Persistence and fluctuation of lateral dimorphism in fishes

Two morphological types ("righty" and "lefty") have been discovered in several fish species and are referred to as a typical example of antisymmetry. It has been suggested, first, that this dimorphism (called laterality) is inheritable; second, that the frequencies of laterality in each species fluctuate around 0.5; and third, that predators mainly exploit prey of the opposite laterality; that is, lefty and righty predators prey on righties and lefties, respectively. The latter is defined as "cross predation"; the antonym "parallel predation" means predation within the same laterality. We hypothesized that cross predation drives alternation of the survival and reproductive advantages between two morphological types, leading to frequency-dependent selection that maintains the dimorphism. To investigate this, we constructed mathematical models of population dynamics of one prey/one predator systems and three-trophic-level systems with omnivory. Mathematical analysis and computer simulations explained the behavior of the laterality frequency in nature well, insofar as cross predation dominated over parallel predation. Furthermore, the simulations showed that when only one of the morphological types exists in a species, the other type can invade. This suggests that dimorphism is maintained in all interacting species.     

Laboratory studies on the feeding habits,reproduction and development of three phytoseiid species,Typhlodromus pomi,Phytoseius macropilis andAmblyseius finlandicus (Acari: Phytoseiidae), occurring on abandoned apple trees in Ontario,Canada

Laboratory studies on predation, reproduction and development were conducted on three phytoseiid species,Typhlodromus pomi (Parrott),Phytoseius macropilis (Banks) andAmblyseius finlandicus (Oudemans). These species were dominant phytoseiid mites on the abandoned apple trees with which ecological experiments were carried out in southern Ontario, Canada. Throught the studies, a rust mite species (Diptacus gigantorhynchus sp. complex), a single consistent prey in the orchard, was used as food. Results showed that the three predators developed well with the rust mites as food, and thatA. finlandicus developed most rapidly and had the highest predation rate. However, this species showed a poor tolerance to low prey densities. These observations suggest that this species is a predacious species and the other two species were more or less general feeders. All species showed the same pre-mating behaviour (Amblyseius-Typhlodromus type), but they exhibited a variety of mating and oviposition behaviours.     

Kinship Influences Cannibalism in the Wolf Spider, Pardosa milvina

Recent studies have called into question the role of Wright's coefficient of relatedness (r) in the interactions among relatives. Kin selection theory predicts a positive relationship between relatedness and frequency of altruistic acts, but a number of researchers have reported the opposite relationship. I used a lycosid spider (Pardosa milvina) to test the hypothesis that genetic relatedness would affect the propensity of a cannibalistic species to prey on genetic relatives. I considered lack of predation to be a form of altruism where the predator incurs a cost (loss of a meal) that benefits potential prey. Specifically, I questioned whether direct genetic offspring would be avoided as prey items and whether the sex or reproductive condition of a cannibalistic predator would affect the likelihood of predation on conspecific juveniles. As predicted by kin selection theory, spiderling mothers ate significantly fewer of their own offspring than they did of nonkin spiderlings of the same age. Adult virgin female and adult male spiders ate significantly more spiders than females that had recently carried spiderlings. Females with egg sacs consumed significantly fewer spiderlings than did virgin female spiders. These findings support Hamilton's rule and suggest that, in some systems, genetic relatedness plays a strong role in governing altruistic behavior toward relatives.     

Models of the influence of predation on aspect diversity in prey populations

By considering a model incorporating behavioral changes by predators and prey evolution, we demonstrate how under certain conditions apostatic predation influences the maintenance of diversity within prey populations, and among different prey species. Further, we estimate the intrinsic diversity wavelength of the system when apostasy combines with other factors to lead to nonuniform distributions of prey along aspect gradients.     

Behavioral laterality and morphological asymmetry in the cuttlefish, Sepia lycidas

Behavioral laterality is widely found among vertebrates, but has been little studied in aquatic invertebrates. We examined behavioral laterality in attacks on prey shrimp by the cuttlefish, Sepia lycidas, and correlated this to their morphological asymmetry. Behavioral tests in the laboratory revealed significant individual bias for turning either clockwise or counterclockwise toward prey, suggesting behavioral dimorphism in foraging behavior. Morphological bias was examined by measuring the curvature of the cuttlebone; in some the cuttlebone was convex to the right (righty), while in others, the cuttlebone was convex to the left (lefty). The frequency distributions of an index of cuttlebone asymmetry were bimodal, indicating that populations were composed of two types of individuals: "righty" and "lefty." Moreover, an individual's laterality in foraging behavior corresponded with the asymmetry of its cuttlebone, with righty individuals tending to turn counterclockwise and lefty ones in the opposite direction. These results indicate that cuttlefish exhibit behavioral dimorphism and morphological antisymmetry in natural populations. The presence of two types of lateral morph in cuttlefish provides new information on the relationship between antisymmetric morphologies and the evolution of individual laterality in behavioral responses in cephalopods. The implications of these findings for the interpretation of ecological meaning and maintenance mechanisms of laterality in cuttlefish are also discussed.     

Skull development in a bothid flounder, <Emphasis Type="Italic">Bothus myriaster</Emphasis> (Pleuronectiformes), with discussion on the homology of the “pseudomesial bar”

Skull development after eye migration was studied in a bothid flounder Bothus myriaster (Bothidae). In the stage immediately following the migration, skull ossification was apparently weaker on the blind side than on the ocular side, such being related to the extensive dorsally directed shift of the blind side eye. The blind side frontal had two initial ossification sites; below (pseudomesial bar in Psettodes) and behind (frontal in bothids) the blind side eye. In bothids, the former was fused with the lateral ethmoid but autogenous to the latter during ontogeny. With increased eye size with growth, the otic region became progressively narrower. The late ossification of the region was considered to provide flexibility for cranial modifications owing to rapid eye enlargement.     

Modelling of predator–prey trophic interactions. Part I: two trophic levels

A class of lumped parameter models to describe the local dynamics in a controlled environment of a two-trophic chain is considered. The class is characterized by a trophic function (functional response of predator to the abundance of prey) depending on the ratio of prey biomass x and a linear function of predator biomass y: f(qx/[(1-)k+y]), where q is the efficiency of the predation process, k is a reference biomass, and (01) specifies the predation model. The trophic function is defined only by some properties determining its shape. A stability analysis of the models has been performed by taking the parameters q and as bifurcation parameters: the regions in the (,q) plane of existence and stability of nonnegative equilibrium states and limit cycles are determined. This analysis shows that the behaviour of the models is qualitatively similar for 0<1 (in particular the null state is always a saddle point), while the value =1 gives rise to some kind of structural instability of the system (in particular the null state becomes an attractor for sufficiently high predation efficiency).     

Heterogeneity in β0 thalassemia from Algeria: Genetic,clinical and molecular studies

Summary Six Algerian patients with ⁰ thalassemia are presented, in addition to the two patients already reported (Godet et al., 1977). Family studies indicate that all the patients had homozygous thalassemia characterized by absence of globin chain synthesis in peripheral blood. The clinical severity varies from one family to the other and within the same family, from typical Cooley's anemia to thalassemia intermedia and appears to be related to the child death rate observed in each family. The / biosynthetic ratio was 0.36–0.40 in seven patients and 0.2 in the most seriously affected patient. The mRNA content in peripheral reticulocytes was less than 1.5% of mRNA in seven patients and 13.3% in one patient. These results indicate that Algerians homozygous for thalassemia are heterozygous at the clinical, biochemical and molecular levels.     

The incidence of some inherited EEG variants in normal Japanese and German males

Summary A sample of 3372 apparently healthy Japanese males was compared with a similar sample of 4622 Germans as to the incidence of some genetically determined variants of the normal electroencephalogram. The following variants were examined: Low voltage EEG (typical and borderline); monotonous -waves; 4–5/sec rhythm; occipital continuous slow -waves (-variants); fronto-precentral -groups; diffuse -waves. Fronto-precentral -groups seemed to be somewhat rarer in Japanese than in Germans. This could possibly be due to technical differences. As to the other variants, incidence was found to be very similar in both race groups.     

The precursor of the F1β subunit of the ATP synthase is covalently modified upon binding to plant mitochondria

We present evidence for a unique covalent modification of a nuclear-encoded precursor protein targeted to plant mitochondria. We investigated the early events of in vitro import for the mitochondrial precursor of the ATP synthase F₁ subunit from Nicotiana plumbaginifolia (pF₁) into plant mitochondria. When pF₁ of 59 kDa was incubated with mitochondria isolated from different higher-plant species, a band of 61 kDa was generated. The 61 kDa protein was a covalently modified form of the 59 kDa pF₁. The modification was dependent on the 25 amino acid long N-terminal region of the presequence of pF₁. The modification was catalysed by an enzyme located in the outer mitochondrial membrane which was specific for higher plants and could not be washed off from the membrane by urea, KCl or EDTA. The modification was ATP- and Ca²⁺-dependent, but it was not affected by inhibitors of protein kinases. No inhibition of the modification was observed with phosphatase, methylation or acylation inhibitors. The modification occurs prior to translocation through the mitochondrial outer membrane. Inhibition of the modification process does not affect the import of the precursor protein, hence precursor modification was not a prerequisite for import. Both the modified and the unmodified pF₁ proteins were strongly associated with the mitochondrial outer membrane.     

Pollen dimorphism in soybean

Summary Microspores of soybean plants (Glycine max (L.) Meer.) of four cultivars were cytologically analysed. The pollen grains showed a clear dimorphism when stained with propionic-carmine from binucleate stage onwards. The majority of the grains are large, deeply stained and with asymmetric division (normal type) while the remainder grains are smaller, lightly stained, uninucleate or with two similar nuclei (P-pollen). The different frequencies of P-pollen on the four cultivars suggest a genotype effect of microspore dimorphism.     

Autosomal recessive “uncomplicated” profound childhood deafness in an arabic family with high consanguinity

Summary An Arabic family has been studied in our genetic counselling centre. This family included 13 cases of heritable uncomplicated profound childhood deafness. All of these were the offspring of first cousin (F.C.) marriages. The inheritance pattern was consistent with autosomal recessive (A.R.) determination of the deafness and all the affected children studied showed identical phenotypic expression.     

Decomposition of organic matter and mineralization of nitrogen in brookston silt loam and alfalfa green manure

Summary C¹⁴ and N¹⁵ doubly labelled alfalfa tissue at addition rates of 5 and 1 ton per acre was incubated in the laboratory for 72 days with virgin and cultivated Brookston silt loam. The alfalfa tissue was more extensively decomposed in the virgin soils than in cultivated soil, but retention of tissue carbon was not affected by rate of addition. Percentage decomposition of organic matter in the virgin soil was greater than that in the cultivated soil. Addition of alfalfa tissue reduced decomposition of soil organic matter in proportion to the rate of addition and resulted in a gain of carbon in the incubation mixture. No priming action was noted.An increase in the rate of tissue addition caused an increase in the amount of nitrogen mineralized from the tissue but had little effect on the amount of nitrogen mineralized from the soil. Nitrogen mineralized from the soil organic matter was preferentially immobilized during the latter part of the incubation period.It appears that the organic matter content of the soil as well as the rate of tissue addition may regulate the priming action of green manures.Published with approval of the Director, Ohio Agricultural Experiment Station as Journal Paper No.94-62.     

Spawning Sounds of the Male Haddock, Melanogrammus aeglefinus

The codfish family, Gadidae, contains many vocal species. The sounds produced are species-characteristic and relatively simple. Unusually within this family, the haddock Melanogrammus aeglefinus, produces a range of sounds in different contexts. Both male and female haddock produce short sequences of repeated knocks during agonistic encounters. During the spawning season, however, male fish produce sounds which vary in their characteristics as courtship proceeds. The repertoire of the male fish consists of a graded series of sounds ranging from a short series of slowly repeated knocks to long sounds of rapidly repeated knocks. The fastest sounds are heard as a continuous humming. Different behavioural acts leading up to the mating embrace are associated with particular sounds, the sounds becoming longer and faster as the level of arousal of the male increases. It is suggested that the sounds serve to bring male and female fish together in the same part of the ocean, and that the sounds also play a role in synchronising the reproductive behaviour of the male and female.     

Is prey predation risk influenced more by increasing predator density or predator species richness in stream enclosures?

The direct lethal impacts and the indirect effects predators have on prey characteristics, such as behavior, have fitness consequences for the prey. Whether the level of predation risk that prey face in the presence of multiple predator species can be predicted from a null model that sums the risk from each predator species in isolation is unclear. In field enclosures, we tested whether the predation risk experienced by Stenonema mayfly larvae from a dragonfly larva (Boyeria vinosa) and a hellgrammite (Corydalus cornutus) together matched the predictions of the multiplicative risk model. We then compared whether any deviations from the models predictions were larger in the presence of two predator species than in the presence of an equivalent density of individuals from either predator species alone, to determine if unique effects arise for the prey in the presence of multiple predator species. We also determined if prey moved preferentially into predator-free refuge spaces or decreased their movement in the presence of predators. Stenonemas risk of predation was reduced compared to the models prediction, but no unique multiple predator species effects were present because this risk reduction was comparable in magnitude to the level exhibited in the presence of each predator species alone. The prey did not move into predator-free refuge spaces in the presence of predators in the field enclosures. Thus, these predators appear to interfere interspecifically and intraspecifically, which may facilitate the coexistence of the predators and the prey.     

Habitat use by bluegill in laboratory pools: where is the refuge when macrophytes are sparse and alternative prey are present?

Synopsis In northern clear-water systems, bluegill, Lepomis macrochira, select habitats based on relative reward rates and risk of predation. However, because freshwater systems to the south are often turbid, and their resident fish species different, bluegill habitat use patterns may differ from those found in northern clear-water systems. Here I examine the effects of elimination of the inshore macrophyte refuge (an indirect effect of turbidity), and decreased pelagic predation rates on bluegill due to the presence of gizzard shad, Dorosoma cepedianum, in laboratory pools. Bluegill used depths 20 cm more often with largemouth bass, Micropterus salmoides, than without them; the presence of a preferred alternate prey, gizzard shad, did not affect this behavior. Though bluegill did not alter their habitat use in response to bass activity, they did school more as predator activity increased. Even in the presence of a preferred alternate prey without macrophytes, bluegill continue to use shallow littoral areas to avoid predation.This Unit is sponsored jointly by The United States Fish and Wildlife Service, Ohio Department of Natural Resources, The Ohio State University, and the Wildlife Management Institute.     

Ultrastructure of cell wall and plugs of tobacco pollen tubes after chemical extraction of polysaccharides

Tobacco pollen tubes grown in vitro and from pollinated tobacco styles were treated by chemical solvents to remove one or more of the following polysaccharides from the tube walls: pectin (ethylenediamine tetraacetic acid); hemicellulose (alkali); callose (alkali; potassium hypochlorite); cellulose (cuprammonium); and all polysaccharides with exception of cellulose (H₂O₂/glacial acetic acid). Both the inner tube wall, which we had regarded as the secondary wall, and the plugs contained, in addition to callose, microfibrils of cellulose and non-cellulosic microfibrils that had pectin-like properties. When using the expressions callosic or callose layer and callose plugs in reference to pollen tubes, one should realize that they do not imply the exclusive presence of callose in the inner tube wall layer and its localized thickenings.Extended version of a contribution (poster) presented at the International Symposium Advances in Plant Cytoembryology in Lublin, Poland, in June 1980 Dedicated to Professor J. Straub (Köln-Vogelsang) on his 70th birthday in 1981     

Development of biofilms in anaerobic reactors

The development of biofilms in polyethylene sheets and particles was studied using downflow reactors with synthetic nutrient media made up of a mixture of volatile fatty acids. Results suggest a preferential immobilization of acetoclastic organisms in the inner space of the surfaces and the colonization by the butyrotrophic bacteria in the outer layers. After 101 days the bioparticles reached a specific acetociastic activity of 72.45mol acetic acid/g protein ·h while the biofilms had 58.80 mol acetic acid/g protein attached ·h. Due to the low density of the polyethylene particles low fluidization velocities would be needed (2m/h) in a downflow fluidized bed reactor.     

A “protective shell” around the larval cocoon of <Emphasis Type="Italic">Cephalodiscus densus</Emphasis> Andersson, 1907 (Graptolithoidea,Hemichordata)

Within the framework of the Italian XVII PNRA expedition (austral summer 2001–2002), several colonies of the Graptolithoidea (=Pterobranchia+Graptolithina) species, Cephalodiscus densus Andersson and C. hodgsoni Ridewood, were collected by trawl from Tethys Bay (Terra Nova Bay, Ross Sea). These organisms were maintained in aquaria for 2 weeks and their behaviour observed. The dissection of some colonies of C. densus allowed the reconstruction of the eggs fate and the documentation of the formation of a protective shell around the cocoons of larvae settled within the parental colony encasement. The shell is produced by cementing size-selected debris, either of organic or inorganic origin, accumulated inside the encasement. This is the first documentation of such a structure within living Hemichordata and it helps to reinterpret some of the resting structures within zooidal tubes or thecae of particularly well-preserved fossil graptolites.