Topic
Oniscus
About: Oniscus is a research topic. Over the lifetime, 27 publications have been published within this topic receiving 394 citations.
Papers
TL;DR: The ability to evaporate water rapidly, and thus to cool the body, may be of survival value when woodlice are exposed to high temperatures for short periods, particularly in littoral forms which may well have been intermediate in the evolution of terricolous from maricolous isopods.
Abstract: 1. Measurements by means of thermocouples, accurate to 0.1°C., were made of the body temperature of the woodlice Armadillidium, Porcellio, Oniscus and Ligia , and of the cockroach Blatta , both alive and dead, in a stream of saturated or dry air at both 20 and 37°C. 2. No difference in temperature depression was found between living and dead woodlice, and in all the animals used there was, after equilibration, no difference greater than 0.1°C. between the air temperature and body temperature if the air were saturated with water vapour. 3. In dry air, the body temperature of all the animals except Ligia settled down after at most 25 min. to a steady temperature which was lower than that of the surrounding air. The body temperature of Ligia continued to rise slowly for at least 2 hr., though remaining well below that of the environment. 4. After 30 min. in dry air at 20 and 37°C. respectively, mean temperature depressions (of at least three readings at each temperature for each species) were, in degrees centigrade: Ligia , 2.6 and 6.8; Oniscus , 1.5 and 2.7; Parcellio , 0.4 and 1.3; Armadillidium , 0.5 and 1.8; and the cockroach Blatta , 0.7 and 2.4. The order of the species in this respect is substantially the same as their order in respect of evaporation rate, which was established previously. 5. Certain anomalies which appear when these figures are compared with previously established figures for insects are probably the result of differences in permeability of the integument and in the site of water loss. The ability to evaporate water rapidly, and thus to cool the body, may be of survival value when woodlice are exposed to high temperatures for short periods, particularly in littoral forms which may well have been intermediate in the evolution of terricolous from maricolous isopods.
40 citations
TL;DR: The view that H. searlei is of terrestrial ancestry and that its forbears were physiologically preadapted for life in inland salt lakes is upheld.
Abstract: The results of field and laboratory investigations concerning the biology of Haloniscus searlei Chilton (Crustacea: Isopoda: Oniscoidea) are reported and discussed. It occurs in Victoria, Tasmania, South Australia, and Western Australia, where, although belonging to the almost exclusively terrestrial Oniscidae, it lives only in inland salt lakes; from these it has been collected at salinities from 8 to 159‰. Breeding females occur throughout the year, but are most abundant in summer. The life-cycle conforms to the typical isopodan pattern. Laboratory investigations provided upper and lower L.D.50 values for salinity with acclimation of 159 and < 1‰ and without acclimation of 118 and 4‰. In resistance to desiccation, H. searlei does not seem to be significantly different from terrestrial isopods, and in air its survival is a matter of hours. Its degree of cuticular impermeability places it between Oniscus and Porcellio in the following series of genera with increasing impermeability: Ligia < Philoscia < Oniscus < Haloniscus < Porcellio < Armadillidium. The pleopods display no modifications for terrestrial breathing. The view that H. searlei is of terrestrial ancestry and that its forbears were physiologically preadapted for life in inland salt lakes is upheld.
31 citations
TL;DR: In this paper, the authors used morphometric analyses performed in univariate (Dice-Leraas diagrams) and multivariate (size-free principal component analysis) approaches, along with qualitative analysis, as well as information on the karyology, to make an assessment on the status of populations of the genus Hylaeamys in the Atlantic Forest.
Abstract: Seven species are included in the genus Hylaeamys. Their limits and distribution, however, are uncertain. We used morphometric analyses performed in univariate (Dice–Leraas diagrams) and multivariate (size-free principal component analysis) approaches, along with qualitative analysis, as well as information on the karyology, to make an assessment on the status of populations of the genus in the Atlantic Forest. On the basis of the evidence we found, it was possible to corroborate the hypothesis that there are actually 2 species in this biome: H. oniscus, a species distributed on the northern bank of the Sao Francisco River, from the State of Alagoas to the State of Paraiba; and H. seuanezi, which occurs on the southern bank of the Sao Francisco River, from the southern portion of Bahia State to the northern part of Rio de Janeiro State. Hylaeamys laticeps, the name formerly used for this entity, was allocated to the synonymy of H. megacephalus, a species that inhabits the Cerrado and Amazon Fores...
22 citations
TL;DR: The ratio of the second ommatin (“oniscoid ommatis”) to xanthommatin increases in the order Asellus, Ligia, Porcellio, Philoscia, Oniscus, Armadillidium, and the ratio of ommin to o mmatin likewise.
21 citations
1 Dec 1975
TL;DR: The author analyzes the ecological steps that were undertaken by isopods in the course of their conquest of the land and the role the tergal tubercles played in this process.
Abstract: Based on a morphological and functional analysis of the tergal tubercles of the desert woodlouse Hemilepistus reaumuri, 12 types of morphologically and/or functionally different tergal tubercles in terrestrial isopods were investigated. Morphological investigation of Hemilepistus reaumuri showed that the number of tubercles remains constant during ontogeny and that the individuality of the tuberculation as a whole is unaffected by the moult. The morphogenesis of a single tubercle is brought about by locally increased mitotic rates of the epidermis cells. In Hemilepistus reaumuri the tubercles function as a digging device. For the other 11 types of tuberculation the morphology of the single tubercles and their arrangement on the tergites are analyzed. For Oniscus, Porcellio, Ligia oceanica, the granulated species of Armadillidium, and Bathytropa granulata an increased resistance to bending of the tergites is considered as the mechanical function of the tubercles. In Ligia oceanica and the species of Armadillidium this mechanical function serves primarily to increase the effectiveness of a clinging behavior as protection against predators. In Oniscus and Porcellio the primary purpose is to avoid too much water loss by transpiration. In species which can roll up into a ball, such as Pentheus tuberculatus and Polyacanthus aculeatus, the tuberculation has been transformed into an apparatus for protection from predators according to the hedgehog principle. In Stegosauroniscm an increase of the diameter is achieved by the tubercles; this probably also serves as a means of avoiding certain predators. The mechanical function of the ridges in Haplophthalminae, some Bathytropa- and Platyarthrus-species and Buddelundiella could not be found; from a biological point of view the ridges seem to form part of a defense system. Finally the author analyzes the ecological steps that were undertaken by isopods in the course of their conquest of the land and the role the tergal tubercles played in this process.
21 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2018 | 1 |
| 2013 | 2 |
| 2011 | 1 |
| 2002 | 1 |
| 1999 | 2 |
| 1995 | 1 |