Purification and partial characterization of a midgut membrane-bound alpha-glucosidase from Quesada gigas (Hemiptera: Cicadidae)

Adults of Quesada gigas (Hemiptera: Cicadidae) have a major alpha-glucosidase bound to the perimicrovillar membranes, which are lipoprotein membranes that surround the midgut cell microvilli in Hemiptera and Thysanoptera. Determination of the spatial distribution of alpha-glucosidases in Q. gigas midgut showed that this activity is not equally distributed between soluble and membrane-bound isoforms. The major membrane-bound enzyme was solubilized in the detergent Triton X-100 and purified to homogeneity by means of gel filtration on Sephacryl S-100, and ion-exchange on High Q and Mono Q columns. The purified alpha-glucosidase is a protein with a pH optimum of 6.0 against the synthetic substrate p-nitrophenyl alpha-D-glucoside and M(r) of 61,000 (SDS-PAGE). Taking into account V(Max)/K(M) ratios, the enzyme is more active on maltose than sucrose and prefers oligomaltodextrins up to maltopentaose, with lower efficiency for longer chain maltodextrins. The Q gigas alpha-glucosidase was immunolocalized in perimicrovillar membranes by using a monospecific polyclonal antibody raised against the purified enzyme from Dysdercus peruvianus. The role of this enzyme in xylem fluid digestion and its possible involvement in osmoregulation is discussed. (C) 2009 Elsevier Inc. All rights reserved.

Cadmium, copper, mercury, and zinc concentrations in tissues of the King Crab (Pseudocarcinus gigas) from southeast Australian waters

The concentrations of cadmium, copper, mercury, and zinc were determined in muscle (body, claw, and leg), hepatopancreas, and gill tissues of Pseudocarcinus gigas, an exceptionally large, long-lived, and deep-dwelling crab species. The accumulation patterns observed are discussed in terms of both intra- and interspecies variations, with particular attention to the possible consequences of the extreme size and depth range of P. gigas. Metal concentrations did not depend significantly on sex of the crab. Significant differences between tissues were detected for all metals, and the distribution of metal between the tissues was different for each metal. Significant correlations were found between metal concentrations in the various tissues and crab size, and these are discussed and rationalised. The concentrations of mercury and zinc in muscle tissue increased with crab size and were high compared to other crab species. The concentrations of cadmium and copper present in edible tissues were not especially high compared to other crab species, but the concentration of cadmium in the hepatopancreas is of dietary concern.

Complete mitochondrial DNA sequences of the decapod crustaceans pseudocarcinus gigas (Menippidae) and macrobrachium rosenbergii (Palaemonidae)

The complete mitochondrial DNA sequence was determined for the Australian giant crab Pseudocarcinns gigas (Crustacea: Decapoda: Menippidae) and the giant freshwater shrimp Macrobrachium rosenbergii (Crustacea: Decapoda: Palaemonidae). The Pse gigas and Mrosenbergii mitochondrial genomes are circular molecules, 15,515 and 15,772 bp in length, respectively, and have the same gene composition as found in other metazoans. The gene arrangement of M. rosenbergii corresponds with that of the presumed ancestral arthropod gene order, represented by Limulus polyphemus, except for the position of the tRNA^Leu(UUR) gene. The Pse. gigas gene arrangement corresponds exactly with that reported for another brachyuran, Portunus trituberculatus, and differs from the M. rosenbergii gene order by only the position of the tRNA^His gene. Given the relative positions of intergenic nonoding nucleotides, the “duplication/random loss” model appears to be the most plausible mechanism for the translocation of this gene. These data represent the first caridean and only the second brachyuran complete mtDNA sequences, and a source of information that will facilitate surveys of intraspecific variation within these commercially important decapod species.

MtDNA diversity of the critically endangered Mekong giant catfish (Pangasianodon gigas Chevey, 1913) and closely related species : implications for conservation

Catfishes of the family Pangasiidae are an important group that contributes significantly to the fisheries of the Mekong River basin. In recent times the populations of several catfish species have declined, thought to be due to overfishing and habitat changes brought about by anthropogenic influences. The Mekong giant catfish Pangasianodon gigas Chevey, 1913 is listed as Critically Endangered on the IUCN Red List. In the present study, we assessed the level of genetic diversity of nine catfish species using sequences of the large subunit of mitochondrial DNA (16S rRNA). Approximately 570 base pairs (bp) were sequenced from 672 individuals of nine species. In all species studied, haplotype diversity and nucleotide diversity ranged from 0.118±0.101 to 0.667±0.141 and from 0.0002±0.0003 to 0.0016±0.0013, respectively. Four haplotypes were detected among 16 samples from natural populations of the critically endangered Mekong giant catfish. The results, in spite of the limited sample size for some species investigated, indicated that the level of genetic variation observed in wild populations of the Mekong giant catfish (haplotype diversity=0.350±0.148, nucleotide diversity=0.0009±0.0008) is commensurate with that of some other related species. This finding indicates that (1) wild populations of the Mekong giant catfish might be more robust than currently thought or (2) present wild populations of this species carry a genetic signature of the historically larger population(s). Findings from this study also have important implications for conservation of the Mekong giant catfish, especially in designing and implementing artificial breeding programme for restocking purposes.

A life history model for the giant crab Pseudocarcinus gigas

This study examined P. gigas populations from Cape Naturaliste (Western Australia) to Flinders Island (Tasmania), investigated reproduction, developed a unique tag to study their movement and growth, and collected new environmental information that allowed the development of a model of the life history for this iconic endemic Australian species.

Seasonal winds drive water temperature cycle and migration patterns of Southern Australian giant crab Pseudocarcinus gigas

The giant crab Pseudocarcinus gigas occurs along the continental shelf break of southern Australia. During the summer alongshore winds cause cooler water to upwell onto the shelf, and the crabs move from deeper water onto the shelf where there is more food. The combination of a preferred thermal niche and a depth-stratified food supply defines the favorable foraging environments that enhance the growth of P. gigas. Climate change is expected to cause a southerly shift of the austral subtropical high-pressure belt, and modelers have predicted more upwelling-favorable winds. The associated increase in the circulation of cooler water across the shelf is likely to provide P. gigas with an increased access to benthic food resources and their growth rate may increase in some regions.

Occurrence of Quesada gigas on Schizolobium amazonicum trees in Maranhão and Pará States, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Oviposition of Quesada gigas (Hemiptera: Cicadidae) in coffee plants

Branches of coffee-plant were collected in Sao Sebastiao do Paraiso County, Minas Gerais State, at the Experimental Station of the Agricultural Research Company (Empresa de Pesquisa Agropecuaria de Minas Gerais - EPAMIG), with the aim of studying various aspects of oviposition by Quesada gigas (Hemiptera: Cicadidae). The number of branches with Q. gigas egg nests was analyzed, as well as the number of nests per branch, the eggs per nest and the diameter of the egg nest location on the branch. The preference for oviposition either on alive or dry branches and the size of the egg were assessed. Egg-laying occurred only on dry branches. The mean of the branch diameter on which the egg nests occurred was 2.5 +/- 0.53 mm. The number of eggs per nest averaged 13.2 +/- 4.9, and the number of egg nests per branch was 2.2 +/- 1.74. The eggs were 1.9 +/- 0.08 mm long by 0.5 +/- 0.04 mm wide. The largest diameters of the branches containing egg nests were found on the upper third of the trees, as well as the greatest amount of branches with egg nests, of egg nests per branch and of eggs per nest. The correlation relationship between all of the experiment variables was positive.

Descrição das ninfas de Quesada gigas (Olivier) (Hemiptera: Cicadidae) associadas ao cafeeiro

Neste trabalho, as ninfas de Quesada gigas (Olivier) são descritas e ilustradas. Uma chave para o reconhecimento dos cinco ínstares ninfais é também apresentada. Foram analisados exemplares coletados em cafezais dos municípios de São Sebastião do Paraíso, Monte Santo de Minas e Patrimônio (Minas Gerais), Franca e Casa Branca (São Paulo). As amostras encontram-se preservadas em álcool a 80% e depositadas na Coleção Entomológica do Departamento de Fitossanidade da FCAV-UNESP, Câmpus de Jaboticabal. Os caracteres analisados foram: antenas, tecas alares, perna anterior, ápice da tíbia meso e metatorácicas e ápice abdominal do macho/fêmea. Foi adotada uma fórmula para indicar a configuração que é apresentada pelas estruturas presentes no fêmur anterior. Ninfas de Q. gigas de primeiro ínstar apresentam fórmula femoral 2-1-0, de segundo ínstar 2-1-3, de terceiro ínstar 2-1-5, de quarto ínstar 2-1-6 e as de quinto ínstar 2-2-8. O primeiro número refere-se à somatória dos dentes posteriores e dentes acessórios, o segundo ao número de dentes intermediários e o terceiro aos dentes do pente femoral. As estruturas apresentadas pelo fêmur protorácico constituem caracteres morfológicos adequados para a identificação dos ínstares ninfais de cigarras.

Seasonal variation of Hepatozoon spp. (Apicomplexa, Hepatozoidae) parasitemia from Boa constrictor amarali (Serpentes, Boidae) and Hydrodynastes gigas (Serpentes, Colubridae)

The aim of this study was to evaluate the parasitemia variation of three Hepatozoon species in Brazilian snakes. This study was conducted between 2001 and 2003 and included Hepatozoon terzii from Boa constrictor amarali, and Hepatozoon migonei and Hepatozoon cyclagrasi from Hydrodynastes gigas. It was observed that the parasitemia tended to decrease in all three Hepatozoon species but the parasites were not eliminated. This data suggest that Hepatozoon infection may be similar to Toxoplasma gondii infection, in that it persists throughout host life.

Salinity influences glutathione S-transferase activity and lipid peroxidation responses in the Crassostrea gigas oyster exposed to diesel oil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aspectos biológicos de Quesada gigas (Olivier, 1790) (Hemiptera: Cicadidae) em cafeeiro

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Distribuição espacial de Quesada gigas (Oliver, 1790) (Hemiptera: Cicadidae) na cultura do café

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Aspectos morfológicos dos aparelhos reprodutores, maturação de ovários e avaliação do desenvolvimento de ninfas de Quesada gigas (Olivier, 1790) (Hemíptera: Cicadidae) em relação a diferentes hospedeiros

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV