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484 results on '"Rebecchi, Lorena"'

156. Cryobiosis survival in tardigrades

Author

Bertolani, Roberto, Rebecchi, Lorena, Boschini, Deborah, and Guidetti, Roberto

Subjects
tardigrades, Cryobiosis, freezing experiment
Published
2006

158. What if the claws are reduced? Morphological and molecular phylogenetic relationships of the genus Haplomacrobiotus May, 1948 (Eutardigrada, Parachela).

Author

Cesari, Michele, Vecchi, Matteo, Palmer, Aparna, Bertolani, Roberto, Pilato, Giovanni, Rebecchi, Lorena, and Guidetti, Roberto

Subjects
TARDIGRADA, ANIMAL species, X-ray spectroscopy, ELECTRON microscopy
Abstract

Eutardigrada systematics relies mainly on the morphology of the sclerified structures of the animals. In particular, the main division of Parachela into four superfamilies relies heavily upon claw morphology; however, this character, alone, may be either inadequate or useless for tardigrades with no claws, or when secondary claw branches are reduced or absent, as in the case of species belonging to the genus Haplomacrobiotus. This is a very uncommon genus, so far reported only in North America. The systematic position of this genus has been debated since its description, having first been placed in the family Macrobiotidae (Macrobiotoidea) and then in the family Calohypsibiidae (Hypsibioidea). Currently, the position of the supposedly related genus Hexapodibius is still debated, being attributed to Isohypsibiidae (Isohypsibioidea) or to Calohypsibiidae (Hypsibioidea), i.e. to two different superfamilies. The morphological (light and electron microscopy), chemical (X-ray spectroscopy), and molecular ( 18S and 28S genes) analyses of a population of Haplomacrobiotus utahensis Pilato & Beasley, 2005 from Snow Canyon State Park (Utah, USA) allowed us to validate the position of this genus within Isohypsibioidea. Our integrated findings placed Haplomacrobiotus in a close relationship with the genus Hexapodibius, and allowed us to erect the new family Hexapodibiidae, comprising the genera Hexapodibius, Parhexapodibius, Haplomacrobiotus, and Haplohexapodibius. [ABSTRACT FROM AUTHOR]

Published
2016
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159. Interspecific relationships of tardigrades with bacteria, fungi and protozoans, with a focus on the phylogenetic position of Pyxidium tardigradum (Ciliophora).

Author

Vecchi, Matteo, Vicente, Filipe, Guidetti, Roberto, Bertolani, Roberto, Rebecchi, Lorena, and Cesari, Michele

Subjects
TARDIGRADA, ANIMAL populations, MICROORGANISMS, BIOMARKERS, LITERATURE reviews
Abstract

Symbiosis can be defined as an interaction between individuals of different biological species. Despite the small number of studies solely devoted to symbiotic interactions between tardigrades and micro-organisms (such as bacteria, fungi and protozoans), numerous reports can be found in the literature, especially as notes in faunal and alpha-taxonomy studies. Here, we review the literature and compile a list of the interactions between tardigrades and micro-organisms, excluding those that constitute food for tardigrades. Furthermore, a genetic study on a tardigrade symbiophoront, the ciliate Pyxidium tardigradum van der Land, 1964 was performed. There are a few records of P. tardigradum on both European and Asian tardigrades, but no morphological discrepancies among populations have been observed. We present here the phylogenetic positioning for P. tardigradum inferred by using nuclear ribosomal markers (18S and 5.8S). The phylogenetic trees showed all P. tardigradum specimens grouped together, and belonging to the family Operculariidae, order Operculariida. Moreover, a study based on the genetic distances between a Portuguese and an Irish population of P. tardigradum was performed using internal transcribed spacers ITS1 and ITS2. The ITS1 and ITS2 sequences showed differences between populations, leading us to hypothesize the presence of cryptic species. [ABSTRACT FROM AUTHOR]

Published
2016
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167. Tardigrada

Author

Rebecchi, Lorena, Guidi, A., and Bertolani, Roberto

Subjects
ultrastructures, tardigrada, male reproductive apparatus, spermatozoa
Published
2000

170. Tardigrada

Author

Bertolani, Roberto and Rebecchi, Lorena

Subjects
reproduction, germ cells, sex condition, fertilization, parental cares, Tadigrada, development
Published
1999

174. Front Matter

Author

Rebecchi, Lorena, primary, Nelson, Diane R., additional, Bertolani, Roberto, additional, and Fontoura, Paulo, additional

Published
2013
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183. Experiences with dormancy in tardigrades

Author

Bertolani, Roberto, Guidetti, Roberto, Jönsson, K. Ingemar, Altiero, Tiziana, Boschini, Deborah, Rebecchi, Lorena, Bertolani, Roberto, Guidetti, Roberto, Jönsson, K. Ingemar, Altiero, Tiziana, Boschini, Deborah, and Rebecchi, Lorena

Abstract

Tardigrades often colonise extreme habitats, in which they survive using both types of dormancy: quiescence and diapause. Together with nematodes and bdelloid rotifers, tardigrades are known to enter quiescence (with several forms of cryptobiosis: anhydrobiosis, cryobiosis, anoxybiosis, osmobiosis) at any stage of their life cycle, from egg to adult. Entering anhydrobiosis, tardigrades contract their body into a so-called tun, loosing most of their free and bound water (>95%), synthesizing cell protectants (e.g., trehalose, glycerol, heat shock proteins) and strongly reducing or suspending their metabolism. Our research on cryptobiosis focused on some ecological and evolutionary aspects. We evaluated: i) the long-term anhydrobiotic survival by comparing quantitative data on recovery from naturally induced desiccation in several species of tardigrades; ii) differences in survival patterns between species and populations by experimentally inducing anhydrobiosis and cryobiosis; iii) phenotypic factors affecting anhydrobiotic survival. As regards diapause, we considered encystment and eggs. Encystment involves at least the synthesis of new cuticular structures. Morphological changes during cyst formation are more complex than those involved in tun formation. We analyzed more in detail encystment processes, comparing a semiterrestrial with a limnic species. Several inter-specific differences have been identified, other than the production of two types of cysts in the semiterrestrial species. Our analysis of life history traits of a laboratory reared strain of a soil tardigrade revealed a particular hatching phenology that involved the production of both subitaneous and resting eggs. The latter need a cue to hatch (dehydration followed by re-hydration). In addition, the evolutionary meaning of dormancy in tardigrades is discussed

Published
2004
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197. Experimentally induced anhydrobiosis in the tardigrade Richtersius coronifer : phenotypic factors affecting survival

Author

Jönsson, K. Ingemar, Rebecchi, Lorena, Jönsson, K. Ingemar, and Rebecchi, Lorena

Abstract

The ability of some animal taxa (e.g., nematodes, rotifers, and tardigrades) to enter an ametabolic (cryptobiotic) state is well known. Nevertheless, the phenotypic factors affecting successful anhydrobiosis have rarely been investigated. We report a laboratory study on the effects of body size, reproductive condition, and energetic condition on anhydrobiotic survival in a population of the eutardigrade Richtersius coronifer. Body size and energetic condition interacted in affecting the probability of survival, while reproductive condition had no effect. Large tardigrades had a lower probability of survival than medium-sized tardigrades and showed a positive response in survival to energetic condition. This suggests that energy constrained the possibility for large tardigrades toenter and to leave anhydrobiosis. As a possible alternative explanation for low survival in the largest specimens we discuss the expression of senescence. In line with the view that processes related to anhydrobiosis are connected with energetic costs we documented a decrease in the size of storage cells over a period of anhydrobiosis, showing for the first time that energy is consumed in the process of anhydrobiosis in tardigrades.

Published
2002
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