Intraspecific Size Research Articles

Light microscopy diagnosis of Babesia bovis and Babesia bigemina kinetes in the haemolymph of artificially infected Boophilus microplus engorged female ticks

The length, width and position of the nucleus of Babesia bovis and Babesia bigemina kinetes from the haemolymph of Boophilus microplus engorged female ticks were recorded. Additionally, the shape of Babesia bovis kinetes were registered as curved, semi-curved or straight. To this aim Boophilus microplus tick larvae from a colony free of Babesia were fed on splenectomised calves artificially infected with either Babesia bovis or Babesia bigemina pathogenic strains. Six engorged female ticks showing an infection of at least ten mature kinetes of Babesia bovis in a sample of haemolymph 5 days after detachment were also monitored 7, 9 and 10 days after collection. The same procedure was followed with six engorged female ticks infected with Babesia bigemina. One hundred and twenty kinetes of each species of Babesia were evaluated. The mean length ± standard deviation and ranges for Babesia bovis kinetes were 14.30 ± 0.922 μm and 11.9−16.3 μm, while the corresponding measures for the kinetes of Babesia bigemina were 11.27 ± 0.900 μm and 9.0−13.1 μm ( P < 0.001, t-test). The width was 3.33 ± 0.315 μm, 2.6−4.0 μm for Babesia bovis and 2.24 ± 0.287 μm, 1.5−2.8 μm for Babesia bigemina kinetes ( P < 0.001). The most common position of the nucleus was central for both species of Babesia. A total of 58% of Babesia bovis kinetes showed the typical curved tail. No effect of time post-collection and individual host ticks in the kinete of Babesia bigemina was found while an unexpected influence of individual host tick in the width of Babesia bovis kinetes was detected ( P < 0.01, analysis of variance). The overlap in the sizes of kinetes from both species of Babesia makes it difficult to apply the results to ticks of unknown babesial infection status. This finding is further complicated by the intra-specific size variations of Babesia kinetes from different geographical origins.

Intraspecific size variation in polyphagous parasitoids (Hym.: Parasitica), of leaf miners and its relation to host size

Wing and body lengths of polyphagous parasitoids of leafminers are analyzed in order to understand the relationship between host and parasitoid sizes. A distinct positive relationship was observed: within each parasitoid species, smaller individuals were reared from smaller hosts. There was no difference between idio-and koinobionts in sexual dimorphism, with females being significantly larger than males in both groups.

Conserved location of genes on polymorphic chromosomes of four species of malaria parasites

The number of chromosomes and the chromosomal location and linkage of more than 50 probes, mainly of genes, have been established in four species of Plasmodium which infect African murine rodents. We expected that the location and linkage of genes would not be conserved between these species of malaria parasites since extensive inter- and intraspecific size differences of the chromosomes existed and large scale internal rearrangements and chromosome translocations in parasites from laboratory lines had been reported. Our study showed that all four species contained 14 chromosomes, ranging in size between 0.5 and 3.5 Mb, which showed extensive size polymorphisms. The location and linkage of the genes on the polymorphic chromosomes, however, was conserved and nearly identical between these species. These results indicate that size polymorphisms of the chromosomes are more likely due to variation in non-coding (subtelomeric, repeat) sequences and show that a high plasticity of internal regions of chromosomes that may exist does not frequently affect chromosomal location and linkage of genes.

Body size and sex ratio in emergent stonefly nymphs (Isogenoides olivaceus: Perlodidae): variation between cohorts and populations

The ecological significance of pattern in animal-size distribution has been receiving increased scrutiny in studies of population regulation and individual energetics. However, few studies have assessed differences in size variation between sequential generations or adjacent populations. Annual variation in body size and sex ratio of emergent perlodid stonefly nymphs, Isogenoides olivaceus (Frison) (Plecoptera: Perlodidae), were examined in populations from two Michigan mesic groundwater rivers. Final nymphal body size was estimated from sex-specific length to mass regression relationships using exuviae collected from each site. Sexual size dimorphism accounted for much of the intraspecific size variation within both populations and cohorts: females were larger ([Formula: see text]) than males ([Formula: see text]). Males showed less size variation than females; unlike those for females, size distributions for males were significantly skewed. Secondary sex ratios were female biased in both populations and all cohorts and ranged between 59.1 and 72.8%. Female sex bias increased with relative male size in both populations.

Character Displacement, Sexual Dimprphism, and Morphological Variation among British and Irish Mustelids

Five native terrestrial mustelids are found in Great Britain. Only three of these occur in Ireland. Farmed American mink have recently established feral populations on both islands. We studied inter— and intraspecific size relationships, sexual size dimorphism, and morphological variation among these mustelids. We viewed each size as a separate morphospecies, skull length as a measure of body size, and the upper canine tooth as the organ used to kill prey. Geographic variation was low in both islands, so we considered the mustelid population of each island a single unit. Community—wide character displacement (evidence by equal size ratios) was found among British mustelids for canine diameter. For skull length it was seen only when the largely vermivorous badger was excluded. When we added feral mink the regular pattern disappeared, but when we substituted the mink for the polecat, which is now restricted to parts of Wales and adjacent England, community—wide character displacement was manifest. For Irish mustelids size ratios were not equal, but the pattern for canines was more regular than for skull lengths. Adding the local feral mink did not result in a regular pattern, but addition of the mink and exclusion of the badger yielded equal ratios for skull length but not for canines. These patterns plus published empirical data support a hypothesis of prey size partitioning. The significant differences in size between some of the British and Irish populations of the same morphospecies suggest the possibility of ecological release among Irish mustelids, whose populations originally derived from British ones. In particular, canine sexual size dimorphism is greater for Irish pine martens, stoats, and mink, as would be expected if there were fewer competitors. For the marten and the stoat, Irish females have evolved to be strikingly smaller than their British counterparts, in each case approximating the size of the male of a missing species (polecat for the marten, weasel for the stoat). For skull length there is no consistent patterns. Finally, morphological variation is greater in Ireland for five or six morphospecies, as predicted by the niche—variation hypothesis.

Shallow water as a refuge habitat for fish and crustaceans in non-vegetated estuaries: an example from Chesapeake Bay

Abundances and size-frequency distributions of common epibenth~c flsh and crustaceans were compared among 3 depth zones (1-35, 35-70, 71-95 cm) of the Rhode River, a subestuary of Chesapeake Bay, USA. In the absence of submerged aquatic vegetation (SAV), interand intraspccific size segregation occurred by depth from May to October, 1989-1992. Small species (Palaemonetes pugjo, Crangon septernspjnosa, Fundulus heteroclitus, F majaljs, Rhithropanope~ls harrisii, Apeltes quadracus, Gobiosorna boscj) were most abundant at water depths 70 cm). In field experiments, mortality of tethered P pugio (30 to 35 mm), small E heteroclitus (40 to 50 mm), and small C. sapjdus (30 to 70 mm) increased significantly with depth. Wc hypothesize that predation risk was size-dependent, creating the observed intraand interspecific size differences among depth zones. For C. sep.temspinosa, burial may modify this size-dc>pendency and create the unusual absence of intraspecific size increase with depth. Historically, f? pugio and Fundulus spp. (and other small species) were not restricted to shallow (<70 cm) waters and were abundant in deeper SAV beds, which provided a structural refuge from predators. Since the recent demise of SAV in Chesapeake Bay, our results indicate many small species have shifted their distributions and now utilize primarily shallow water as an alternate refuge habitat.

Chromosome size polymorphism and DNA rearrangements in plasmodium

Protozoan parasites often follow a complex life cycle that features the display of many distinct developmental stages. The life cycle of many of these parasites takes place in two different hosts, Such organisms are therefore adapted to differentiate cyclically, growing and developing in very different environments. The malaria parasite is a good example of a unicellular parasite demonstrating complex differentiation pattems. Here short periods of rapid asexual proliferation are alternated with sexual differentiation. The haploid parasite sequentially multiplies by mitotic divisions in the liver and the blood of the vertebrate host, followed by sexual development in the midgut of mosquitoes and the production of infectious sporozoites in the salivary glands of the mosquitoes. Malaria parasites have a unique biology that enables them to complete the complex differentiation cycles necessary for survival in two different hosts. The question addressed here is whether the organization and molecular biology of the chromosomes of malaria parasites have similarly unique features that play a direct role in the progression of the parasite through its life cycle. Research on genome organization has revealed that malaria parasites apparently exhibit a remarkable plasticity of their genome, as shown by intra-specific size differences between homologous chromosomes. Based on the characterization of several mechanisms involved in the generation of chromosome size polymorphism in several Plasmodium species, the presence of unique molecular processes with specific functions has been the subject of speculation. It has been proposed that size polymorphism could be associated with programmed DNA rearrangements that are involved in the regulation of gene transcription or in generating diversity in

Breeding Success in a North and a Central European Population of the Great Tit Parus major

To study possible density-dependent processes and differences in reproductive success between populations of the Great Tit breeding at high and low latitudes longterm data from Oulu, Finland (17 yr) and Budapest, Hungary (19 yr) were analysed. Large fluctuations and low productivity as a consequence of high nestling mortality were recorded in the northern population, where neither intranor interspecific density-dependent effects were found. High density and high productivity were shown in the Central European population, where intraspecific density-dependent clutch size reduction was found. Interspecific density-dependent clutch size reduction and hatching failure due to competitor species were also found in this population.

Population structure and yield-per-recruit analysis of the giant periwinkleTurbo sarmaticusin the Cape St Francis region, South Africa

The density, biomass and population structure of Turbo sarmaticus at three different sites in the Cape St Francis region, together with its distribution along the tidal gradient, were investigated. Differences in density and population structure between sites can be attributed mainly to different degrees of exposure to wave action. An intra-specific size gradient was found, mean shell length decreasing in an upshore direction. The yield potential of the species was investigated and it appears that present levels of exploitation in the study area are sustainable. The present minimum legal size should not be lowered.

Interspecific and Intraspecific Size Class Competition Affecting Resource Use and Growth of Perch, Perca fluviatilis

Interspecific and intraspecific size-class competition affecting resource use and growth of perch (Perca fluviatilis )

Competitive Exclusion, Character Convergence, or Optimal Foraging: Which Should We Expect?

A review of the theoretical and empirical literature is made, to show that character convergence among competing species is much more likely than traditional theory predicts.Several factors appear to influence the probability that such convergences will occur, including body size,trophic niche width, intraspecific density dependence,population abundance and size structure, competition coefficients, foraging rate,genotypic and phenotypic variance, food/energy characteristics, diffuse competition, frequency and density dependent selection and community stability.There are also several mechanisms of character convergence that are caused by predation and abiotic factors and both phenotypic and genotypic convergences among competing species are possible.In particular, intraspecific, optimal foraging constraints mays sometimes take precedence over the competitive exclusion principle

Distribution, body size, and brood characteristics of four species of mysids (Crustacea: Peracarida) in the Avon‐Heathcote Estuary, New Zealand

Four species of mysids are resident in the Avon-Heathcote Estuary, Christchurch. Tenagomysis macropsis is by far the most abundant daytime species and has a wide distribution, not linearly correlated with salinity. Tenagomysis novae-zealandiae and T. chiltoni are much less abundant, increase in numbertoward the upper estuarineregion, and (especially T. chiltoni) have distributions significantly correlated with salinity (P < 0.05–0.001). T. chiltoni has a spring/summer population maximum. Gastrosaccus australis appears to be an obligate nocturnal plankter and its; distribution in the system is unresolved. The largest mysid was T. chiltoni and the smallest T. novae-zealandiae, although there was considerable intraspecific size variation. For all 3 Tenagomysis species, males were mature at a smaller size than females, whereas the opposite was true for G. australis. For each species, ovigerous females generally achieved the maximum size recorded. Embryo numbers carried in the marsupium ranged from 4 to 25 for T. macropsis, from 6 to 19 for T. novae-zealandiae, and from 22 to 39 for T. chiltoni. Embryo sizes for the New Zealand species are in accord with the range found generally for coastal mysids.

Comparative population ecology of the dragonflies Libellula lydia and Libellula luctuosa (Odonata: Libellulidae)

Temporal and spatial patterns of habitat use, population size structure, and survivorship were compared over three generations of Libellula lydia and Libellula luctuosa in a small pond in Indiana. The two species were univoltine, had similar phenologies, and converged on the same within-pond habitats. There was little evidence for any spatial and (or) temporal habitat partitioning that might be expected between such morphologically and ecologically similar species. Larval populations of each species were highly size structured because oviposition and hatching were extended over 3 months in summer. Intraspecific size differences were greater than those frequently reported to accommodate interspecific coexistence. Thus, intraspecific resource partitioning and cannibalism should have an important effect on population dynamics. Both similar and disparate interspecific size combinations frequently co-occurred in time and space so that competition and predation should simultaneously affect coexistence. Larval mortality was high in late summer and fall, negligible in winter, and high again in spring. Fewer than 10% of either species survived to emerge from the pond. Interodonate predation is a likely source of much of this larval mortality, given that other odonates are among the most abundant large predators in fishless ponds.

Why Are Bonsai Plants Small? A Consideration of Cell Size

Size determinants of organisms are still a great puzzle. Analysis of dwarfs or giants within a certain taxon is a promising tool for a functional understanding of size control. Bonsai cultivation techniques lead to the most extreme forms of environmentally induced plant dwarfism. It is shown that no such changes take place at the level of cell size of leaves. Leaves of four out of six species of Bonsai had even bigger cells than leaves of normal trees, which is similar to what was observed in genetically dwarf plants from high altitudes. These results illustrate the insignificance of intraspecific cell size variations for explanations of differences of size and growth of plants. Genetic control of cell size is stronger than the most severe environmental impact as it is received by Bonsais. The relevance of concepts developed for the control of cell size and cell division in unicellular organisms for meristematic plants is discussed.

Habitat Selection and Space Partitioning among two Mediterranean Blenniid Species

Abstract. The utilization of the spatial resources of two syntopic blenniid species ‐ Blennius cunevue and Blennius incognitas ‐ has been investigated in silu and under laboratory conditions. Both species occupy bore holes of the mussel Lithophugu in the sublittoral zone. B. cunevue dominates the more shallow zone (x̄= 0.68 m) and prefers smaller (x̄= 12.76 mm diameter) and horizontal bore holes. B. incognitus inhabits the same depth range as B. cunevue but occupies larger bore holes (x̄= 14.57 mm) in a deeper zone (x̄= 0.86 m). Individuals of B. incognitus do not prefer a special inclination angle. The two blenniid species defend territories with different intraspecific sizes: the mean territory radius of B. cunevue is 6.87 mm, of B. incognitusx̄= 10.95. Mechanisms to reduce competition include different activity rhythm, interspecific social dominance, and differences in territoriality. B. cunevue is the dominant species; its territories arc defended against conspecifics and against B. incognitus.

Life History and Size Structure of Larval Dragonfly Populations

Comparative data on emergence, adult activity, and larval development were used to interpret patterns of phenology, voltinism, and developmental synchrony in a 14-species assemblage of dragonflies (Odonata:Anisoptera). Interspecific differences in these characteristics provided an opportunity to interrelate life history, population size structure, and the potential for intra- and interspecific interactions. Larval populations of most species comprised an extraordinary size range of individuals at any one time. In many species, this intraspecific size variability was primarily due to developmental asynchrony within generations (e.g., Libellula lydia, Celithemis elisa, Perithemis tenera). Oviposition in these species occurred throughout most of the summer so that the timing of instar development varied considerably among broods. By fall, the largest larvae in these populations were 5 to 10 times the size of smaller conspecifics. In other asynchronous breeders, an even wider size range of co-occurring conspe...

The influence of temperature on the depth distribution of sympatric Erpobdellidae (Hirudinoidea)

Inter- and intra-specific differences in the behavioral responses of two sympatric Erpobdellidae, Nephelopsis obscura and Erpobdella punctata, to overall water temperature change and thermal gradients were investigated in the laboratory. The results are compared with the seasonal migratory patterns recorded in lentic field habitats. While temperature preference does act as a directional factor in the spring movements to shallow water, only starved small N. obscura and starved large nonreproductive E. punctata showed a preference for colder temperatures after acclimation to a summer temperature of 20 °C. Thus, other components of the population do not use temperature as a cue for their movements to deeper waters in the autumn. It is suggested that the seasonal differential depth distributions shown by components of both species result in a spatial separation of potential competing size groups complementing the inter- and intra-specific size class differences in food resource utilization and temporal differences in resource allocation already demonstrated.

The reproductive strategy of the gregarious parasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae) : 2. Host size discrimination and regulation of the number and sex ratio of progeny in a single host.

Host size of Pteromalus puparum, a gregarious pupal parasitoid, shows a wide inter- and intraspecific variation. Experiments were made to study the regulation of the number and sex ratio of progeny per host by the parasitoid. The parasitoid could discriminate inter- and intraspecific size differences of the host and regulate the number of eggs according to the host size when a single female attacked the host. The sex ratio of progeny (proportion males) was about 0.1. The number of progeny laid by the female agreed with the energetically most efficient number og eggs in order to maximize total weight of progeny per host but not with the reproductively most efficient number of eggs to maximize the total fecundity of the progeny. The parasitoid laid smaller number of eggs in a half buried host, but the number was much larger than a half of those in a fully exposed host. When more than one female attacked a single host, the number and sex ratio of progeny per host increased with the number of females attacking the host, but the number of progeny per female decreased. The change of the sex ratio agreed with the prediction of the local mate competition model.

Intraspecific Resource Partitioning in the Bunble Bees Bombus Ternarius and B. Pennsylvanicus

I tested for an association between intraspecific size differences and differences in resource utilization in worker bumble bees (Bombus ternarius and B. pennsylvanicus). Bees were observed foraging in two fields in Minnesota where flower species with short corollas and species with long corollas occurred in both single—species and mixed—species stands. In mixed—species stands, foragers on the species with short corollas were found to have shorter proboscides than conspecific foragers on the species with long corollas. However, proboscis lengths of foragers on the species with a long corolla in single—species stands did not differ from those on the species with a short corolla in single—species stands. Thus, where a choice exists, bumble bee foragers select the species having a corolla most compatible to their proboscis length. I then compared conspecific foragers on a single flower species in one—species versus mixed—species stands. For foragers on flowering species with a short corolla, proboscis length was significantly shorter in the mixed—species than in the single—species stand, but this difference was not found for the species with a long corolla. Thus, presence of other flowering species can influenced the pollinator population of a species, relative to a single—species stand. Resource choice by foragers was analyzed using a probability function, calculated as the ratio of foragers with a given proboscis length on the species with a long corolla to the number with that proboscis length collected on both species. The shape of the probability function was fitted to a sigmoidal curve using probit analysis Regression of the linearized probabilities was significant. This procedure is a better measure of intra— or interspecies association than are measures such as niche overlap, because it quantifies a continuous distribution and accounts for variance in the species distribution.

Aerobic metabolism of the lizardVaranus exanthematicus: Effects of activity, temperature, and size

Oxygen consumption $$(\dot V_{O_2 } )$$ was measured at rest and during spontaneous activity at body temperatures of 25 and 35°C in 14 fasting Savanna monitor lizards,Varanus exanthematicus ranging in weight from 172 to 7500 g. The allometric relationship between metabolic rate at 25°C and body weight (W) is given by: $$\dot V_{O_2 }$$ (ml O2 STPD·g−1·hr−1)=0.88W −0.43 (Fig. 2). Although statistical comparisons are equivocal, this intraspecific size dependence exceeds that reported for interspecific comparisons among reptiles and other vertebrate groups (Fig 3). A reproducible diurnal pattern of activity was observed in undisturbed animals with minimum values of $$\dot V_{O_2 }$$ between 2400 and 0800 h (Fig. 1). Spontaneous activity and $$\dot V_{O_2 }$$ generally reached peak values between 1200 and 2000 hrs. The average ratio of active aerobic metabolic rate (AMR) to minimum (standard) aerobic metabolic rate (SMR) was 8.2. This voluntary AMR/SMR inVaranus exceeds the AMR/SMR for most reptiles stimulated to exhaustion. The high aerobic capacity is consistent with other evidence for efficient exchange and transport of respiratory gases inV. exanthematicus; e.g., low or absent intracardiac shunt flow resulting in high arterial saturation and low ventilation $$(\dot V/\dot V_{O_2 } )$$ and perfusion $$(\dot Q/\dot V_{O_2 } )$$ requirements.