leaf-cutter ant,Atta colombica

Summary Atta colombica uses chemical mass recruitment that allows the rapid exploitation of resources. Most foragers thus search only within patches. Accumulation of extra foragers at patches results in sampling of alternate food items and area-restricted search as patch resources are depleted.Individual workers have a higher probability of removing a leaf fragment the earlier they arrive at a bait. Workers that arrive when much of the resource is gone travel further on the bait (within the patch) but do not spend significantly more time at the patch. They give up after 50–80s.Foraging effort is centered on the extensive trail system, not on the nest a predicted by time and energy foraging models. Search effort is also trail centered. The probability that an item will be discovered decreases with distance from the trail and increasing litter depth. Trail traffic and trail quality together mave no significant effect although this may be because they act antagonistically.Economic considerations predict that trials should be built to high quality and very productive sites. If trails are built as a result of recruitment and recruitment reflects patch quality and productivity, characteristics of forage sites are physically embodied in the trail system.Leaf cutter foraging is better understood as a long term optimization that effectively exploits resources over the lifetime of the colony than as prudent predation that husbands resources.     

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.     

Potential effects of a resuspension event on the vertical distribution of copepod eggs in the sea bed: a laboratory simulation

Adult female Acartia tonsa and Labidocera aestiva were obtained from inshore marine waters near Turkey Point, Florida (29°54.5N;84°31W) during April and May 1991. For each species, eggs spawned overnight in the laboratory were collected, mixed with sediment, and added to a plastic tube (26 to 29 cm longx5 cm diam) to yield a 2 cm-thick layer. This tube was connected to a 245 cm-long tube, seawater was added and the contents were thoroughly mixed by turning the assembly end-over-end several times. The vertical distribution of eggs in the sediments following resuspension varied according to the grain size of the sediments. For sediments of 125 m particle-diameter, 68 to 72%, and 70 to 73% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm.For sediments 63 to <125 m particle-diameter, 34 to 36% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm. For sediments of <63 m particle-diameter, egg distribution was uniform for both species throughout the 2 cm layer. The results indicate that the vertical distribution of eggs in the sea bed following a resuspension event should be highly dependent upon the grain-size composition of the sediments.     

Ecological investigations of the late-stage phyllosoma and puerulus larvae of the western rock lobster Panulirus longipes cygnus

The distribution and abundance of the late-stage phyllosoma larvae of Panulirus longipes cygnus George and the distribution and densities of the final larval stage, the puerulus, both in the plankton and at settlement along the coast, were investigated. A total of 3,617 late-stage phyllosoma (Stages VI to IX) and 301 puerulus larvae were caught at 187 plankton stations during the July to November periods 1974, 1975 and 1976 off the west coast of Australia between 29°00 to 32°30S and 113°30 to 115°00E. The depth range sampled was 0 to 35 m on the continental shelf and 0 to 90 m off the shelf. During onshore/offshore cruises with similar sampling effort on and off the shelf, 1,169 late-stage phyllosoma larvae were taken, of which only 9 were caught on the shelf, and these near the outer edge. A series of cruises sampling two areas beyond the shelf near 29°30 and 32°00S yielded 2448 late-stage phyllosoma, with greater densities of larvae in the northern location. The settlement of puerulus-stage larvae along the coast in the same geographical range was also greater in the north than in the south. The data from the onshore/offshore cruises showed a definite effect of moon phase on numbers of puerulus larvae caught on the shelf, with higher catches near new moon. The low numbers of puerulus larvae (usually 0, 1 or 2 individuals) caught at all stations showed that the puerulus stage is sparsely distributed in the plankton. Fewer puerulus larvae were present at the surface than at lower depths, but it was not possible to determine a depth preference for the puerulus between 10 m and the lowest depths sampled because of the low catch numbers. No relationships were found between puerulus larvae density and surface-water temperature, salinity, or plankton biomass at each station. Data on the larval distributions indicate that, near the end of their planktonic existence, the majority of the late-stage phyllosoma larvae of P. longipes cygnus are not carried onto the shelf, where mixing of oceanic and continental shelf waters occurs only on the outer third, but are transported southward by oceanic circulation beyond the shelf. The puerulus moults from the last phyllosoma stage beyond the shelf and completes the larval cycle by swimming across the shelf and settling in the shallow reef areas.