Genetic population structure of the German cockroach, Blattella germanica: Absence of geographical variation

The genetic structure of 31 populations of the German cockroach, Blattella germanica (L.), located in two French cities 900 km apart, was estimated by enzyme gel electrophoresis. A set of 41 loci was analysed. Eight loci (4 Est, 3 Lap and 1 Got) were polymorphic. Diversity was estimated at different geographical levels: the overall population, between cities and within a city. Hierarchical F-statistics indicated significant genetic differentiation between all populations and among populations within each city, but no differentiation between cities. F_ST values for populations within each city and for the overall sample were substantially dissimilar. In addition, a cluster analysis did not separate populations according to their geographical origin but according to the predominance of either of the two alternative Est-4 alleles. The results of this analysis point to the absence of genetic differentiation on a large geographical scale: no large-scale geographical distance effect was detected. However, we evidenced strong genetic substructuring on a local scale, within cities.     

Comparisons of morphology and esterase levels between Blattella germanica and Blattella nipponica (Blattodea: Blattellidae)

The habitat of the cockroach varies by species. The German cockroach, Blattella germanica, lives in human dwellings, while the Japanese field roach, Blattella nipponica, lives in a mountainous region. Based on phylogenetic analysis of mtCOI, the two species are closely related to each other and B. germanica is divergent from wild species such as B. nipponica. Their habitats and walking speed differ even though the two species have similar morphology. We hypothesized that habitats might influence walking speed by changes to appendage morphology and enzyme‐based physiological differences. We compared the length of the appendages and differences in a multifunctional enzyme superfamily, the esterases (EST, EC 3.1), including acetylcholinesterase (AChE, EC 3.1.1.7), which is related to central nervous system function. We found that phenotypes such as appendage length and esterase isozyme expression were clearly different between the two species. These differences might be responsible for the observed difference in walking speed.     

Testing German shepherd puppies to assess their chances of certification

Behavioral activity of 7-week-old German shepherd puppies was tested and the activities analyzed if they could be used for predicting police efficiency of the individual. In total 206 individuals sired by 42 sires and 44 dams were used. The activities were divided into 10 tasks in which reactions and behavior of pups were scored from 0 to 5 points. All pups were tested separately from other conspecifics. Probability that the puppy will pass the certification was tested by a logistic regression. Of the 206 puppies, 148 passed the certification while 58 failed. Some tested behavioral variables were moderately to highly correlated with one another. Therefore we applied a factor analysis. Three factors were retained accounting for 100% of the shared variance. After inspection of the rotated factor pattern matrix and its confidence intervals, it appeared that variables “Independent movement and interactions with the tester”, “Negotiating obstacles”, “Entering a room”, “Behavior toward a person”, and “Behavior in new environments” loaded on Factor 1 (“Factor for movement”), while variables “Response to distracting stimuli caused by a shovel”, “Response to a distracting noise while left alone in a room”, and “Response to loud distracting stimuli” on Factor 2 (“Factor for responding to noise”) and variables “Retrieval” and “Tug of war” on Factor 3 (“Factor for attitude to predation”). In the final logistic regression model, the probability that the puppy will pass the certification depended on the higher weight at the time of testing (, P = 0.0005), on the “Factor for attitude to predation” (, P = 0.0007), on the “Factor for responding to noise”, where the higher the score, the weaker was the response (, P = 0.0232), and on the “Factor for movement” showing an increasing probability with decreasing score (, P = 0.0219). The tests in our study seem to be a good base which might enable selection for suitable dogs as early as 7 weeks of age. The puppies having high probability to pass certification in adulthood were heavy individuals willing to chase, catch, and fetch a tennis ball, and follow a rag drawn away from them, while weakly responding to a distracting noise in various situations and showing low activity while negotiating obstacles and moving and interacting with the tester. To conclude, contrary to skeptical assumptions expressed by various authors, the specific puppy tests for police dogs provide a reliable tool for predicting future service ability of a puppy. Differences in methodology are likely to contribute to a lack of consensus among various studies.     

Reactivity of German Cockroach Allergen, Bla g 2, Peptide Fragments to IgE Antibodies in Patients' Sera

Bla g 2 is a cockroach allergen of great importance. This study was conducted to identify IgE-binding epitope(s) of Bla g 2 using the recombinant protein technique. Approximately 50% of tested sera showed IgE reactivity to Pichia-expressed Bla g 2 (PrBla g 2) and E. coli-expressed Bla g 2 (ErBla g 2). Only 5.3% of serum samples showed stronger reactivity to PrBla g 2 than ErBla g 2, indicating that serum was reactive to conformational or carbohydrate epitopes. The full-length and 5 peptide fragments of Bla g 2 were produced in E. coli. All fragments showed IgE-binding activity to the cockroach-allergy patients'' sera. Specifically, peptide fragments of amino acid residue 1-75 and 146-225 appeared to be important for IgE-binding. The information about the IgE-binding epitope of Bla g 2 can aid in the diagnosis and treatment for cockroach allergies.     

Adaptive radiation within New Zealand endemic species of the cockroach genus Celatoblatta Johns (Blattidae): a response to Plio-Pleistocene mountain building and climate change

The South Island of New Zealand offers unique opportunities to study insect evolution due to long-term physical isolation, recent alpine habitats and high levels of biotic endemism. Using DNA sequence data from cytochrome oxidase subunit 1, we investigated the phylogeographical pattern among 10 endemic cockroach species within the genus Celatoblatta Johns (Blattidae). We tested the hypothesis that an ancestral cockroach species underwent rapid speciation in response to major climatic differentiation induced by mountain building. Results suggest that speciation was a twofold process, with an interspecific radiation of Pliocene/Pleistocene age followed by intraspecific diversification during the mid Pleistocene. Average genetic distance (maximum likelihood GTR + I + Gamma) was 9.17%, with a maximum of 14.5%. Data revealed eight deep well-supported branches, each with terminal clades. Six clades were differentiated according to morphological species, while the seventh was composed of three sympatric species. We consider the latter to be a phylogenetic species, possibly as a result of hybridization within a defined geographical area. This finding seriously challenges species distinctions for these three cockroach species. Correlation between genetic distances and a Climate Similarity Index (CSI) was negative, suggesting that species found in similar habitats are also genetically closely related. A Mantel test on within-clade genetic distances vs. linear geographical distance was positive, suggesting allopatric isolation for those haplotypes. We present a model of speciation for South Island Celatoblatta.     

Effect of carbon dioxide on the Oriental cockroach Blatta orientalis

Exposure to high concentrations of carbon dioxide (CO2) killed adult and nymphal stages of the oriental cockroach Blatta orientalis L. (Dictyoptera: Blattidae) with LT50 values of 11.5-16.2 h for 60% CO2 in air and 5.7-7.1 h for 100% CO2 at 20 degrees C; corresponding LT50s at 28 degrees C were 2.8-4.6 h for 60% CO2 in air and 2.3-3.6 h for 100% CO2. Complete kill of mobile stages was obtained within 24 h using 60% CO2 at 20 degrees C. Survivors of treatments with 100% CO2 at 28 degrees C remained completely paralysed for up to 3 days post-treatment and took up to 5 days to regain normal movement, but adult females then resumed production of oothecae with no significant loss in fecundity. Oothecae 5 or 30 days after deposition required 60-84 h exposure to 60% CO2 at 20 degrees C to prevent emergence of nymphs but less time using 100% CO2 at 28 degrees C. At 28 degrees C, when adult females were treated with 100% CO2 and 52% r.h. for 6 h (giving 100% mortality) loss of weight was significantly greater than that following treatment with air at 52% r.h. for 6 h (giving no mortality). However, significantly greater weight loss also occurred when they were treated with dried air (< 10% r.h.) for 6 h, also with no mortality. The toxicity of CO2 to mobile stages of the oriental cockroach appeared to result from irreversible effects on the nervous system, rather than from water loss during exposure.     

Learning from history: morphology's challenges in Germany ca. 1900

A century ago, Carl Gegenbaur's program of vertebrate evolutionary morphology faced its greatest challenges. The controversy over the evolutionary origin of the vertebrate paired limbs between 1875 and 1906 illustrates the failure of the traditional methods of comparative anatomy and embryology (supported by Haeckel's biogenetic law) to choose between different phylogenetic hypotheses. The controversy over morphology's status as science intensified at the turn of the twentieth century, when the legitimacy of historical explanation itself as a mode of scientific understanding came under fire. Gegenbaur's intellectual grandson, Hermann Braus, sought to defend the legitimacy of phylogenetic reconstruction while updating it to include experimental and causal-analytical approaches, but was unable to sustain a viable synthetic research program. The article concludes with reflections on approaches to the past used by historians and evolutionary morphologists.     

Fatty acyl-CoA elongation in Blatella germanica integumental microsomes

Insect cuticular hydrocarbons are synthesized de novo in integumental tissue through the concerted action of fatty acid synthases (FASs), fatty acyl-CoA elongases, a reductase, and a decarboxylase to produce hydrocarbons and CO2. Elongation of fatty acyl-CoAs to very long chain fatty acids was studied in the integumental microsomes of the German cockroach, Blatella germanica. Incubation of [1-14C]palmitoyl-CoA, malonyl-CoA, and NADPH resulted in the production of 18-CoA with minor amounts of C20, C22, C24, C30, and C32 labeled acyl-CoA moieties. Similar experiments with [1-14C]stearoyl-CoA rendered C20-CoA as the major product, and lesser amounts of C22 and C24-CoAs were also detected. After solubilization of the microsomal FAS, kinetic parameters were determined radiochemically or by measuring NADPH consumption. The reaction velocity was linear for up to 3 min incubation time, and with a protein concentration up to 0.025 microg/microl. The effect of the chain length on the reaction velocity was compared for palmitoyl-CoA, stearoyl-CoA, and eicosanoyl-CoA. The optimal substrate concentration was 10 microM for C16-CoA, between 8 and 12 microM for C18-CoA, and close to 3 microM for C20-CoA. In vivo hydrocarbon biosynthesis was inhibited from 55.5 to 72.5% in the presence of 1 mM trichloroacetic acid, a known inhibitor of elongation reactions.     

The mechanism and modes of inhibition of arginine kinase from the cockroach (Periplaneta americana)

The kinetic mechanism and evaluation of several potential inhibitors of purified arginine kinase from the cockroach (Periplanta americana) were investigated. This monomeric phosphagen kinase is important in maintaining ATP levels during the rapid energy demands of muscle required for contraction and motility. Analysis reveals the following dissociation constants (mM) for the binary complex: E.Arg P-->E+Arg P, K=1.0; E.Arg-->E+Arg, K=0.45; E.MgATP-->E+MgATP, K=0.17; E.MgADP-->E+MgADP, K=0.12; and the ternary complex: Arg P.E.MgADP-->E.MgADP+Arg P, K=0.94; Arg.E.MgATP-->E.MgATP+Arg, K=0.49; MgATP.Enz.Arg-->E.Arg+MgATP, K=0.14; MgADP.E.Arg P-->E.Arg P+MgADP, K=0.09. For a particular substrate, the ratio of the dissociation constants for the binary to ternary complex is close to one, indicating little, if any, cooperativity in substrate binding for the rapid equilibrium, random addition mechanism. The time course of the arginine kinase reaction exhibits a pronounced curvature, which, as described for enzyme from other sources, is attributed to formation of an inhibitory catalytic dead-end complex, MgADP.E.Arg. The curvature is accentuated by the addition of monovalent anions, including borate, thiocyanate, and, most notably, nitrite and nitrate. This effect is attributed to stabilization of the dead-end complex through formation of a transition state analog. However, the substantial decrease in initial velocity (92%) caused by nitrate is due to an additional inhibitory effect, further characterized as non-competitive inhibition (Ki=8.0 mM) with the substrate L-arginine. On the other hand, borate inhibition of the initial velocity is only 30% with significant subsequent curvature, suggesting that this anion functions as an inhibitor mainly by formation of a transition state analog. However, some component of the borate inhibition appears to be mediated by an apparent partial competitive inhibition with L-arginine. D-arginine is not a substrate for arginine kinase from the cockroach, but is an effective competitive inhibitor with a Ki=0.31 mM. L-Canavanine is a weak substrate for arginine kinase (Km=6.7 mM) with a Vmax for the pure enzyme that is approximately one-third that of L-arginine. However, initial velocity experiments of substrate mixtures suggest that competition between L-canavanine and L-arginine may not be a simple summation effect and may involve a structural modification. Sensitivity of arginine kinase activity to D-arginine as well as nitrate and borate anions, coupled with the fact that L-arginine is an essential amino acid for the cockroach, suggest that arginine kinase could be a useful chemotherapeutic target for the control of cockroach proliferation.     

Evidence for cocladogenesis between diverse dictyopteran lineages and their intracellular endosymbionts

Bacteria of the genus Blattabacterium are intracellular symbionts that reside in specialized cells of cockroaches and the termite Mastotermes darwiniensis. They appear to be obligate mutualists, and are transmitted vertically in the eggs. Such characteristics are expected to lead to equivalent phylogenies for host and symbiont, and we tested this hypothesis using recently accumulated data on relationships among termites and cockroaches and their Blattabacterium spp. Host and symbiont topologies were found to be highly similar, and various tests indicated that they were not statistically different. A close relationship between endosymbionts from termites and members of the wood-feeding cockroach genus Cryptocercus was found, supporting the hypothesis that the former evolved from subsocial, wood-dwelling cockroaches. The majority of the Blattabacterium spp. sequences appear to have undergone similar rates of evolution since their divergence from a common ancestor, and an estimate of this rate was determined based on early Cretaceous host fossils. The results support the idea that the stem group of modern cockroaches radiated sometime between the late Jurassic and early Cretaceous-not the Carboniferous, as has been suggested on the basis of roach-like fossils from this epoch.