Body size and fecundity in the waterstrider Aquarius remigis: a test of Darwin's fecundity advantage hypothesis

The general female bias in body size of animals is usually attributed to fecundity selection. While many studies have demonstrated a positive relationship between body size and fecundity, the most common interpretation of fecundity selection is that larger females have larger abdomens and can hold more eggs, yet the relationship between abdomen size and fecundity has rarely been examined. For the waterstrider, Aquarius remigis, we find a significant relationship between body size and fecundity and demonstrate that the target of fecundity selection is abdomen size. Thus, larger females have higher fecundities because they have larger abdomens and not because of their total size per se. The rate at which fecundity increases with increasing abdomen size exceeds that which would be expected due to a simple volume constraint and suggests that other factors, such as increased ability to obtain resources, may contribute to the increase in fecundity with body size. Selection intensities estimated from our data indicate that fecundity selection could be a significant selective force on both total and abdomen lengths. Previous studies have found that abdomen size increased faster than body size and thus, larger females had relatively larger abdomens. The relationship of abdomen length and thorax length in A. remigis is hypoallometric and indicates that larger females have relatively smaller abdomens. We hypothesize that this may reflect conservation of abdomen size in females developing under poor conditions. Finally, while egg size is not directly related to body size, we find a trade-off between egg size and number when female abdomen length is held constant, suggesting that selection on egg size may influence abdomen length only indirectly through its effects on fecundity.     

Body temperature and thermoregulation in two species of yellowjackets,Vespula germanica and V. maculifrons

In spite of the abundance and broad distribution of social wasps, little information exists concerning thermoregulation by individuals. We measured body temperatures of the yellowjackets Vespula germanica and V. maculifrons and examined their thermoregulatory mechanisms. V. germanica demonstrated thermoregulation via a decreasing gradient between thorax temperature and ambient temperature as ambient temperature increased. V. maculifrons exhibited a constant gradient at lower ambient temperatures but thorax temperature was constant at high ambient temperatures. Head temperature exhibited similar patterns in both species. In spite of low thermal conductances, a simple heat budget model predicts substantial heat loads in warm conditions in the absence of thermoregulation. Both species regurgitated when heated on the head. A smaller volume of regurgitant was produced at lower head temperatures and a larger volume at higher head temperatures. Small regurgitations resulted in stabilization of head temperature, while large ones resulted in 4°C decreases in head temperature. Regurgitation was rare when wasps were heated upon the thorax. Abdomen temperature was 3–4°C above ambient temperature, and approached ambient temperature under the hottest conditions. No evidence was found for shunting of hot hemolymph from thorax to abdomen as a cooling mechanism. The frequency of regurgitation in workers returning to the nest increased with ambient temperature. Regurgitation may be an important thermoregulatory strategy during heat stress, but is probably not the only mechanism used in yellowjackets.Abbreviations M _b body mass - M _th thorax mass - T _a ambient temperature - T _ab abdomen temperature - T _b body temperature - T _h head temperature - T _th thorax temperature - C _t thermal conductance     

An investigation into the metamorphosis of the mutant lethal-translucida of drosophila melanogaster

Summary Development of lethal translucida pupae is under normal conditions predominantly blocked in the early pupal stages. Imaginal differentiation, though almost exclusively restricted to the head and thorax, is exhibited in only 20–30% of the individuals.When ltr pupae are subjected to pure oxygen both the frequency and the intensity of imaginal differentiation is strongly increased. Then 60–70% of the pupae shows metamorphosis of the head and thorax, whereas abdominal differentiations could be observed in about 20%.The minimal time during which the pupae must be kept in oxygen, to give a maximum percentage of metamorphosing individuals in air, is 100–120 hours for differentiations of the head and thorax and about 140 hours for those of the abdomen.These experimental results suggest that part of the incomplete metamorphosis in homozygous ltr pupae is due to an insufficient supply of oxygen.The differentiation of normal eye implants within non-metamorphosed ltr pupae showed that the reaction capacity of the imaginal tissues in the ltr/ltr genotype is also significantly weakened.In the discussion of the results, our data have been related to those of Chen on lowered oxygen consumption in ltr pupae. It seems probable that in those ltr pupae showing metamorphosis of the head and thorax, a better oxygen supply existed already from the time of puparium formation.With 6 text-figures.This work was started in 1949 in the Institute of Zoology and Comparative Anatomy of the University of Zurich.     

Sex‐specific selection and sexual size dimorphism in the waterstrider Aquarius remigis

We estimated selection on adult body size for two generations in two populations of Aquarius remigis, as part of a long‐term study of the adaptive significance of sexual size dimorphism (SSD). Net adult fitness was estimated from the following components: prereproductive survival, daily reproductive success (mating frequency or fecundity), and reproductive lifespan. Standardized selection gradients were estimated for total length and for thorax, abdomen, genital and mesofemur lengths. Although selection was generally weak and showed significant temporal and spatial heterogeneity, patterns were consistent with SSD. Prereproductive survival was strongly influenced by date of eclosion, but size (thorax and genital lengths in females; total and abdomen lengths in males) played a significant secondary role. Sexual selection favoured smaller males with longer external genitalia in one population. Net adult fitness was not significantly related to body size in females, but was negatively related to size (thorax and total length) in males.     

Morphology of the sweet potato whitefly,Bemisia tabaci (Homoptera,Aleyrodidae) relative to virus transmission

 The stylet bundle of the sweet potato whitefly, Bemesia tabaci, consists of paired mandibles and maxillae. The latter interlock to form the food and salivary canals. Its salivary system consists of paired primary and accessary glands in the thorax. Primary and accessory gland ducts on each side of the nerve cord fuse to form lateral ducts that course anteroventrally to the midline and continue in parallel down the hypopharynx to eventually fuse to form the single afferent duct of the salivary pump. Saliva exiting the pump via the efferent duct enters the salivary canal of the maxillae. Food from the maxillary food canal passes from the antecibarium to the postcibarium or sucking pump and, per os, to the pharynx and esophagus of the foregut. The esophagus extends from the head to the base of the abdomen where it and the anterior midgut intimately mingle with the anterior hindgut to form a filter chamber. The midgut then proceeds dorsocaudally before looping anteroventrally to join the hindgut. The latter gives off two fingerlike Malpighian tubules before entering the filter chamber, whence it proceeds dorsocaudally to the anus within the vasiform orifice. Where possible, the morphology of Bemisia is discussed in relation to plant virus transmission and the morphologies of more thoroughly studied homopteran vectors such as aphids and leafhoppers. Accepted: 9 July 1996     

Notes on the biology of the Oriental amblyoponine ant Myopopone castanea: Queen‐worker dimorphism,worker polymorphism and larval hemolymph feeding by workers (Hymenoptera: Formicidae)

Queen‐worker dimorphism, worker polymorphism and worker behavior in the Oriental amblyoponine ant Myopopone castanea were studied. Queen body size was large (head width, 3.0 mm) with 24 to 32 ovarioles while workers showed a remarkable size variation in both body size (head width 1.48 to 2.18 mm) and ovariole number (6 to 22). Both head width and abdomen width showed allometric growth against thorax width. Workers performed larval hemolymph feeding as was described for Amblyopone silvestrii queens.     

The alimentary canal of Bemisia tabaci and Trialeurodes abutilonea (Homoptera,Sternorrhynchi): histology,ultrastructure and correlations to function

Summary The midguts of Bemisia tabaci and Trialeurodes abutilonea are looped so that the anterior and posterior extremities are in contact with each other. The basal lamina is breached at this point so that opposing basal epithelial membranes of either extremity are contiguous. On the anal side of the contact is a filter-organ, consisting of oesophageal, Malpighian and modified ventricular epithelial cells. Comparison with model systems indicates that the filter-organ acts as an osmoregulatory device. It appears that fluid food is directed into the looped midgut and concentrated by passive transport of water across the contact point, through the filter-organ, and then into the hindgut. The filter-organ of both species is attached to the contact point, but in T. abutilonea it is thereafter suspended in the alimentary lumen, free of the alimentary wall. In B. tabaci, the oesophageal cells of the filter-organ are attached to the alimentary wall. This constitutes the major difference in gut histology between the two species. Dissections indicate that the midgut can be moved through the petiole, from the abdomen to the thorax, and back again. This, and the absence of Malpighian tubules, suggests that the midgut services the excretory needs of the flight muscles.     

Determination of the site of pheromone emission in the virgin females Culicoides nubeculosus Meigen (Diptera: Ceratopogonidae)

The zone of emission of the sex pheromone from the body of Culicoides nubeculosus was investigated. The amount of pheromone emitted was evaluated by counting the number of matings between males and females exposed to a flow of air coming from a chamber containing virgin females. The number of matings is higher than that recorded when the air flow comes from an empty chamber (control). Three parts of the body were examined: head, thorax and abdomen. Each part was studied by neutralizing the effect of the others. The head was neutralized by decapitation and the females continued to emit pheromone. The head is, therefore, not indispensible for pheromone emission. The roles of the thorax and abdomen were studied by coating these with paraffin wax. When the thorax is coated, pheromone emission continues, but when the abdomen is coated, it stops. It appears that the abdomen alone is responsible for emission of the sex pheromone.     

Detection of ALMB-toxin in the Larval Body of Myrmeleon bore by Anti-N-terminus Peptide Antibodies

Antibodies were raised against a synthetic antigen carrying the N-terminus peptide of ALMB-toxin, which had been isolated from the antlion, Myrmeleon bore, that exhibited high specificity to the toxin. Analyses with the antibodies showed the toxin to be present mainly at the larval stage and localized in a region from the thorax to abdomen of the larval body.     

CHANGES IN TITER OF THE BRAIN HORMONE DURING DEVELOPMENT OF THE SILKWORM, BOMBYX MORI

Changes in titer of brain hormone (BH) extracted from the brain, head, and thorax and abdomen during the development of Bombyx mori from the 4th larval molting up to 6 days after adult emergence were investigated. The hypothesis is presented that high secretory activity of the brain is not reflected in a corresponding change in its BH titer, while low secretory activity brings about an accumulation of BH in the brain. An interesting finding is that extremely high titers of BH were found in the thorax and abdomen, from 4 days after pupation to adult emergence, of females only. This sexual difference was, however, not found in all of the races examined.     

Infection of ‘Candidatus Phytoplasma ulmi’ reduces the protein content and alters the activity of detoxifying enzymes in Amplicephalus curtulus

It has been reported that insecticide‐detoxifying enzymes such as glutathione S‐transferases (GST) and esterases are affected by microbial infections in hemipteran insect vectors. The total protein content, and GST and α‐ and β‐esterase activities were quantified in ‘Candidatus Phytoplasma ulmi’‐infected and uninfected adults of Amplicephalus curtulus Linnavuori & DeLong (Hemiptera: Cicadellidae) at 25, 35, and 45 days after the acquisition access period (AAP) in the head‐thorax and abdomen sections. The total protein content was lower in phytoplasma‐infected leafhoppers 25, 35, and 45 days after the AAP. Thirty‐five days after the AAP, the GST and β‐esterase activities had increased (26 and 69%, respectively) compared to the control. However, 45 days after the AAP, the phytoplasma‐infected leafhoppers displayed lower GST (87%) and β‐esterase (253%) activities than the uninfected individuals. On the other hand, the α‐esterase activity proved to be unaffected by the phytoplasma infection. Forty‐five days after the AAP, females had a higher phytoplasma titer (46%) in their head‐thorax than in their abdomen sections, whereas males showed a higher titer in their abdomens (75%). In addition, the GST and β‐esterase activities in the abdomen were affected negatively by 96–98% as a result of the increasing ‘Ca. Phytoplasma ulmi’ titer. These results indicate that an infection of ‘Ca. Phytoplasma ulmi’ alters the metabolic activities of A. curtulus.     

Blocking of malaria parasite development in mosquito and fecundity reduction by midgut antibodies in Anopheles stephensi (Diptera: Culicidae)

Rabbits were immunized three times with extracts of Anopheles stephensi midgut. Immunized rabbits showed a high titer of antibodies when characterized by ELISA. We investigated the effect of anti-mosquito midgut antibodies on mosquito fecundity, longevity, mortality, engorgement, and the development of the malaria parasite in mosquitoes. Fecundity was reduced significantly (38%) and similarly hatchability by about 43.5%. There was no statistically significant effect on mortality, longevity, and engorgement. When the mosquito blood meal contained anti-midgut antibodies, fewer oocysts of Plasmodium vivax developed in the mosquito midgut and the proportion of mosquitoes becoming infected was significantly reduced. We also found that the midgut antibodies inhibit the development and/or translocation of the sporozoites. Antisera raised against midgut of A. stephensi recognized eight polypeptides (110, 92, 70, 45, 38, 29, 15, 13 kDa) by Western blotting. Cross-reactive antigens/epitopes present in other tissues of A. stephensi were also examined both by Western blotting and in vivo ELISA. Together, these observations open an avenue for research toward the development of a vector-based malaria parasite transmission blocking vaccine and/or anti-mosquito vaccine.     

Homeotic gene expression in the locust Schistocerca: An antibody that detects conserved epitopes in ultrabithorax and abdominal-A proteins

To investigate what role homeotic genes may play in morphological evolution, we are comparing homeotic gene expression in two very different insects, Drosophila (Diptera) and Schistocerca (Orthoptera). In this paper we describe a monoclonal antibody, FP6.87, that recognizes the products of both the Ultrabithorax (Ubx) and abdominal-A (abd-A) genes in Drosophila, via an epitope common to the carboxy terminal region of these two proteins. This antibody recognizes nuclear antigens present in the posterior thorax and abdomen of Schistocerca. We infer that it recognizes the Schistocerca homolog of UBX protein, and probably also of ABD-A. As the distribution of Schistocerca ABD-A protein is already known, we can use this reagent to map the expression of Schistocerca UBX in the thorax and anterior abdomen, where ABD-A is not expressed. Both the general domain, and many of the details, of UBX exp ression are remarkably conserved compared with Drosophila. Thus UBX expression extends back from T2 in the ectoderm (including the CNS), but only from A1 in the mesoderm. As noted for other bithorax complex genes in Schistocerca, expression begins in the abdomen, at or shortly before the time of segmentation. It only later spreads anteriorly to the thorax. For much of embryogene-sis, the expression of UBX in the thoracic epidermis is largely restricted to the T3 limb. Inthis limb, UBX is strikingly regulated, in a complex pattern that reflects limb segmentation. Reviewing these and earlier observations, we conclude that evolutionary changes affect both the precise regulation of homeotic genes within segments, and probably also the spectrum of downstream genes that respond to homeotic gene expression in a given tissue. Overall domains of homeotic gene expression appear to be well conserved between different insect groups, though a change in the extent and timing of homeotic gene expression may underlie the modification of the posterior abdomen in different insect groups. © 1994 Wiley-Liss, Inc.     

Leaf abscission phenology of a scrub oak: consequences for growth and survivorship of a leaf mining beetle

Brachys tessellatus is a leaf-mining beetle that attacks Quercus laevis (turkey oak), a deciduous scrub oak in the fall line Sandhills of the southeastern United States. This oak species varies substantially in leaf abscission phenology. In the fall of 1994 we examined leaf abscission patterns at three sites in central South Carolina and found that leaves containing active miners abscised earlier than leaves without active miners. To quantify the effect of leaf abscission phenology on the survivorship and body size of leaf miners within the abscised leaves, we marked naturally and manually abscised leaves, left leaves on the ground to over-winter, and then collected leaves before beetles emerged the following spring. We found that beetles inside leaves that were abscised early in the season were more likely to be killed by predators, and that they produced smaller pupae than beetles within leaves abscised later in the season. We also evaluated the relationship between adult beetle body size and fecundity; body size of B. tessellatus is positively correlated with lifetime fecundity and daily oviposition rate indicating that effects of leaf-abscission phenology on beetle body size likely translate into effects on beetle fitness. We discuss how B. tessellatus has adapted to variation of leaf abscission phenology of oaks by evolving developmental plasticity that permits successful completion of larval development over a range of season lengths.     

A Record of the Cubed Snailfish, <Emphasis Type="Italic">Liparis tessellatus</Emphasis> (Pisces: Liparidae), in Peter the Great Bay,Sea of Japan

A specimen of the cubed snailfish, Liparis tessellatus was captured in Peter the Great Bay, Sea of Japan. The capture of L. tessellatus from this area a century after the first record is evidence that at present this species still inhabits Peter the Great Bay.Original Russian Text Copyright © 2005 by Biologiya Morya, Sokolovskii, Sokolovskaya.     

Midgut antibodies reduce the reproductive capacity of Anopheles stephensi (Diptera: Culicidae)

Rabbits immunized with polypeptides of midgut of glucose fed A. stephensi resulted in high titer of antibodies (10(4)-10(6)) as detected by ELISA. Effect of antisera on fecundity, hatchability and engorgement was investigated. Fecundity was reduced drastically (62.4%). Eight polypeptides were recognized by the antisera raised against midgut tissues viz., 92, 85, 55, 52, 45, 38, 29 and 13 kDa. Cross reactivity of these antibodies with different tissues of A. stephensi as well as different species of Anopheles was also analyzed. The results indicated that anti-mosquito midgut antibodies had the potential to disrupt the reproductive physiology of mosquitoes in view of the present study, there is a need for further investigation with target antigens.     

PBAN gene architecture and expression in the fire ant, solenopsis invicta

The PBAN/pyrokinin peptides are a major neuropeptide family characterized by a common FXPRLamide at the C-termini. These peptides are distributed ubiquitously in the Insecta and are involved in many essential endocrine functions, e.g. pheromone production. We report the gene architecture of the fire ant Solenopsis invicta PBAN (Soi-PBAN) gene, including the exon and intron boundaries. Furthermore, we quantified expression of the Soi-PBAN mRNA in the head, thorax and abdomen of the fire ant. The Soi-PBAN gene is comprised three exons and two introns, all composed of 13,358 nucleotides, which is 2-4 times larger than lepidopteran PBAN genes. The overall pattern of the PBAN immunoreactive neuron number and localization was similar for female and male alates, inseminated female delates, workers and queens. The Soi-PBAN mRNA expression level was highest in the head, followed by the thorax, and abdomen of adult ants. Expression in the abdominal tissues was expected to be similar to the head, or at least higher than thorax because strong PBAN immunoreactive neurons were detected previously in brain-subesophageal and abdominal ganglia. This result suggests that another FXPRL gene could be dominant in the abdomen rather than Soi-PBAN gene.     

Visual Cues in Mate Recognition by Males of the Damselfly, Coenagrion puella (L.) (Odonata: Coenagrionidae)

Coenagrion puella males search actively for mates and are not aggressive to other males. To study the role of visual cues in male–female discrimination, four types of models were used: (1) bodies of intact insects, (2) models of painted males, (3) models of male–female chimerae, and (4) models of female body parts. Abdomen coloration pattern and presence of wings were the most important cues for sexual recognition by males. Step-by-step elimination of male coloration pattern leads to an increase in the tandem response rate. A female model painted as a male repelled males like the intact male model. The absence of either the head or the thorax slightly decreased the number of tandem responses, but models without both the head and the thorax were not recognized as a mate. Abdomen thickness larger than that of a normal female decreased the attractiveness of the model. Models of the gynochrome female were significantly more attractive than models of the androchrome one. Female models containing male parts were less attractive than models without any structure at this place. Using principal-components analysis, it is shown that models repelling males usually were those containing an intact male abdomen or a female abdomen painted with blue. The results indicate that C. puella males can distinguish males from females visually by morphological structures and coloration pattern.     

Surplus Killing by Predatory Larvae of <Emphasis Type="Italic">Corethrella appendiculata</Emphasis>: Prepupal Timing and Site-Specific Attack on Mosquito Prey

Surplus or ‘wasteful’ killing of uneaten prey has been documented in the fourth larval instar of various species of the mosquito genus Toxorhynchites that occur in treeholes and other phytotelmata. Here we document surplus killing by the predatory midge Corethrella appendiculata, which in Florida cohabits treeholes and artificial containers with larvae of Toxorhynchites rutilus. Provided with a surfeit of larval mosquito prey, surplus killing was observed only in the fourth instar of C. appendiculata, peaking in intensity in the final 24 h prior to pupation, as observed for Toxorhynchites spp. Attack sites identified from videotaped encounters with mosquito prey were divided among head, thorax, abdomen, and siphon. Consumed mosquito larvae (n = 70) were attacked primarily on the head (46%) or siphon (34%), but surplus-killed prey (n = 30) were attacked predominantly on the thorax (83%). Despite its independent evolution among different insect species in aquatic container habitats, the functional significance of prepupal surplus killing remains unclear.     

Saccadic head and thorax movements in freely walking blowflies

Visual information processing is adapted to the statistics of natural visual stimuli, and these statistics depend to a large extent on the movements of an animal itself. To investigate such movements in freely walking blowflies, we measured the orientation and position of their head and thorax, with high spatial and temporal accuracy. Experiments were performed on Calliphora vicina, Lucilia cuprina and L. caesar. We found that thorax and head orientation of walking flies is typically different from the direction of walking, with differences of 45° common. During walking, the head and the thorax turn abruptly, with a frequency of 5–10 Hz and angular velocities in the order of 1,000°/s. These saccades are stereotyped: head and thorax start simultaneously, with the head turning faster, and finishing its turn before the thorax. The changes in position during walking are saccade-like as well, occurring synchronously, but on average slightly after the orientation saccades. Between orientation saccades the angular velocities are low and the head is held more stable than the thorax. We argue that the strategy of turning by saccades improves the performance of the visual system of blowflies.