An evaluation of lekking behavior in the fiddler crab Uca spp

The reproductive behavior of Uca spp. has been extensively studied, especially the relationships between the dimorphically enlarged male claw and reproductive success. In contrast, little is known about the apparent congregations of adult males in marsh areas lacking vegetative cover where they engage in behaviors thought to attract mates. Similar congregations and displays in avian and mammalian species are termed 'leks.' In order to test the hypothesis that open-area assemblages of Uca spp. are functioning as leks, we examined the sex ratios, juvenile/adult ratios, and the percentage of time that adult males spend eliciting reproductive behaviors within open and vegetated areas of marsh habitats. Moreover, to evaluate whether differences in sediment-based food resources could explain open-area aggregations, we compared substratum organic content of open and vegetated areas of marsh habitats. Substrate was also examined to determine if grain size composition varied between open and vegetated areas and might preclude the construction of breeding burrows in vegetated areas of the marsh. Three species of Uca from four marsh habitats in biogeographically distinct regions of North America were sampled including Dauphin Island, Alabama, Hunting Island, South Carolina, Saxis, Virginia, and Wallops Island, Virginia. Comparisons of male/female and juvenile/adult ratio means indicated that greater numbers of adult males occurred in open areas of all marshes. In addition, adult males allocated significantly greater time to reproductive behaviors in open rather than in vegetatively covered areas across-all biogeographic regions and among all species. Food levels (sediment organic content) in open areas were equal to or less than sediment organic contents in vegetated areas in marsh habitats at Dauphin Island and Hunting Island, the two marshes where the variable was examined. Similarly, substratum granulometry analysis revealed no significant differences between open and vegetatively covered areas of the marshes at Dauphin Island or Hunting Island that might influence choice of burrow location. Collectively, these observations support the hypothesis that lek behavior is an integral component of the reproductive repertoire in Uca spp.     

Delayed courtship in the fiddler crab Uca musica terpsichores

Courting male fiddler crabs of the species Uca musica terpsichores congregate in the upper central portion of the colony, while receptive females leave their burrows located at the colony's periphery and wander among the communally displaying males prior to choosing a mate. I observed that courting males in a newly-established population were significantly smaller than courting males in large high-density colonies. This observation led to a series of translocation experiments designed to ascertain whether high population density influences the size (=age) at which males begin to court. Smaller courting males from a low-density population failed to court after being placed among larger courting males in a high-density population. The reciprocal translocation revealed that smaller noncourting males from the high-density population would start courting shortly after being placed in a low-density population. Smaller males placed in the high-density population were subsequently observed significantly further away from where they were initially placed than were larger males similarly translocated. The results suggest that smaller males delay courtship activities once they are forced, via encounters with larger males, to the periphery of the colony. I believe that both intrasexual selection (competition from larger males) and intersexual selection (female choice of large males) are responsible for the delay in male courtship activities.     

Visual shape discrimination in the fiddler crab,Uca pugilator

1. Research into the visual shape discrimination abilities of compound‐eyed animals has almost exclusively been limited to insects, the crustaceans having been virtually ignored. The two groups have many dissimilarities, having primarily adapted in different habitats to different lifestyles. Differences may exist in visual systems and visually mediated behavior.

2. Fiddler crabs (Uca pugilator), without training, differentially approached dissimilar silhouettes presented simultaneously, demonstrating visual discrimination between stationary, geometric shapes of equal‐area. The strength of response was ordered hierarchically: vertical rectangle, horizontal rectangle, triangle, square, circle.

3. Basic geometric shapes were used to facilitate replication and comparison with research findings from other species.

     

Genetic diversity in lac resin-secreting insects belonging to Kerria spp., as revealed through ISSR markers

The Indian lac insect Kerria lacca is harnessed in India for commercial production of lac, which has diversified industrial applications. Many of the geographical races of this species are under threat of extinction due to increasingly drastic local deviations in climate patterns. Thus, there is need for documentation and conservation of the lac insect biodiversity adapted especially for local climatic conditions and host species. The genetic diversity among twenty lines of commercially important Kerria spp. was analyzed using Inter-Simple Sequence Repeat (ISSR) technique. Seventeen ISSR primers produced 96.1% genetic polymorphism in the lac insect lines under study. The clustering dendrogram segregated the twenty lines into four major clusters with similarity coefficients between 0.25 and 0.81. The first three principal coordinates revealed 43.1% of the total genetic variation. The above results reveal significant genetic variability in the lines, which could be used for genetic improvement of lac insects.     

Behavioural evidence for body colour signaling in the fiddler crab Uca perplexa (Brachyura: Ocypodidae)

In the reproductive season, mature females of the fiddler crab Uca perplexa leave their burrows and wander about their habitat for mating. To clarify whether the fiddler crabs respond to colour or luminosity, I examined the behavioural responses of the males to the wandering females before and after the females were painted white, red, black or blue. The behaviours of the males were categorized into three types: lateral–circular wave and lateral–straight wave for courting, and repelling. Before painting, almost all of the males courted the females. After painting, significantly fewer males courted the red-, black- and blue-painted females than courted the white-painted females. These results mean that the fiddler crabs can discriminate colours or luminosity. The role of body colour as a visual signal in crab society is discussed.     

Neurosecretion in the sinus gland of the fiddler crab,Uca pugnax

The ultrastructure of the sinus gland of the fiddler crab, Uca pugnax, was investigated and found to be similar to that in other crustaceans. Five types of neurosecretory axon terminals were tentatively identified on the basis of the size, shape, and electron density of granules within the axons. Release of neuro-secretory material appears to be by exocytosis.     

Candidatus Monilibacter spp., common bulking filaments in activated sludge, are members of Cluster III Defluviicoccus

Two alphaproteobacterial Neisser negative ‘Nostocoida limicola’ morphotypes differing slightly in their trichome diameter and filament regularity were dominant populations in the Bendigo, Victoria, Australia activated sludge community removing phosphorus (P). Neither responded to the FISH probes available for any of the other alphaproteobacterial ‘N. limicola’ morphotypes. Instead both fluoresced with the DF988 FISH probe designed originally to target alphaproteobacterial cluster II Defluviicoccus tetrad forming organisms. A 16S rRNA based clone library from this biomass revealed that the alphaproteobacterial clones grouped closely with Candidatus ‘Monilibacter batavus’ and Defluviicoccus clones in a cluster separate from the existing cluster I and II Defluviicoccus. When a FISH probe was designed against these, it only hybridized to the thinner and less abundant ‘N. limicola’ morphotype. Micromanipulation–RT-PCR was used to selectively recover the main ‘N. limicola’ morphotype and a FISH probe designed against the 16S rRNA clones generated from it showed only this filament fluoresced. From FISH based surveys, both ‘N. limicola’ variants occurred frequently in phosphorus removal activated sludge systems in Australia treating domestic waste. The data suggest that they represent two new strains of Candidatus ‘Monilibacter’, which on this evidence are filamentous members of the genus Defluviicoccus, a potential competitor for the polyphosphate accumulating organisms in these communities.     

Antimicrobial resistance in Staphylococcus spp., Escherichia coli and Enterococcus spp. in dogs given antibiotics for chronic dermatological disorders, compared with non-treated control dogs

   

The aim of this study was to evaluate antimicrobial resistance in canine staphylococci, Escherichia coli and enterococci, which were isolated from 22 dogs with pyoderma and a history of previous antibiotic treatment, compared to bacterial isolates from 56 non-treated control dogs. Two isolates of each bacterial species per dog were investigated, if detected. Staphylococcal isolates from dogs with pyoderma (35 isolates) were more resistant to sulphatrimethoprim than the isolates from controls (56 isolates) (57% vs. 25%, p < 0.004). Multiresistance in staphylococci was also more common in dogs with pyoderma (29% vs. 9%, p = 0.02). A similar trend among isolates of E. coli was detected (24 and 74 isolates from treated and control dogs, respectively), but the differences were not significant. Resistance for macrolide-lincosamides was approximately 20% among staphylococci in both groups. Resistance to ampicillin among enterococci was 4%–7%. The age of the dogs might have an impact on resistance: multiresistance among staphylococcal isolates from younger dogs (≤5 years) was more common than in older dogs (≥6 years) (24%, vs. 0%, 63 and 27 isolates, respectively, p = 0.02). Staphylococci in younger dogs were more resistant to tetracycline (48% vs. 11%, p < 0.001) and sulphatrimethoprim (48% vs. 15%, p < 0.01) than those in older dogs. In contrast, the isolates of E. coli from older dogs tended to be more resistant, although a significant difference was detected only in resistance to tetracycline (13% vs. 2% of 40 and 50 isolates respecthely, p = 0.04)). The results of this small study indicate that resistance in canine staphylococci in the capital area of Finland is comparable with many other countries in Europe. Resistance in indicator bacteria, E. coli and enterococci, was low.     

RXR isoforms and endogenous retinoids in the fiddler crab, Uca pugilator

The pleiotropic effects of circulating ecdysteroids in the adult fiddler crab, Uca pugilator, during molting, regeneration, and reproduction are mediated by a limited number of receptor proteins. We hypothesize that hormonal effects in vivo may be the result of complex interactions between at least two receptor heterodimer conformations that differentially respond to multiple ecdysteroid/retinoid signals. Two splicing variants of the fiddler crab retinoid-X-receptor (UpRXR) differ from one another by the addition of a 33 amino acid insert in the ligand-binding domain. We show here that the ecdysteroid receptor in the fiddler crab (UpEcR) behaves differently depending upon the UpRXR isoform with which it is partnered. The two UpRXR variant partners for UpEcR confer slightly different responses in the binding of Ponasterone A (PA)—a naturally occurring ecdysteroid in the blood of Uca. UpRXR can bind 9-cis retinoic acid (9cRA) as well as terpenoids. 9cRA and the naturally occurring terpenoid, methyl farnesoate, influence the binding of PA to UpEcR/UpRXR dimers. Endogenous retinoids are found in the blastema of regenerating limbs of Uca and they (plus blood-borne terpenoids) may add additional levels of differential response by target tissues. Thus, the two sets of heterodimers tested here may represent different dynamic complexes whose properties are defined by the specific heterodimeric subunits involved and the specific ligands available.     

The evolution of waving displays in fiddler crabs (Uca spp., Crustacea: Ocypodidae)

Male fiddler crabs are commonly recognized by the presence of a single massive claw used in a variety of contexts, including territorial defence, agonistic interactions, and courtship behaviour. The most common behavioural context involving these enlarged chelipeds is their use in waving displays, which are remarkably diverse among species. Although the waving display is one of the most obvious behavioural features of male fiddler crabs, little is known about their main evolutionary trends during the diversification of the genus. The present study employed phylogenetic comparative methods to investigate the evolution of waving behaviour in a sample of 19 species of Uca from Central and North America. Digital recordings were used to quantify the temporal dynamics of waving behaviour in each species. Multivariate ordination methods were used to assess whether different elements of the display showed distinct evolutionary dynamics, particularly with respect to body size and the environment where species are most commonly found. Most of the interspecific variation in displays involves differences in the overall waving velocity, with no correspondence to their local environments, nor their body size. Interestingly, despite the strong concentration of variance in the first two ordination axes, there was no statistically significant evidence for phylogenetic signals in their respective scores. These results suggest that the overall structure of waving displays is evolutionarily labile, at the same time as being concentrated in a few particular axes of variation, possibly indicating evolution along lines of least resistance. The approach employed in the present study highlights the utility of phylogenetic comparative methods for elucidating the evolution of complex behavioural characteristics, such as the waving display in male fiddler crabs. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 307–315.