Search results for "crab"
showing 10 items of 65 documents
Isotopic Niche and Trophic Position of the Invasive Portunid Portunus segnis Forskål, (1775) in Elounda Bay (Crete Island, Eastern Mediterranean)
2022
There is a growing recognition that an advanced understanding of the trophic characteristics of an invasive consumer can provide important information on its ecological impact. In recent years, the blue swimming crab Portunus segnis, one of the earliest Lessepsian invaders, has considerably expanded its distribution range in the Mediterranean Sea, yet, its trophic habits in invaded areas remain scarcely investigated. In this study, we used carbon and nitrogen stable isotopes analysis (SIA) to determine the trophic position and isotopic niche of the crab compared with other representatives of the flora and fauna occurring in Elounda Bay (Crete). P. segnis showed a trophic position of 3.9, hi…
Behavioral responses of the parasitoid Melittobia digitata to volatiles emitted by its natural and laboratory hosts
2010
Responses of macropterous females of the ectoparasitoid Melittobia digitata Dahms (Hymenoptera: Eulophidae) to direct and indirect cues emitted by its natural hosts as well as laboratory hosts were investigated using a Y-tube olfactometer. To locate the nest ofmud dauber wasps, Trypoxylon politum Say (Hymenoptera: Crabronidae), and one of their inquilines, Anthrax spec., parasitoids exploit volatiles from the freshly built nest mud and the empty cocoon constructed by the wasps, as well as their meconium. However, the parasitoids did not respond to odors emitted by older nest mud or by the host stages that are attacked (T. politum prepupae and Anthrax spec. larvae). Melittobia digitata was n…
The first confirmed record of the Atlantic blue crab Callinectes sapidus Rathbun, 1896 (Decapoda, Brachyura) from Maltese waters
2022
The invasive portunid species Callinectes sapidus is hereby recorded for the first time from Maltese waters, thus updating the known distribution of this decapod of Atlantic origin within the Mediterranean. Potential introduction pathways of the species to Maltese waters are discussed.
Evaluating the quality of the Mexican fruit-fly, Anastrepha ludens, as host for the parasitoid Melittobia digitata
2013
We investigated the presence of Melittobia digitata (Hymenoptera: Eulophidae) and its associations with its natural hosts in Veracruz, Mexico. The parasitoid was confirmed to be present and found to attack prepupae of Trypoxylon and Sceliphron (Hymenoptera: Crabronidae and Sphecidae, respectively) mud daubers as well as pupae of the Mexican fruit fly Anastrepha ludens (Diptera: Tephritidae). Since A. ludens is a very important pest of citrus and mango in Mexico and Central America, we evaluated, in laboratory experiments, the quality of A. ludens as host of M. digitata comparing the development of the parasitoid in another unrelated fly species (Sarcophaga [Neobellieria] bullata) (Diptera: …
Xanthine oxidase catalyzes the oxidation of retinol.
2007
In mammals, xanthine oxidase (E.C. 1.17.3.2) catalyzes the hydroxylation of a wide variety of heterocyclic substrates such as purines, pyrimidines, and pterins, in addition to aldehydes [1] as all-trans-retinaldehyde [2-5]. Here, we show that buttermilk xanthine oxidase was capable to oxidizing all-trans-retinol (t-ROL) to all-trans-retinaldehyde (t-RAL) that was successively oxidized to all-trans-retinoic acid (t-RA). A rise in the enzyme activity, when t-ROL-CRBP complex was assayed, with respect to the free t-ROL, was observed. Furthermore, treatment of the enzyme with Na2S and glutathione resulted in a significant increment in catalytic activity toward t-ROL and t-RAL, due to the recons…
The diversity and evolution of chelicerate hemocyanins
2012
Abstract Background Oxygen transport in the hemolymph of many arthropod species is facilitated by large copper-proteins referred to as hemocyanins. Arthropod hemocyanins are hexamers or oligomers of hexamers, which are characterized by a high O2 transport capacity and a high cooperativity, thereby enhancing O2 supply. Hemocyanin subunit sequences had been available from horseshoe crabs (Xiphosura) and various spiders (Araneae), but not from any other chelicerate taxon. To trace the evolution of hemocyanins and the emergence of the large hemocyanin oligomers, hemocyanin cDNA sequences were obtained from representatives of selected chelicerate classes. Results Hemocyanin subunits from a sea s…
The INTEGRAL/SPI response and the Crab observations
2004
The Crab region was observed several times by INTEGRAL for calibration purposes. This paper aims at underlining the systematic interactions between (i) observations of this reference source, (ii) in-flight calibration of the instrumental response and (iii) the development and validation of the analysis tools of the SPI spectrometer. It first describes the way the response is produced and how studies of the Crab spectrum lead to improvements and corrections in the initial response. Then, we present the tools which were developed to extract spectra from the SPI observation data and finally a Crab spectrum obtained with one of these methods, to show the agreement with previous experiments. We …
Modalités fonctionnelles et évolutives des parasitoses développées par les crabes Pinnotheridae aux dépens des échinides fouisseurs
2010
Ce travail s’est intéressé aux liens existant entre la stratégie d’exploitation développée par un crustacé ectoparasite et son comportement reproductif. Le crabe Pinnotheridae Dissodactylusprimitivus exploite deux espèces Spatangidae vivant dans la Mer des Caraïbes, Meomaventricosa et Plagiobrissus grandis. Des approches comportementales, démographiques etgénétiques ont été adoptées afin de mettre en lumière le fonctionnement et la biologie de cettesymbiose. Par son comportement alimentaire, le crabe occasionne des lésions tégumentairessur ses hôtes. Celles-ci affectent la fitness de M. ventricosa, au travers de son développementgonadique. Dissodactylus primitivus exploite ses deux espèces …
Molecular Structure of the Arthropod Hemocyanins
1992
Hemocyanin is an extracellular, blue protein that occurs in high concentrations in the blood of many arthropods, including spiders, scorpions, horseshoe crabs, crustaceans, and at least two centipedes. Serving as an ### oxygen carrier, it is functionally equivalent to hemoglobin, but performs reversible oxygen binding between two copper ions. Hemocyanin is composed of a number of subunits that assemble in an extremely large macro-molecular entity. These particles, which are similar in size to viruses or ribosomes, exhibit a complex allosteric behavior during oxygen binding. There is growing evidence that this functional plasticity has evolved upon, and answers to, ecophysiological constrain…
The size and shape of shells used by hermit crabs: A multivariate analysis of Clibanarius erythropus
2009
Shell attributes such as weight and shape affect the reproduction, growth, predator avoidance and behaviour of several hermit crab species. Although the importance of these attributes has been extensively investigated, it is still difficult to assess the relative role of size and shape. Multivariate techniques allow concise and efficient quantitative analysis of these multidimensional properties, and this paper aims to understand their role in determining patterns of hermit crab shell use. To this end, a multivariate approach based on a combination of size-unconstrained (shape) PCA and RDA ordination was used to model the biometrics of southern Mediterranean Clibanarius erythropus populatio…