Residency Duration and Shelter Quality Influence Vibratory Signalling Displays in A Territorial Caterpillar

Residents are more likely to win territorial disputes than intruders. One explanation for this prior resident advantage is that residents place a higher value on the resource and are therefore more motivated to win. Although value asymmetry models of animal contests often assume that contestants use information about resource value, information on the proximate cues affecting territorial behaviour is often lacking. We use a simple model system – territorial behaviour in the masked birch caterpillar (Drepana arcuata) to identify factors that affect territorial behaviour. Late instar caterpillars occupy solitary silken leaf shelters, which they defend against wandering conspecifics with a vibratory display. We evaluated how a caterpillar identifies itself as the owner and the factors that influence a resident's motivation to signal. To do so, we conducted three experiments between size‐matched residents and intruders to assess how residency duration and shelter quality independently affected territorial displays during the early stages of a contest. Experiment 1 (Time Exp.) demonstrated that resident signalling rates increase with increased duration on the leaf prior to introducing the intruder. Residents also signal more than intruders after residency periods of 1–3 min and longer, demonstrating that residents gather information about resource value shortly after occupying a leaf. Experiment 2 (Squatter Exp.) aimed to disentangle the effects of time on the leaf and silk accumulation. Squatters (individuals in a shelter made by another) placed for 1–3 min on a leaf containing a full silk shelter signalled more to intruders than did caterpillars placed on a fresh leaf for 1–3 min. Experiment 3 (Shelter Removal Exp.) showed that residents whose shelters had been removed signal less than those occupying an intact shelter, despite an equal length of time investing in them. Our experiment is the first to covary both prior residency duration and territory quality, and we find that the motivation of caterpillars to signal is a function of both of these attributes.     

Shelter competition between resident male red swamp crayfish Procambarus clarkii (Girard) and conspecific intruders varying by sex and reproductive status

The shelter defense dynamics of reproductively active (Form I) male red swamp crayfish Procambarus clarkii (Girard) were investigated by staging serial intrusions by male, maternal or non-maternal female conspecifics after one day of residence. The male residents showed a direct contest advantage only against non-maternal females, and won a significantly higher proportion of the encounters against non-maternal females than against either male or maternal female intruders. However, there was no significant difference in success against male or maternal female intruders. Further experiments against male intruders showed that increasing male prior residence to either 2 or 4 days did not significantly improve the residents’ proportion of successful encounters. A final experiment revealed extremely low shelter fidelity in male P. clarkii, the most likely reason why male shelter defense against conspecific males and maternal females is not successful. These results, combined with those of past research, suggest that non-maternal females, juveniles and recently molted conspecifics are most vulnerable to predation and cannibalism, since males and maternal females easily out-compete non-maternal females for shelter, and adults out-compete juveniles. These findings may have implications for P. clarkii aquaculture and general management.     

Vibration‐mediated territoriality in the warty birch caterpillar Drepana bilineata

Abstract The warty birch caterpillar Drepana bilineata produces two distinct types of vibrational signals (mandible drumming and anal scraping) during interactions with conspecifics. Vibrational signalling is characterized using standard and high‐speed videography synchronized with laser‐doppler vibrometry, and behavioural experiments test the hypothesis that signalling functions to advertise occupancy of birch (Betula) leaves. Drumming involves raising the head and striking the leaf with the sharp edges of the open mandibles. Anal scraping involves dragging a pair of specialized oar‐shaped setae against the leaf surface. Staged encounters between leaf residents and conspecific intruders result in the resident signalling, with rates increasing as the intruder moves closer. Intruders signal significantly less often than residents. Conflicts are typically resolved within a few minutes, with the resident winning in 61% of the trials, and the intruder winning in 6%. Contests that last more than 30 min are deemed ‘ties’ and comprise the remaining 33% of trials. The results support the hypothesis that vibrational signals function to advertise leaf occupancy. Vibrational communication is believed to be widespread in Drepanoidea caterpillars, but has only been described in two species to date: D. bilineata (present study) and Drepana arcuata. It is proposed that differences in territorial behaviour and signalling between these species are related to their relative investments in silk leaf mats and shelters. The proximate and ultimate bases for the evolution of vibrational communication in caterpillars are discussed.     

Assessment of fish size on shelter choice and intraspecific interactions by round gobies <Emphasis Type="Italic">Neogobius melanostomus</Emphasis>

Synopsis We examined shelter occupancy and behavioural interactions in non-reproductive male round gobies, Neogobius melanostomus,an invasive fish, to determine if gobies can assess one another’s prowess effectively. Results of laboratory experiments revealed a significant, positive relationship between body size (total mass) and time for individual fish to occupy shelters. Shelter size selection did not vary with body size, but males that abandoned shelters were smaller than those that remained. Overall, the number of interactions between residents and intruders were low with most interactions occurring between large residents and large intruders. A size differential between residents and intruders of 3% was sufficient to predict the proportion of victories in conflicts between round gobies. This ability of the round goby to perceive size differences between themselves and potential opponents reduces the number of interactions and may account for the occurrence of high densities of round gobies observed in the field.     

Induction of sieve-tube elements in the ray system ofMorus alba L

The effect of exogenous supply of a morphactin — chlorflurenol (IT-3456) CME 74050 p at three concentrations of 100, 500, and 1000 ppm (all applied as dispersions in lanolin paste after scraping the epidermis during December, 1976) was studied on two-year-oldMorus alba plants. Almost three months after the treatment of the regulator, along with the normal sievetube elements of the axial system, these elements were recorded in the ray system as well, arranged either vertically or horizontally. In the latter state, they appear to act as a by-pass between the normally formed sieve elements located on either side of the ray. We have termed them ‘ray-sieve-tube elements’ to distinguish them from the normal elements. Simultaneously, some sieve-tube elements having sieve plates on their lateral walls were also noticed in the axial system. A direct correlation was observed between the multiplicity of induction of both element types and increasing concentration of the regulator.     

Asymmetrical Resource Ownership Increases Owners’ and Reduces Non‐Owners’ Motivation to Fight in the Mangrove Rivulus,Kryptolebias marmoratus

Resource ownership often increases an individual's aggressiveness and its probability of defeating a competitor. Individuals contesting resource owners could therefore incur higher costs, making individuals reluctant to compete with owners. We tested the hypothesis that animals use asymmetry in resource ownership as a cue for contest costs and adjust contest decisions accordingly. Using a mangrove rivulus fish (Kryptolebias marmoratus), we staged (1) contests with a randomly assigned asymmetry in resource ownership (one fish was provided with a shelter) and (2) contests in which neither fish had a shelter. Owners that were in their shelters at the contest start showed a greater tendency to fight and won more contests than their intruder opponents; those outside the shelter at the start did not. Compared with fish in contests with no shelters at stake, shelter owners had a higher tendency to fight whether or not they were in their shelters at the start; intruders, however, had a lower tendency to fight only against owners that were inside the shelter at the start. These results demonstrate (1) that ownership status influences both owners’ and intruders’ contest decisions (and in opposite directions), producing a detectable ownership advantage and (2) that intruders required confirmation of their opponents’ ownership status before retreating without challenging them. Ownership status per se is therefore important to the fish's contest decisions.     

Neuroendocrine and behavioral response to social confrontation: residents versus intruders, active versus passive coping styles

We investigated in the present study the neuroendocrine correlates in intruder and resident rats of a social confrontation. Adult male Wistar rats (intruders) were introduced into the home cage of a well-trained resident to induce characteristic agonistic interactions including physical attacks prior to separation by a wire mesh. The hypothalamic-pituitary-adrenal (HPA) axis activity and the intrahypothalamic release of arginine vasopressin (AVP) were monitored via chronically implanted jugular venous catheters and microdialysis probes aimed at the hypothalamic paraventricular nucleus (PVN), respectively. Based on the behavioral data collected during the 30-min confrontation, intruders and residents were additionally classified into two different subgroups: intruders which showed almost no freezing behavior (active copers) versus those showing pronounced freezing behavior (passive copers) and residents which were either predominantly aggressive or non-aggressive. The neuroendocrine data show that social confrontation caused a significantly increased secretion of the adrenocorticotropic hormone (ACTH) into plasma in both intruder subgroups, independently of their coping strategy. In contrast, plasma ACTH in residents was increased in response to social confrontation in non-aggressive animals only, whereas aggressive residents failed to mount an ACTH response. Interestingly, plasma AVP decreased in response to social confrontation in active intruders. As measured in microdialysates, the two groups of residents and passive intruders failed to show significant changes of intra-PVN release of AVP. In contrast, an increased release of this neuropeptide within the PVN could be monitored for active intruders. The data of the present study suggest that the different interpretation of an aversive encounter results in differences in the neuroendocrine response and intrahypothalamic vasopressinergic signaling in intruders versus residents.     

Shelter competition between resident male red swamp crayfish Procambarus clarkii (Girard) and conspecific intruders varying by sex and reproductive status

The shelter defense dynamics of reproductively active (Form I) male red swamp crayfish Procambarus clarkii (Girard) were investigated by staging serial intrusions by male, maternal or non-maternal female conspecifics after one day of residence. The male residents showed a direct contest advantage only against non-maternal females, and won a significantly higher proportion of the encounters against non-maternal females than against either male or maternal female intruders. However, there was no significant difference in success against male or maternal female intruders. Further experiments against male intruders showed that increasing male prior residence to either 2 or 4 days did not significantly improve the residents' proportion of successful encounters. A final experiment revealed extremely low shelter fidelity in male P. clarkii, the most likely reason why male shelter defense against conspecific males and maternal females is not successful. These results, combined with those of past research, suggest that non-maternal females, juveniles and recently molted conspecifics are most vulnerable to predation and cannibalism, since males and maternal females easily out-compete non-maternal females for shelter, and adults out-compete juveniles. These findings may have implications for P. clarkii aquaculture and general management.     

Nature of interference potential of leaf debris of Ageratum conyzoides

The present study investigated the allelopathic interference of leaf debris of Ageratum conyzoides (billy goat weed; Asteraceae)—a weed of cultivated land—against rice (Oryza sativa). Seedling length and dry weight of rice were significantly reduced (16–20%) in soil from A. conyzoides infested fields compared to the soil from an area devoid of the weed. It indicated the presence of certain phytotoxins in the A. conyzoides infested soil. To explore the possible contribution of the weed in releasing these phytotoxins, growth studies involving leaf debris extracts and amended soils (prepared by incorporating leaf debris—5, 10, 20 g kg⁻¹ soil, w/w, or its extracts—0.5%, 1.0% and 2.0%, v/v) were conducted. The growth of rice was severely inhibited in A. conyzoides leaf debris- and debris extract-amended soils compared to unamended control soil. A significant amount of water-soluble phenolics, the potent phytotoxins, was found in the A. conyzoides infested soil, leaf debris, and debris-amended soils. These phenolics were identified as gallic acid, coumalic acid, protocatechuic acid, catechin and p-hydroxybenzoic acid. Among these, protocatechuic acid was in the maximum amount (35.72%) followed by coumalic acid (33.49%) and these two accounted for >69% of total phenolic compounds. Further, there was a significant increase in the available nutrient content in soil amended with A. conyzoides leaf debris thus ruling out the possibility of any resource depletion upon residue incorporation and their negative role in causing growth reduction. Based on the observations, the present study concludes that leaf debris of A. conyzoides deleteriously affects the early growth of rice by releasing water-soluble phenolic acids into the soil environment and not through soil nutrient depletion.     

Post-dispersed pine seed removal and its effect on seedling establishment in a Mexican Temperate Forest

In order to assess the impact of seed removal and seedling establishment for four species of pines, we designed experiments with and without the exclusion of seed removers in three vegetation types (pine forest, oak-alder forest, and subalpine grassland). Seed removal was significantly different between species of pines (P < 0.01), as was the interaction between the vegetation types and category of exclusion (remover) (P < 0.0001). The significant difference in terms of seed removal was between P. patula and P. montezumae (33.0 and 17.9%, respectively). Seed removal was significant between pine forest—without exclusion (20.0%) versus oak-alder forest—without exclusion (7.0%). There was significant interaction between seedling establishment of the pine species and vegetation type (P < 0.0001). Highlighting differences between the pine forest—P. teocote (84.1%) versus oak-alder forest—P. patula (19.0%), oak-alder forest—P. pseudostrobus (45.0%), pine forest—P. patula (20.2%), pine forest—P. pseudostrobus (45.6%), subalpine grassland—P. montezumae (24.3%), subalpine grassland—P. patula (27.9%), and subalpine grassland—P. pseudostrobus (17.5%). The impact of the food preferences of rodents and other granivores for P. patula and P. pseudostrobus seeds, as well as the poor survival of seedlings of these species in the pine and oak-alder forest are both factors which may explain the dominance of P. teocote in the study region.     

Matter of Size or Matter of Residency Experience? Territorial Contest in a Green Hairstreak,Chrysozephyrus smaragdinus (Lepidoptera: Lycaenidae)

Territorial residents usually win asymmetrical owner‐intruder contests and a variety of hypotheses have been proposed to explain this phenomenon. In the butterfly Chrysozephyrus smaragdinus (Lepidoptera: Lycaenidae), male territorial residents defended their territories against intruders during numerous contests and kept them for many successive days. Field observations and experiments were conducted to examine the factors related to this superiority of residents. Forewing length did not differ between residents and intruders, suggesting that body size is not correlated with resource holding potential. Removal–replacement experiments demonstrated that residency did not serve as an arbitrary means for contest settlement, and did not support the recently presented alternative hypothesis that males with higher body temperature are more likely to win. New residents fought longer in defense of the territory as their residence duration in the territory increased. I discuss these results in light of game theory and suggest that the superiority of residents in C. smaragdinus may be based on the asymmetry of resource (territory) value for residents and intruders.     

Convergence of tree water use within an arid-zone woodland

We examined spatial and temporal patterns of tree water use and aspects of hydraulic architecture in four common tree species of central Australia—Corymbia opaca, Eucalyptus victrix, E. camaldulensis and Acacia aneura—to better understand processes that constrain water use in these environments. These four widely distributed species occupy contrasting niches within arid environments including woodlands, floodplains and riparian environments. Measurements of tree water use and leaf water potential were made at two sites with contrasting water table depths during a period of high soil water availability following summer rainfall and during a period of low soil water availability following 7 months of very little rainfall during 2007. There were significant differences in specific leaf area (SLA), sapwood area to leaf area ratios and sapwood density between species. Sapwood to leaf area ratio increased in all species from April to November indicating a decline in leaf area per unit sapwood area. Despite very little rainfall in the intervening period three species, C. opaca, E. victrix and E. camaldulensis maintained high leaf water potentials and tree water use during both periods. In contrast, leaf water potential and water use in the A. aneura were significantly reduced in November compared to April. Despite contrasting morphology and water use strategies, we observed considerable convergence in water use among the four species. Wood density in particular was strongly related to SLA, sapwood area to leaf area ratios and soil to leaf conductance, with all four species converging on a common relationship. Identifying convergence in hydraulic traits can potentially provide powerful tools for scaling physiological processes in natural ecosystems.     

The epiphytic communities of various ecological types of aquatic vegetation of five pastoral ponds

Five small water bodies located within the agricultural region of Wielkopolska (west Poland) underwent investigation. Periphyton samples were collected from various macrophyte habitats representing rush vegetation (in five water bodies), submerged aquatic plants (in three) and nymphaeids (in one): Palędzie — Ceratophyllum demersum, Potamogeton crispus, Typha latifolia; Batorowo — Phragmites australis; Piotrowo — Potamogeton natans, Ceratophyllum submersum, Typha latifolia; Tarnowo Podgórne — Typha latifolia; Dąbrówka — Zannichellia palustris, Potamogeton pectinatus, Phragmites australis. The main goal of the study was to determine the composition and abundance of the periphytic communities inhabiting various types of rush and water vegetation of five water bodies located within a mid-field landscape area. Diatoms such as Achnanthidium minutissimum, Amphora ovalis, Cocconeis placentula orNavicula cincta revealed significantly higher densities in the zone of elodeids, while green algae prevailed among nymphaeids. As a result of this study it was found that the epiphytic algae were characterised by much lower diversity in respect to a specific water body, though much greater diversity was observed in its relation to the type of substratum. Two types of habitats were distinguished — the first of simple build (helophytes and nympheids) and the second containing the complicated architecture of plant stems (elodeids).     

Territorial behavior of the Korean wood-feeding cockroach, <Emphasis Type="Italic">Cryptocercus kyebangensis</Emphasis>

We investigated the territorial behavior of Cryptocercus kyebangensis from the viewpoint of offspring protection. Aggressive behavior against adult intruders occurred more frequently in resident adults with their young than those without their young. Resident adults without offspring more frequently attacked intruders of the same sex than those of the opposite sex, whereas those with offspring attacked regardless of the sex of adult intruders. In paired residents, cooperative territorial behavior occurred in a higher proportion in pairs with offspring than those without offspring. Responses of residents to nymphal intruders depended on the head capsule size of the intruders. Resident adults rarely attacked intruders smaller than their own offspring but frequently attacked larger intruders. Resident nymphs frequently attacked intruders smaller than themselves, whereas they escaped or showed jerking behavior when they encountered larger intruders. Electronic Publication     

The olfactory pathway mediates sheltering behavior of Caribbean spiny lobsters, <Emphasis Type="Italic">Panulirus </Emphasis><Emphasis Type="Italic">argus</Emphasis>, to conspecific urine signals

The “noses” of diverse taxa are organized into different subsystems whose functions are often not well understood. The “nose” of decapod crustaceans is organized into two parallel pathways that originate in different populations of antennular sensilla and project to specific neuropils in the brain—the aesthetasc/olfactory lobe pathway and the non-aesthetasc/lateral antennular neuropil pathway. In this study, we investigated the role of these pathways in mediating shelter selection of Caribbean spiny lobsters, Panulirus argus, in response to conspecific urine signals. We compared the behavior of ablated animals and intact controls. Our results show that control and non-aesthetasc ablated lobsters have a significant overall preference for shelters emanating urine over control shelters. Thus the non-aesthetasc pathway does not play a critical role in shelter selection. In contrast, spiny lobsters with aesthetascs ablated did not show a preference for either shelter, suggesting that the aesthetasc/olfactory pathway is important for processing social odors. Our results show a difference in the function of these dual chemosensory pathways in responding to social cues, with the aesthetasc/olfactory lobe pathway playing a major role. We discuss our results in the context of why the noses of many animals contain multiple parallel chemosensory systems.     

Nondestructive determination of leaf chlorophyll content in two flowering cherries using reflectance and absorptance spectra

Leaf chlorophyll quantification is a key technique in tree vigor assessment. Although many studies have been conducted on nondestructive and in-field spectroscopic determination, it is reasonable to develop species-specific chlorophyll indices for accurate determination, because leaf spectra can vary independently of chlorophyll content due to leaf surface and structural differences among species. The present study aimed to develop optimal reflectance and absorptance indices for estimating the leaf chlorophyll content of Cerasus jamasakura (Siebold ex Koidz.) H. Ohba var. jamasakura and Cerasus × yedoensis ‘Somei-yoshino,’ and to examine their performance by comparing them with 46 published chlorophyll indices and SPAD. For 96 and 100 leaf samples, measurements were taken using a spectroradiometer with a leaf-clip attachment and a SPAD-502 chlorophyll meter, and chlorophyll content was determined by extraction with N,N′-dimethylformamide. The optimal leaf chlorophyll indices were then developed systematically by testing eight types of indices. As a result, we confirmed that the optimal chlorophyll indices performed better than any of the published leaf chlorophyll indices or SPAD, giving RMSEs that were approximately twice as good as those for SPAD, and found that the newly proposed index type—a difference and ratio combination type—may be a useful form of chlorophyll content estimation. We also found that absorptance indices achieved equivalent results to reflectance indices despite the hypothesis that absorptance measurement is direct and has more potential. Among the published indices, the reflectance ratio index of Datt [Datt B (1999) Int J Remote Sens 20(14):2741–2759] and the red edge chlorophyll index of Ciganda et al. [Ciganda V, Gitelson A, Schepers J (2009) J Plant Physiol 166:157–167] were effective at estimating the leaf chlorophyll contents of both flowering cherries.     

Comparative study of different methods for capturing airborne pollen,and effects of vegetation and meteorological variables

The atmosphere of Mar del Plata city (Argentina) was monitored using three different pollen traps—Burkard, Rotorod, and Tauber—during a flowering season (mid-winter to springtime) in order to compare the diversity and amounts of pollen grains collected in each trap. Sixty three percent of taxa diversity was simultaneously recorded by all three apparatuses. The five most abundant types of pollen in the three traps were Platanus, Ulmus, Quercus, Poaceae, and Fraxinus. The Tauber trap contained the most pollen from taxa with the largest grains, and exclusively trapped ten pollen types with entomophilous characteristics. The amount of pollen in each trap and local/extra-local plant abundance were compared to elucidate the effect of the method used on the pollen–vegetation relationship. The correlation coefficients for total pollen were positive and significant between all pairs of traps. The maximum peak was observed first in the Burkard trap, in agreement with an increase in temperature, but the general pattern in the three traps was similar, with a maximum in early spring. Opposite deviations from the mean value were observed for the Burkard and Tauber data; these deviations were associated negatively with wind speed and relative humidity, respectively. This paper discusses whether in some cases the pollen records could be used in an equivalent manner, although with some limitations.     

Fine structure of olfactory epithelium inSchizothoraichthys progastus McClelland andSchizothorax richardsonii Gray (Cyprinidae: Teleostei) from Garhwal Himalaya (India)

The olfactory epithelium of two closely related species of snowtrout—Schizothoraichthys progastus McClelland andSchizothorax richardsonii Gray (Subfamily: Schizothoracinae. family-Cyprinidae, Teleostei), from a perennial glacier-fed river Mandakini of Garhwal hills was studied by employing transmission electron microscopic method The olfactory lamella comprises two epithelia—anterior and posterior, with a stroma sandwiched in between. Both are strartified. The anterior one is thicker than posterior. InSchizothoraichithys progastus, the sensory part of epithelium has two types of receptor cells—ciliated receptor cells and rod cells whilst inSchizothorax richardsonii, there arc three types of receptor cells—ciliated receptor cells, microvillous receptor cells and rod cells in addition to sustentacular cells, basal cells and mucous cells. While inhabiting similar hillstream habitat, the differential ecological niches, feeding habits etc., account for the presence of different receptor cell types in these species, It implies the possible diversification at cellular and physiological levels so as to minimize the competition by using varied olfactory cues.     

Increases in Desert Shrub Productivity under Elevated Carbon Dioxide Vary with Water Availability

Productivity of aridland plants is predicted to increase substantially with rising atmospheric carbon dioxide (CO₂) concentrations due to enhancement in plant water-use efficiency (WUE). However, to date, there are few detailed analyses of how intact desert vegetation responds to elevated CO₂. From 1998 to 2001, we examined aboveground production, photosynthesis, and water relations within three species exposed to ambient (around 38 Pa) or elevated (55 Pa) CO₂ concentrations at the Nevada Desert Free-Air CO₂ Enrichment (FACE) Facility in southern Nevada, USA. The functional types sampled—evergreen (Larrea tridentata), drought-deciduous (Ambrosia dumosa), and winter-deciduous shrubs (Krameria erecta)—represent potentially different responses to elevated CO₂ in this ecosystem. We found elevated CO₂ significantly increased aboveground production in all three species during an anomalously wet year (1998), with relative production ratios (elevated:ambient CO₂) ranging from 1.59 (Krameria) to 2.31 (Larrea). In three below-average rainfall years (1999–2001), growth was much reduced in all species, with only Ambrosia in 2001 having significantly higher production under elevated CO₂. Integrated photosynthesis (mol CO₂ m⁻² y⁻¹) in the three species was 1.26–2.03-fold higher under elevated CO₂ in the wet year (1998) and 1.32–1.43-fold higher after the third year of reduced rainfall (2001). Instantaneous WUE was also higher in shrubs grown under elevated CO₂. The timing of peak canopy development did not change under elevated CO₂; for example, there was no observed extension of leaf longevity into the dry season in the deciduous species. Similarly, seasonal patterns in CO₂ assimilation did not change, except for Larrea. Therefore, phenological and physiological patterns that characterize Mojave Desert perennials—early-season lags in canopy development behind peak photosynthetic capacity, coupled with reductions in late-season photosynthetic capacity prior to reductions in leaf area—were not significantly affected by elevated CO₂. Together, these findings suggest that elevated CO₂ can enhance the productivity of Mojave Desert shrubs, but this effect is most pronounced during years with abundant rainfall when soil resources are most available.