The management of metabolic energy storage during the life cycle of mayflies: a comparative field investigation of the collector-gatherer <Emphasis Type="Italic">Ephemera danica</Emphasis> and the scraper <Emphasis Type="Italic">Rhithrogena semicolorata</Emphasis>

The concentration and seasonal dynamics of the major energy storage components, triglycerides and glycogen, were measured in two species of mayfly (Rhithrogena semicolorata and Ephemera danica) with contrasting life cycle strategies living in a small mountain stream. E. danica is a burrowing, semivoltine collector-gatherer; R. semicolorata is univoltine and scrapes periphyton from stones. This is the first publication which focuses on the role of metabolic energy sources during the larval life span of two mayfly species until the larvae emerge. Although triglycerides are the major energy reserve in both species (>84% of total energy storage) throughout the whole larval development their seasonal dynamic differed considerably. In R. semicolorata the triglyceride concentration declined during the last weeks prior to emergence in both sexes. The same pattern was found in female larvae of E. danica, but not in male E. danica. It is suggested that females use triglycerides in the last larval stages for egg maturation, which is completed in the last larval instar. In male E. danica the triglyceride concentrations remained high until emergence, presumably due to their high energy demands as adults for their swarming flights. Glycogen concentrations did not show such a difference between species and sexes. Its significance as a storage substrate for energy is rather low; however, concentrations decreased in both species and sexes prior to emergence.     

Cannibalistic behaviour of the vulnerable and endemic Baetica ustulata (Rambur 1838) (Orthoptera: Tettigoniidae: Ephippigerinae): first report

Little is known about the biology of the vulnerable and endemic Orthoptera Baetica ustulata. Here, we describe for the first time a case of cannibalism in this species. Cannibalism across Orthoptera is well documented and is mainly associated with swarming behaviour, which is absent in B. ustulata. Given that Ephippigerinae produce the largest spermatophylax across tettigonids, cannibalism in this katydid may represent a major resource of specific nutrients for producing an optimal nuptial gift in its difficult and hostile habitat.     

Male induction and function of workers' excitability during swarming in leaf-cutting ants (Atta and Acromyrmex) (Hymenoptera,Formicidae)

Worker excitation in species of Atta and Acromyrmex prior to and during the swarming of reproductives is initiated by secretions from the male mandibular glands. During this phase, workers are highly aggressive, attacking all foreign objects. Field data suggest that this behavior is not only advantageous in protecting sexuals as they swarm, but also to prime workers to execute queens trying to initiate colonies near mature colonies following nuptial flights.     

Comparison of the life cycles of two sympatric estuarine polychaetes, Hediste diadroma and H. atoka (Polychaeta: Nereididae), in the Nanakita River estuary, northeastern Japan

The life cycles of two species of estuarine polychaetes, Hediste diadroma and H. atoka, were investigated using field surveys and colonization experiments in the Nanakita River estuary, Japan. Lactate dehydrogenase (LDH) allozyme banding patterns in starch gel electrophoresis were used to distinguish between the species. We found differences in the life cycle, reproductive ecology, and distribution of the two polychaetes. H. diadroma exhibited conspicuous reproductive swarming behavior during the spring tide in April to early May. After hatching, the trochophore larvae may be transported out to sea and return to the river estuary at the =3-setiger stage. By late July, juveniles settled into brackish water, where they completed the 1-year life span. In contrast, H. atoka never exhibited this conspicuous reproductive swarming behavior. The reproductive period of this species spanned most of the year, except winter. H. atoka juveniles hatched mainly as 3-setiger nectochaetes, which immediately became benthic. The juveniles actively dispersed during the 4-to 7-setiger stage, although they could also do so at any later stage. The life span of H. atoka was about 6 months. In small river estuaries, river flooding may flush sediment and benthic animals out to sea and create vacant habitats for colonization by polychaetes. In the Nanakita River estuary, H. atoka maintained a large and stable population in Gamo Lagoon, located 250m upstream from the river mouth, whereas H. diadroma was rarely found there. Swimming excursions of juvenile H. atoka at any stage in the life cycle may ensure its distribution to new vacant habitats, and its life-cycle characteristics may allow large populations to build rapidly. As a result, H. atoka was able to maintain dominance in both the river and the lagoon in the Nanakita River estuary.     

POPULATION STRUCTURE,LOCAL MATE COMPETITION,AND SEX-ALLOCATION PATTERN IN THE ANT MESSOR ACICULATUS

Population-genetic structure and sex-allocation ratios were investigated for the ant Messor aciculatus, a species that conducts mass nuptial flights. An electrophoretic survey on two polymorphic loci revealed excessive homozygosities in two populations. Because inbreeding inside nests does not occur, the heterozygote deficiency may result from population subdivision rather than assortative inbreeding during nuptial flights. Assuming no inbreeding, a simulation based on the observed genotype distribution in the study site suggested that, on average, a breeding swarm consists of alates from only 1.7 colonies. This population genetic structure seems to cause local mate competition (LMC), a factor that can shift population sex ratio toward females. The sex-allocation ratio to males in the population (0.166 ± 0.030; mean ± SE) was significantly female biased and lower than the expected optima for queens (0.5) and for workers (0.25) without LMC. Sex-ratio variability among colonies was explained by a pattern of constant male investment, which is predictable assuming LMC. Thus, the study provides the first evidence of LMC in ants with mass nuptial flights and contradicts previous assumptions about breeding structure in swarming ants. The results suggest that LMC can affect sex-allocation patterns for ant colonies and populations.     

A CtrA homolog affects swarming motility and encystment in <Emphasis Type="Italic">Rhodospirillum centenum</Emphasis>

The α-proteobacterium, Rhodospirillum centenum, has a complex life cycle that allows adaptation to different environments. Transitions between vegetative swim cell and swarmer cell types depend on whether the organism is growing in liquid surroundings or on a solid substrate. Moreover, starvation can induce vegetative cells to differentiate into quiescent cysts. This paper describes the results of our investigation into the role of a putative DNA-binding response regulator that is homologous to CtrA, the cell cycle regulator from Caulobacter crescentus. Deletion of ctrA from the R. centenum genome resulted in a viable strain with impaired swarming motility coupled with an increased tendency to form cysts. Conversely, overexpression of wild type CtrA or a phosphomimetic allele, CtrAD51E, suppressed cyst cell formation, whereas overexpression of a CtrAD51A allele failed to suppress encystment but did prevent swarming motility. Thus, we propose that CtrA participates within a two-component signal transduction pathway that promotes swarming motility while contributing to the suppression of cyst cell formation.     

Two putative histidine kinases are required for cyst formation in <Emphasis Type="Italic">Rhodospirillum Centenum</Emphasis>

The photosynthetic bacterium, Rhodospirillum centenum, has a flexible life cycle that permits it to survive starvation as dormant cyst cells. Previous studies have identified some of the key regulators for encystment and demonstrated that the control of development is intricate. This complexity may arise from the need to integrate several environmental signals to mediate a switch from one mode of energy metabolism to another and to ensure that a transition to dormancy is initiated only when necessary. We searched for additional regulators of development by screening for encystment deficient strains after subjecting wild type R. centenum to mini-Tn5 mutagenesis. Analysis of “hypo-cyst” strains led to the identification of two genes that encode putative hybrid histidine kinases (cyd1 and cyd2). Cells with deletions of either gene fail to form cysts under conditions that normally induce development. Furthermore, the deletion strains exhibit altered swarming behavior suggesting that Cyd1 and Cyd2 affect behaviors utilized when the organism is attached to a substrate.     

中国林蛙婚垫的显微结构变化及其与睾酮的关系

用光镜观察中国林蛙（Rana chensinensis）婚垫显微结构的年周期变化,并对婚垫内的睾酮（T）和雄激素受体（AR）进行免疫细胞化学检测,其结果表明：婚刺的形成是由生发细胞增生、颗粒细胞数量增多和体积增大所致,其消退是由角质细胞包裹的颗粒细胞小体脱落所致。婚腺发育与婚刺形成同步,在林蛙婚配期间婚腺的分泌活动最旺盛。T和AR在颗粒细胞、生发细胞和婚腺内的分布与婚垫显微结构的变化周期一致,说明婚垫的形成与消退受T调控。婚垫发育的变化剧期与精子发生进程和精巢系数具相关性,即婚垫的形态特征可间接反应精巢的发育状况．     

Long‐term monitoring of the life history of a riverine mayfly Ephemera orientalis (Ephemeroptera: Ephemeridae) in the Han River in Seoul,Korea

Climatic change often affects life history aspects of aquatic insects. Long‐term monitoring was conducted to understand the life history variability of the riverine mayfly Ephemera orientalis in the Han river, where habitat is largely disturbed by summer floods. Water level of the study site, Godeok‐dong area in Seoul, is regulated by the Paldang Dam located approximately 14 km above the study site. E. orientalis often emerged in large numbers around the study area. Larvae were sampled monthly from April 2006 to July 2010 using a Surber sampler (50 × 50 cm, mesh 0.25 mm, two replicates). Additional qualitative sampling was conducted using a hand net. As a result, based on the larval body size distribution, E. orientalis had a univoltine life cycle with two distinct slow growing cohort groups: the S1group emerged during May–June and the S2 group emerged during August–September. Our previous study conducted in Gapyeong stream in Gyeonggi‐do showed that E. orientalis normally had three cohort groups, S‐1 and S‐2 groups and the F‐group (a fast growing cohort developed during May–August). However, the Han River population of E. orientalis lacked such a fast growing cohort. It is most probable that habitat disturbances caused by high water level during the rainy season negatively affected the development of the fast growing cohort (F‐group) in the Han River area. The relationships between monthly E. orientalis population data and water level in the Han River are presented.     

Zooplankton swarms: characteristics,proximal cues and proposed advantages

This review focuses on monospecific swarms of four taxonomic groups of small crustaceans: three groups are marine copepods: oithonids (Oithona and Dioithona), Acartia species and Calanus species; and the fourth group includes freshwater cladoceran species in the Order Anomopoda. For each of these groups there is a substantial literature on swarming behavior from field studies and laboratory experiments. Swarming characteristics of each taxonomic group are reviewed, proximal cues for swarming are described, comparisons are made for proposed advantages of swarming, and future research directions are suggested. Swarming characteristics of Calanus spp. are distinctly different from those of the smaller crustaceans: the oithonids, acartiids and cladocerans. In a conceptual model proposed for the smaller crustaceans, swarming behavior is affected by their interactions with light cues, water currents and turbulence, behavior of their predators and prey, and abundance of other trophic levels.     

Non-random Mating in the Dance Fly Empis borealis: The Importance of Male Choice

In the dance-fly Empis borealis (Diptera, Empididae), females form swarms to which males, carrying a nuptial gift, come for mating. We examined whether males or females were choosy and/or competed for mates. First, measurements of the size relationships between copulating males and females, nuptial gifts and the swarming females from different swarms were assessed. Second, male visiting time in differently sized female swarms was recorded. Larger (wing-length) females participated disproportionately in copulations in each swarm, but not for the population at large. Female mating status (virgin/non-virgin) or proximity to oviposition (egg size) did not influence the likelihood of copulation. No assortative mating pattern was found: male size and size of nuptial gift did not correlate with size of the mating female. The time spent by males in swarms increased with the number of females present and it took longer when males left a swarm without copulation than when doing so. Male visiting time per female was negatively correlated with number of females in swarms. Males more often left smaller than larger swarms without mating. We conclude that E. borealis males discriminate among females but find no evidence for male competition or for female choice. It is still a question to what degree females compete for males.     

Partial Proteome of the Corynetoxin‐Producing Gram‐Positive Bacterium,Rathayibacter toxicus

Rathayibacter toxicus is a Gram‐positive bacterium that is the causative agent of annual ryegrass toxicity (ARGT), a disease that causes devastating losses in the Australian livestock industry. R. toxicus exhibits a complex life cycle, using the nematode Anguina funesta as a physical vector to carry it up to the seed head of the host plant. ARGT is caused by a tunicamycin‐like corynetoxin that is produced in R. toxicus‐infected seed galls. We analyzed protein expression in R. toxicus under stationary growth phase conditions to obtain a more complete understanding of the biology of this organism and identify potential targets for immunoassay development. A total of 323 unique proteins were identified, including those with putative roles in secondary metabolism and pathogenicity. The proteome analysis for this complex phytopathogenic Gram‐positive bacterium will facilitate in the characterization of proteins necessary for host colonization and toxin production, and assist in the development of diagnostic assays. Data are available via ProteomeXchange with identifier PXD004238.     

Factors affecting post-flight behavior in primary reproductives of the Formosan subterranean termite, Coptotermes formosanus (Isoptera: Rhinotermitidae)

After swarming, reproductive dealates of the Formosan subterranean termite, Coptotermes formosanus, run together in tandem. The tandem running is an age-related behavioral activity in C. formosanus. This behavior was not evoked in pre-flight alates less than 6-d-old that were artificially dealated. Female age was more important than male age for evoking tandem behavior. Females and males, older than 35 days, did not exhibit this behavior. Mating status was not important for female and male dealates to form the tandem pairs. The titers of the major tergal gland component, trilinolein, did not decline significantly and remained high, not only in virgin females, but also in mated females for a period of time after swarming. On the other hand, increasing amounts of the female-specific compound trilinolein were detected in male dealates 7, 14, and 42 days after pairing. This suggests that trilinolein in the females might be transferred to the males as a nuptial gift in C. formosanus. In addition, females have structurally different lateral setae that may constitute a morphological factor involved in the tandem behavior in this species. Covering the setae with dimethyl sulfoxide prevented the tandem behavior.     

Limits to Nuptial Gift Production by Male Fireflies, Photinus ignitus

Males of diverse insect species provide females with nuptial gifts, and limits on males' ability to produce these gifts may influence courtship behavior and mating systems. In the firefly Photinus ignitus, males transfer a complex spermatophore to females during mating. We provided firefly males unlimited access to responsive females to examine whether spermatophore production limits male mating success. Male spermatophore mass decreased significantly across sequential matings, and the percentage of successful matings declined during the second half of each male's life span. Male body mass explained a significant proportion of variation in size of the first spermatophore produced by P. ignitus males, but this relationship disappeared with second spermatophores. This study indicates that males' ability to produce spermatophores declines over their lifetime and that limits on nuptial giftproduction can constrain male mating success in Photinus fireflies.     

INTEGRATING PHYLOGENY AND EXPERIMENTAL ETHOLOGY: FROM PATTERN TO PROCEs

Phylogenetic systematics offers ethologists a method for uncovering macroevolutionary patterns of behavioral diversity, which can be used to generate predictions for experimental investigation of microevolutionary processes. I used phylogenetic methods to disentangle the contributions of various selection pressures in the evolution of sexually dimorphic nuptial coloration in gasterosteid fishes in general, and Gasterosteus aculeatus in particular. Based upon the phylogenetic relationships between breeding colors and breeding behaviors in the gasterosteids, three predictions relevant to a discussion of nuptial coloration in G. aculeatus were proposed. The origin and elaboration of nuptial coloration was (1) weakly associated with male/male interactions (intrasexual selection), (2) moderately associated with parental care (natural selection) and (3) strongly associated with male/female interactions (intersexual selection). I tested the hypothesized macroevolutionary relationships between male breeding color and behavior in two sets of experiments studying changes in male nuptial coloration across the breeding cycle and female choice based on intensity of male color. The results of these experiments at the microevolutionary level of analysis corroborated the macroevolutionary predictions and confirmed the original intuition of previous researchers: male body color intensity is an important component of female mate choice in G. aculeatus. This study demonstrates that a phylogenetic hypothesis can generate predictions that are experimentally testable and falsifiable.     

Phospholipid composition and pheromonal activity of nuptial secretion of the male German cockroach, Blattella germanica

As a part of the sequential courtship behavior of the German cockroach, Blattella germanica, females feed on the nuptial secretion from the male tergal glands. The pheromonal secretion, consisting mainly of oligosaccharides and phospholipids, strongly elicits a feeding response in virgin females. The phospholipids were composed of phosphatidylethanolamine and phosphatidylcholine. Their fatty acid compositions were determined by chromatographic and enzymatic methods. Although an authentic blend of phospholipids (1,2-dioleoylphosphatidylethanolamine and 1,2-dioleoylphosphatidylcholine) showed a marginal phagostimulant activity, addition of the blend to an authentic blend of oligosaccharides (maltose and maltotriose) strongly enhanced the activity to nearly the level of the crude extract. These results indicate that the nuptial feeding behavior is elicited by a synergistic action between phospholipids and oligosaccharides.     

Resource Level Affects Relative Performance of the Two Motility Systems of Myxococcus xanthus

The adventurous (A) and social (S) motility systems of the microbial predator Myxococcus xanthus show differential swarming performance on distinct surface types. Under standard laboratory conditions, A-motility performs well on hard agar but poorly on soft agar, whereas the inverse pattern is shown by S-motility. These properties may allow M. xanthus to swarm effectively across a greater diversity of natural surfaces than would be possible with one motility system alone. Nonetheless, the range of ecological conditions under which dual motility enhances effective swarming across distinct surfaces and how ecological parameters affect the complementarity of A-motility and S-motility remain unclear. Here we have examined the role of nutrient concentration in determining swarming patterns driven by dual motility on distinct agar surfaces, as well as the relative contributions of A-motility and S-motility to these patterns. Swarm expansion rates of dually motile (A⁺S⁺), solely A-motile (A⁺S⁻), and solely S-motile (A⁻S⁺) strains were compared on hard and soft agar across a wide range of casitone concentrations. At low casitone concentrations (0–0.1%), swarming on soft agar driven by S-motility is very poor, and is significantly slower than swarming on hard agar driven by A-motility. This reverses at high casitone concentration (1–3.2%) such that swarming on soft agar is much faster than swarming on hard agar. This pattern greatly constrained the ability of M. xanthus to encounter patches of prey bacteria on a soft agar surface when nutrient levels between the patches were low. The swarming patterns of a strain that is unable to produce extracellular fibrils indicate that these appendages are responsible for the elevated swarming of S-motility at high resource levels. Together, these data suggest that large contributions by S-motility to predatory swarming in natural soils may be limited to soft, wet, high-nutrient conditions that may be uncommon. Several likely benefits of S-motility to the M. xanthus life cycle are discussed, including synergistic interactions with A-motility across a wide variety of conditions.     

Swarming populations of<Emphasis Type="Italic">Salmonella</Emphasis> represent a unique physiological state coupled to multiple mechanisms of antibiotic resistance

Salmonella enterica serovar Typhimurium is capable of swarming over semi-solid surfaces. Although its swarming behavior shares many readily observable similarities with other swarming bacteria, the phenomenon remains somewhat of an enigma in this bacterium since some attributes skew away from the better characterized systems. Swarming is quite distinct from the classic swimming motility, as there is a prerequisite for cells to first undergo a morphological transformation into swarmer cells. In some organisms, swarming is controlled by quorum sensing, and in others, swarming has been shown to be coupled to increased expression of important virulence factors. Swarming in serovar Typhimurium is coupled to elevated resistance to a wide variety of structurally and functionally distinct classes of antimicrobial compounds. As serovar Typhimurium differentiates into swarm cells, thepmrHFIJKLM operon is up-regulated, resulting in a more positively charged LPS core. Furthermore, as swarm cells begin to de-differentiate, thepmr operon expression is down-regulated, rapidly reaching the levels observed in swim cells. This is one potential mechanism which confers swarm cells increased resistance to antibiotics such as the cationic antimicrobial peptides. However, additional mechanisms are likely associated with the cells in the swarm state that confer elevated resistance to such a broad spectrum of antimicrobial agents. Published: September 26, 2003     

Cryptic lineages of a common alpine mayfly show strong life‐history divergence

Understanding ecological divergence of morphologically similar but genetically distinct species – previously considered as a single morphospecies – is of key importance in evolutionary ecology and conservation biology. Despite their morphological similarity, cryptic species may have evolved distinct adaptations. If such ecological divergence is unaccounted for, any predictions about their responses to environmental change and biodiversity loss may be biased. We used spatio‐temporally replicated field surveys of larval cohort structure and population genetic analyses (using nuclear microsatellite markers) to test for life‐history divergence between two cryptic lineages of the alpine mayfly Baetis alpinus in the Swiss Alps. We found that the more widespread and abundant cryptic lineage represents a ‘generalist’ with at least two cohorts per year, whereas the less abundant lineage is restricted to higher elevations and represents a ‘specialist’ with a single cohort per year. Importantly, our results indicate partial temporal segregation in reproductive periods between these lineages, potentially facilitating local coexistence and reproductive isolation. Taken together, our findings emphasize the need for a taxonomic revision: widespread and apparently generalist morphospecies can hide cryptic lineages with much narrower ecological niches and distribution ranges.