Physiological Adaptations of Freshwater Crayfishes that Permit Successful Aquacultural Enterprises

SYNOPSIS. There are over 400 species and three families of freshwatercrayfishes. Many species are collected for food and/or fishbait but fewer than ten are commercially cultivated. We discussthe physiological adaptations that permit these species to besuccessfully cultivated. The most important cultured speciesinclude: Northern Hemisphere—Cambaridae— Orconectesimmunis, Procambarus clarkii, and Procambarus zonangulus, andSouthern Hemisphere—Parastacidae—Cherax destructor.Procambarus clarkii is, by far, the most important species andhas been successfully introduced to all continents, save Antarcticaand Australia, from its native North America. All species maybe cultivated entirely in closed, intensive systems; however,economics are such that they are commercially produced, forthe most part, by establishing perpetuating populations in earthenpond systems. All species tolerate low oxygen, adapt well toaerial exposure, and persist for extended periods in burrowsystems in the absence of surface waters. The cultured specieshave high fecundities, rapid growth rates, and mature quickly.Aquaculture of freshwater crayfish is in its infancy. Therefore,it is likely that additional species with favorable adaptationsdiscussed here will be identified for cultural purposes     

Aspects of the Social Ethology of Some Kalahari Rodents

Studied the social structure of nine rodent species in a subdesert environment by means of direct observation and live- and snaptrapping. Six social groupings — asocial, solitary dispersed; social, solitary clustered; social, communal pair; social, communal but non-colonial; social, communal with little contact; social, communal with close contact (colonial) — are recognized. Diurnal species tend to live in colonies, probably with mutual warning systems against predators. For most species the social structure exhibited is an adaptation to predation, with the effect of food requirements playing a subsidiary role. Larder hoarding is common in solitary and asocial species.     

Stomatal Features in the Leaf of Aganosma dichotoma (Roth) K. Schum

Paracytic and anisocytic types of mature stomata are found inthe leaf of Aganosma dichotoma. Stomata with one guard cell,stomata with degenerated guard cells, and contiguous stomataare common. Stomata with arrested pore development are alsofound in certain cases. A single guard cell without any porehas not been designated as a stoma with one guard cell in thepresent investigation. Ontogeny of contiguous stomata have beentraced. Subsidiary cells are, morphologically, just like theircontiguous guard cells. Subsidiary cells may retain their shapeand contents even when their contiguous stoma becomes mature,or may change their shape and lose their contents. They mayor may not divide. Subsidiary cells form a whorl of more thantwo subsidiary cells around a stoma by their divisions. Degenerationof guard cell(s)— their contents and nuclei—havebeen traced. In certain cases guard cells divide forming morethan two guard cells associated to a single pore. Cytoplasmicconnections are found between two guard cells of nearby stomata,and between a guard cell and an epidermal cell. Near the wound,the epidermal cells over the veins become meristermatic givingrise to new epidermal cells but no meristemoid.     

The impact of environmental and social factors on learning abilities: a meta-analysis

Since the 1950s, researchers have examined how differences in the social and asocial environment affect learning in rats, mice, and, more recently, a variety of other species. Despite this large body of research, little has been done to synthesize these findings and to examine if social and asocial environmental factors have consistent effects on cognitive abilities, and if so, what aspects of these factors have greater or lesser impact. Here, we conducted a systematic review and meta-analysis examining how different external environmental features, including the social environment, impact learning (both speed of acquisition and performance). Using 531 mean-differences from 176 published articles across 27 species (with studies on rats and mice being most prominent) we conducted phylogenetically corrected mixed-effects models that reveal: (i) an average absolute effect size |d| = 0.55 and directional effect size d = 0.34; (ii) interventions manipulating the asocial environment result in larger effects than social interventions alone; and (iii) the length of the intervention is a significant predictor of effect size, with longer interventions resulting in larger effects. Additionally, much of the variation in effect size remained unexplained, possibly suggesting that species differ widely in how they are affected by environmental interventions due to varying ecological and evolutionary histories. Overall our results suggest that social and asocial environmental factors do significantly affect learning, but these effects are highly variable and perhaps not always as predicted. Most notably, the type (social or asocial) and length of interventions are important in determining the strength of the effect.     

Dynamics of dolphin porpoising revisited

Porpoising is the popular name for the high-speed surface piercingmotion of dolphins and other species, in which long, ballisticjumps are alternated with sections of swimming close to thesurface. The first analysis of this behavior (Au and Weihs,1980) showed that above a certain "crossover" speed this behavioris energetically advantageous, as the reduction in drag dueto movement in the air becomes greater than the added cost ofleaping. Since that publication several studies documented porpoisingbehavior at high speeds. The observations indicated that thebehavior was more complex than previously assumed. The leapswere interspersed with relatively long swimming bouts, of abouttwice the leap length. In the present paper, the possibilityof dolphins using a combination of leaping and burst and coastswimming is examined. A three-phase model is proposed, in whichthe dolphin leaps out of the water at a speed U_f, which is thefinal speed obtained at the end of the burst phase of burstand coast swimming. The leap is at constant speed and so theanimal returns to the water at U_f, goes to a shallow depth andstarts horizontal coasting while losing speed, till it reachesU_i. At that point it starts active swimming, accelerating toU_f. It then starts the next leap. Ranges of speeds for whichthis three-stage swimming is advantageous are calculated asa function of animal and physical parameters. Notation C—Constant defined in equation (12) C_D—Coasting drag coefficient D—Drag g—Gravitational acceleration H—Height of jump J—Energy required for jump k—Ratio of swim length to jump length l—Distance L—Total distance (eq. 28) m—Added mass M—Animal mass M₁—Total mass r—Coefficient defined in eq. (22) R—Ratio of energies, for three-phase swimming R₂—Ratio of energies, for burst and coast swimming t—Time T—Thrust U—Speed V—Body volume W—Weight     

Coordination of Behavioral Sequences Between Individuals During Prey Capture in a Social Spider, Anelosimus eximius

The analysis of collaborative predation sequences performed by groups of 10 individuals (females) in a nonterritorial permanent-social spider, A. eximius, shows that prey-captures are organized in successive steps. Spiders begin by throwing sticky silk, which hinders the prey in the web; they then throw dry silk, which completes the immobilization of the prey. The third step is characterized by bites that paralyze the prey that will be then carried. A concordance test reveals a coordination of the individual's acts that explains the collaborative prey-capture efficiency. No individual specialization in one type of act has been shown. On the contrary, by using living preys or artificially dead vibrated preys, we show that all individuals have equipotential behaviors. Furthermore, each spider is able to adjust its behavior to the state of the prey. Individuals already involved in prey transportation can again display bites or sticky silk throwing if the prey is artificially vibrated. This mechanism, which corresponds to stimergic processes responsible for self-organized phenomena, already described in social insects, permits a coordination of individual acts without the recourse of direct communication. These results permit us to understand better how individuals coordinate their acts and lead us to support the hypothesis that the transition between solitary species and social species in spiders could have been sudden.     

Grazing of echinoderm larvae (Paracentrotus lividus and Arbacia lixula) on naturally occurring particulate matter

Larvae (72 hr old) of P. lividus and A. lixula grazed on varioussuspensions of natural particulate matter with a size rangeof 2 to 30 microns, and on two species of algae (Phaeodactylumtricor-nutum and Nitzschia sp.) — Larvae graze most in the size range where the particleconcentration is highest. — If larvae deplete certain size categories of particlesthey then graze other size ranges in which the concentrationis still high. — The grazing rate of the two species varied between 988and 91.949 µm³ per pluteus per hour. — For A. lixula larvae the grazing rate increases withincreasing temperature to a maximum at 22°C.     

THE ECOLOGY OF SUBARCTIC MOLLUSCS IN THE LOWER NELSON RIVER SYSTEM, MANITOBA, CANADA

A total of 18 stream habitats were sampled on the Lower NelsonRiver system within the area bounded by 56°10'—50'Nand 93°50'—94°50'W, where discontinuous permafrostis present. Thirteen gastropod species were found, with a meancommunity species richness of 3.4. Gastropod richness was adverselyaffected by hydroelectric dams, but was positively correlatedwith macrophyte richness and proportion of clay in the sediments.Some interspecific associations were evident. Species proportionsin communities were related to sediment particle size, whichreflected amount of turbulence. Young were recruited into thepopulations until mid-September. (Received 22 April 1991; accepted 23 September 1991)     

Community analysis of Belarusian lakes: relationship of species diversity to morphology, hydrology and land use

In the glacial lake district of northern Belarus, limnologistscollected extensive biological, chemical and physical data on550 lakes (51% of all Belarusian glacial lakes). This largedata set provided a unique opportunity to examine subtle relationshipswith great statistical power. Our purpose was to use multivariateand correlation analyses to explore relationships of speciesrichness with morphological and hydrological parameters. A multivariateanalysis of the environmental data suggests that the Belarusianlakes can be separated along gradients of size, hydraulic residencetime and watershed development (land use). In most instances,species richness for major planktonic and benthic groups wascorrelated significantly with lake size and land use. Speciesrichness values were correlated less with watershed size orhydraulic residence time. In each community, there was a groupof species characterized by higher correlations with principalcomponent analysis (PCA) axes. These groups are as follows:for phytoplankton—diatoms, for zooplankton—rotifers,and for zoobenthos—molluscs. For lakes both in pristineand developed watersheds, we found small but significant negativespecies–area correlations for littoral crustaceans. Asurvey of the relevant literature shows scale dependence forthe correlation between species richness and lake size. Forpelagic crustaceans, the species–area correlation wassignificant (and positive) for lakes with developed watershedsbut not for pristine watersheds.     

Water Stress and --SH-Dependent Physiological Activities in Young Maize Plants

In young maize plants, water stress affects the —SH-dependentactivities: photosynthesis and dark respiration are reducedto about 60% at the wilting point; protein synthesis is inhibitedeven by moderate stress; and nitrate reductase activity is immediatelyinhibited also, prior to significant changes in the water statusof the plant As protoplasmatic protein denaturation occurs,protein —SS—increases at the expense of —SH,with consequent decrease of the —SH/—SS— ratio.The linear correlation between —SH/—SS— ratioand —SH-dependent activities suggests a strict dependencebetween them. A moderate increment both in rhodanese activityand labile sulphide content has been also demonstrated at thebeginning of the stress.     

Gamete Recognition and Egg Activation in Sea Urchins

SYNOPSIS. Free-spawning marine invertebrates face the challengeof ensuring that gametes of the same species come into contact,recognize, bind to and fuse with one another once they havebeen released by the adults. Coordinated spawning, chemoattractionand specific cell-cell recognition events help to overcome thischallenge. One marine invertebrate, the sea urchin, has servedas a model system for the study of gamete recognition and fertilizationfor over 100 years. Recent biochemical and molecular advancesin this area have begun to address the questions that have beenraised by the results of elegant physiological observations.The picture of fertilization that is emerging is characterizedby highly specific cell-cell interactions between proteins onthe surfaces of the gametes. These proteins then mediate thebinding and subsequent events that lead to activation of theegg and delivery of the male genetic material. Because of theserecent insights, the sea urchin egg is in a position to provideanswers to one of the central debates in developmental biology—themechanism of egg activation. Does the sperm deliver an activatingfactor? Does sperm binding trigger a receptor-mediated signal?Or is the mechanism a complex combination? With the tools andknowledge gained from the study of sea urchin fertilization,testing of these hypotheses should be feasible in the near future.     

Pain as a Cause of Aggression

Aggressive behavior can be elicited by aversive stimuli as anunconditioned reflex. Electric shock, heat, physical blows,and intra-cranial stimulation are among the stimuli which willelicit fighting. Various characteristics of the stimulus—suchas frequency of presentation, intensity, and duration, in thecase of shock—and of the environment in general, influencethe rate at which pain-elicited fighting occurs. Characteristicsof the animals—such as sex, age, sensory impairment, species,and social experience— also influence the occurrence ofrespondent aggression. Aggression can be conditioned according to both the operantand the respondent paradigms. Since both operant and respondentaggression can occur concurrently, interesting interactionsresult. Depending upon a number of variables, respondent aggressionexerts a disruptive influence on social behavior controlledby aversive stimuli. The interference of aggression with behaviormaintained by aversive stimuli may cause us to revise our opinionof the efficiency of aversive stimuli in social situations. Although pain is probably a source of human aggression, furtherresearch with infra-human animals, as well as actual researchwith humans, should elucidate the relationship between aversivestimuli and aggression in man.     

DNABIND: an interactive microcomputer program searching for nucleotide sequences that may code for conserved DNA-binding protein motifs

This paper presents a simple program for interactive searchingfor nucleotide sequences that may code for the helix—turn—helix,zinc finger or leucine zipper motifs in proteins. The helix—turn—helixmotifs are predicted using the recently published method ofDodd and Egan, while zinc fingers and leucine zippers are searchedfor by our original methods. DNABIND is shown to detect allfour known helix—turn—helix motifs in bacteriophagelambda genes and both zinc fingers of the adrl gene of yeast.     

Effects of Light Adaptation on the Temporal Resolution of Deep-sea Crustaceans

The effects of light adaptation on flicker fusion frequencywere examined in the photoreceptors of 13 species of deep-seacrustaceans. Light adaptation produced a significant increasein the maximum critical flicker fusion frequency (CFF_max) in7 species—all 6 species of euphausiids in the study, and1 species of oplophorid (Group 1). This is the first exampleof an increase in temporal resolution due to light adaptationin a deep-sea species. In the other six species—2 oplophorids,1 pandalid, 1 pasiphaeid, 1 penaeid and 1 sergestid (Group 2)—lightadaptation had no effect, or resulted in a decrease in the flickerfusion frequency. The mean dark-adapted CFF_max of the Group1 species was significantly higher, and the mean response latencysignificantly lower, than those of the Group 2 species. Possibleexplanations for these differences include the activity andbioluminescence mode of preferred prey items, as well as theretention of larval/juvenile adaptations in adult eyes.     

Phyllotaxis in the Oil Palm: Arrangement of Fronds on the Trunk of Mature Palms

Estimates of Equivalent Phyllotaxis Index—E.P.I.—arepresented for palms of various ages, measuring the arrangementof fronds on the cylindrical trunk. It is contended that accurateE.P.I. estimates can most readily be obtained from the trunksof older (20-year) palms where the fronds have sloughed offleaving clear scars. The technique is thus in contrast withprevious work in this species and so are some of the resultsobtained. Measures of E.P.I. decrease further up the trunk—correspondingit is suggested to an increase in the ratio of longitudinalto radial growth-rates. Various internal and external competitivestress situations are invoked to account for this phenomenon.The values for E.P.I. are interpreted in terms of Fibonacciparastichies and also in terms of some growth-rate parameterestimates.     

Confirmation of the presence of a Cu(II)/topa quinone active site in the amine oxidase from fenugreek seedlings

Amine oxidase from etiolated seedlings of fenugreek (Trigonellafoenum—graecum) has been isolated by a purification procedureinvolving three chromato—graphic steps. The homogeneousenzyme is of pink colour with a visible absorption maximum at500 nm. The dimeric enzyme (2 75 kDa) is a slightly acidicprotein (pl 6.8) containing 8% neutral sugars. N—ter—minalamino acid sequence of the enzyme shows a high degree of similarityto other plant and microbial copper—containing amine oxidases.The best substrates of the enzyme are aliphatic diamines andsome polyamines, whereas inhibitors are substrate analogues,copper complexing agents, some alkaloids and several other compounds.Spectrophotometric titra—tions with phenylhydrazines demonstratedone reactive carbonyl group per subunit of the enzyme and redox—cyclicquinone staining after native electrophor—esis indicatedthe presence of a quinone cofactor. Differential pulse polarographyshowed the existence of a copper/quinone—containing activesite. The resonance Raman spectroscopy and the pH—dependentshift of the absorption spectrum of the enzyme p—nitrophenylhydrazoneconfirm unambiguously the identity of the cofactor with topaquinone. EPR spectra of the enzyme are in accordance with thoseof tetragonal cupric complexes as known for other copper—containingamine oxidases. Besides the copper, Mn(II)ions were detectedthat partially occupy another metal site in the enzyme, buttheir catalytical importance is unlikely. Key words: Fenugreek, Trigonella foenum—graceum, amine oxidase, topa quinone     

Two Types of Embryo Sac Development in Scrophularia himalensis Royle

The development of the embryo sac in Scrophularia himalensisRoyle (tribe Cheloneae, Scrophulariaceae) has been investigated.The ovules are anatropous, unitegminal and tenuinucellar. Twotypes of embryo sac development—the monosporic (polygonumtype) and the bisporic (allium type)—coexist in this species.This is the first record of its kind in Scrophularia as previousworkers reported only the Polygonum type of development in thetribe Cheloneae.     

Glycosylation sites identified by solid-phase Edman degradation: O-linked glycosylation motifs on human glycophorin A

The human red blood cell sialoglycoprotein, glycophorin A (GpA),contains a ‘mucin-like’ extensively O-glycosylatedextracellular domain which carries the MN blood group antigens.We have revised the sites of O-glyccsylation in the extracellulardomain of GpA by automated solid-phase Edman degradation, whichallowed positive identification and quantitation of O-glycosylatedSer and Thr residues, as well as the single N-glycosylationsite. One N-linked and 16 O-linked sites were identified. Carbohydratewas absent on Ser 1, Ser14, Ser15, Ser23, Thr28 and Thr58 inGpA. We propose that the glycosyltransferases present in erythrocytesrecognize specific flanking sequences around potential O-glycosylationsites. All 16 O-glycosylation sites are explained on the basisof four motifs. Three motifs are associated with Thr-glycosylation:Xaa—Pro—Xaa—Xaa where at least one Xaa = Thr;Thr—Xaa—Xaa—Xaa where at least one Xaa = Thr;Xaa—Xaa—Thr—Xaa where at least one X = Argor Lys. The fourth motif is associated with Ser-glycosylation:Ser—Xaa—Xaa—Xaa where at least one Xaa = Ser.These simple rules explain the glycosylation (or lack of it)on 21 of 22 Ser/Thr in the extracellular domain of GpA. glycophorin A O-glycosylation motif solid-phase Edman degradation     

The Role of Soil Arthropods in Community Energetics

Though the primary development of principles of energetics waspioneered in aquatic studies, considerable information has accruedfrom more recent investigations of terrestrial species. Studiesof soil organisms—particularly arthropods—have givenus some understanding of the applicability of principles ofenergetics to terrestrial communities. Data from soil communitieshave yielded an annual energy budget for oribatid mites, ecologicalefficiencies for two trophic levels, and a series of herbivore:carnivoreratios for a number of communities. Energy-flow analyses ofthe problems of species abundance in community organization,the relationship of population production and maintenance, andthe energy relationships of the soil to above-ground communitieshave also been attempted. As data accumulate, however, the inadequacyof the Lindeman model becomes apparent, and there are prospectsfor change in this conceptual scheme.