Longterm effects of incubation temperatures on the morphology and locomotor performance of hatchling lizards (Bassiana duperreyi, Scincidae)

The phenotypes of hatchling reptiles are known to be affected by the thermal environments they experience during incubation, but the evolutionary and ecological significance of this phenotypic plasticity remains unclear. Crucial issues include: (i) the magnitude of effects elicited by thermal regimes in natural nests (as opposed to constant-temperature incubation); (ii) the persistence of these effects during ontogeny; and (iii) the consistency of these effects across different test conditions (does the thermal regime during embryogenesis simply shift the hatchling's thermal optimum for performance, or actually modify overall performance ability regardless of temperature?). We examined these questions by incubating eggs of scincid lizards (Bassiana duperreyi) from montane southeastern Australia, under two fluctuating-temperature regimes that simulated ‘cold’ and ‘hot’ natural nests. These thermal regimes substantially modified hatchling morphology (mass, body length, tail length, and the relationship between these variables), locomotor performance (running speeds over distances of 25 cm and lm), anti-predator ‘tactics’ and survival rates. The differences in locomotor performance persisted throughout the 20 weeks of our experiment. Lizards that emerged after ‘hot’ incubation were faster runners than their ‘cold’-incubated siblings under all thermal conditions that we tested. Thus, incubation temperatures modified overall locomotor ability, with only a minor effect on the set-point for optimum performance. The magnitude, persistence and consistency of these incubation-induced phenotypic modifications suggest that they may play an important role in evolutionary and ecological processes within lizard populations.     

Offspring sex is not related to maternal allocation of yolk steroids in the lizard Bassiana duperreyi (Scincidae)

The eggs of birds and reptiles contain detectable levels of several steroid hormones, and experimental application of such steroids can reverse genetically determined sex of the offspring. However, any causal influence of maternally derived yolk steroids on sex determination in birds and reptiles remains controversial. We measured yolk hormones (dihydrotestosterone, testosterone, and 17 beta-estradiol) in newly laid eggs of the montane scincid lizard Bassiana duperreyi. This species is well suited to such an analysis because (1) offspring sex is influenced by incubation temperatures and egg size as well as by sex chromosomes, suggesting that yolk hormones might somehow be involved in the complex pathways of sex determination, and (2) experimental application of either estradiol or fadrozole to such eggs strongly influences offspring sex. We obtained yolk by biopsy, before incubating the eggs at a temperature that produces a 50:50 sex ratio. Yolk steroid levels varied over a threefold range between eggs from different clutches, but there were no significant differences in yolk steroids, or in relative composition of steroids, between eggs destined to become male versus female. Further, yolk steroid concentrations were not significantly related to egg size. Thus, yolk steroid hormones do not appear to play a critical role in sex determination for B. duperreyi.     

Seamount egg‐laying grounds of the deep‐water skate Bathyraja richardsoni

Highly localized concentrations of elasmobranch egg capsules of the deep‐water skate Bathyraja richardsoni were discovered during the first remotely operated vehicle (ROV) survey of the Hebrides Terrace Seamount in the Rockall Trough, north‐east Atlantic Ocean. Conductivity–temperature–depth profiling indicated that the eggs were bathed in a specific environmental niche of well‐oxygenated waters between 4·20 and 4·55° C, and salinity 34·95–35·06, on a coarse to fine‐grained sandy seabed on the seamount's eastern flank, whereas a second type of egg capsule (possibly belonging to the skate Dipturus sp.) was recorded exclusively amongst the reef‐building stony coral Solenosmilia variabilis. The depths of both egg‐laying habitats (1489–1580 m) provide a de facto refuge from fisheries mortality for younger life stages of these skates.     

Temperature‐correlated shifts in the timing of egg‐laying in House Finches Haemorhous mexicanus

Although temperature‐correlated shifts in the timing of egg‐laying have been documented in numerous bird species, the vast majority of species examined to date have been those that breed in Europe and have an animal‐based diet during breeding. However, given that the timing of breeding can be driven, either in the proximate or in the ultimate sense, by seasonal fluctuations in food availability, the relationship between temperature and laying may differ with diet. Here, we report on patterns of reproductive timing in House Finches Haemorhous mexicanus, a North American species that breeds on a primarily seed‐based diet. Analysing nest records from House Finches in California spanning more than a century, we found that egg‐laying occurred significantly earlier in warmer springs. We also found that although the timing of egg‐laying does not show long‐term changes in most of California, in the hottest region of the state (the southeast desert basin) it has advanced significantly.     

Taste input from tarsal sensilla is related to egg‐laying behavior in Papilio hospiton

In herbivorous insects, host selection involves various sensory modalities (sight, smell, taste), but the contact chemoreceptors capable of detecting stimuli both from host and non‐host plants play an important role in the final steps of oviposition behavior. Female butterflies scratch and drum the leaf surface and taste the compounds present in plant saps with their tarsal chemosensilla. We assumed that tarsal taste sensitivity may be related to the breadth of host selection in ovipositing females of Papilio hospitonGéné (Lepidoptera: Papilionidae). The spike activity of tarsal taste basiconic sensilla was recorded in response to stimulation with NaCl, bitter compounds, and carbohydrates, with the aim of characterizing the gustatory receptor neurons (GRNs) and of comparing the response patterns in the light of differences in acceptability of host plants. Then we studied the sensitivity of GRNs to saps of the host plants Ferula communis L., Peucedanum paniculatumLoisel, Pastinaca latifolia (Duby) DC. (all Apiaceae), and Ruta lamarmorae Bacch., Brullo et Giusso (Rutaceae), and evaluated the relationship between taste sensitivity and oviposition preference. The results indicate that (1) each sensillum houses sugar‐, bitter‐, and salt‐sensitive cells; (2) the spike activity of the gustatory neurons in response to plant saps produces a different response pattern across all active GRNs; and (3) the number of eggs laid on each plant is highest on F. communis and lowest on R. lamarmorae. These results suggest that the varying activity of the tarsal GRNs may affect host plant acceptability and that ovipositing females of P. hospiton seem to be able to discriminate between host plants.     

Quantifying the effects of host discrimination on egg‐laying decision of the cowpea seed beetle,Callosobruchus maculatus

Many parasitic and endophagous insect species are capable of discriminating among the quality of their hosts. However, there is no appropriate way to quantify their discrimination performance. In this study, we quantified how oviposition of the cowpea seed beetle, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae), was affected by the relative contributions of both egg number and host size discrimination. The effect of egg density and resource heterogeneity on these discrimination performances was also explored. Egg‐distribution predictions were made by combining time‐dependent available resource fitness (egg discrimination) and host weight factors (size discrimination). The χ² test was then used for goodness‐of‐fit testing. The effects of both egg and size discrimination on oviposition in environments with different levels of resource heterogeneity were compared. It was found that host size, rather than the number of eggs on the host, plays a larger role in the egg‐laying decision for most individual seed beetles, especially when egg density is high. Host size discrimination behavior was reinforced when the beetles experienced increasing resource heterogeneity, but the performance might reach a plateau. This is the first quantitative evaluation of the effect of host discrimination on egg‐laying decisions of seed beetles.     

Age‐related degeneration of the egg‐laying system promotes matricidal hatching in Caenorhabditis elegans

The identification and characterization of age‐related degenerative changes is a critical goal because it can elucidate mechanisms of aging biology and contribute to understanding interventions that promote longevity. Here, we document a novel, age‐related degenerative change in C. elegans hermaphrodites, an important model system for the genetic analysis of longevity. Matricidal hatching—intra‐uterine hatching of progeny that causes maternal death—displayed an age‐related increase in frequency and affected ~70% of mated, wild‐type hermaphrodites. The timing and incidence of matricidal hatching were largely independent of the levels of early and total progeny production and the duration of male exposure. Thus, matricidal hatching appears to reflect intrinsic age‐related degeneration of the egg‐laying system rather than use‐dependent damage accumulation. Consistent with this model, mutations that extend longevity by causing dietary restriction significantly delayed matricidal hatching, indicating age‐related degeneration of the egg‐laying system is controlled by nutrient availability. To identify the underlying tissue defect, we analyzed serotonin signaling that triggers vulval muscle contractions. Mated hermaphrodites displayed an age‐related decline in the ability to lay eggs in response to exogenous serotonin, indicating that vulval muscles and/or a further downstream function that is necessary for egg laying degenerate in an age‐related manner. By characterizing a new, age‐related degenerative event displayed by C. elegans hermaphrodites, these studies contribute to understanding a frequent cause of death in mated hermaphrodites and establish a model of age‐related reproductive complications that may be relevant to the birthing process in other animals such as humans.     

γ‐Octalactone,an effective oviposition stimulant of Bactrocera tryoni

Insects commonly rely on olfactory, gustatory and visual cues when deciding where to lay eggs. The olfactory cues that stimulate oviposition in the Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), are not well understood. Here, we show that two known oviposition stimulants of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)—γ‐octalactone and benzothiazole—strongly elicit aggregation and oviposition in B. tryoni. Two other known oviposition stimulants of B. dorsalis—ethyl tiglate and 1‐octen‐3‐ol—elicit aggregation but not oviposition. Highlighting species overlap, but also differences, in oviposition stimulants, these findings have practical application for mass‐rearing in which vast numbers of flies are reared for sterile insect technique programs and may also have practical application in the development of pest management and monitoring tools.     

Evolution of reptilian placentation: Development of extraembryonic membranes of the Australian scincid lizards,Bassiana duperreyi (Oviparous) and Pseudemoia entrecasteauxii (Viviparous)

A prominent model for the evolution of placentation among Reptilia is based on placental structure among species in the Eugongylus group of Australian lygosomatine skinks. We studied the development of the extraembryonic membranes of an oviparous species, Bassiana duperreyi, and a viviparous species, Pseudemoia entrecasteauxii, within this taxonomic group. We observed differences in the timing of development of shared features and in the structure of extraembryonic membrane epithelia in the two species. In the viviparous species, there is earlier vascularization of the yolk sâc and increased vascular support for the abembryonic yolk sac splanchnopleure. Structural differences between species result in partitioning of the egg into two distinct hemispheres and produce epithelia which appear functionally histotrophic in both the chorioallantoic membrane and the bilaminar omphalopleure of the viviparous species. We propose that the evolution of placentation in P. entrecasteauxii involved a combination of heterochrony and structural innovation. Further, because our interpretation of placental structure of this species provides new information relevant to placental function, we propose a revision of a classic model for the evolution of placentation among Reptilia. This model predicts specific relationships among reproductive characteristics and thus is testable by comparative analysis among other species within the Eugongylus group of Australian skinks. © 1996 Wiley-Liss, Inc.     

Cues used in host‐seeking behavior by frog‐biting midges (Corethrella spp. Coquillet)

We investigated the role of carbon dioxide and host temperature in host attraction in frog‐biting midges (Corethrella spp). In these midges, females are known to use frog calls to localize their host, but the role of other host‐emitted cues has yet not been investigated. We hypothesized that carbon dioxide acts as a supplemental cue to frog calls. To test this hypothesis, we determined the responses of the midges to carbon dioxide, frog calls, and both cues. A significantly lower number of midges are attracted to carbon dioxide and silent traps than to traps broadcasting frog calls. Adding carbon dioxide to the calls does not increase the attractiveness to the midges. Instead, carbon dioxide can have deterrent effects on frog‐biting midges. Temperature of calling frogs is not a cue potentially available to the midges. Contrary to our hypothesis, there was no supplemental effect of carbon dioxide when presented in conjunction to calls. Midge host‐seeking behavior strongly depends on the mating calls emitted by their anuran host. Overall, non‐acoustic cues such as host body temperature and carbon dioxide are not important in long‐distance host location by frog‐biting midges.     

Identifying reproductive events using archival tags: egg‐laying behaviour of the small spotted catshark Scyliorhinus canicula

The use of archival depth telemetry as a means of remotely assessing the reproductive rates of free‐ranging fishes is explored. This is achieved by electronically tracking the vertical movements of individual female small spotted catsharks Scyliorhinus canicula in the natural environment, whilst simultaneously evaluating the temporal and vertical distributions of egg‐laying in this species. Distinctive patterns of short‐term (0·3–3·7 h), shallow‐water activity are documented in the time–depth profiles of female S. canicula that occur at an appropriate depth (1·0–2·3 m) and periodicity (every 10–12 days) to represent egg‐laying behaviour. Putative egg‐laying behaviour was exhibited simultaneously by two individually tracked female S. canicula during late‐spring and early‐summer. The results highlight that, provided species behaviour is suitable and complementary methods such as previous data, laboratory experiments and field surveys can be used to validate the patterns observed, archival depth telemetry offers an unobtrusive means by which egg production and egg‐laying behaviour of free‐living fishes can be estimated. As precise information regarding life‐history parameters is difficult to obtain for free‐ranging fish species, this technique could be used to improve the parameterization of species demographic models that are relevant to the management of wild fish populations.     

Predatory risk increased due to egg‐brooding in Armadillidium vulgare (Isopoda: Oniscidea)

Cost of reproduction is associated with a reduction in subsequent survival or future breeding success. A decrease in survival rate of parents during or after reproduction reduces the probability of their future reproduction. However, few studies have demonstrated such survival costs to parents. Females of Armadillidium vulgare hold their eggs in a marsupium and brood these until the young hatch. Caring for eggs in a marsupium seems to place a large burden on brooding females, and it restricts their predator avoidance behaviour. As such, costs of care may increase the mortality rates of brooding females. To reveal the costs of parental care, we examined the effects of egg brooding on behaviour and predation risk. Egg‐brooding females decreased speed of locomotion and rolling duration, and were killed by predators at a higher rate. Our results indicate that egg brooding in A. vulgare has costs in the form of predation risk.     

Prospects of herbivore egg‐killing plant defenses for sustainable crop protection

Due to a growing demand of food production worldwide, new strategies are suggested to allow for sustainable production of food with minimal effects on natural resources. A promising alternative to the application of chemical pesticides is the implementation of crops resistant to insect pests. Plants produce compounds that are harmful to a wide range of attackers, including insect pests; thus, exploitation of their natural defense system can be the key for the development of pest‐resistant crops. Interestingly, some plants possess a unique first line of defense that eliminates the enemy before it becomes destructive: egg‐killing. Insect eggs can trigger (1) direct defenses, mostly including plant cell tissue growth or cell death that lead to eggs desiccating, being crushed or falling off the plant or (2) indirect defenses, plant chemical cues recruiting natural enemies that kill the egg or hatching larvae (parasitoids). The consequences of plant responses to eggs are that insect larvae do not hatch or that they are impeded in development, and damage to the plant is reduced. Here, we provide an overview on the ubiquity and evolutionary history of egg‐killing traits within the plant kingdom including crops. Up to now, little is known on the mechanisms and on the genetic basis of egg‐killing traits. Making use of egg‐killing defense traits in crops is a promising new way to sustainably reduce losses of crop yield. We provide suggestions for new breeding strategies to grow egg‐killing crops and improve biological control.     

Preferred egg laying sites in Palmacorixa nana (Heteroptera : Corixidae)

Female Palmacorixa nana showed clear preference for wood oviposition substrates over Elodea and plexiglass in both laboratory and field experiments. Wood was chosen because of its rigidity and rough surface. These data raise the possibility that males could gain access to females by controlling localized resources.Present address: Department 0f Entomology University 0f Alberta Edmonton, Alberta, Canada T6 G 2E3Present address: Department 0f Entomology University 0f Alberta Edmonton, Alberta, Canada T6 G 2E3     

Serotonin modulates locomotory behavior and coordinates egg‐laying and movement in Caenorhabditis elegans

Biogenic amines have been implicated in the modulation of neural circuits involved in diverse behaviors in a wide variety of organisms. In the nematode C. elegans, serotonin has been shown to modulate the temporal pattern of egg‐laying behavior. Here we show that serotonergic neurotransmission is also required for modulation of the timing of behavioral events associated with locomotion and for coordinating locomotive behavior with egg‐laying. Using an automated tracking system to record locomotory behavior over long time periods, we determined that both the direction and velocity of movement fluctuate in a stochastic pattern in wild‐type worms. During periods of active egg‐laying, the patterns of reversals and velocity were altered: velocity increased transiently before egg‐laying events, while reversals increased in frequency following egg‐laying events. The temporal coordination between egg‐laying and locomotion was dependent on the serotonergic HSN egg‐laying motorneurons as well as the decision‐making AVF interneurons, which receive synaptic input from the HSNs. Serotonin‐deficient mutants also failed to coordinate egg‐laying and locomotion and exhibited an abnormally low overall reversal frequency. Thus, serotonin appears to function specifically to facilitate increased locomotion during periods of active egg‐laying, and to function generally to modulate decision‐making neurons that promote forward movement. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 303–313, 2001     

Carpus and tarsus patterns in some Arabian lizards (Reptilia: Agamidae, Lacertidae, Scincidae)

Within the families Agamidae, Lacertidae and Scincidae, the carpal and tarsal elements, the sesamoidea and the ossification pattern show considerable variability. Furthermore, carpal and tarsal structure in the lizards studied here is not unique to the genera in question and identical or very similar conditions occur in other lizards. These elements contain sufficient anatomical information to make them taxonomically valuable.     

Phenotypic variation in an oviparous montane lizard (Bassiana duperreyi): the effects of thermal and hydric incubation environments

Recent studies have shown that incubation temperatures can profoundly affect the phenotypes of hatchling lizards, but the effects of hydric incubation environments remain controversial. We examined incubation-induced phenotypic variation in Bassiana duperreyi (Gray, 1938; Sauria: Scincidae), an oviparous montane lizard from south-eastern Australia. We incubated eggs from this species in four laboratory treatments, mimicking cool and moist, cool and dry, warm and moist, and warm and dry natural nest-sites, and assessed several morphological and behavioural traits of lizards after hatching. Incubation temperature influenced a lizard's hatching success, incubation period, tail length and antipredator behaviour, whereas variation in hydric conditions did not engender significant phenotypic variation for most traits. However, moisture affected incubation period slightly differently in males and females, and for a given snout-vent length moisture interacted weakly with temperature to affect lizard body mass. Although incubation conditions can substantially affect phenotypic variation among hatchling lizards, the absence of strong hydric effects suggests that hatchling lizards react less plastically to variation in moisture levels than they do to thermal conditions. Thus, our data do not support the generalization that water availability during embryogenesis is more important than temperature in determining the phenotypes of hatchling reptiles.     

Worker laying in leafcutter ant Acromyrmex subterraneus brunneus （Formicidae, Attini）

We studied the process of offspring production in queenless colonies of Acromyrmex subterraneus brunneus, and particularly evaluated the ovary development of workers as a function of their age. For this, subcolonies were set up and evaluated at different periods of isolation from the queen （2, 4 and 6 months）, besides individually labeled age groups. The subcolonies were assessed according to offspring production and ovaries containing oocytes or not. The evaluations showed worker oviposition and development of males originating from worker-laid eggs. At 2 months＇ absence of the queen, eggs and larvae were found, with eggs in a higher proportion than larvae. After 4 months, the proportion of eggs had reduced while larvae had increased, and a pupa was found in one subcolony. At 6 months, besides a higher share of larvae, one pupa and one adult male were found. Dissection of workers revealed ovaries containing oocytes during the periods of evaluation. Only a group of medium-sized and large workers, 23.3%, 20.9% and 37.5% of the population from each period assessed in queenless subcolonies respectively, presented developed oocytes in the ovary. The same was observed in colonies with a queen, with 17.6%, 19.6% and 7.8% of the group of dissected workers from each time period, respectively. With respect to worker age, we observed by dissection of the ovary, that the greatest percentage of individuals with ovarioles containing oocytes occurred at 45 days （6 weeks） up to 90 days （12 weeks）. These results probably are associated with the workers reproduction and the laying of trophic and reproductive eggs in colonies with and without a queen; these eggs have distinct functions in each situation.     

Divergent morphologies, performance, and escape behaviour in two tropical rock-using lizards (Reptilia: Scincidae)

The present study quantified microhabitat use, morphology, performance (sprinting, climbing, clinging, and jumping), and escape behaviour of two closely related tropical rock-using lizards. Specifically, the study tested whether: (1) a flatter body and longer limbs enhance performance in rocky habitats; (2) escape behaviour supports predictions based on habitat openness; and (3) there is a trade-off between sprinting and climbing performance. Despite the occupation of generally similar rocky habitats, the habitat of Carlia scirtetis was more open and composed of larger boulders with more regular surfaces, whereas the habitat of Carlia mundivensis was composed of more undergrowth and leaf litter, consisting of smaller boulders with irregular surfaces. The longer legs, flatter body, and greater sprinting and climbing ability of C. scirtetis, supports ecomorphological predictions. By contrast to predictions based on habitat openness, C. scirtetis allowed a potential threat to approach closer and ran further to a refuge than C. mundivensis , suggesting that escape behaviour as determined by performance may be species-specific or decoupled in these two species. The increased sprint speed of C. scirtetis highlighted a performance trade-off, with climbing speed lagging behind that of sprint speed. These results suggest that subtle differences in the structural microhabitat and the degree of habitat openness may ultimately result in substantial differences in morphology, performance, and threat behaviour in closely-related lizard species.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 85–98.