Does allometry account for shape variability in <Emphasis Type="Italic">Ephedrus persicae</Emphasis> Froggatt (Hymenoptera: Braconidae: Aphidiinae) parasitic wasps?

We analysed linear measurements on various parts of the body and the configuration of 11 landmarks on the wing in a large sample of Ephedrus persicae that had emerged from 13 aphid host species, to assess whether static allometry (a measure of the scaling relationship between traits in a population of individuals at the same ontogenetic stage) accounts for variation in body shape. The analysed specimens came from several localities in Europe, Asia Minor, Japan and South America, and cover a large portion of the distribution area of E. persicae. We found that allometry accounts for variation in body shape among different biotypes within the E. persicae group. The allometric slopes for head size (HD), petiolus width (PETW), mesoscutum width (MSC), and ovipositor sheath length (OVPL) diverged significantly among biotypes, indicating biotype-specific allometries. The analysis of allometric variation in wing shape showed that the pattern and direction of allometric changes also differed among individuals that had emerged from different hosts. Our results (observed divergences in the directions of allometric slopes of particular morphometric traits and wing shape) suggest that allometric relations within E. persicae are not conserved, so that allometry itself changes, evolving differently in aphid parasitoids that emerge from different hosts.     

The evolution of aggression: can selection generate variability?

Three models--the war of attrition, the size game and the badges of dominance game--are described, in which natural selection can maintain genetic variability for aggression. The models differ in whether or not the traits that settle contests are costly in contexts other than fighting, and also in whether signals are used. It is concluded that contests will be settled by non-costly traits only if the value of the contested resource is small relative to the cost of fighting, and that 'honest' signalling of aggressiveness is stable only if individuals giving signals that are inconsistent with their behaviour suffer costs. The literature on 'badges of dominance' in birds is reviewed. New data on great tits, greenfinches and corn buntings show that there is plumage variability within age and sex that sometimes serves to settle contests, and that, in the first two species but not the third, the badges are uncorrelated with size, and settle contests only over trivial resources.     

Neuronal variability: noise or part of the signal?

Sensory, motor and cortical neurons fire impulses or spikes at a regular, but slowly declining, rate in response to a constant current stimulus. Yet, the intervals between spikes often vary randomly during behaviour. Is this variation an unavoidable effect of generating spikes by sensory or synaptic processes ('neural noise') or is it an important part of the 'signal' that is transmitted to other neurons? Here, we mainly discuss this question in relation to sensory and motor processes, as the signals are best identified in such systems, although we also touch on central processes.     

Environmental variability and fisheries: what can models do?

This review is based on 58 climate-fisheries models published over the last 28 years that describe the impacts of fishery pressure and environmental variability on populations and ecosystems and include basic principles of population dynamics. It points out that the incorporation of environmental factors in fishery models has already been done and is of great importance for future models used in the assessment of marine resources. The work is guided by the questions to what extent have these models a) enhanced our understanding of the interrelationships between the environment, the fishery and the state of the exploited resources and b) helped to improve the prediction of population dynamics and the assessment of marine resources. For each of the six most commonly used model categories a case study is critically analyzed. The problems of “breaking relationships” between environmental factors and the biological response used in models, the trade-off between model complexity (realism) and simplicity (data availability) and the potential of multivariate climate indices for forecasting ecosystem states and for use as proxies for combined models are discussed, as are novel non-linear and spatially explicit modeling approaches. Approaches differ in terms of model complexity, use of linear or non-linear equations, number of parameters, forecast time horizon and type of resource modelled. A majority of the models were constructed for fish and invertebrate stocks of the northeast Pacific and the epicontinental seas of the Atlantic, reflecting the advancement of fisheries science in these regions. New, in parts highly complex models and sophisticated approaches were identified. The reviewed studies demonstrate that the performance of fished stocks can better be described if environmental or climatic variability is incorporated into the fisheries models. We conclude that due to the already available knowledge, the greatly enhanced computer power, new methods and recent findings of large-scale climatic/oceanographic cycles, fisheries modeling should progress greatly in the coming years.     

Is assemblage variability related to environmental variability? An answer for riverine fish

We examine the variability of riverine fish assemblages in terms of assemblage stability (i.e. variability of numbers of individuals within species over time and variability of assemblage total density), assemblage persistence, and assemblage species richness using data from a 9-yr survey of 27 sites within 18 coastal streams of North-western France. To do so, we test a hypothesized directional model for the expected relationships between environmental variability, assemblage variability, assemblage persistence, and assemblage species richness: 1) environmental variability within a given system is likely to generate variable local population size within this system, thus increasing local assemblages variability; 2) environmental variability should increase extinction rates (or, under constant colonization rates, decrease persistence), because the more population sizes vary within an assemblage, the more likely they are to become zero in some period of time; 3) assemblage variability should reduce assemblage species richness by increasing extinction rates within populations composing these assemblages. Results are compatible with our starting hypotheses and show that assemblage variability increased with environmental variability (i.e. discharge variability), that assemblage persistence decreased with environmental variability, and that species richness decreased with assemblage variability after environmental factors were controlled for. Thus, disturbance regimes, in our case, can alter the stability properties of assemblages and extrinsic determinants of assemblage variability may be an important determinant of assemblage species richness. These results have important conservation and management implications, due to the strong impact of river regulation on flow regimes.     

Comparisons of δ<Superscript>13</Superscript>C of photosynthetic products and ecosystem respiratory CO<Subscript>2</Subscript> and their responses to seasonal climate variability

This study investigated the relationship between ¹³C of ecosystem components, soluble plant carbohydrates and the isotopic signature of ecosystem respired CO₂ (¹³C_R) during seasonal changes in soil and atmospheric moisture in a beech (Fagus sylvatica L.) forest in the central Apennine mountains, Italy. Decrease in soil moisture and increase in air vapour pressure deficit during summer correlated with substantial increase in ¹³C of leaf and phloem sap soluble sugars. Increases in ¹³C of ecosystem respired CO₂ were linearly related to increases in phloem sugar ¹³C (r²=0.99, P0.001) and leaf sugar ¹³C (r²=0.981, P0.01), indicating that a major proportion of ecosystem respired CO₂ was derived from recent assimilates. The slopes of the best-fit lines differed significantly (P0.05), however, and were about 0.86 (SE=0.04) for phloem sugars and about 1.63 (SE=0.16) for leaf sugars. Hence, changes in isotopic signature in phloem sugars were transferred to ecosystem respiration in the beech forest, while leaf sugars, with relatively small seasonal changes in ¹³C, must have a slower turnover rate or a significant storage component. No significant variation in ¹³C was observed in bulk dry matter of various plant and ecosystem components (including leaves, bark, wood, litter and soil organics). The apparent coupling between the ¹³C of soluble sugars and ecosystem respiration was associated with large apparent isotopic disequilibria. Values of ¹³C_R were consistently more depleted by about 4 relative to phloem sugars, and by about 2 compared to leaf sugars. Since no combination of the measured pools could produce the observed ¹³C_R signal over the entire season, a significant isotopic discrimination against ¹³C might be associated with short-term ecosystem respiration. However, these differences might also be explained by substantial contributions of other not measured carbon pools (e.g., lipids) to ecosystem respiration or contributions linked to differences in footprint area between Keeling plots and carbohydrate sampling. Linking the seasonal and inter-annual variations in carbon isotope composition of carbohydrates and respiratory CO₂ should be applicable in carbon cycle models and help the understanding of inter-annual variation in biospheric sink strength.     

Temporal variability of benthic algal δ<Superscript>13</Superscript>C signatures influences assessments of carbon flows in stream food webs

Stream food web function is often assessed using carbon stable isotope assessments of the relative contribution of autochthonous and allochthonous sources of organic matter to consumer diets. As a result, variability in source signatures can strongly influence the assessment of carbon flows. To examine the implications of temporal source variability on food web interpretations, benthic algal δ¹³C signatures were measured over 8 weeks in five streams in subtropical Queensland, Australia. All food webs were largely driven by benthic algal carbon; however, substantial week-to-week variation in benthic algal δ¹³C signatures modified the calculated contributions of algae to consumer diets, with differences in autochthonous contributions of up to 11% between weeks. In addition, variable algal signatures led to many occasions in which the δ¹³C signatures of some consumers was beyond the range of available sources, meaning the mixing model analyses did not have a valid solution. Together, these findings suggest that temporal variability in algal δ¹³C signatures can strongly influence the interpretation of carbon flows in stream food webs. Future food web studies should assess the temporal variability of sources prior to sampling consumers, in order to characterise end member signatures and their relevance to consumers at the time of collection.     

Leaf δ<Superscript>13</Superscript>C variability with elevation,slope aspect,and precipitation in the southwest United States

Leaves from several desert and woodland species, including gymnosperms and angiosperms with both C₃ and C₄ physiology, were analyzed to detect trends in '¹³C_leaf with elevation and slope aspect along two transects in southeastern Utah and south-central New Mexico, USA. The main difference between the two transects is the steeper elevational gradient for mean annual and summer precipitation in the southern transect. For any given species, we found that isotopic differences between individual plants growing at the same site commonly equal differences measured for plants along the entire altitudinal gradient. In C₃ plants, '¹³C_leaf values become slightly enriched at the lowest elevations, the opposite of trends identified in more humid regions. Apparently, increasing water-use efficiency with drought stress offsets the influence of other biotic and abiotic factors that operate to decrease isotopic discrimination with elevation. For some species shared by the two transects (e.g., Pinus edulis and Cercocarpus montanus), '¹³C_leaf values are dramatically depleted at sites that receive more than 550 mm mean annual precipitation, roughly the boundary (pedalfer-pedocal) at which soils commonly fill to field capacity in summer and carbonates are leached. We hypothesize that, in summer-wet areas, this may represent the boundary at which drought stress overtakes other factors in determining the sign of '¹³C_leaf with elevation. The opposition of isotopic trends with elevation in arid versus humid regions cautions against standard correction for elevation in comparative studies of '¹³C_leaf.     

The Early-Middle Pleistocene faunal assemblages of Gesher Benot Ya'aqov: Inter-site variability

This study investigates faunal remains from the site of Gesher Benot Ya‘aqov, analyzing how hominins may have utilized vertebrates and exploring paleoenvironments during the Early and Middle Pleistocene. Based on analyses of a range of vertebrates, results show that the species distribution of terrestrial vertebrates (microvertebrates and mammals) at the site of Gesher Benot Ya‘aqov shows relative stasis above the Matuyama-Brunhes Boundary (MBB) (0.78 Ma). However, consistency in faunal remains at the site reflecting stasis does not seem to reflect accurately the paleoenvironment. Marked changes are demonstrable in the lake-margin sedimentary background, archaeological remains, and agents of accumulation and damage, as well as in the density of medium-large mammals. This study emphasizes the significance of studying assemblages as a whole rather than the species representation on its own.     

Avian body size changes and climate change: warming or increasing variability?

There has been a growing interest in whether established ecogeographical patterns, such as Bergmann's rule, explain changes in animal morphology related to climate change. Bergmann's rule has often been used to predict that body size will decrease as the climate warms, but the predictions about how body size will change are critically dependent on the mechanistic explanation behind the rule. To investigate change in avian body size in western North America, we used two long‐term banding data sets from central California, USA; the data spanned 40 years (1971–2010) at one site and 27 years (1983–2009) at the other. We found that wing length of birds captured at both sites has been steadily increasing at a rate of 0.024–0.084% per year. Although changes in body mass were not always significant, when they were, the trend was positive and the magnitudes of significant trends were similar to those for wing length (0.040–0.112% per year). There was no clear difference between the rates of change of long‐distance vs. short‐distance migrants or between birds that bred locally compared to those that bred to the north of the sites. Previous studies from other regions of the world have documented decreases in avian body size and have used Bergmann's rule and increases in mean temperature to explain these shifts. Because our results do not support this pattern, we propose that rather than responding to increasing mean temperatures, avian body size in central California may be influenced by changing climatic variability or changes in primary productivity. More information on regional variation in the rates of avian body size change will be needed to test these hypotheses.     

Surface structures of the antennular flagella of the hermit crab Pagurus alaskensis (Benedict): A light and scanning electron microscopy study

The surface structures of the antennular flagella of Pagurus alaskensis are described in detail. Attention is directed towards the surface morphology of two types of possible sensilla: (1) exoskeletal pores (1.0–3.0 μm in diameter); (2) setae of various kinds. In addition, small (0.1–0.2 μm) pits occur in the exoskeleton which are not considered to be sensory in function. The exoskeletal pores are found at fairly specific locations on both the inner and outer flagella, particularly on the short segments of the outer flagella. Neither the inner nor the outer flagella are bilaterally symmetrical with respect to their setal armature. On the outer flagellum six groups of setae may be distinguished: lateralmesial; dorsal; ventral; accessory; aesthetasc; setae of the distal segment. On the inner flagellum setae of the mesial and lateral rows form distinctive groups. The morphology, orientation and locations of all the flagellar setae are defined and where possible the numbers of the various morphological types within the specific setal groups are given. It is noteworthy that many setal types have obvious apical pores and yet no pores could be found in the chemoreceptive aesthetasc setae. The functions of the various setae are discussed in relation to their topographical position and to existing electrophysiological and behavioral data. Some suggestions are made about future experiments to demonstrate the central connections of specific sensilla or groups of sensilla and to show their significance in the whole animal.     

Setal morphology of grooming appendages in the spider crab,Libinia dubia

In crustaceans, grooming behaviors decrease fouling by removing debris from the exoskeleton and body structures; these grooming behaviors improve respiration, sensory reception, movement, and reproduction. Setal morphologies of the following grooming appendages in the decapod crustacean spider crab Libinia dubia are examined including the first pereiopod (cheliped), first, second, and third maxillipeds (mouthparts), and first, second, and third epipods (internal extensions of the maxillipeds). The objective of this study was to describe setal morphologies of these grooming appendages and to elucidate possible functions and efficiencies of setal structures. Spider crabs are hypothesized to have elaborate setal morphologies, mainly for cleaning specialized decorating setae as well as for cleaning inside the gill chamber, which has a higher likelihood of becoming fouled compared to other decapods such as shrimps. Fourteen setal types are documented and included several varieties of serrate and pappose setae as well as simple setae, cuspidate setae, papposerrate setae, and canoe setae. Maxillipodal epipods in the gill chamber are free of fouling, suggesting the setation on the third maxilliped protopod has an efficient functional morphology in removing debris before water enters the gill chamber. Serrate setae may function for detangling and separating structures whereas pappose setae may function for fine detailed grooming. The cheliped is the only grooming appendage that can reach decorating setae and it contains only pappose setae; thus decorating setae is not likely groomed in a manner that would greatly decrease fouling. J. Morphol. 277:1045–1061, 2016. © 2016 Wiley Periodicals, Inc.     

Flagellar setae of the second antennae in decapod shrimps: sexual dimorphism and possible role in detection of contact sex pheromones

Summary

The antenna 2 (antennal) flagella of decapod shrimps are chemotactile, and their setae are proposed as sensilla involved in recognition of females by males via a contact sex pheromone on the surface of the female. Male recognition of females receptive to mating occurs in many caridean species upon contact of male antennal flagella with the surface of a newly molted parturial female. The hypothesis of sexual dimorphism in the number and kind of setae on the antennal flagella of four caridean and one penaeid shrimp species was tested with setal counts and observations on setal morphology. Unique male antennal setae (“male-specific sensilla”) were not identified in any of the species investigated. However, the abundance of antennal setae was significantly greater in males than in breeding females in the palaemonid carideans Palemonetes pugio and Macrobrachium ohione. In the hippolytid caridean Thor manningi and alpheid caridean Alpheus normanni, no sexual dimorphism in setal abundance was demonstrated. In the penaeoid Rimapenaeus similis, males had a higher abundance of antennal setae than the larger breeding females but so did juvenile females, similar in size to males. The sexual dimorphism in antennal sensilla in the palaemonid species and its absence in A. normanni might be related to their different mating systems, but no such association is suggested for T. manningi and R. similis. Setal morphology suggestive of chemoreceptive function (a terminal pore) was observed in all species.     

Setal morphology of the grooming appendages of Macrobrachium rosenbergii (Crustacea: Decapoda: Caridea: Palaemonidae) and review of decapod setal classification

Setae are vital in grooming activities and aiding in the removal of epibionts and sedimentary fouling from the body surfaces of decapod crustaceans. Thus, the setal structures and their arrangement on the grooming appendages and sensory structures of the commercially important shrimp, Macrobrachium rosenbergii, were examined using scanning electron microscopy. Macrobrachium rosenbergii is extensively grown in aquaculture and exhibits unique male morphological forms, termed morphotypes. The three male morphotypes are termed blue‐clawed males, orange‐clawed males, and small‐clawed or undifferentiated males and all three differ in their dominance, behavior, body morphology, and reproductive success. Seven setal types, two of which have never been described in the literature, are identified on the grooming appendages (third maxillipeds, first, second, and fifth pereopods) and antennae: simple, serrate, serrulate, spiniform, pappose, crinoid, and spinulate. The latter two setae are newly identified. Certain setal types, such as serrate and serrulate setae were located and associated with specific grooming appendages such as the first pereopods. The types of setae on the grooming appendages varied among females and male morphotypes and the novel setal types (crinoid and spinulate) were found only on two of the male morphotypes. A literature review of terminology related to the structure of setae and setal types in decapod crustaceans is offered as the usage of various terms is ambiguous and conflicting in the literature. The intention of this review is to provide future authors with a comprehensive collection of terms and images that can be used to describe various aspects of setal morphology in decapods. J. Morphol. 275:634–649, 2014. © 2014 Wiley Periodicals, Inc.     

Observations on the honey bee tracheal mite <Emphasis Type="Italic">Acarapis woodi</Emphasis> (Acari: Tarsonemidae) using low-temperature scanning electron microscopy

Observations were made of cryo-preserved honey bee tracheal mites Acarapis woodi (Rennie) using scanning electron microscopy. We describe various new morphological attributes of A. woodi based on the ability of the cryo-technique to capture live mites in natural positions and observe the Low-Temperature Scanning Electron Microscopy (LT-SEM) photographs under a 3-D viewer. Most striking was the observation that each leg has the ability to independently twist its segments with the ambulacrum rotating a minimum of 180° during locomotion; this is a more sophisticated form of locomotion than has been proposed for the Acari. Adult daughter mites are known to be the dispersal instar moving from the tracheal tube to the thoracic hairs of the bee and then transferring to a new bee. We hypothesize that adult tarsal claws and setae on the legs play a role in attachment to hairs during dispersal. However, our evidence is that none of the life stases use their tarsal claws within the tracheal tubes. Larvae were observed to be freely moving within the tracheal system, their tarsal claws rendered inoperative due to an enlarged swollen pulvillar pad. The solenidia of leg I are now known to have striations and the famulus is bifurcated. The bifurcated famulus, solenidial striations, and segmentation of leg IV of females may have taxonomic implications in the family Tarsonemidae. The body and leg setae of adults appear to be used as a tactile tool to sense the amount of space within the tracheal tubes; most of the setae are oriented distally and may help the mite to measure the space or radius of the tracheal tubes. The modified caudal region of the male revealed remnants of the h ₁ and h ₂ setae and a smooth clean surface, void of a film, supporting that pharate nymphs are not attached in this species.This revised version was published online in May 2005 with a corrected cover date.     

Ultrahydrophobicity indicates a non-adhesive default state in gecko setae

Geckos may represent the world’s most demanding adhesives application. The adhesive setae on the toes of climbing geckos must adhere strongly yet avoid fouling or attachment at inappropriate times. We tested the hypothesis that gecko setae are non-adhesive in their unloaded default state by comparing the water droplet contact angle (θ) of isolated setal arrays to the smooth surface of eye spectacle scales of tokay geckos (Gekko gecko). At equilibrium, θ was 98.3 ± 3.4° in spectacle scales of live geckos and 93.3 ± 3.5° in isolated spectacles. Isolated setal arrays were ultrahydrophobic, with θ of 160.6 ± 1.3° (means ± SD). The difference in θ of setal arrays and smooth spectacles indicates a very low contact fraction. Using Cassie’s law of surface wettability, we infer that less than 6.6% of the surface of unloaded setae is solid and at least 93.4% is air space. We calculated that the contact fraction must increase from 6.6% in the unloaded state to 46% in the loaded state to account for previously measured values of adhesion. Thus gecko setae may be non-sticky by default because only a very small contact fraction is possible without mechanically deforming the setal array.     

The structure and growth of the statocyst in the Australian crayfish Cherax destructor

The morphology of the statocyst of the Australian crayfish Cherax destructor was examined using scanning electron microscopy. It resembles in general structure, size, and position the statocysts of crayfish described previously, and the size and distribution of the fields of setae on the floor of the capsule are similar but not the same. Over the size range examined, the relationship between the carapace length, the length of the basal antennular segment, the diameter of the statocyst capsule, and the total number of setae are all linear. The number and position of setae on the floor of the statocyst capsule were mapped for animals in two size classes (small, ca. 20 mm; large, ca. 50 mm) to test for changes in their arrangement during growth. The change in the ratio of setal number to statocyst size between the two size classes was about three times greater for the anterior setal field than for the other fields. We propose that differential development of the setal fields may be related to changes in the force-monitoring requirements of the animals as they increase in size, but this remains to be experimentally tested.     

The idiosomal chaetotaxy of astigmatid mites

Within the Astigmata, setal homologies with the general chaetotaxic systems developed for acariform mites by F. Grandjean have never been convincingly established. This study deals with all body regions, exclusive of legs and gnathosoma, mostly utilizing as models astigmatid species from three different families. Six hypotheses which attempt to explain the ontogeny of segments, setae and cupules in the caudal bend region are compared using three-dimensional views obtained by scanning electron microscopy. The hypotheses are evaluated by in-group comparisons testing their consistency with presumed segmental boundaries, and by out-group comparisons with oribatid mites. The strongest, most parsimonious hypothesis suggests that larval astigmatid mites possess segment F, but not its setae, and the two pairs posterior to segment F are h _l and h ₂, whilst the five setae added in the protonymph are h ₃, f ₂ and ps _1–3. Six pairs of structures on the deutonymphal anal plate are identified as modified setae, and evidence supporting their homologies with setae of other instars is discussed for the first time. A comparison of the principal chaetotaxic systems used for the dorsal and anal regions of the Astigmata is presented. Application of Grandjean's setal signatures to these regions, as well as to the coxisternal and genital regions, is discussed and illustrated by examples.     

The setal morphology of the larval phases of the Argentinean red shrimp Pleoticus muelleri Bate, 1888 (Decapoda: Solenoceridae)

Summary

The setal morphology is described for the larval stages of the solenocerid shrimp Pleoticus muelleri based upon scanning electron microscope studies. Sixty-five different types of setae are recognized and some currently used terms for describing setae are reviewed.     

Morphology and distribution of setae on the antennules of the Caribbean spiny lobster Panulirus argus reveal new types of bimodal chemo-mechanosensilla

This study describes the morphology and distribution of setae on the lateral and medial flagella of the antennules of the spiny lobster Panulirus argus in an effort to identify antennular chemoreceptors in addition to the well-studied aesthetasc chemosensilla. Setae were examined using light and electron microscopy, and their distribution on flagellar annuli was analyzed. We identified ten setal types based on external morphology: hooded, plumose, short setuled, long simple, medium simple, short simple, aesthetasc, guard, companion, and asymmetric setae, with the last four types being unique to the "tuft" located on the distal half of the lateral flagellum. The three setal types whose ultrastructure was examined--hooded, long simple, and medium simple setae--had characteristics of bimodal (chemo-mechanoreceptive) sensilla. The antennules have four distinct annular types based on their setal complement, as shown by cluster analysis. This basic distribution of non-tuft setal types is similar for both lateral and medial flagella. Annuli in the tuft region have tuft setal types superimposed on a basic organization of non-tuft setal types. These results show that the antennules possess a diverse set of setae, that these setae have a highly ordered arrangement on the antennules, that at least four (and probably many more) of these setal types are chemosensilla, and suggest that most antennular chemosensilla are bimodally sensitive.