Analysis of the heterochromatin of <Emphasis Type="Italic">Cebus</Emphasis> (Primates,Platyrrhini) by micro-FISH and banding pattern comparisons

The karyotype of the neotropical primate genus Cebus (Platyrrhini: Cebidae), considered the most ancestral one, shows the greatest amount of heterochromatin described among Platyrrhini genera. Banding techniques and restriction enzyme digestion have previously revealed great variability of quantity and composition of heterochromatin in this genus. In this context, we use fluorescence in situ hybridization (FISH) to analyse this genomic region and discuss its possible role in the diversification of Cebus. We used a heterochromatin probe for chromosome 11 of Cebus libidinosus (11qHe+ CLI probe), obtained by chromosome microdissection. Twenty-six specimens belonging to the families Atelidae, Cebidae, Callitrichidae and Pithecidae (Platyrrhini) were studied. Fourteen out of 26 specimens were Cebus (Cebidae) individuals of C. libidinosus, C. xanthosternos, C. apella, C. nigritus, C. albifrons, C. kaapori and C. olivaceus. In Cebus specimens, we found 6 to 22 positive signals located in interstitial and telomeric positions along the different species. No hybridization signal was observed among the remaining Ceboidea species, thus reinforcing the idea of a Cebus-specific heterochromatin composed of a complex system of repetitive sequences.     

Characterization of the orchid bee Euglossa viridissima (Apidae: Euglossini) and a novel cryptic sibling species,by morphological,chemical, and genetic characters

In orchid bees, males signal their availability as mates by fanning ‘perfumes’, i.e. blends of volatiles that are collected from environmental sources and stored in hind leg pouches. The chemical composition of such perfumes in males with either two or three mandibular teeth has previously led to the discovery of two sympatric, cryptic lineages within Euglossa viridissima Friese on the Yucatan peninsula, Mexico. Here, we combine chemical, morphological, and genetic data for an integrated characterization of the two lineages. The lectotype of E. viridissima Friese in the Museum of Natural History in Vienna has two mandibular teeth, and the species name viridissima must thus be assigned to the predominantly bidentate lineage, whereas the completely tridentate lineage is described as a novel species, Euglossa dilemma sp. nov. Bembé & Eltz. Chemical profiling and microsatellite genotyping revealed that E. viridissima males can occasionally (～10% of individuals) express a third mandibular tooth, but this tooth is not positioned centrally on the mandible as in E. dilemma, but is displaced towards the tip. Thus, males of the two lineages can be unambiguously diagnosed by mandibular characters alone. Based on 889 bp of CO1 sequence data, we confirm that E. viridissima and E. dilemma constitute a monophyletic group within the genus Euglossa. However, CO1 alone failed to separate these two lineages due to the lack of parsimony‐informative sites. Both species occur in broad sympatry across Central America, but the orchid bees recently introduced to Florida have three mandibular teeth in males, i.e. belong to E. dilemma. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1064–1076.     

Sexual dimorphism and interpopulation differences in lizard hind limb length: locomotor performance or chemical signalling?

Intraspecific variation in morphology has often been related to fitness differences through its effects on performance. In lizards, variation in hind limb length can be shaped by natural selection for increased locomotor performance, sexual selection on the number or size of femoral pores involved in chemical signalling, or both. Here, we analyse the selective forces involved in sexual dimorphism and differences in hind limb length between two populations of Psammodromus algirus living at different elevation. Males were more robust and had longer hind limbs and limb segments than females, and low‐elevation lizards had longer limbs than high‐elevation lizards. However, differences in locomotor performance were small and non‐significant, making natural selection for faster runs an unlikely explanation for the observed pattern. On the other hand, males had more femoral pores than females, and lizards had more pores at lower elevation, although the difference was significant only for males (which invest more in chemical signalling). In males, the number of pores, which remains constant along a lizard's life, was not correlated with hind limb length. However, femur length was positively correlated with mean pore size, allowing low‐elevation males to have larger than expected pores, which could increase the effectiveness with which they spread their signals in a dry and warm habitat where chemicals become volatile rapidly. Also, saturation of the sexual coloration of the head was higher for low‐elevation males, suggesting that sexual selection pressures may be more intense. Overall, our results indicate that sexual selection plays a significant role in shaping intraspecific variation in hind limb length. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 318–329.     

Brood parasitism is associated with increased bacterial contamination of host eggs: bacterial loads of host and parasitic eggs

Factors related to bacterial environment of nests are of primary interest for understanding the causes of embryo infection and the evolution of antimicrobial defensive traits in birds. Nest visitors such as parasites could act as vectors for bacteria and/or affect the hygienic conditions of nests and hence influence the nest bacterial environment. In the present study, we explored some predictions of this hypothetical scenario in the great spotted cuckoo (Clamator glandarius)–magpie (Pica pica) system of brood parasitism. Great spotted cuckoos visit the nests of their magpie hosts and frequently damage some of the host eggs when laying eggs or on subsequent visits. Therefore, it represents a good system for testing the effect of nest visitors on the bacterial environment of nests. In accordance with this hypothesis, we found that the bacterial load of magpie eggshells was greater in parasitized nests, which may suggest that brood parasitism increases the probability of bacterial infection of magpie eggs. Moreover, comparisons of bacterial loads of cuckoo and magpie eggs revealed that: (1) cuckoo eggshells harboured lower bacterial densities than those of their magpie hosts in the same nests and (2) the prevalence of bacteria inside unhatched eggs was higher for magpies than for great spotted cuckoos. These interspecific differences were predicted because brood parasitic eggs (but not host eggs) always experience the bacterial environments of parasitized nests. Therefore, the results obtained in the present study suggest that parasitic eggs are better adapted to environments with a high risk of bacterial contamination than those of their magpie hosts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 836–848.     

Parthenogenesis did not consistently evolve in insular populations of Ischnura hastata (Odonata,Coenagrionidae)

1. The evolutionary advantages that have driven the evolution of sex are still very much debated, and a number of benefits of parthenogenesis over sexual reproduction have been proposed. In particular, parthenogenetic individuals are thought to exhibit higher probabilities of establishment following arrival in new, isolated habitats such as islands. 2. One notable example of parthenogenesis occurring in islands is the damselfly Ischnura hastata, an American species that has colonised the Azores archipelago, where the populations consist only of females. This is the only known example of parthenogenesis within the insect order Odonata. 3. Here, two island populations of I. hastata were studied, one in the Galapagos and one in Cuba, to test whether island colonisation is consistently associated with parthenogenesis in this species. Field capture–mark–recapture studies and laboratory rearing of field‐collected eggs were undertaken in both areas. 4. Sex ratios in the field were found to be heavily female‐biased among mature individuals; however, fertility rates of field‐collected eggs were high, and the sex ratios in the laboratory did not differ from 1 : 1. Data from laboratory rearing showed that shorter larval development times and shorter adult life spans in males result in protandry, which might explain the skewed sex ratios in the field. 5. These findings are consistent with sex differences in key demographic parameters which could predispose I. hastata to parthenogenesis. However, the Azores population of I. hastata remains the only documented case of asexual reproduction in this insect group.     

Comparative analysis of overwintering physiology in nine species of semi‐aquatic bugs (Heteroptera: Gerromorpha)

In semi‐aquatic bugs (Heteroptera: Gerromorpha), the strategies of overwintering in a cryothermic state (i.e. at body temperatures below the equilibrium freezing point) remain largely unexplored. The present study provides an analysis of the ecophysiological aspects of overwintering in nine gerromorphan species. All nine species avoid ice formation by means of a more or less extensive supercooling of their body fluids. There is a tight correlation between the supercooling point (SCP) and the lower lethal temperature. Different species use different physiological adjustments to increase the likelihood of survival in a supercooled state. These include stabilization of the supercooled state by active antifreeze factors that cause thermal hysteresis between equilibrium melting and freezing points, the accumulation of low‐molecular weight sugars and polyols with putative cryoprotective functions, or by having a relatively high body fluid osmolality, combined with a low level of hydration. The majority of species under study overwinter only as adults, whereas Velia caprai Tamanini can overwinter either as an adult or in the egg stage. The supercooling capacity of V. caprai adults is insufficient to prevent the risk of lethal freezing. The adults therefore survive only opportunistically in suitable microhabitats, and/or during mild winters. The survival of V. caprai in winter is assured by extensive supercooling and having overwintering eggs that are highly cold tolerant.     

New piophilid in town: the first Palaearctic record of Piophila megastigmata and its coexistence with Piophila casei in central Spain

The genus Piophila Fallén (Diptera: Piophilidae) is known from only two species: Piophila casei (L.) is a major pest, a cosmopolitan species and is commonly used as a forensic indicator, whereas Piophila megastigmata McAlpine has until now only been recorded in a natural environment in South Africa. The present work reports the first occurrence of P. megastigmata in the Palaearctic region from specimens collected by carrion‐baited traps throughout different natural habitats of central Spain. Furthermore, the species was also collected with P. casei on corpses of domestic pigs used in a carrion succession study in a periurban habitat in central Spain. Both species occurred on carrion in different seasons, but P. megastigmata was more abundant than P. casei in autumn, arriving earlier at the carcasses and persisting for a longer period. The contrary pattern was observed in spring. The presence of P. megastigmata in different localities in central Spain and its coexistence with P. casei in a periurban habitat make it a potentially useful new tool for legal medicine in Europe; thus this species must be considered in forensic entomology studies.     

Optimization of the coating of octyl-CALB with ionic polymers to improve stability and decrease enzyme leakage

Abstract

Lipase B from Candida antarctica (CALB) immobilized on octyl-agarose (OC) was submitted to coating with polyethylenimine (PEI) and dextran sulfate (DS). Using lowly loaded enzyme preparations, the properties of OC-CALB preparations hardly improved, suggesting too large the distance between enzyme molecules. However, using OC-CALB preparations with maximum loading, CALB stability was greatly improved in different conditions after PEI coating. Moreover, the CALB release from the OC support in the presence of detergents, or during thermal or organic solvent inactivations was greatly reduced after this treatment (PEI plus DS coating). The results pointed that the main positive effect of this coating could be derived from the physical intermolecular crosslinking of the CALB molecules with the polymers that reduce the enzyme desorption from the support. The coating of OC-CALB-PEI with DS only produced a minimal improvement on enzyme performance. Even though the enzyme release was much more difficult after physical crosslinking, all enzyme molecules could be released from the OC support combining an ionic detergent (SDS), high buffer concentration, pH 3 and 45?°C, while using the OC-CALB just 2% SDS at pH 7 and 25?°C was enough to release all enzyme. The support could be reused several cycles. Thus, this strategy permitted to greatly reduce the enzyme desorption during operation and to improve enzyme stability while keeping the enzyme immobilization reversibility.