Omnivory in cyclopoid copepods: comparisons of algae and invertebrates as food for three, differenfly sized species

We examined the importance of algal versus invertebrate preyfor three cyclopoid copepods by comparing reproductive successfor females fed on three diets: exclusively algal food, exclusivelyinvertebrate prey and a combination of algal plus invertebrateprey. The three cyclopoid species represent a distinct gradientin body size: Tropocyclops prasinus mexicanus (small body size),Diacyclops thomasi (medium body size) and Mesocyclops edax (largebody size). Our results provide strong evidence for the potentialimportance of algae in the diet of adult cyclopoid copepods.However, the role of herbivory is dependent on species bodysize. We found that algae are the key dietary factor for reproductivesuccess of the small T.p.mexicanus. In contrast, the availabilityof invertebrate prey had a greater influence on reproductionby the two larger species. Overall, cyclopoid copepods shouldbe generally considered as having the potential to derive theirenergy from either animal or algal sources. This has importantconsequences for interpretations of the forces influencing zooplanktoncommunity diversity as well as for general food web theory.     

Feeding styles of five species of bottom-feeding fishes of the high Paraná river

Synopsis In this study the diets of five species of bottom-feeding fishes (Prochilodus lineatus, Steindachnerina insculpta, Loricariichthys platymetopon, Trachydoras paraguayensis and Iheringichthys labrosus) were analyzed. Samples were taken in the High Paraná River basin and its floodplain from August 1987 to July 1988 and in February, August and September 1991. The results demonstrated that P. lineatus and S. insculpta were ileophagous, L. platymetopon was detritivorous and I. labrosus and T. paraguayensis were benthophagous. The feeding activity was higher during the flood period for P. lineatus and in dry season for T. paraguayensis. P. lineatus and S. insculpta fed mainly during the day, while I. labrosus and T. paraguayensis during the day and dusk, respectively.     

Comparative feeding ecology of Tropocyclops prasinus mexicanus (Copepoda, Cyclopoida)

The herbivorous and carnivorous feeding biology of Tropocyclopsprasinus mexicanus, an especially small cyclopoid copepod, wasstudied under in situ food conditions in three different lakesand under experimentally augmented food supplies. The mass-specificfood uptake is compared to that of two larger species—Cyclopskolensis and Cyclops vicinus. Under in situ food conditions,T.p.mexicanus depended to a larger extent on algae than invertebrateprey and showed lower mass-specific ingestion rates than thetwo larger species. Daily mass-specific uptake rates for algaeranged between 10 and 24% of its body mass versus 0.7–7%for invertebrate prey. The larger species C.vicinus and C.kolensisingested a total dry mass equivalent to 106% or up to 143% oftheir body mass with algae contributing 66 and 81%. However,under enriched food availability, T.p.mexicanus is able to ingesta biomass equivalent to its body mass, with an algae (54%) andprey (40%) portion similar to that of the larger species. Bodysize appears to be an important factor for the relative importanceof algal versus invertebrate prey for cyclopoid copepods.     

An example of niche partitioning in three coexisting freshwater cyclopoid copepods

Vertical distributions at noon and midnight of copepodites,males and females of three coexisting species of freshwatercyclopoid copepods, Cyclops vicinus (a cold-water form), Thermocyclopscrassus and Mesocyclops leuckarti (warm-water forms), were studiedin Dreiangel Lake, a small eutrophic gravel pit. The largestspecies, C. vicinus, inhabits deep water layers, both at noonand midnight, while the smaller species, T.crassus and M.leuckarti,inhabit upper water layers. In all three species, copepoditesand males live closer to the water surface than females. Insummer, abundance of the smallest species (T.crassus) is highest,although finite birth rates are lowest. The distribution patternsand population characteristics suggest that the vertical distributionof cyclopoid copepods in Oreiangel Lake is mainly governed byfish predation; different temperature tolerances and preferencesof the three species may also be of significance.     

Crown Spread Patterns for Five Deciduous Broad-leaved Woody Species: Ecological Significance of the Retention Patterns of Larger Branches

Patterns of crown spread and branch retention of two shade-intolerantspecies (Betula platyphyllaandB. maximowicziana) were comparedwith three more tolerant species (Quercus mongolica,Acer sieboldianumandMagnoliaobovata). Branching height (height of the lowest living branch)rose more rapidly with age for the twoBetulaspecies than forthe shade tolerant species. Branching heights ofA. sieboldianumandM.obovatawere similar, irrespective of tree height and age, andlarger trees tended to produce wider crowns than theBetulaspecieswhen trees of similar height were compared. In all species,the branch basal area (cross-sectional area of a branch at itsbase) and the leaf area per branch generally increased as thebranch position on a stem became lower. Therefore, retaininglarger branches contributed significantly to the support ofa larger leaf area per tree. The number of larger branches (branchbasal area >80 cm²) for bothBetulaspecies was significantlysmaller than that of the shade tolerant species. The branchretention pattern ofBetulaspecies was probably a consequenceof intolerance of the leaves to shade. The decline ofBetulaspecieswith forest succession is likely to occur through their inabilityto retain branches with a large base area in closed forests.Copyright1997 Annals of Botany Company Shade tolerance; crown spread; branch retention; branch size; broad-leaved woody species; leaf area index per tree     

Salt Tolerance in the Triticeae: K/Na Discrimination in Synthetic Hexaploid Wheats

Ion concentrations were measured in the leaves of synthetichexaploid wheats and their parents growing in saline hydroponicculture. The synthetic hexaploids contained genomes from a tetraploidwheat (Triticum diccocum, T. durum, T. araraticum or T. timopheevi)and from a diploid species (T. monococcum, T. urartu, T. boeoticumor Aegilops squarrosa). Leaf Na concentrations were low, andK concentrations high, in Ae. squarrosa, T. araraticum and allof the synthetic hexaploids, but high in T. dicoccum and T.durum. At low salinities leaf Na concentrations were particularlyhigh in T. durum in comparison with the other species. Theseresults suggest that the enhanced K/Na discrimination character,originally found in Ae. squarrosa and BBAADD genome hexaploidwheats, is also present in diploid wheat and in GGAA genometetraploid wheats. It is suggested that this character has beenlost in the evolution of the BBAA genome tetraploid wheats. Key words: Salt, ion transport, A genome, Triticum spp     

THE MORPHOLOGY OF THE OSPHRADIUM IN RELATION TO FEEDING HABITS IN MESO- AND NEOGASTROPODS

The morphology of the osphradium in nine species of meso- andneogastropods was examined using scanning electron microscopy.Herbivores and detritivores (Littorina, Aporrhais) have simpleosphradia consisting of long ridges, covered in ciliary tufts,and flanked on either side by bands of densely ciliated epithelium.Another herbivore Rhinoclavis has the central ridge dividedinto lobes. In carnivorous and predatory species (Polinices,Cypraea, Nucella, Nassarius, and Conus) the osphradium is shorter,larger and divided bi- or triserially, into leaflets. Conusstri-atus which feeds upon the most mobile and least predictableprey (fish) has the largest and most elaborate osphradium, withthe leaflets divided into digitiform processes. The sedentary,ciliary-feeding, Crepidula is anomalous in having an osphradiumdivided into leaflets, although these are vestigial along oneside.     

The Influence of Foliar Applications of Urea on the Nodulation Pattern of Certain Leguminous Species

In greenhouse experiments with seven species of legumes, thespraying of urea on to the leaves was shown to affect nodulationadversely, without impairing the growth of the plants. In Phaseolusvulgaris, Vicia sativa, and Pisum sativum three-times-weeklysprays of 1 per cent. aqueous urea either prevented or markedlyreduced nodule development during the 8-week experimental period.In Medicago sativa and Trifolium pratense the urea treatmentresulted in a delay in nodulation so that numbers of nodulesat the first sampling (4 weeks) were reduced, while numbersat later samplings were higher since nodulation had been delayeduntil the root system was larger and provided a greater numberof potential nodule sites. In Trifolium hybridum and T. repensthe urea-treated plants showed reduced nodulation throughoutthe 6-week experimental period. In these experiments the advance effects on nodulation cannotbe due to high concentration of combined nitrogen in the rootingmedium, but it is suggested they derive from a high level ofnitrogen within the plant.     

Developing a DNA barcode library for perciform fishes in the South China Sea: Species identification,accuracy and cryptic diversity

DNA barcodes were studied for 1,353 specimens representing 272 morphological species belonging to 149 genera and 55 families of Perciformes from the South China Sea (SCS). The average Kimura 2‐parameter (K2P) distances within species, genera and families were 0.31%, 8.71% and 14.52%, respectively. A neighbour‐joining (NJ) tree, Bayesian inference (BI) and maximum‐likelihood (ML) trees and Automatic Barcode Gap Discovery (ABGD) revealed 260, 253 and 259 single‐species‐representing clusters, respectively. Barcoding gap analysis (BGA) demonstrated that barcode gaps were present for 178 of 187 species analysed with multiple specimens (95.2%), with the minimum interspecific distance to the nearest neighbour larger than the maximum intraspecific distance. A group of three Thunnus species (T. albacares, T. obesus and T. tonggol), a pair of Gerres species (G. oyena and G. japonicus), a pair of Istiblennius species (I. edentulous and I. lineatus) and a pair of Uranoscopus species (U. oligolepis and U. kaianus) were observed with low interspecific distances and overlaps between intra‐ and interspecific genetic distances. Three species (Apogon ellioti, Naucrates ductor and Psenopsis anomala) showed deep intraspecific divergences and generated two lineages each, suggesting the possibility of cryptic species. Our results demonstrated that DNA barcodes are highly reliable for delineating species of Perciformes in the SCS. The DNA barcode library established in this study will shed light on further research on the diversity of Perciformes in the SCS.     

Nouvelles formulations des regles ecologiques connues sous le nom de reegle de Bergmann et loi de Jordan: Amendments of the ecological rules known as Bergmann's and Jordan's rules

Measurements of populations of planktonic and micronektonicspecies from the Atlanto-mediterranean region (about 10,000specimens) have lead to improvements in Bergmann's rule relatingto the increase in size with latitude. There are three cases : Mediterranean specimens may be smaller(e.g. the mysid Eucopia hansent), equal to (e.g. the decapodcrustacean Gennadas elegans) or larger than Atlantic ones (e.g.the thecosomatous genus Cymbulia). All the species in the last group have their principal distributionin warm ocean waters. In the Atlantic, tropical species (e.g.the euphausiid Euphausia gibboides) decrease in size in thenorthern parts of their range while temperate species (e.g.the decapod crustacean Sergesles corniculum) decrease in sizetowards both the pole and the equator. The comparison with the number of vertebrae of fish, which increasesas does the size according to Jordan's rule, is interesting:though correct for cold water species (e.g. Merlucdus merluccius),this rule cannot be applied to warm water species (e.g. Merlucciussenegalensis). Thus, these rules must be corrected like this:- "a species reachesits maximal size in high, intermediate or low latitudes of itsarea if it has a boreal, temperate or tropical distribution"; - "the number of vertebrae increases with latitude for borealfish and decreases for tropical ones".     

Suspension feeding and kleptoparasitism within the genus Trichotropis (Gastropoda: Capulidae)

The marine gastropod Trichotropis cancellata is a facultativekleptoparasite, either suspension feeding or parasitically stealingfood from tube-dwelling polychaete worms. To determine whetherconclusions drawn from long-term studies in the San Juan Islands,Washington, about the relative importance of suspension feedingand kleptoparasitism can be applied generally to T. cancellataacross its biogeographic range, I expanded earlier studies toAlaska and British Columbia. Kleptoparasitism is pervasive throughoutthe range of T. cancellata, occurring with equal frequency throughoutthe areas studied. The average density and size of worm hostsare relatively constant across this range. Snail and worm densitiesare not significantly correlated at the larger scale of site(averaged over nearby sampling locations clustered around acity), but are correlated at the smaller local scale (withina sampling location). Larger worms do not support more snails.The abundance of uninfected worm hosts is usually not limiting,except potentially in some sampling locations in southwest Alaskawhere the use of a novel host (a holothurian) may be the resultof low densities of uninfected worms. Additionally, I documentedthe feeding behaviours of other trichotropid species in theseregions. Trichotropis conica is the second confirmed kleptoparasitewithin the genus Trichotropis, with kleptoparasitism as frequentin this species as in T. cancellata. Like T. cancellata, allsizes observed of T. conica are kleptoparasites. On the otherhand, Trichotropis insignis is an obligate suspension feeder.Further studies are needed to determine exactly how many timesthis behaviour has arisen and been lost in Capulidae and relatedfamilies. (Received 31 May 2007; accepted 19 October 2007)     

Studies on the Physiology of Nodule Formation: VIII. The Influence of the Size of the Rhizosphere Population of Nodule Bacteria on Root Hair Infection in Clover

With an adequate inoculum the number of infected root hairsin three species of clover (Trifolium parviflorum, T. patensand T. glomeratum) increased exponentially with time in twophases; the increase was rapid during the first 8-10 days beforenodulation begins, but slower afterwards. T. parviflorum hadmost infections and T. glomeratum the fewest. Experiments on varying inoculum size, using an avirulent mutanstrain of Rhizobhtm trifolii as diluent, showed that root-hairinfection was differentially limited by inoculum size duringthe two phases. Infection in all three species was about doubledby doubling the density of the virulent bacteria in the rhizospherebefore nodulation begins. After nodulation bacterial densityhad to be increased much more than twice to double the numberof infections. This increase in the infecting population wasinversely related to the numbers of infections formed on thethree host species. Early infection and nodulation were promoted by high bacterialdensity in the rhizosphere.     

Isozyme Variation in Wild and Cultivated Species of the Genus Trifolium L. (Leguminosae)

Isozyme patterns for PGI (phosphoglucoisomerase), MDH (malatedehydrogenase), EST (esterase) and SOD (superoxide dismutase)were evaluated in 36 accessions of eight Trifolium species,namely T. incarnatum, T. polymorphum, T. pratense, T. repens,T. resupinatum, T. riograndense, T. subterraneum and T. vesiculosum.Similarity between species and accessions was estimated by Jaccard’ssimilarity index based on presence or absence of bands. TheUPGMA method was utilized for the groupings and dendrogram constructionwith the aid of the NTSYS-PC program. Interspecific similaritywas low (J 0.351). The dendrogram presented eight groups, eachone corresponding to a taxonomic species. Most of the accessionsof the same species grouped together at J > 0.50, exceptT. riograndense, T. repens and T. pratense. These three speciesshowed the lowest similarity between their accessions, reflectinghigher intraspecific variation. Some accession-specific bandswere identified. The species groupings are consistent with traditionaltaxonomic species delimitation. Therefore isozyme patterns,especially when several systems are employed, are useful andreliable biochemical markers for the taxonomic delimitationand characterization of Trifolium germplasm. Copyright 2000Annals of Botany Company Genetic diversity, germplasm characterization, isoenzymatic variability, biochemical markers, isozymes,Trifolium     

Distribution and Accumulation of Thiophenes in Plants and Calli of Different Tagetes Species

The diversity of thiophenes (natural biocides) and the differencesbetween the concentrations of these compounds in the leavesand roots of Tagetes erecta L., T. patula L. cv. Nana furia,and T. minuta L. (marigolds) indicated the presence of at leasttwo different sites of accumulation: leaves and roots. Leafexplants of Tagetes, however, are used by preference to obtaincallus cultures. Once subcultured, secondary (C₂) calli of T.patula obtained from leaves of 4 to 7-week-old plants, containedhigher amounts of accumulated thiophenes (up to 80% of the amountsin the leaves) than original (C₁) or twice subcultured calli(C₃). The concentrations of thiophenes in C₂ calli of T. minutawere about half those of C₁ calli, while the concentrationsof thiophenes of C₁ calli amounted to 1-2% of the leaf values.Most of the C₃ calli of T. minuta did not contain thiophenesat all. Although C₁ calli of T. erecta also contained considerableamounts of thiophenes, the C₂ calli died, most likely owingto high levels of accumulated polyphenolic compounds. The combinationof species effects and the physiological state of plants andcalli provides adequate information to decide whether Tagetescalli are able to produce thiophenes or not. It is concludedthat the ability to produce thiophenes does not depend on theorgan used, but on the genetic information present in the species,and on the physiological state of plants and calli, particularlytheir age. Key words: Callus, explant selection, Tagetes erecta, Tagetes minuta, Tagetes patula, thiophenes     

The Comparative Biology of Closely Related Species: VI. ANALYSIS OF THE GROWTH OF TRIFOLIUM REPENS AND T. FRAGIFERUM IN PURE AND MIXED POPULATIONS

An analysis was made of the first season's growth of pure andmixed stands of Trifolium repens and T. fragiferum. T. repens,although having smaller seeds and cotyledon area, achieved afaster early rate of leaf production than T. fragiferum andquickly developed a larger area of leaf both in pure standsand in mixtures. By the 18th and 21st weeks from sowing, T.fragiferum had more elongated petioles than T. repens, leaveswere borne higher in the canopy and contributed an increasingpart to the Leaf Area Index of mixtures. The increase in leaf area of swards with time was largely associatedwith increased area of individual leaves. The differences betweenspecies were largely due to differences in number of leaves. These results are discussed in relation to the conditions underwhich stable associations of species may be formed.     

Sexual dimorphism of heads and abdomens: Different approaches to ‘being large’ in female and male lizards

Sexual‐size dimorphism (SSD) is widespread in animals. Body length is the most common trait used in the study of SSD in reptiles. However, body length combines lengths of different body parts, notably heads and abdomens. Focusing on body length ignores possible differential selection pressures on such body parts. We collected the head and abdomen lengths of 610 lizard species (Reptilia: Squamata: Sauria). Across species, males have relatively larger heads, whereas females have relatively larger abdomens. This consistent difference points to body length being an imperfect measure of lizard SSD because it comprises both abdomen and head lengths, which often differ between the sexes. We infer that female lizards of many species are under fecundity selection to increase abdomen size, consequently enhancing their reproductive output (enlarging either clutch or offspring size). In support of this, abdomens of lizards laying large clutches are longer than those of lizards with small clutches. In some analyses, viviparous lizards have longer abdomens than oviparous lizards with similar head lengths. Our data also suggest that male lizards are under sexual selection to increase head size, which is positively related to winning male–male combats and to faster grasping of females. Thus, larger heads could translate into higher probability to mate. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 665–673.     

Effects of Temperature on the Circadian Conidiation Rhythm of Temperature-Sensitive Mutants of Neurospora crassa

Period lengths at different temperatures and phase responsecurves at a high temperature (35°C) of circadian conidiationrhythms were examined in 13 temperature-sensitive (un) strainsof Neurospora crassa. Two strains, un-16 and un-18, had longerperiod lengths than the wild-type strain even at permissivetemperatures. Period lengths of six strains, un-4, un-11, un-16,un-18, un-19 and un-22, changed differently from that of thewild-type strain at restrictive temperatures. However, the shapeof phase response curves for high temperature (35°C) for3 h was almost the same for all un strains and the wild-typestrain. We isolated 97 temperature-sensitive mutants with periodlengths from 19.2 to 24.8 h and determined the dependence ontemperature of the period length of the conidiation rhythm foreach mutant. The mutants could be divided into four differentgroups in terms of their responses to changes in temperature. (Received September 8, 1993; Accepted March 10, 1994)     

The Diatom Genus Tabellaria: II. Taxonomy and Morphology of the Plankton Varieties

Plankton samples of Tabellaria from all the lakes of the EnglishLake District have been examined and evidence of morphologicallydistinct populations has been found in samples from (a) a singlelake at one time, (b) different lakes, and (c) a single lakeat different times. Clone cultures have been used to study thenature of these differences. Fifteen characters have been foundto show quantitative or qualitative variation in plankton populationsof Tabellaria, and the morphological diversity of differentpopulations is largely due to different combinations of thesecharacters. All known plankton populations of Tabellaria arereferred to the species T. flocculosa.     

SPECIES DISCRIMINATION AMONG PELAGIC HETEROPODS: RESOLUTION OF THE PTEROTRACHEA HIPPOCAMPUS--P. MINUTA PROBLEM

Four species of Pterotrachea are currently recognized, two ofwhich (P. hippocampus Philippi, 1836, and P. minuta Bonnevie,1920) have very similar morphologies. These two species havebeen distinguished mainly on the basis of eye and visceral nucleusshapes; the former with wide, triangular eyes and a short, broadnucleus, and the latter with narrower, triangular eyes and ataller, more slender nucleus. Quantitative and qualitative morphologicaldata were obtained from specimens of P. hippocampus and P. minuta collectedduring two oceanographic sampling programs in the North AtlanticOcean. Comparisons of eye and visceral nucleus shapes (representedby their length to width and length to retinal width ratios,respectively), plotted against body length showed linear decreases,with no justification for the recognition of two separate species.Examination of eye shape across a wide range of body sizes showedthat the width of the retina increases disproportionately with bodygrowth (by elongation and medial upturning) beginning at a length ofabout 21-22 mm. As a result, the overall appearance of the eyeat this body size changes such that smaller animals (less than21-22 mm) have eyes corresponding with those of P. minuta, whilethe eyes of individuals larger than this body length match thoseof P. hippocampus. Several authors have distinguished femalesof the two species by the presence (P. hippocampus) or absence (P.minuta) of cuticular spines anterior to the eyes. Examinationof female specimens showed that those less than about 30 mmlacked these spines, while those above this size possessed them.Thus, cuticular spines represent a secondary female sexual characteristic. Other morphological features that have been used by previousauthors to distinguish the two species were examined and rejected.Because P. hippocampus was described prior to P. minuta, itis herein regarded as the senior synonym of P. minuta. (Received 12 June 1997; accepted 21 May 1999)     

The Effects of Rootzone Salinity and Hypoxia on Shoot and Root Growth in Trifolium Species

The effect of concurrent salinity (0-60 mM NaCl) and rootzonehypoxia (flooding for up to 15 d) on shoot and root growth andshoot ion concentrations of six species of Trifolium (T. subterraneumL., T. fragiferum L., T. michelianum Savi., T. isthmocarpumBot., T. purpureum Lois., and T. repens L.), was studied intwo greenhouse experiments. There was a significant salinityx flooding effect for shoot yield but no significant salinityx flooding x species interaction although individual speciesdiffered significantly (P < 0·001) in their growthresponse to the saline or flooded conditions separately. Concentrationsof Na and Cl in the shoots of all species increased with increasingperiods of saline flooding and there was a significant salinityx flooding interaction. Sodium and Cl concentrations were significantlyhigher (P < 0·001) in T. purpureum, the species inwhich shoot growth was most depressed by saline flooding, thanother species. In T. michelianum, T. fragiferum and T. repens,fresh and dry weight of roots increased with flooding underboth saline and non-saline conditions while in T. subterraneumroot growth decreased. A significant proportion of the increasedroot growth in the first three species occurred as new adventitiousroots. These roots had higher percentages of internal gas spaceswithin the root tissue even in the presence of salinity comparedwith roots from non-flooded conditions. There were also significantlymore gas spaces in the total root tissue in T. fragiferum andT. repens under saline-flooding than in roots of T. subterraneum.Electron micrographs of the root cross sections illustratedthe presence of these gas spaces or aerenchyma. Trifolium fragiferum, T. repens and T. michelianum are morelikely to be suited to growth in soils prone to high salinityand to flooding than are T. subterraneum, T. purpureum and T.ishmocarpum.Copyright 1993, 1999 Academic Press Trifolium subterraneum, Trifolium fragiferum, Trifolium michelianum, Trifolium isthmocarpum, Trifolium purpureum, Trifolium repens, salinity, flooding, hypoxia, adventitious roots, aerenchyma, subterranean clover, white clover, strawberry clover, purple clover, balansa clover