Morphological and developmental analysis of peripheral antennal chemosensory sensilla and central olfactory glomeruli in worker castes of Camponotus compressus (Fabricius, 1787)

The antennal lobes of different castes of the ant species Camponotus compressus show a marked diversity in the organization of their olfactory glomeruli. Notably, there is a significant difference in the number and size of glomeruli between the reproductives and the workers and among the different worker castes. In this report, we investigate the notion that these caste-specific differences in glomerular number might be accounted for, at least in part, by the differences in numbers of olfactory sensilla that target the antennal lobe. For this, we examine the number of sensilla on the antennal flagella of all the individual castes of C. compressus. This analysis reveals a striking correlation between sensillar number and the number of antennal glomeruli in a given caste. As a first step in investigating the causal mechanisms that might give raise to this correlation, we carry out an initial characterization of olfactory system development in the minor workers of C. compressus. We analyze the temporal pattern of innervations of the developing antennal lobe by olfactory sensory neuron axons. We document the development of the olfactory glomeruli in the antennal lobe during this process, which occurs during early pupal stages. Our findings provide the basis for future manipulative developmental studies on the role of sensory afferent number in glomerular development of different castes within the same species.     

Characterization of 8 polymorphic microsatellite loci in the neotropical ant-garden ant, Camponotus femoratus (Fabricius)

Camponotus femoratus is an abundant and behaviorally dominant ant in lowland Amazonian rainforests, where this species participates in a complex and obligate seed-dispersal mutualism. C. femoratus typically cohabits with another ant species Crematogaster levior in an apparently amiable but poorly understood interaction. Despite these outstanding characteristics, the population genetics and dispersal patterns of C. femoratus are unknown. We isolated eight polymorphic microsatellite loci for C. femoratus from a genomic library enriched for di-, tri-, and tetra-nucleotide repeats. We detected 2 to 17 alleles per locus, with levels of observed heterozygosity ranging from 0.286 to 0.714.     

Caste- and sex-specific adaptations within the olfactory pathway in the brain of the ant Camponotus floridanus

Olfaction plays a key role in mediating ant behavior, and ant societies are characterized by caste- and sex-specific division of labor. We propose that caste- and sex-specific adaptations in the olfactory pathway promote differences in olfactory behavior. This study compares olfactory centers in the brain of large (major) workers, small (minor) workers, virgin queens, and males of the carpenter ant Camponotus floridanus. The number of glomeruli in the antennal lobe was similar in the female castes, although the glomerular volumes differed. Males had approximately 45% fewer glomeruli compared to females (approximately 258 and approximately 434) and one antennal sensory tract was absent. A dual output pathway to the mushroom bodies was present in males. In contrast to females, however, the number of glomeruli connected to the medial antennocerebral tract was substantially smaller than those associated with the lateral tract. All glomeruli in the male antennal lobe contained serotonergic processes, whereas in the female castes glomeruli in the large tract six cluster lacked serotonergic innervations. We conclude that differences in general glomerular organization are subtle among the female castes, but sex-specific differences in the number, connectivity and neuromodulatory innervation of glomeruli are substantial and likely to underlie differences in olfactory processing and learning.     

Comparative dynamics of gestalt odour formation in two ant species Camponotus fellah and Aphaenogaster senilis (Hymenoptera: Formicidae)

Abstract. Ant colonies experience continuous shifts in worker populations, which may affect odour composition in the nest. A major question regarding the dynamics of gestalt formation is that of the speed at which the scent of a new individual will be incorporated into the gestalt. It is predicted from the gestalt model of colony odour that workers have to exchange recognition cues continuously to maintain themselves within the gestalt and become well integrated within their colony. Using radioactive tracers the rates of transfer were measured between a labelled donor ant and one or 10 recipient ants, as a close approximation to the within-nest situation. The labelled hydrocarbons were first transferred to a small number of individuals and progressively to all the individuals of the group so that the distribution of hydrocarbon transfer rate approached a normal distribution. Furthermore, in Camponotus fellah Dalla Torre, which performs trophallaxis, homogeneity was reached more rapidly than in Aphaenogaster senilis Mayr, which does not show this behaviour. In the latter species, the gestalt seems to be maintained mainly by allogrooming. These experiments were accompanied by behavioural observations to ascertain the respective importance of trophallaxis and allogrooming in the behavioural time-budget of the ants. In A. senilis , allogrooming was more frequent than in ants that trophallax, which corroborates the role of allogrooming in the establishment of the gestalt in this species.     

Pollination, breeding system, and genetic structure in two sympatric Delphinium (Ranunculaceae) species

Two sympatric Delphinium species, D. barbeyi and D. nuttallianum, are ecologically and morphologically similar. However, D. barbeyi has multiple, large inflorescences while D. nuttallianum has a single, small inflorescence. These differences in floral display should result in greater intraplant pollen transfer in D. barbeyi, leading to higher rates of self-pollination through geitonogamy. Reduced gene flow by pollen should in turn produce greater population differentiation among populations of D. barbeyi relative to D. nuttallianum. We tested these predictions by comparing pollinator behavior, breeding systems, outcrossing rates, and population genetic structure of sympatric populations of the two species in Colorado. Bumble bee and hummingbird pollinators visit more flowers and inflorescences per foraging bout in D. barbeyi than in D. nuttallianum. The species differed in breeding system; D. barbeyi produced more seeds by autogamy (9 vs. 2%) than D. nuttallianum and suffered no reduction in seed set in hand-self vs. outcross pollinations, in contrast to a 41% decline in D. nuttallianum. The outcrossing rate in one D. barbeyi population was 55%, but ranged from 87 to 97% in four D. nuttallianum populations. Genetic differentiation among population subdivisions estimated by hierarchical F statistics was >10 times greater in D. barbeyi ( = 0.055-0.126) than D. nuttallianum ( = 0.004-0.009) at spatial scales ranging from metres to 3.5 km. Spatial autocorrelation analysis also indicated more pronounced local genetic structure in D. barbeyi than D. nuttallianum populations. Fixation indices (F(IS)) of D. barbeyi adults were much lower than expected based on mating system equilibrium and suggest that differences in the degree of self-compatibility and/or the timing of postpollination selection/inbreeding depression between the two species further contribute to the genetic differences between them.     

A peculiar case of parasitisation with two new species of wasps parasitizing the rice leaf-roller Pelopidas mathias (Fabricius, 1798) (Lepidoptera: Hesperiidae) from southern India

Systematic Parasitology - Paddy, Oryza sativa L. (Poales: Poaecea) is infested by a series of lepidopteran, coleopteran, hemipteran, and acarine pests in India. Of the long list, the species Rice...     

Possible species specific courtship sounds by two sympatric cichlid fishes in Lake Malawi, Africa

Sounds were produced by the males of two species of cichlid fishes while courting females. Each courtship sound consisted of a series of distinct pulses occurring in rapid succession. Courtship sounds produced by Tramitichromis cf. intermedius and Copadichromis conophorus were significantly different in pulse rate and individual pulse durations. For C. conophorus calls (n=127) the mean ± sd number of pulses per call was 10 ± 3 and call duration was 181 ± 59 ms. There was a significant positive linear relationship between call duration and the number of pulses (r²=0.912, p < 0.001). The dominant frequency of the pulses in calls was 471 ± 50 (range 372–594) Hz (n=40 calls). T. cf. intermedius also produced a pulsed courtship call; data (mean ± sd) from two male T. cf. intermedius: 9 ± 2 pulses per call and duration 199 ± 44 ms (n=20 calls). The linear regression between call duration and number of pulses was positive (r²=0.463, p=0.001). Pulse rate within calls of T. cf. intermedius compared to C. conophorus were significantly different (p=0.018). Individual pulse durations were also significantly different (p=0.043) between species. However, interpulse intervals were not significantly different (p=0.177). These cichlids produced courtship sounds that were distinct by individual pulse durations and by pulse repition rate in a call.     

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds

Electroantennogram (EAG) responses of male and female Oedipodinae grasshoppers, Oedaleus decorus asiaticus B.-Bienko and Angaracris barabensis Pall to 37 plant volatile compounds were recorded. The two species have sympatric distribution and synchronous seasonal activity in Inner Mongolia Grasslands. They have different host plant preference with Oedaleus decorus asiaticus graminivorous and A. barabensis forbivorous. The EAG response profiles to 37 compounds of the two species and their both sexes were similar. Most of the green leaf volatiles elicited higher EAG responses in both species and sexes than terpenic compounds and some aromatic compounds. Strong EAG responses were elicited by 6-carbon alcohols (1-hexanol, Z-hexen-2-ol-1, E-2-hexen-1-ol, E-hexen-3-ol-1), aldehyde (E-2-hexen-1-al), ester (Z-hexen-3-yl acetate), and 7-carbon alcohols (1-heptanol) in both species and sexes. Monoterpenes with functional groups of alcohols and aldehydes were more stimulating than other monoterpenes tested. The sesquiterpenes tested elicited relatively low responses. Benzaldehyde elicited the highest responses for both species among aromatic components. Oedaleus decorus asiaticus showed higher EAG responses than A. barabensis to the green leaf volatiles, 1-decanol, 1-nonanol, 1-pentanol, hexanal, Z-hexen-3-yl acetate and to the sesquiterpenes (-)-trans-caryophyllene. Males have higher responses than females in Oedaleus decorus asiaticus. No sexual difference was observed in A. barabensis. Dose-dependent responses to six selected chemicals were observed from females. In both species, all the chemicals tested elicit EAG responses at concentration between 10^-3 mol/L and 10^-2 mol/L, except that the responses of A. barabensis to terpineol had a threshold concentration of 10-2 mol/L benzaldehyde and 1-hexanol had the highest slopes in dose curves, while 1-octen-3-ol showed the smallest slope in responses to the six chemicals tested. Comparative studies on the responses of two antennal sections and the whole antenna to six selected chemicals were carried out using females of both species. A significant EAG response was only recorded from the distal part of the antenna and not from the proximal seven segments.     

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds

Two Oedipodinae grasshopper species Oedaleus decorus asiaticus B.-Bienko and Angaracris baraben-sis Pall. (Orthoptera: Acrididae) are important pests on the natural grasslands in Inner Mongolia and often require insecticide treatment during outbreaks[1]. They both prefer overgrazed steppes and xerophytous habi-tats, and have thus been suggested as indicator species for steppe deterioration in typical steppe zones of In-ner Mongolia[2]. The two species have a sympatric distribution and sync…     

The use of the anaesthetic, enflurane, for determination of metabolic rates and respiratory parameters in insects, using the ant, Camponotus maculatus (Fabricius) as the model

This study investigated the effects of the anaesthetic, enflurane, on metabolic rates and ventilation patterns in the spotted sugar ant, Camponotus maculatus, using flow-through respirometry. The standard metabolic rate was not affected by the anaesthetic. While the ants were anaesthetised they exhibited a similar discontinuous gas exchange cycle to that observed when they were voluntarily motionless, but their spiracles remained open for a longer time during the open or burst phase even though the amount of CO(2) emitted during this phase remained constant. We discuss this finding in the context of the central nervous system control of the spiracle muscle. For both the determination of standard metabolic rate and ventilation patterns the individual ant has to be motionless. From this study we recommend the use of enflurane to ensure immobility in ants, and other small active insects, during the determination of standard metabolic rates, but the anaesthetic cannot be used to quantify the respiration pattern.     

Foraging patterns in three sympatric forest ant species, Prenolepis imparis, Paratrechina melanderi and Aphaenogaster rudis (Hymenoptera: Formicidae)

Abstract.

• 1 Ecological segregation was studied in Aphaenogaster rudis Emery, Paratrechina melanderi (Wheeler) and Prenolepis imparis (Say), the three commonest surface-foraging ants in a Maryland (U.S.A.) hardwood forest community.
• 2 P.imparis retreats from the surface during mid-summer, but shows more cool-season activity than do the other two species. P.melanderi is most active during the warmest months of the years. A.rudis is the most generalized of the three species in its seasonal activity pattern.
• 3 P.imparis is a highly aggressive species which forms large mobilizations at rich food sources. P.melanderi is a timid species which forms small mobilizations. A.rudis is intermediate in both respects.
• 4 Based on the results of baiting trials, P.imparis shows an apparent preference for protein-fat food, P.melanderi prefers carbohydrate food, and A.rudis exhibits no significant preference for either fclod type.
• 5 As a result of its extended seasonal activity, weak circadian periodicity, and lack of food specialization, A.rudis has the broadest annual niche of the three species studied.
• 6 The unusual seasonal activity pattern of P.imparis results in a relatively low degree of annual niche overlap between this species and either of the other two. Overlap between A.rudis and P.melanderi is substantially higher.
• 7 Experimental manipulations confirm that rates of resource removal by a behaviourally subordinate species (Amdis) are reduced in the presence of a dominant species (P.imparis).
• 8 Persistence of these three widespread, abundant, relatively generalized ant species in local sympatry may in part reflect their differential success in: (a) finding food, (b) defending food, and (c) handling food items of different sizes.

     

Ovary organization and oogenesis in two species of Lumbriculida (Annelida,Clitellata)

The aim of the present study is to describe the organization of the ovary and mode of oogenesis at the ultrastructural level in two representatives of Lumbriculida – Lumbriculus variegatus and Stylodrilus heringianus. In both species studied, the ovaries are small and conically shaped structures that are attached to the intersegmental septum via a thin ligament. The ovaries are composed of germline cysts formed by germ cells interconnected by stable cytoplasmic bridges. As a rule, the cyst center is occupied by a poorly developed anuclear cytoplasmic mass, termed a cytophore, whereas the germ cells are located at the periphery of the cyst. Germline cysts are enveloped by somatic cells. The ovaries of the species studied are polarized, i.e., along the long axis of the ovary there is an evident gradient of germ cell development. The data obtained suggest ovary meroism, i.e., two categories of germ cells were found: oocytes, which continue meiosis, gather nutrients, grow and protrude into the body cavity, and nurse cells, which do not grow and are supposed to supply oocytes with cell organelles and macromolecules via the cytophore. The ovary structure and mode of oogenesis in the species studied were compared with those of other clitellate annelids. As a rule, in all clitellates studied to date, the ovaries are composed of germline cysts equipped with a cytophore and associated with somatic cells; however, the ovary morphology differs between taxa regarding several quantitative and qualitative features. The ovary organization and mode of oogenesis in L. variegatus and S. heringianus strongly resemble those found in Tubificinae and Branchiobdellida studied to date. Our results also support a sister-group relationship between Lumbriculida and a clade comprising ectoparasitic clitellates (i.e., Branchiobdellida, Acanthobdellida and Hirudinida) with Branchiobdellida as a plesiomorphic sister group to Acanthobdellida and Hirudinida.     

Social organisation and interspecific interactions in two sympatric species of Ranidella (Anura)

Summary The socio-spatial organisation of two sympatric species of anurans was investigated by analyses of the spatial and temporal structure of breeding assemblages. Ranidella signifera breeds earlier in the year than its congener, R. parinsignifera, though there is an overlap of 6 to 8 weeks. Males of both species show high affinities for discrete spatial locations (preferred calling stations). These stations are regularly-spaced, and temporally-stable. Satellite behaviour occurs, though most satellites are past or future residential males. There appears to be a spatial-energetic limit to the number of calling residents of both species that a pond can support. There is no differentiation of calling sites between the two species, and the males of R. parinsignifera appear to displace their congeners from the preferred stations located on the land/water interface of ponds. The breeding season of R. signifera in sympatry is abbreviated relative to nearby (20 km) allopatric localities. The breeding seasons of conspecific males and females are well-synchronised, though the ratio of males to females is high early in the breeding season.     

Demonstration of interspecific competition between two sympatric egg parasitoids of Riptortus pedestris (Fabricius) in laboratory condition

Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) acts as a facultative hyperparasitoid of Gryon japonicum (Ashmead) (Hymenoptera: Platygastridae) sympatric parasitoid of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae). A longer period of host egg exploitation by both parasitoid species would be beneficial for O. nezarae, while G. japonicum tends to be successful when the parasitoids have only a short exploitation period. We demonstrated the interspecific competition by measuring parasitism in nine combinations of host densities (10, 20, and 40 eggs) and exploitation times (1, 3, and 5 days). To reflect the gregarious-solitary dichotomy of the two species, three O. nezarae and one G. japonicum mated females were compared in addition to a one-to-one competition design. We found that O. nezarae was the better competitor when exploitation time was longer than 1 day, irrespective of host density. Total parasitism rate and progeny emergence of O. nezarae were 1.6–2.8 and 4.7–7.3 times higher than for G. japonicum in three-to-one competition design, respectively. Although G. japonicum females were more effective in host finding (as shown by their higher per capita rate of parasitism when exploitation time was short), their progeny suffered high mortality from the larval interspecific competition inside multiparasitized host eggs. These results suggest that gregarious O. nezarae is the superior competitor when host eggs are available for longer period of time while solitary G. japonicum is superior when host resources are available for only a limited time.     

Niche partitioning and morphospace in early stages of two sympatric Diogenichthys species (Myctophidae)

Diet and morphospace of larval stages of two sympatric lanternfish Diogenichthys atlanticus and D. laternatus from the south-east Pacific Ocean were compared and the covariance between both variables was assessed for each species. Diogenichthys atlanticus stomach contents consisted mainly of copepod nauplii and digested remains and this species had a broader niche than D. laternatus, in which stomach contents were highly digested. No dietary overlap was found between both species. The covariance between skull shape and diet for D. atlanticus was given by a wider mouth gape related to the presence of copepod nauplii, whilst for D. laternatus, a shorter snout and posteriorly displaced eye were related to the presence of highly digested stomach contents. Interspecific differences between diets and skull shapes suggest that both species may have undergone morphological or niche divergence to avoid competition, such as feeding at different hours or depth stratification.     

Parallel occurrence of asynaptic sex chromosomes in gray voles (Microtus Schrank, 1798)

In many eutherian species, pairing and recombination of X and Y chromosomes are indispensable for normal meiotic progression and correct segregation of sex chromosomes. The rodent subfamily Arvicolinae provides an interesting exception. The majority of arvicoline species with asynaptic sex chromosomes belong to the genus Microtus sensu lato. However, some vole species of the genus Microtus and other genera display normal X-Y pairing in meiosis. These observations indicate that synaptic condition was typical for the common ancestor of all voles, but the gaps in taxonomic sampling makes impossible to identify a lineage or lineages, in which the asynapsis occurred. The methods of electron and fluorescent microscopy were used to study the synapsis of sex chromosomes in males of some additional species of the subfamily Arvicolinae. This extended taxonomic list allowed us to identify asynaptic species in every large lineage of the tribe Microtini. Apparently, the ability of sex chromosomes to pair and recombine in male meiosis was lost in arvicoline evolution for at least three times independently. Our results indirectly suggest the unnecessity of sex chromosome pairing in male meiosis of arvicoline rodents, and presence of alternate molecular mechanism of sex chromosome segregation in this large mammalian tribe.     

Thermoregulatory strategies in two closely related sympatric Scarabaeus species (Coleoptera: Scarabaeinae)

Abstract. The thermoregulation strategies of Scarabaeus sacer L. and Scarabaeus cicatricosus Lucas were studied in the Doñana National Park, Spain. In this area, both species coexist, showing the same habitat and food preferences. However, S. cicatricosus is active during warmer parts of the day compared to S. sacer. Both species thermoregulate their thoracic temperature but, whereas the abdomen of S. sacer is a passive thermal window, S. cicatricosus actively thermoregulates abdominal temperature by increasing heat transfer from the thorax to the abdomen at high T_a values. In the case of S. sacer, their endothermy indicates an adaptive capacity to thorax heat retention, as occurs mainly in winter‐flying insects. This mechanism, possibly related to the aerodynamic flight posture in Scarabaeinae, could be an effective barrier to retard the rate of abdominal heat loss during flight. This endothermic strategy makes flight difficult at higher temperatures, although it allows flight during cooler periods of the day. On the other hand, S. cicatricosus showed a different adaptive behaviour to S. sacer. In this case, a significant decrease in abdominal heat loss at higher ambient temperatures would indicate a decrease in heat transfer from the thorax to the abdomen, as occurs in some desert and semiarid insects. This ‘heat exchanger’ mechanism observed in S. cicatricosus could be due to the irregular posture adopted during flight, with the posterior legs clearly extended and separate from the body. This behaviour increases turbulence and convective cooling, favouring exposure of the soft abdominal tergal cuticle and, subsequently, water loss. Thus, for S. cicatricosus, the well‐adapted ‘heat exchanger’ permits flight during periods of the day when temperatures would possibly be lethal for those species with high endothermy. From an adaptive viewpoint, these mechanisms of thermoregulation may explain how both closely‐related sympatric species respond in different ways to environmental temperature, favouring their coexistence.     

Quaternary refugia in southwestern Iran: insights from two sympatric moth species (Insecta, Lepidoptera)

Alternating glacial and interglacial periods led to range shifts (contractions and expansions), persistence in distinct glacial refugia and extinction events in various temperate organisms. Today, the integrative analysis of molecular markers and spatial distribution models conducted for multiple taxa allows the detection of phylogeographical patterns, thus reconstructing major biogeographical events in their shared evolutionary history. In this study, the effects of past climate change on the evolutionary history of two sympatric moth species (Gnopharmia colchidaria s.l. and G. kasrunensis) and their host plants (Prunus scoparia and P. fenzliana) were inferred for the largely neglected biodiversity hot spot Iran. We complementarily analyzed the population structure of both moth species (187 specimens, based on COI) in congruence with batched species distribution models (SDMs) for all four taxa and for the times of the Last Glacial Maximum (21 ky BP), 6 ky BP and today. Coincidence of SDMs and the distribution of haplotype lineages indicated a shared refugium for the southwestern Zagros Mountains and potential species-specific refugial areas in the southern Caucasus and the Kope-Dagh Mountains. Both moth species experienced past population expansion.     

Locomotor activity patterns of two sympatric species Orchestia montagui and Orchestia gammarellus (Crustacea,Amphipoda)

Freshly adult individuals of two sympatric species, Orchestia gammarellus and Orchestia montagui, collected in spring from the supralittoral zone of Bizerte lagoon (Northern of Tunisia) at Menzel Jemil, were housed in a controlled environment cabinet. Locomotor activity rhythm was recorded in isolated individuals and groups by infrared actograph every 20 min by a data-logger, at a constant temperature of 18 ± 0.5 °C under constant darkness. According to double-plotted actograms and waveform curves, results showed the presence of two different locomotor patterns; in fact, individuals of O. gammarellus concentrated their activity during the hours of subjective night, whereas O. montagui were active during the subjective night and beyond the subjective dawn. Furthermore, whatever the species studied, periodogram analysis indicated a distinct circadian pattern of activity. Moreover, whatever the experiment condition is, the most clearly defined rhythms were found in O. gammarellus. In contrary to O. gammarellus, the group effect on the locomotor rhythm parameters seems to be less marked in O. montagui. On the other hand, a highly inter-individual variability was observed in the activity time for these two species and especially for O. montagui groups.