Chemical composition and effects of water extracts of petroleum on eggs of the sand dollar Melitta quinquiesperforata

Sperm and eggs of sand dollars, Melitta quinquiesperforata (Leske), were subjected to two petroleum oils, and effects determined. The oils chosen were Kuwait crude and No. 2 fuel oil, supplied by the American Petroleum Institute. Water-soluble extracts (WSF) from oil-sea water mixes were prepared and the major aromatic components in the WSF of the fuel oil were identified. WSF of No. 2 fuel oil depressed respiration, mobility of sperm, interfered with fertilization and cleavage, and retarded larval development. The effects were detectable at dilutions of 4% and less (about 0.6 ppm of WSF). Kuwait crude was much less toxic. There was no effect on water permeability of the egg membrane. Results are compared with similar studies on other marine organisms.     

Reproductive cycles in two populations of the Pacific sand dollar Dendraster excentricus

East Pacific swimming crabs are poorly known ecologically. We trawled samples along 4 estuarine-continental shelf transects to provide information on the population structure and species composition of portunids along environmental stress gradients. Portunids comprised almost 99% of the benthic crabs. Callinectes toxotes dominates the freshest estuarine areas, but is replaced by C. arcuatus in estuary mouth and shallow-shelf samples. Deeper shelf samples are dominated by Euphylax robustus and Portunus sper. Great numbers of E. dovii, a pelagic species, were taken on the shelf; their size distribution implies intraspecific competition. Evidence is given that differences in salinity tolerance account for differential landward limits, but competition, predation by fishes, increased fouling and decreased available food exclude eurytopic species from physicochemically equable shelf waters.     

Diverticulum sand in a miniature sand dollar Sinaechinocyamus mai (Echinodermata: Echinoidea)

Sinaechinocyamus mai (Wang) were collected from the low intertidal zone at Tunghsiao, western Taiwan, periodically from July 1990 to July 1991 and May 1993. The mean body length was 7.3±1.01 mm from 146 juveniles and adults. All individuals contained sand grains in their intestinal diverticula. The densities of sand dollars ranged from 1.2 to 2.5 mg cm^-3 and had an inverse linear relationship to the body length. The percentage of sand weight in the diverticulum to the wet body weight is inversely correlated to the body length, indicating that juveniles contain a higher proportion of sand than adults. The ratio of sand weight to body length did not change significantly during the study period. 74% of the diverticulum sand was 0.075 to 0.125 mm in diameter, whereas only 0.1% of the sand in the substrate was this size. The sand in both the diverticulum and the substratum consisted of feldspars and quartz (88.4%) and iron oxide (11.6%). The sand grains of the diverticulum were eliminated from the anus.     

Larval abundance and recruitment of the sand dollar Dendraster excentricus in Monterey Bay,California, USA

Seasonal abundance of planktonic larvae of the sand dollar Dendraster excentricus was determined in Monterey Bay, California, USA. Larvae were counted from two offshore stations and also over a coastal sand dollar bed, and these data were compared with settlement in the sand dollar bed, with adult population structure and with adult reproductive condition. These measurements were made during the period July 1978 to October 1980 and in October 1981. Sand dollar larvae were most abundant in the plankton during the summer, a period when phytoplankton productivity tended to be high and currents were relatively slow and variable. In some years, small-scale current variations appeared to prevent many larvae in the open bay from reaching the nearshore sand dollar beds; however, in other years, massive shoreward transport of the larvae evidently did occur, since the adult population in the sand dollar bed exhibited a mode in size, indicating a large settlement. A comparison of settled individuals in 1980 and the adult size-frequency distribution in 1981 gives an estimated mortality rate of 88% yr^-1 for early juveniles of D. excentricus.     

Fertilisation, embryogenesis and larval development in the tropical intertidal sand dollar Arachnoides placenta in response to reduced seawater pH

We examined the response of the tropical sand dollar Arachnoides placenta to reduced seawater pH in experiments spanning ca. 50 % of the planktonic larval duration. A. placenta inhabits intertidal sandy beaches where we observed a minimum in situ pH range 0.06 pH units (pH 8.10–8.16). The responses of gametes and larvae to seawater pH were tested in vitro in ambient (pH 8.14, pCO₂ = 525.7 μatm, total alkalinity = 2,651 μmol kg soln^?1) and three reduced pH seawater treatments (7.8–7.0). Percentage fertilisation decreased significantly with decreasing pH across a range of sperm/egg ratios (4:1 up to 4,000:1). A. placenta reached the advanced pluteus stage in 4 days, and during this time, we saw no difference in survival rate of larvae between the ambient (67 %) and pH 7.79 (72 %) treatments. Four-day survival was, however, reduced to 44 and 11 % in the pH 7.65 and 7.12 treatments, respectively. Larval development and morphometrics varied among pH treatments. Embryos reared in pH 7.12 exhibited arrested development. Larvae reared at pH 7.65 showed delayed development and greater mortality compared with those reared at pH 7.79 and 8.14. When larval morphometrics are compared among larvae of the same size, differences in larval width and total arm length between pH treatments disappear. These results suggest that variation in larval size among the three highest pH treatments at a given time are likely the result of slower development and apparent shrinkage of surviving larvae and not direct changes in larval shape. There were no differences in the percentage inorganic content (a proxy for calcification) in larvae reared in either an ambient or a pH 7.7 treatment. The responses of fertilisation and development to decreased pH/increased pCO₂ in A. placenta are within the range of those reported for other intertidal and subtidal echinoid species from colder latitudes.     

An experimental analysis of compliance in dynamic emissions markets

Two important design elements for emission trading programs are whether and to what extent firms are able to bank emissions permits, and how these programs are to be enforced. In this paper we present results from laboratory emissions markets designed to investigate enforcement and compliance when these markets allow permit banking. Banking is motivated by a decrease in the aggregate permit supply in the middle of multi-period trading sessions. Consistent with theoretical insights, our experiments suggest that high permit violation penalties have little deterrence value in dynamic emissions markets, and that the main challenge of enforcing these programs is to motivate truthful self-reports of emissions.     

An experimental study of song type function in the bobolink (Dolichonyx oryzivorus)

Summary We tested the hypothesis that the alpha and beta songs of male bobolinks (Dolichonyx oryzivorus) have separate intrasexual and intersexual functions by presenting caged males and caged females on the territories of male bobolinks. Although all males in our study population share both alpha and beta songs, we found no evidence for a specialized intersexual function of alpha song or a specialized intrasexual function of beta song. Territorial males increased their singing rate of both alpha and beta songs during both the male presentations and the female presentations. The proportions of the two song types did not change between control and experimental periods for either male or female presentations. We found no evidence in support of specialized intrasexual and intersexual functions of note types. Only 10% of the vocalizations initiated by territorial males were complete alpha or beta songs, while 87% were song fragments, and the remaining 3 % were compound songs. We did find that territorial males responded to simulated male intruders by increasing the proportion of fragmented songs and decreasing the proportion of compound songs. Moreover, males included fewer notes per song initiated and sang a higher proportion of songs that included only introductory notes during male presentations. We conclude that the vocal response of territorial male bobolinks to conspecific male intruders is to sing short, simple sequences of either song type. We found no consistent changes in vocal behavior of territorial males in response to female presentations other than increases in song rates.     

An experimental and theoretical analysis of floating wood diffusion coefficients

Environmental Fluid Mechanics - Wood transport during high flow events is here treated as an advective–diffusive phenomenon. A theoretical definition of the governing equation is first...     

Seasonal and diel variation in movement rhythms of sand dollar, Peronella lesueuri (Valenciennes 1841), in Cockburn Sound, Western Australia

Rates and direction of movement in the sand dollar Peronella lesueuri were measured in summer and winter in Cockburn Sound, a large coastal embayment in south-western Australia. P. lesueuri was found to have a diurnal activity pattern throughout the year and had a greater movement rate in the summer (mean of 5.3 cm h^?1, day; 3.9 cm h^?1, night) than in the winter (mean of 2.7 cm h^?1, day; 2.0 cm h^?1, night). Seasonal change in temperature and physiological requirements by the sand dollar are the most likely reason for the seasonal differences. Reasons for diurnal variation were not clear. Direction of movement was found to be random at both times of the year. Based on these movement rates, one sand dollar can bioturbate an approximate area of 0.1 m² day^?1 and 36.4 m² year^?1. At a conservative density estimate of 0.5 sand dollars per m² it takes approximately 20 days for the sand dollars to rework the entire area of the sediments in the habitats they occupy.     

An experimental and theoretical analysis of the effect of added weight on the energetics and hydrostatic function of the swimbladder of European sea bass (Dicentrarchus labrax)

We conducted experiments to determine the effect of the increasing ultrasonic/radio transmitter weight on the routine metabolic rate of sea bass. We measured the oxygen consumption (MO₂) of fish tagged externally with a dummy transmitter made of a hollow pipe, the weight of which was adjusted with lead to represent in water 0, 1 and 4% (R_tf) of the animal weight. We then developed a theoretical model to estimate, for a given fish size, the range of added weight that fish can compensate for through swimbladder regulation. When R_tfБ%, MO₂ of untagged and tagged fish did not differ significantly. However, when R_tf reached 4%, fish that carried a tag incurred a significant elevation of oxygen consumption, which represented 28% of their total useable power (or metabolic scope). This result strongly supports the view that a high R_tf ratio contributes to a decrease in available metabolic energy by diverting energy from, e.g., growth or swimming performance. A comparison between the tagged fish and the theoretical model reinforced the hypothesis that, when R_tf attained 4%, the increase in metabolic rate reflected a supplementary and costly swimming effort necessary to maintain vertical position. In this condition, the swimbladder cannot regulate the buoyancy of tagged fish.     

流动沙丘上生态垫防风固沙效果初步评价

北京及其周边地区分布的大量裸露沙荒地是北京近年来沙尘暴频发的主要沙源之一,而增加其地表覆盖状况则是遏止就地扬沙起尘的有效措施之一。以北京西北部河北宣化黄羊滩为例,对流动沙丘上铺设生态垫并栽植灌木的防风固沙效果进行了初步研究。研究结果表明,与沙柳沙障相比,生态垫确实可以降低近地表的输沙率,提高生态垫下土壤的养分含量,一定程度上提高柠条的地径和高度,可见生态垫是一种很好的促进流沙固定和植被恢复的地表覆盖材料;与其它两种生态垫铺设方式(品字状和带状)相比,全铺可以显著降低近地表的输沙率,提高其下土壤的养分含量,但柠条的生长状况却略差,这可能与全铺降低了小雨入渗的可能性有关;就两种部分铺设的方式而言,无论从降低近地表的输沙率还是促进柠条的生长上来看,品字状都明显优于带状。从生态和经济的角度综合考虑,品字状铺设显然是该区域流沙防治措施中较好的选择。     

Female choice of a non-bodily ornament: an experimental study of cichlid sand craters in Cyathopharynx furcifer

In many species of East African cichlids, males build sand craters or “bowers” to attract females for spawning. It is commonly assumed that these exaggerated sexual traits have a function similar to bodily ornaments. In non-bodily ornaments, however, the behaviour creating the structure may serve as an additional source of information to potential partners, providing multiple signals for mate choice. We tested whether and to what extent females use these signals for choosing males by observing the individual sampling behaviour of female Cyathopharynx furcifer in the field. In addition, we experimentally manipulated crater characteristics in the field and laboratory. We found that females spawn preferably with owners of large and well-maintained craters, but when crater size was enlarged or reduced, the resulting building activity of crater owners affected female choice more strongly than the manipulated crater size per se. We discuss the importance of multiple signals in species constructing extended phenotypes.     

Coastal sand dune vegetation: An extreme case of species invasion

The coastal sand-dune flora of the Gulf and Caribbean region of Mexico was analyzed to understand differences in floristic composition and richness found along the coast. Each of the 655 species reported was classified according to its ecology and distribution range by checking herbaria specimens, literature and specialists. Three groups were formed: (a) species with predominantly coastal distribution; (b) ruderal or secondary species frequently found inland, common of disturbed areas such as roadsides, abandoned fields or forming part of secondary growths; (c) inland species frequently found in other vegetation types such as tropical dry or seasonal forest and grassland. A total of 71 coastal species, 237 ruderal/secondary and 336 species from other community types were found. The distribution of these groups was analyzed along 44 sites of the Gulf and Caribbean, in the different dune habitats and for the dominant growth forms. Coastal species are more widely distributed; they predominate in habitats with sand movement and the herbaceous component prevails. Ruderal/secondary species and especially those belonging to other vegetation types frequently appear in only one or two sites occupying more protected or stabilized habitats. The two latter groups considerably increase species richness of sand dune flora, but also pose interesting problems for dune conservation.     

Marine food-web analysis: An experimental study of demersal zooplankton using isotopically labelled prey species

Short-term incubations in seawater containing H¹⁴CO₃ ^- or ³H₂O in place of the naturally predominant isotopes can yield highly radioactive preparations of living phytoplankton or zooplankton. Subsequent in situ incubation of these labelled organisms with the community from which they were taken results in the rapid transfer of radioisotope to those species which prey upon them. This technique has been employed to map a portion of a marine food web involving demersal zooplankton; experiments were conducted in summer and autumn on a coral reef and in a subtropical estuary. Similar results were obtained from these initial experiments at each study site during both seasons. Prey supplied as zooplankton (124 to 410 m nominal diameter), which consisted mainly of Oithona oculata, was fed upon by zooplankton size classes ranging from 410 to 850 m and containing amphipods, ostracods, cumaceans and polychaetes. In experiments employing labelled phytoplankton as prey a wide size spectrum was used (10 to 106 m) in order to include representative samples of most of the available planktonic autotrophs as estimated by primary production measurements. In two separate experiments, only 7 out of 63 samples evidenced grazing of phytoplankton by demersal zooplankters. In contrast, labelled diatom auxospores, employed in one experiment as they constituted the most numerically abundant species in the water column, were found to be grazed upon in nearly half the samples examined.     

An experimental study of paternal behavior in red-winged blackbirds

Summary The effect of brood size and female nesting status on male parental behavior was investigated in red-winged blackbirds Agelaius phoeniceus using brood size manipulation experiments. Male redwings allocated parental effort on the basis of brood size and nestling age. Males began assisting females only at nests with at least three offspring older than three days. Female nesting status had no singificant influence on male parental care. When females were unable to meet a brood's demand for food, males assisted females with nestling feeding. Females did not reduce the amount of food delivered to nestlings when males assisted. The amount of food brought to nestlings by the male was additional to the amount of food provided by the female. Male assistance increased fledgling success. When female provisioning was sufficient to meet a brood's demand for food males did not assist. The value of male parental care varied inversely with the ability of the female to meet nestling food demands. The ability of unassisted females to provide sufficient food and to raise a brood of nestlings successfully appeared to be influenced by resource abundance.     

An experimental test of alternative population augmentation scenarios

Human land use is fragmenting habitats worldwide and inhibiting dispersal among previously connected populations of organisms, often leading to inbreeding depression and reduced evolutionary potential in the face of rapid environmental change. To combat this augmentation of isolated populations with immigrants is sometimes used to facilitate demographic and genetic rescue. Augmentation with immigrants that are genetically and adaptively similar to the target population effectively increases population fitness, but if immigrants are very genetically or adaptively divergent, augmentation can lead to outbreeding depression. Despite well‐cited guidelines for the best practice selection of immigrant sources, often only highly divergent populations remain, and experimental tests of these riskier augmentation scenarios are essentially nonexistent. We conducted a mesocosm experiment with Trinidadian guppies (Poecilia reticulata) to test the multigenerational demographic and genetic effects of augmenting 2 target populations with 3 types of divergent immigrants. We found no evidence of demographic rescue, but we did observe genetic rescue in one population. Divergent immigrant treatments tended to maintain greater genetic diversity, abundance, and hybrid fitness than controls that received immigrants from the source used to seed the mesocosms. In the second population, divergent immigrants had a slightly negative effect in one treatment, and the benefits of augmentation were less apparent overall, likely because this population started with higher genetic diversity and a lower reproductive rate that limited genetic admixture. Our results add to a growing consensus that gene flow can increase population fitness even when immigrants are more highly divergent and may help reduce uncertainty about the use of augmentation in conservation.     

An estimating function approach to the inference of catch-effort models

A class of catch-effort models, which allows for heterogeneous removal probabilities, is proposed for closed populations. The model includes three types of removal probabilities: multiplicative, Poisson and logistic. The usual removal and generalized removal models then become special cases. The equivalence of the proposed model and a special type of capture-recapture model is discussed. A unified estimating function approach is used to estimate the initial population size. For the homogeneous model, the resulting population size estimator based on optimal estimating functions is asymptotically equivalent to the maximum likelihood estimator. One advantage for our approach is that it can be extended to handle the heterogeneous populations in which the maximum likelihood estimators do not exist. The bootstrap method is applied to construct variance estimators and confidence intervals. We illustrate the method by two real data examples. Results of a simulation study investigating the performance of the proposed estimation procedure are presented.     

An experimental study of the relationship between below-ground structure and meiofaunal taxa

An experimental study was conducted in a South Carolina, USA salt marsh to examine relationships between meiofaunal-sized tube structure and densities of burrowing meiofauna. Abundance of the tube-building polychaete Manayunkia aestuarina Bourne was increased by erecting exciosure areas from June–August 1979. Non-manipulated areas of identical dimensions were staked out in adjacent locales. Densities of burrowing meiofauna and nematode trophic groups, and volumes of Spartina alterniflora root mat and tube-builders were monitored approximately every 2 wk from each experimental treatment. Volumes of tube-builders were significantly higher inside exclosure sites on all dates in July and August. Root-mat volume and total number of nematodes were not different between treatments at any time. The dominant copepod species, Stenhelia (D.) bifidia, and the nematode species, Spirinia sp., first increased in number inside manipulated sites and then decreased in abundance as tube volume increased. No general trend was apparent for nematode trophic groups when areas with increased volumes of tubebuilders were compared to unmanipulated sites. The fact that densities of S (D.) bifidia and Spirina sp. decreased only when tube-builders attained highest abundance suggests that negative interactions between tube-builders and these meiofaunal taxa may be effective only at elevated abundances.     

An experimental field test of host-finding mechanisms in a Caribbean gnathiid isopod

Field experiments were conducted from dusk to dawn off St. John (18° 18′ 59.32″ N, 64° 43′ 24.5″ W) and Guana Island (18° 28″ 28.31″ N, 64° 34′ 30.83″ W), Virgin Islands from June through August 2008-2010 to assess the sensory cues used by the nocturnal/crepuscular fish-parasitic gnathiid isopod, Gnathia marleyi, to locate fish hosts. Experimental traps providing both visual and olfactory cues from live French grunts (Haemulon flavioliniatum) attracted significantly more gnathiids than traps providing only visual cues or control traps (empty or with a rock), which were not significantly different from each other. In another experiment, traps providing both cues and only olfactory cues attracted significantly more gnathiids than empty control traps, but were not significantly different from each other. Our findings suggest that during nocturnal and crepuscular periods, visual cues provided by resting or slow-moving fish are not alone sufficient to attract gnathiids, while olfactory cues alone are. The traps designed for this study offer a new method of sampling free-living gnathiid isopods.     

An experimental evaluation of transgenerational isotope labelling in a coral reef grouper

Transgenerational isotope labelling (TRAIL) using enriched stable isotopes provides a novel means of mass-marking marine fish larvae and estimating larval dispersal. The technique, therefore, provides a new way of addressing questions about demographic population connectivity and larval export from no-take marine protected areas. However, successful field applications must be preceded by larval rearing studies that validate the geochemical marking technique, determine appropriate concentrations and demonstrate that larvae are not adversely affected. Here, we test whether injection of enriched stable barium isotopes (¹³⁵Ba and ¹³⁷Ba) at two dose rates produces unequivocal marks on the otoliths of the coral reef grouper Epinephelus fuscoguttatus. We also assess potential negative effects on reproductive performance, egg size, condition and larval growth due to injection of adult female fish. The injection of barium isotopes at both 0.5 and 2.0 mg Ba/kg body weight into the body cavities of gravid female fish was 100% successful in the geochemical tagging of the otoliths of larvae from the first spawning after injection. The low-dose rate produced no negative effects on eggs or larvae. However, the higher dose rate of 2 mg Ba/kg produced small reductions in yolk sac area, oil globule area, standard length and head depth of pre-feeding larvae. Given the success of the 0.5 mg Ba/kg dose rate, it is clearly possible to produce a reliable mark and keep the concentration below any level that could affect larval growth or survival. Hence, enriched Ba isotope injections will provide an effective means of mass-marking grouper larvae.