Season and Body Size Influence Movement of Hydropsychid Caddisfly Larvae (Trichoptera: Hydropsychidae)

1992 ◽  
Vol 49 (2) ◽  
pp. 259-265 ◽  
Author(s):  
B. L. Kerans
Keyword(s):  
Body Size ◽  
Relative Size ◽  
Relative Weight ◽  
Central Area ◽  
Size Class ◽  
Directional Bias ◽  
Large Size ◽  
Small Size Class ◽  
First Choice ◽  
Large Size Class

Movement patterns of fifth-instar Hydropsyche slossonae larvae were investigated in artificial streams. In the first choice experiment, larvae were released into a central area and their upstream or downstream crawling or drifting was monitored. A second experiment used the same design; however, fifth instars collected during spring and fall were divided into two, nonoverlapping, relative size-classes (large and small) to determine how these factors influenced movement parameters. In both experiments, larvae always drifted more frequently than they crawled, but in experiment 2, drifting tendency declined with increasing weight in spring. In both experiments, there was no statistically detectable directional bias to crawling nor change in relative crawling direction with season or size-class. In experiment 2, drifting larvae were lighter than nondrifting larvae in the large size-class, but equal in weight in the small size-class. This result was unrelated to absolute weight, as large size-class larvae in fall were similar in weight to small size-class larvae in spring. It is possible that the relative weight differential of drifting and nondrifting larvae in one size-class but not the other may be related to sexual rather than body size differences.

Diet, feeding behaviour and habitat utilisation of the blue stingray Dasyatis chrysonota (Smith, 1828) in South African waters

2003 ◽  
Vol 54 (8) ◽  
pp. 957 ◽  
Author(s):  
David A. Ebert ◽  
Paul D. Cowley
Keyword(s):  
Surf Zone ◽  
Stomach Contents ◽  
Size Class ◽  
Behaviour Pattern ◽  
Medium Size ◽  
Secondary Importance ◽  
Size Classes ◽  
Important Prey ◽  
Large Size ◽  
Large Size Class

Analysis of stomach contents for Dasyatis chrysonota revealed that diet varied with size and habitat. The diet of all size classes in the surf zone was comprised primarily of Callianassa spp., Donax spp. and unidentified polychaete species. The medium and large size classes fed primarily on Donax spp., whereas the very large size class fed mainly on Callianassa spp. Polychaetes were of secondary importance as prey for the medium size class. The diet of D. chrysonota in the nearshore zone consisted mainly of Balanoglossus capensis and Callianassa spp. Balanoglossus capensis decreased from an index of relative importance (IRI) of 75.3% for the medium size class to 59.9% for the very large size class, whereas Callianassa spp. increased from 22.8% to 39.4% between the medium and the very large size classes. The offshore zone was the only area in which small size class D. chrysonota were caught. The diet of these small D. chrysonota was primarily polychaetes and amphipods. Polychaetes increased in importance in the medium size class, but declined in each successively larger size class. Conversely, Pterygosquilla armata capensis became the single most important prey item for the very large size class, comprising an IRI of 50.9%. The behaviour pattern used by D. chrysonota to locate and extract prey is described.

scholarly journals Estudio del polen de Phaseolus chiapasanus Piper (Leguminosae: Phaseolinae)

2017 ◽  
pp. 25
Author(s):  
Alfonso Delgado-Salinas ◽  
Enrique Martínez-Hernández ◽  
Pilar Fernández-Ortuño
Keyword(s):  
Pollen Grains ◽  
Size Class ◽  
Important Research ◽  
Large Size ◽  
Large Size Class ◽  
The Creation ◽  
Taxonomical Revision ◽  
Document Relationships ◽  
Genus Vigna

In the course of a taxonomical revision of the genus Phaseolus and considering the recently important research realized in the Phaseolus-Vigna complex, where the palynological attributes for the genus were precised, the present paper describes the pollen of Phaseolus chiapasanus Piper. The large-size class pollen grains of Ph. chiapasanus are tricolporate, brevicolpate, pseudo-operculate; semitectate, and widely reticulate. The structure of the infratectum could be considered of the granular-collumelar type. Some of the attributes found in the polen of Ph. Chiapasanus were not known for the genus, though such attributes are commonly found in the subgenus Sigmoidotropis of the genus Vigna. Ph. chiapasanus shows a series of morphological and palynological differences that open the possibility for the creation of a new section within the genus. More detailed studies will definitely by needed to better document relationships to other species of the genus.

scholarly journals Changing the relative size of the body parts of Drosophila by selection

1962 ◽  
Vol 3 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Relative Size ◽  
Cell Number ◽  
High Ratio ◽  
Growth Patterns ◽  
The Body ◽  
Mass Selection ◽  
Body Parts ◽  
Wing Size ◽  
Thorax Length

1. Mass selection for both high- and low-ratio of wing to thorax length has been carried out on a population of Drosophila melanogaster. The response to selection was immediate and sustained. When the experiment was stopped after ten generations, the wing area in the two selected lines differed by about 30%. The heritability estimate worked out at 0·56 ± 0·08.2. Thorax length remained comparatively unchanged during selection nor was there any change in wing shape. There was some evidence of assymetry of response since there was a relatively greater change in favour of smaller rather than larger size.3. The tibia length of all pairs of legs showed correlated changes so that the lines with larger or smaller wing sizes had also larger and smaller legs.4. The normal allometric relation between wing and thorax length, associated with variation in body-size, apparently also changed, so that for a given change in thorax length there was a greater or smaller proportional change in wing size in the high- or low-ratio lines.5. The changes in relative wing size are due to changes in cell number.6. It is suggested that the genetic changes due to selection act in the early pupal period when the imaginal discs are undergoing differentiation and proliferation to form imaginal hypoderm and appendages.7. Tests of genetic behaviour failed to show any departure from additivity in crosses which involved the unselected population and the high-ratio line. But highly significant departures existed in the cross to the low-ratio line. Relatively smaller wing size behaves as largely recessive. Stability of the normal wing/thorax ratio involves dominance and probably also epistasis. The genetic properties of the relative size of the appendage are apparently similar to those which characterize body-size as a whole.8. It is suggested that selection provides a valuable tool for studying the constancy or lability of the growth patterns which determine morphology.

scholarly journals Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

2015 ◽  
Vol 282 (1810) ◽  
pp. 20151008 ◽  
Author(s):  
Kristina Noreikiene ◽  
Gábor Herczeg ◽  
Abigél Gonda ◽  
Gergely Balázs ◽  
Arild Husby ◽  
...  
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Relative Size ◽  
Strong Support ◽  
Brain Evolution ◽  
Brain Regions ◽  
Independent Evolution ◽  
Mosaic Model

The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback ( Gasterosteus aculeatus ). We found that heritabilities were low (average h 2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average r G = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high ( r G = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks.

Ontogeny of fetal hepatic and placental growth and metabolism in sheep

1992 ◽  
Vol 263 (3) ◽  
pp. R619-R623
Author(s):  
I. Vatnick ◽  
A. W. Bell
Keyword(s):  
Oxygen Consumption ◽  
Fetal Liver ◽  
Relative Size ◽  
Relative Weight ◽  
Dry Weight ◽  
Maximum Growth ◽  
Late Gestation ◽  
Progressive Decline ◽  
Highly Correlated

Ontogeny of fetal hepatic and placental growth and in vitro oxygen consumption (VO2) was investigated in fetal lambs at 75, 100, and 136 days postconception. Fetal hepatic relative weight and placental absolute and relative weights declined during this period. Oxygen consumption per gram dry weight of fetal liver and maternal placenta declined between mid and late gestation while fetal placental VO2 was unchanged. Estimated VO2 of the whole placenta did not change while the estimated total hepatic VO2 increased more than threefold between 75 and 136 days. Total hepatic VO2 was highly correlated with total placental VO2 at 136 days (r = 0.84). The results suggest that the placenta reaches its maximum growth and metabolic capacity before 100 days and possibly at or before midgestation. Changes in hepatic weight-specific total VO2, in addition to the declining relative size of the fetal liver, must contribute to the progressive decline in metabolic rate of the whole fetus during the second half of pregnancy. Correlations between placental and fetal liver weights and metabolic rates suggest the possibility of placental regulation of fetal hepatic growth and metabolism.

scholarly journals Evidence for benthic body size miniaturization in the deep sea

2006 ◽  
Vol 86 (6) ◽  
pp. 1339-1345 ◽  
Author(s):  
Janne I. Kaariainen ◽  
Brian J. Bett
Keyword(s):  
Body Size ◽  
Deep Sea ◽  
Size Structure ◽  
Size Class ◽  
The Body ◽  
Significant Shift ◽  
Individual Biomass ◽  
Wet Weight ◽  
Accumulation Curves ◽  
Average Individual

The benthic body size miniaturization hypothesis states that deep-sea communities are dominated by organisms of smaller body size, although some field studies have produced contradictory results. Using appropriate sample sets, this study tests this hypothesis by contrasting the benthic communities of the Fladen Ground (North Sea, 150 m) and the Faroe–Shetland Channel (1600 m). Samples were collected for large (500 μm) and small macrofauna (250–355 μm), meiofauna (45 μm) as well as an intermediate sized ‘mesofauna’ (180 μm) to ensure comprehensive coverage of the full meio- and macro-faunal body size-range. The body size structure of the benthos was compared using two methods. The more widely used average individual biomass method involves dividing the total sample biomass by sample abundance. Additionally, body size accumulation curves were constructed by assigning all specimens into a logarithmic size-class and then plotting the cumulative percentage of individuals present in each size-class. The results seem to support the hypothesis that the deep-sea environment is a small organism habitat. Although these findings only represent two locations, the overall body size accumulation curves clearly display a statistically significant shift towards smaller body sizes at the deeper site. The magnitude of the effect is appreciable with median metazoan body size reducing from 14.3 μg wet weight in the Fladen Ground to 3.8 μg wet weight in the Faroe–Shetland Channel. The average individual biomass measurements are shown to be of limited value and can lead to potentially misleading conclusions if the underlying size structure is not analysed in detail.

Spatial and temporal variation in morphology in Australian whistlers and shrike-thrushes: is climate change causing larger appendages?

2020 ◽  
Vol 130 (1) ◽  
pp. 101-113
Author(s):  
Isabelle R Onley ◽  
Janet L Gardner ◽  
Matthew R E Symonds
Keyword(s):  
Climate Change ◽  
Body Size ◽  
Temporal Variation ◽  
Relative Size ◽  
Bird Species ◽  
Spatial And Temporal Variation ◽  
Climatic Warming ◽  
Morphological Response ◽  
Allen’S Rule ◽  
Spatio Temporal

Abstract Allen’s rule is an ecogeographical pattern whereby the size of appendages of animals increases relative to body size in warmer climates in order to facilitate heat exchange and thermoregulation. Allen’s rule predicts that one consequence of a warming climate would be an increase in the relative size of appendages, and evidence from other bird species suggests that this might be occurring. Using measurements from museum specimens, we determined whether spatio-temporal variation in bills and legs of Australian Pachycephalidae species exhibits within-species trends consistent with Allen’s rule and increases in temperature attributable to climatic warming. We conducted regression model analyses relating appendage size to spatio-temporal variables, while controlling for body size. The relative bill size in four of the eight species was negatively associated with latitude. Tarsus length showed no significant trends consistent with Allen’s rule. No significant increases in appendage size were found over time. Although bill size in some species was positively correlated with warmer temperatures, the evidence was not substantial enough to suggest a morphological response to climatic warming. This study suggests that climate change is not currently driving adaptive change towards larger appendages in these species. We suggest that other adaptive mechanisms might be taking place.

Effet de certains paramètres physico-chimiques sur les relations prédateurs–proies dans les populations de copépodes cyclopoïdes des mares temporaires d'eau douce

1986 ◽  
Vol 64 (1) ◽  
pp. 8-11
Author(s):  
Louise Vallières ◽  
Antoine Aubin
Keyword(s):  
Organic Matter ◽  
Body Size ◽  
Dissolved Oxygen ◽  
Water Temperature ◽  
Feeding Ecology ◽  
Mineral Content ◽  
Abiotic Factors ◽  
Size Class ◽  
Regression Analyses ◽  
Physical And Chemical

Copepod populations of three temporary freshwater pools (Alnus unit, Carex unit, and Molinia unit) were studied using a standard approach (species versus abiotic factors) and a holistic one (body size and feeding ecology). Multiple regression analyses of data indicate that the physical and chemical features of water (temperature, pH, dissolved oxygen, mineral content, and depth) explain 62 to 98% of the variability of carnivorous copepods, while the abundance of their prey accounts for much less. No size class of prey seems to be preferred. The abundance of decaying organic matter, typical of such pools, would result in an overabundance of prey. Predators would then be under the control of nonalimentary factors.

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