Female genital structures of Metridinidae (Copepoda: Calanoida)

The female genital structures of six calanoid copepod species, belonging to the genera Gaussia, Metridia and Pleuromamma, were studied using light and scanning electron microscopy (SEM). The copulatory pores and seminal receptacles are paired in Gaussia and Metridia, but unpaired in Pleuromamma. A thin epicuticle and a spermatophoral plug are the mechanisms by which the pores are closed before and after copulation. The pores open directly into the receptacles, which are reduced to shallow integumentary depressions in Gaussia. The mode of insemination suggests two matings in females of Gaussia and Metridia, but only one in Pleuromamma. Paired gonopores and egg-laying ducts are present in the three genera, with a characteristic, closed semicircular configuration; these are opened during egg-laying by the action of retractor muscles of the gonoporal plates. The seminal ducts, which open into the gonopores, are long, thin and paired in Gaussia and Metridia, whereas in Pleuromamma they are short, broad and unpaired. The opening of the seminal and egg-laying ducts is synchronized. The shell ducts are paired in Gaussia and Metridia, unpaired in Pleuromamma; these arise from glands situated in the lateral expansions of the last prosomite and lead into the distal part of each egg-laying duct in Gaussia and Metridia and of the egg-laying duct receiving the seminal duct in Pleuromamma. The position and anatomy of these structures are compared to those of other families and genera, and a functional interpretation of their morphology is proposed. The main evolutionary trends of the different structural patterns of female calanoid genitalia are presented in tabular form. Received: 30 December 1996 / Accepted: 11 February 1997     

Turbulent air–water flows in hydraulic structures: dynamic similarity and scale effects

In hydraulic structures, free-surface aeration is commonly observed: i.e., the white waters. The air bubble entrainment may be localised (hydraulic jumps, plunging jets) or continuous along an interface (water jets, chutes). Despite recent advances, there are some basic concerns about the extrapolation of laboratory results to large size prototype structures. Herein the basic air bubble entrainment processes are reviewed and the relevant dynamic similarities are discussed. Traditionally, physical studies are conducted using a Froude similitude which implies drastically smaller laboratory Reynolds numbers than in the corresponding prototype flows. Basic dimensional analyses are developed for both singular and interfacial aeration processes. The results are discussed in the light of systematic investigations and they show that the notion of scale effects is closely linked with the selection of relevant characteristic air–water flow properties. Recent studies of local air–water flow properties highlight that turbulence levels, entrained bubble sizes and interfacial areas are improperly scaled based upon a Froude similitude even in large-size models operating with the so defined Reynolds numbers ρ _w × q _w/μ _w up to 5 E+5. In laboratory models, the dimensionless turbulence levels, air–water interfacial areas and mass transfer rates are drastically underestimated.     

A stereoscan electron microscope study of male reproductive characters in the Jaera albifrons group of species (Crustacea: Isopoda)

The male secondary sex characters of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet are described with the Stereoscan electron microscope (S.E.M.). These characters, which are present on the peraeopods, are the only means of identification for these Jaera species which together form the Jaera albifrons group (Isopoda, Asellota). The male praeoperculum (modified, fused, first pair of pleopods) and appendix masculinae (modified endites of the second pair of pleopods) have also been studied with the S.E.M. and possible functions of the various sex characters are discussed. Both the male operculum and appendix masculinae are similar for each species, suggesting that copulation with females of a different species is anatomically possible. The fact that hybrids are rarely collected in ecological investigations is discussed with reference to the present known information. Two methods of copulation for the members of this group have been proposed and these are discussed. A method of sperm transfer along the male operculum is outlined.     

Anchorage of embryos in Spirorbinae (Polychaeta)

Methods of incubation are taxonomically important in Spirorbinae. About half of the known species incubate in the operculum, but the remainder are usually described simply as incubating within the tube. Studies of tube incubation show that the embryos are anchored in various ways. They form an egg string, which is attached to the tube by a posterior filament in Spirorbis and Spirorbella; they adhere more generally to the tube wall in Circies and Paradexiospira; they are attached to specialised thoracic stalks in Protolaeospira, Helicosiphon and Romanchella; they adhere to the body surface in Metalaeospira and probably in Eulaeospira; they are not attached to either body or tube in Paralaeospira. Tube incubation is found predominantly in temperate or cold waters. In most species from the southern hemisphere, embryos are anchored to the bodies of the parents, but in most species from the northern hemisphere, embryos are fixed to the walls of the parent tubes.     

Notes on the Nerita (Archaeogastropoda) populations of Aldabra Atoll,Indian Ocean

Nerita undata, N. plicata, N. polita, N. albicilla and N. textilis are common intertidal gastropods on Aldabra Atoll. Each species prefers a different level on the shore and/or different degrees of exposure to wave action. Patterns of zonation, population size-frequency structure and biomass are given. N. undata exhibits 2 distinct ecophenotypes. Normal types occur on expsed to moderately sheltered shores but are replaced by type B in extremely sheltered conditions. Differences in shell morphology and population structure are also noted. Foraging by all species was confined to hours of darkness, generally at low tide. Activity of N. polita was induced slightly on overcast days. N. undata and N. textilis are cryptically coloured and often visible during the day. N. plicata is conspicuous, but is protected by a strong shell. N. polita and N. albicilla are often brightly and variably coloured, but both are concealed during daylight. No Nerita were found infected with trematodes, suggesting that the degree of infection was extremely low. Habitats of the Aldabran Nerita are compared with 3 species on Barbados, West Indies.     

A further contribution to the study of fish populations by capture-recapture experiments

In capture-recapture experiments, fish populations can be studied by two different sampling procedures. In both procedures, tagged fish are released on capture, but untagged fish are in one procedure released after tagging, in the second procedure they are retained. Using the two sampling techniques, Rafail (1971a,b) gave expressions for the estimation of an assumed constant (C) of proportionality between probabilities of capture of tagged to untagged fish which are simplified here to forms easier for calculation. The estimation of this constant (C) aids in estimation of abundance and mortality rates of untagged fish which are assumed to differ from those of tagged fish.     

The histology,histochemistry and ultrastructure of the cement apparatus of three adult sessile barnacles,Elminius modestus,Balanus balanoides and Balanus hameri

The histology, histochemistry and ultrastructure of the cement gland cells of 3 species of sessile barnacles are described. Cells of both Elminius modestus Darwin and Balanus balanoides (L.) (membranous bases) are similar histologically and ultrastructurally, and within the cells there are 2 distinct regions. One is the site of secretion accumulation, the other the site of secretion synthesis. In Balanus hameri Ascanius (calcareous base) the cells are different in that the cytoplasm is more homogeneous. In all 3 species protein is the final secretion product (cement) of the cement cells. The mode of discharge of secretion from the cells differs between the membrane based and calcareous based barnacles. In the former, there is a series of collecting canals within the cytoplasm of the cement cells (intracellular canals) which join with the larger extracellular cement ducts. Secretion passes into the intracellular canals and is moved along to the larger cement ducts, which have an inner chitin lining. In Balanus hameri (calcareous base) there are no intracellular collecting canals. Secretions are thought to pass from the cement cells into the cement duct cells direct. The cement ducts in this species are not chitin lined.     

Gametogenesis in Harmothoe imbricata (Polychaeta: Polynoidae)

The processes of gametogenesis in Harmothoe imbricata are described and illustrated. For most of their development the gametes are attached to the walls of segmental blood vessels. In males, only meiosis and sperm differentiation occur while the cells are free in the coelom. In females, oocytes are only released into the coelom briefly, after vitellogenesis has been completed. H. imbricata thus differs from most polychaete species so far described — where in males the spermatogonia divide mitotically to form rosettes after they have been released into the coelom, and in females the whole of vitellogenesis occurs after release of oocytes into the coelom. The oocytes of H. imbricata enter the first metaphase of meiosis before they are shed at spawning. The elongated head of the sperm in H. imbricata is atypical of polychaetes in general.     

Functional morphology of the gonads of the articulate brachiopodTerebratulina retusa

The reproductive anatomy, and ultrastructural features of the gonads of the articulate brachiopodTerebratulina retusa (Linnaeus), are documented based on collections made between October 1985 and October 1986 from the Firth of Lorn, west coast of Scotland. This species is dioecious, and maturity is achieved in both sexes at shell lengths greater than ~5.5 mm. There is no obvious external sexual dimorphism except for slight differences in the coloration of the gonads; testes are white/cream, ovaries are yellow/orange. The gonads occur as four palmate lobes, a pair in each valve. Gonads are formed within a mantle sinus (vascula genitalia), which is an anterior extension of the coelom, that opens posteriorly into the visceral cavity and to the exterior via a pair of metanephridia. The latter serve as gonoducts during spawning. Gametes are borne on genital lamellae formed from a reticulate lattice of connective tissue. The lamellae are an extension of the ileoparietal band and are fused along one margin to the inner mantle membrane. Developing oocytes are closely affixed to the genital lamellae and originate from a pool of proliferating germ cells at its base. Vitellogenic oocytes that are at an advanced stage are released from the genital lamellae, but are retained within thevascula genitalia. Liberated oocytes continue to accumulate yolk and eventually occlude thevascula genitalia, before being spawned. Coelomocytes were identified within the gonads. In spent females these cells appear to be phagocytic and involved in the resorption of necrotic material, while in the male they may serve as nutritive cells.     

Taxonomic revisions in the marine biflagellate fungi: The ultrastructural evidence

The ultrastructure of the genera Althornia, Aplanochytrium, Japonochytrium, Schizochytrium and Thraustochytrium is described, and all are regarded as members of the new order Thraustochytriales Sparrow. Species considered are Althornia crouchii, Aplanochytrium kerguelensis, Hyalochlorella marina, Japonochytrium sp., Schizochytrium aggregatum, Thraustochytrium kinnei and T. striatum. All but H. marina are, on ultrastructural evidence, related genera, and some speculative suggestions are made about possible interrelationships both between the species discussed, between the Thraustochytriales and Labyrinthulales, and between these two and other major taxa.     

On the use of nearest neighbor contingency tables for testing spatial segregation

For two or more classes (or types) of points, nearest neighbor contingency tables (NNCTs) are constructed using nearest neighbor (NN) frequencies and are used in testing spatial segregation of the classes. Pielou’s test of independence, Dixon’s cell-specific, class-specific, and overall tests are the tests based on NNCTs (i.e., they are NNCT-tests). These tests are designed and intended for use under the null pattern of random labeling (RL) of completely mapped data. However, it has been shown that Pielou’s test is not appropriate for testing segregation against the RL pattern while Dixon’s tests are. In this article, we compare Pielou’s and Dixon’s NNCT-tests; introduce the one-sided versions of Pielou’s test; extend the use of NNCT-tests for testing complete spatial randomness (CSR) of points from two or more classes (which is called CSR independence, henceforth). We assess the finite sample performance of the tests by an extensive Monte Carlo simulation study and demonstrate that Dixon’s tests are also appropriate for testing CSR independence; but Pielou’s test and the corresponding one-sided versions are liberal for testing CSR independence or RL. Furthermore, we show that Pielou’s tests are only appropriate when the NNCT is based on a random sample of (base, NN) pairs. We also prove the consistency of the tests under their appropriate null hypotheses. Moreover, we investigate the edge (or boundary) effects on the NNCT-tests and compare the buffer zone and toroidal edge correction methods for these tests. We illustrate the tests on a real life and an artificial data set.     

Microbial associations in sponges. III. Ultrastructure of the in situ associations in coral reef sponges

Symbiotic cyanobacteria are associated with marine sponges in three ways: the majority are free-living in the mesohyl; large aggregates occur in cyanocytes (specialized, vacuolated archeocytes); and few are present in digestive vacuoles. The cyanobacteria in Jaspis stellifera and Neofibularia irata are morphologically similar to those described in Mediterranean sponges, whereas those in Pericharax heteroraphis are different. The freeliving bacterial populations are morphologically similar, although the number of bacteria varies between the species. The fourth sponge Ircinia wistarii contains a mixed bacterial population unlike those in the other sponges. Sponge digestion of microbial associates is rare and not considered to contribute significant nutrients.     

The occurrence and need for conservation of metallophytes on mine wastes in Europe

Metalliferous substrates are important in the distribution of various plants such asArmeria maritima, Minuartia verna, Thlaspi alpestre, Silene maritima andCochlearia officinalis, in parts of the United Kingdom. Metalliferous substrates are similarly important for a slightly different assemblage of metallophytes in the Aachen-Liège orefield in Belgium and Germany. The significance of metalliferous substrates in the distribution of the metallophytes varies from orefield to orefield and this is investigated. Certain sites, by virtue of their environmental and species diversity, are outstanding as habitats for the metallophytes and some of these are described. Observations on the importance and problems of the conservation of the metallophyte habitats are included.     

Aeolian dynamics in relation to vegetation in a blowout complex in the Meijendel dunes, The Netherlands

Changes in surface elevation in a former blowout in the coastal dunes of Meijendel, The Netherlands, have been monitored almost weekly during one year at 48 erosion pin sites, distributed over 12 units. The units are characterized by specific geomorphological processes. The changes in elevation are caused by wind, slope wash and mass movements. At almost each pin, periods of erosion alternate with periods of accumulation in a random way. Erosion and accumulation sequences are relatively long in areas dominated by aeolian activity, but even here they are randomly distributed. It is the balance between the effects of periods of erosion and periods of accumulation which determines the formation of blowouts or dunes. Units with the highest degree of erosion or accumulation at the end of the year of monitoring also show the highest fluctuations in elevation during that year. In the accumulation units there is even a significant positive correlation between surface lowering by erosion and surface rise by accumulation. Plant species in the blowout are divided into four groups on the basis of responses to aeolian dynamics: (1)Sedum acre is the only species associated with deflation; it might be suitable for blowout stabilization; (2)Ammophila arenaria, Festuca rubra andOnonis repens are associated with aeolian accumulation and can be used for the stabilization of accumulation sites; (3)Erodium cicutarium, Koeleria macrantha andCorynephorus canescens, occurring at lower aeolian activity; (4)Tortula ruralis var.ruraliformis andGalium verum are found where slope wash and mass movements (Galium) are active. In the relationship between aeolian dynamics and vegetation, the former appears to be the independent variable: there is no consistent relationship between accumulation and vegetation cover. This means that the formation of blowouts and adjacent dunes is not controlled by vegetation with its present cover.     

“Anting” in Blue Jays: evidence in support of a food-preparatory function

Summary.  Anting, the plumage-dipping behavior to which ants (mostly formicines) are commonly subjected by birds (mostly passerines), is shown in tests with hand-raised Blue Jays (Cyanocitta cristata) and the ant Formica exsectoides to be instinctive: the birds displayed typical renditions of the behavior on the first occasion that they encountered ants. Evidence is presented supportive of the view that anting is a strategy by which birds render ants fit for ingestion. Formicine ants are ordinarily protected by their formic acid-containing spray. Being wiped into the bird’s plumage causes them to discharge that spray, without harm to the bird, to the point of almost total emptying of the glandular sac in which the secretion is stored. The ants are therefore essentially secretion-free by the time they are swallowed. Further evidence indicates that it is the ant’s possession of the acid sac that triggers the anting behavior in the bird. If F. exsectoides are surgically deprived of their acid sac, they are eaten by the birds without first being subjected to anting. Data are also presented indicating that the ant’s crop, which is especially capacious in formicines (its contents may amount to over 30% of the formicine’s mass), and which appears to survive the anting procedure intact, constitutes, at least when laden, a valuable component of the trophic package that the bird accesses by anting.     

Determination of traces of fluorine,chlorine, bromine,cadmium and lead in plastic materials

This paper describes the quantitative determination of F, Cl, Br, Cd and Pb in plastic materials. The concentration of the elements Cl, Br, Cd and Pb is first semiquantitatively measured by X‐ray fluorescence spectrometry (XRF) directly in the solid sample with a detection limit of approximately 10 μg/g. Afterwards, F and any of the other elements which exceed the limit values for materials which are disposable without special precautions are measured after the digestion of the material. The samples are digested either under pressure in an oxygen atmosphere for F, Cl and Br or under pressure with nitric acid for Cd and Pb. The digestion converts the halides to the anions which are measured potentiometrically (F^‐, Br^‐) or with ion chromatography (Cl^‐). Cd and Pb are measured by graphite furnace atomic absorption spectrometry (GF‐AAS). The determination limits achieved are 20 μg/g for F and Br, 250 μg/g for Cl, 0.01 μg/g for Cd and 0.2 μg/g for Pb, all below the limit values set by current regulations in Switzerland.     

Mechanistic aspects of the thermal formation of halogenated organic compounds including polychlorinated dibenzo‐p‐dioxins. Part V†: Hypotheses and summary

The hypotheses on the de novo syntheses of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo‐p‐dioxins (PCDDs), based on known literature, are presented. Polychlorinated benzenes and polychlorinated phenols are probably key intermediates.

In the present article, hypotheses that may account for the presence of polychlorinated dibenzofurans (PCDFs) and dibenzo‐p‐dioxins (PCDDs) in the effluents from municipal and industrial incinerators are put forward. These hypotheses are based on the previously surveyed literature (Ref. 203–206) and experimental results on laboratory scale and thermodynamic calculations are considered. The interconnections of various reaction steps are speculative and no technological information was added to account for conditions in real incinerators. Conclusion of the discussions on the related subject matter, presented in the Parts I‐IV (Ref. 203–206), are also described in this paper.     

Harvesting in an eight-species ecosystem

The theory for a general equilibrium ecosystem model that can include large number of interacting species is presented. Features include: (1) individual plants and animals are assumed to behave as if they are maximizing their net energy intake, (2) short- and long-run equilibriums are obtained, (3) species’ population adjustments depend on individual net energies. The theory is applied using simulations of an eight-species Alaskan marine ecosystem for which a “natural” equilibrium is calculated. Humans are introduced by adding a regulated open access fishery that harvests one of the species. Fishing impacts the fish population as well as the populations of other species, including Stellar sea lions, an endangered species. The sensitivity of fish and nonfish species populations to harvesting are calculated.     

Structure and evolution of song form in the wrens Thryothorus sinaloa and T. felix

Summary The songs of two species of wrens, Thryothorus sinaloa and T. felix, are less similar than previously believed. We have found that song structure, bout patterning, and other aspects of singing behavior are widely divergent between the two species, which are sympatric over much of their ranges. The nature of these differences supports the hypothesis of contrast reinforcement in bird song. Further evidence is provided by essentially parallel differences in another pair of sympatric species, T. pleurostictus and T. maculipectus. A cluster analysis of song form of the above four species plus one other, T. ludovicianus, suggests that those species which are allopatric are the most similar in song form, while sympatric species are the most dissimilar. We relate various features of singing behavior in the two species to some aspects to their ecology, and examine relationships among various song parameters within the genus Thryothorus. The parallel differences in pairs of sympatric Thryothorus in structure of song units, temporal organization of song, and duetting, along with the close correlation of groups of song parameters in the five species of Thryothorus leads us to propose that strategies or adaptive complexes of singing characteristics may exist in the genus.     

北京河流大型底栖动物空间格局及其环境响应研究

大型底栖动物群落结构及多样性对于区域河流环境状况具有重要的指示意义。基于2014年5月—2015年8月间北京市河流大型底栖动物群落结构调查数据,分析底栖动物的生物多样性特征和空间格局。调查共发现大型底栖动物151种(或分类单元),隶属于5门9纲67科127属,水生昆虫占绝对优势。聚类分析表明76个采样点可被分为4组,组1主要包含北部山区的潮白河水系,具有较为典型的山溪型河流底栖动物特征,组2主要包含永定河山峡段和北运河水系的清河,组3主要包含大清河水系和北运河水系的温榆河、北沙河、南沙河等,二者具有城市河流兼有山溪型河流底栖动物的特征,组4主要包含北运河水系,具有典型的城市河流底栖动物特征。优势种分析表明:组1的优势种为热水四节蜉(Baetis thermicus)、秀丽白虾(Exopalaemon modestus)和网栖石蛾(Cheumatopsyche sp.),组2为直突摇蚊(Orthocladius sp.)、钩虾(Gammarus sp.)和长足摇蚊(Tanypus sp.),组3为摇蚊科幼虫(larvae of Chironomidae)和寡毛类(Oligochaeta),组4是以中华摇蚊(Chironomus sinicus)为代表的摇蚊幼虫。功能摄食类群研究表明:组1以收集者和滤食者占绝对优势,相对丰度分别为60%和29.6%;组2、组3、组4均以收集者占绝对优势,相对丰度分别为97.7%、90%、97.5%。物种数、Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数的组间差异性显著(P0.05)。研究表明,北京河流大型底栖动物受河流自然环境变化的影响显著,形成了典型的山区-城市底栖动物空间格局,山区河流中保持了较高的生物多样性,城市河流及其过渡区的大型底栖动物退化明显,大型底栖动物能够明显指示环境状况的变化并可指导河流环境的保护与恢复。