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Respiratory physiology of the Oniscidea: Aerobic capacity and the significance of pleopodal lungs

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Abstract

The radiation of the terrestrial isopods (sub-order Oniscidea) has been accompanied by evolution of pleopodal lungs in the sections Tylida and Crinocheta. To understand the significance of such lungs for aerobic respiration, comparative studies were conducted using 6 species. Ligia occidentalis, lacking lungs, behaved as a metabolic conformer in reduced PO(2), and showed decreased V(.-)O(2) in low humidity and following dehydration. In species possessing lungs, metabolism was insensitive to dehydration. However, lung development did not show a clear relationship to metabolic regulation: Porcellio dilatatus was a metabolic conformer while Tylos punctatus and Armadillidium vulgare were efficient regulators. The metabolic conformers did not accumulate lactate during moderate hypoxia (10% O(2)), indicating that reduced V(.-)O(2) is not compensated with anaerobic glycolysis. In contrast, Alloniscus perconvexus, a littoral species with limited metabolic regulation, showed the largest lactate accumulation during hypoxia and also possessed the highest tissue LDH activity. It is hypothesized that these are adaptations to periodic hypoxia in sand burrows and the high metabolic cost of burrowing. Differences in lactate accumulation during immersion were curious, with the largest increases occurring in L. occidentalis and A. perconvexus that tolerate prolonged immersion in seawater. Possible functions of this lactate accumulation may include modulation of hemocyanin oxygen affinity.

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... These families have more developed respiratory organs and better tolerate dry conditions than other isopods (Edney 1951; Kuenen 1959). For example, the marine littoral genus Ligia possesses simple plate-like pleopods, similar to those of aquatic isopods, while terrestrial genera such as Porcellio and Armadillidium have evolved invaginated lungs in the exopodites (Wright and Ting 2006). The invaginated lungs of A. vulgare form “pseudotracheae,” which are interpreted as an adaptation for respiration that allows A. vulgare to take up 94% of its normal oxygen requirement in dry air, when the integument is also dry (Cloudsley-Thompson 1977). ...
... Though most terrestrial isopods seek similar microhabitats, they differ markedly in their ability to tolerate dry conditions. The families Oniscidae, Porcellionidae, and Armadillidiidae are found in progressively drier areas and show increasing morphological specialization (Cloudsley-Thompson 1977; Wright and Ting 2006). These families have more developed respiratory organs and better tolerate dry conditions than other isopods (Edney 1951; Kuenen 1959). ...
... These “gill-like” organs, called pleopods, are located on the ventral abdominal segments (Edney 1951). To preserve their function in environments where the relative humidity is less than saturating, the outer surface of the pleopods must be kept moist (Cloudsley-Thompson 1977; Little 1983; Wright and Ting 2006). Evaporation from the pleopods is one of the most important physiological factors affecting the survival and distribution of isopods (Edney 1951, 1953, 1968; Cloudsley-Thompson 1969). ...
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Water balance of the terrestrial isopod, Armadillidium vulgare, was investigated during conglobation (rolling-up behavior). Water loss and metabolic rates were measured at 18 +/- 1 degrees C in dry air using flow-through respirometry. Water-loss rates decreased 34.8% when specimens were in their conglobated form, while CO2 release decreased by 37.1%. Water loss was also measured gravimetrically at humidities ranging from 6 to 75 %RH. Conglobation was associated with a decrease in water-loss rates up to 53 %RH, but no significant differences were observed at higher humidities. Our findings suggest that conglobation behavior may help to conserve water, in addition to its demonstrated role in protection from predation.
... For example, the concentration of oxygen in wet, decaying beech logs (a potential habitat for isopods) can be reduced 40-fold, reaching concentrations as low as 0.5% [9]. Some isopods inhabit periodically submerged sand burrows in intertidal zones, where they can be exposed to hypoxic conditions [10]. Isopods were also reported to inhabit altitudes reaching 4725 m a.s.l. ...
... Our experimental results indicate that when exposed to hypoxic conditions, P. scaber chooses to occupy microsites with low temperatures. In nature, woodlice inhabit sites with different oxygen conditions [10], so our evidence suggests that isopods exposed to poor oxygen conditions, e.g., those due to rapid decomposition or high altitude, might prefer to stay in cooler sites. The links between oxygen availability and preferred temperatures have rarely been studied, but the available evidence shows that oxygen deprivation also decreases preferred temperatures in some species of protists [42], fish [43,51], amphibians, reptiles [41], and even Thermal biology of the common rough woodlice under hypoxia mammals [42]. ...
... The two-stage gas-exchange system of isopods might be expected to increase the hypoxia sensitivity of thermal performance compared to the one-stage tracheal system of insects [30] because the affinity of haemocyanin to oxygen decreases with an increase in temperature [44]. The tracheal system delivers oxygen directly to insect tissues and lacks specialized carriers of oxygen [10], but binding proteins are used by some insects for oxygen storage [53]. Klok et al. [30] and Stevens et al. [31] compared the CT max of isopods and insects by measuring the metabolic rate and examining their activity. ...
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Environmental temperatures and oxygen availability are important for the balance between oxygen supply and demand. Terrestrial organisms are generally perceived to be less limited by access to oxygen than their aquatic counterparts. Nevertheless, even terrestrial environments can be deficient in oxygen, especially for organisms occurring in soil, litter, wood, rotten fruit or at high elevations. While isopods are the best adapted to a terrestrial lifestyle among crustaceans, many species, including woodlice, occupy environmental gradients of temperature and oxygen. To investigate whether mismatches between oxygen supply and demand can result in a loss of performance in a terrestrial organism, we studied the effects of atmospheric oxygen concentration on the thermal performance of the common rough woodlouse (Porcellio scaber). We compared the thermal preference, thermal sensitivity of running speed, and tolerance to extreme temperatures of woodlice exposed to one of two oxygen concentrations (21% - normoxia, 7% - hypoxia). Under hypoxia, P. scaber preferred microhabitats with temperatures that were on average 3°C lower than those preferred under normoxia. The running speed tended to reach its maximum at a lower temperature under hypoxia than under normoxia (25.13°C vs 28.87°C, respectively, although p was equal to 0.09), and normoxic woodlice ran approximately 1.5-fold faster than hypoxic woodlice at the point of maximum speed. Heat tolerance was significantly lower under hypoxia (38.9°C) than under normoxia (40.7°C), but there was no difference in cold tolerance (5.81°C under normoxia and 5.44°C under hypoxia). Overall, our results indicate that environmental gradients of temperature and oxygen may shape the physiological performance of terrestrial ectotherms, likely via their effects on the balance between oxygen supply and demand, which may have fitness consequences for these organisms in nature.
... The lungs limit the direct contact of the respiratory organs with ambient air, which helps to conserve water (Hornung, 2011;Schmidt and W€ agele, 2001). The lungs consist of a large number of branched tubules (pseudotracheae) formed by a thin respiratory epithelium (Bielawski and Babula, 1980;Wright and Ting, 2006). The apical side of the epithelial cells is covered with a cuticle (Bielawski and Babula, 1980). ...
... Interestingly, the cuticle that covers cells surrounding the spiracles can create microfolds (Fig. 1A, B) that trap water; these humidify the entering air and serve as additional protection from drought (Babula, 1981). In insects with a tracheal system, oxygen diffuses directly into tissues and cells without mediation by oxygen-binding proteins (Klok et al., 2004;Wright and Ting, 2006). In contrast, terrestrial isopods possess a hemocyanin protein that binds oxygen in the lungs and then transports it via the hemolymph to the tissues (Klok et al., 2004;Wright and Ting, 2006). ...
... In insects with a tracheal system, oxygen diffuses directly into tissues and cells without mediation by oxygen-binding proteins (Klok et al., 2004;Wright and Ting, 2006). In contrast, terrestrial isopods possess a hemocyanin protein that binds oxygen in the lungs and then transports it via the hemolymph to the tissues (Klok et al., 2004;Wright and Ting, 2006). ...
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Terrestrial isopods have evolved pleopodal lungs that provide access to the rich aerial supply of oxygen. However, isopods occupy conditions with wide and unpredictable thermal and oxygen gradients, suggesting that they might have evolved adaptive developmental plasticity in their respiratory organs to help meet metabolic demand over a wide range of oxygen conditions. To explore this plasticity, we conducted an experiment in which we reared common rough woodlice (Porcellio scaber) from eggs to maturation at different temperatures (15 and 22 °C) combined with different oxygen levels (10% and 22% O2). We sampled animals during development (only females) and then examined mature adults (both sexes). We compared woodlice between treatments with respect to the area of their pleopod exopodites (our proxy of lung size) and the shape of Bertalanffy’s equations (our proxy of individual growth curves). Generally, males exhibited larger lungs than females relative to body size. Woodlice also grew relatively fast but achieved a decreased asymptotic body mass in response to warm conditions; the oxygen did not affect growth. Under hypoxia, growing females developed larger lungs compared to under normoxia, but only in the late stage of development. Among mature animals, this effect was present only in males. Woodlice reared under warm conditions had relatively small lungs, in both developing females (the effect was increased in relatively large females) and among mature males and females. Our results demonstrated that woodlice exhibit phenotypic plasticity in their lung size. We suggest that this plasticity helps woodlice equilibrate their gas exchange capacity to differences in the oxygen supply and metabolic demand along environmental temperature and oxygen gradients. The complex pattern of plasticity might indicate the effects of a balance between water conservation and oxygen uptake, which would be especially pronounced in mature females that need to generate an aqueous environment inside their brood pouch.
... Woodlice generally inhabit habitats close to the soil surface (both endoand epigeic), like decaying leaf litter, rotten wood etc. These places are relatively moist, but they are also expected to become oxygen deficient (hypoxic) during certain periods, such as floodings or heavy rainfall (Wright and Ting, 2006). With regard to the effect of hypoxia on isopods, there is evidence that hypoxia lowers their critical temperatures (Antoł et al., 2019;Klok et al., 2004;Stevens et al., 2010;Verberk et al., 2018), their thermal preference and performance (Antoł et al., 2019), their respiration rate (Wright and Ting, 2006) and slows down growth (Hoefnagel and Verberk, 2015, but see Antoł et al., 2020;Horváthová et al., 2015) as well as the development of their eggs and offspring (Horváthová et al., 2017). ...
... These places are relatively moist, but they are also expected to become oxygen deficient (hypoxic) during certain periods, such as floodings or heavy rainfall (Wright and Ting, 2006). With regard to the effect of hypoxia on isopods, there is evidence that hypoxia lowers their critical temperatures (Antoł et al., 2019;Klok et al., 2004;Stevens et al., 2010;Verberk et al., 2018), their thermal preference and performance (Antoł et al., 2019), their respiration rate (Wright and Ting, 2006) and slows down growth (Hoefnagel and Verberk, 2015, but see Antoł et al., 2020;Horváthová et al., 2015) as well as the development of their eggs and offspring (Horváthová et al., 2017). Furthermore, isopods enlarge the size of their lungs during development in chronic hypoxia (Antoł et al., 2020). ...
Article
Terrestrial isopods have evolved adaptations to reduce water loss, which is necessary for life in low humidity environments. However, the evolution of a waterproofed cuticle to prevent loss of water to the environment could also impede oxygen uptake from the environment. We therefore postulate an evolutionary trade-off between water retention and gas exchange in this group of soil animals. The outcome of this trade-off is expected to be affected by both differences across species (different types of lung) and differences within species (body size and resulting surface area to volume ratios). To test these ideas, we compared two sympatric isopods: Porcellio scaber and Oniscus asellus. While P. scaber possesses covered lungs typical for drier habitats, O. asellus has simple open respiratory fields which are in direct contact with external air. For each species, we assessed how individuals across a broad range in body size differed in their hypoxia and desiccation tolerance. In addition, we assessed how hypoxia and low humidity affected their thermal preference. We found clear effects of species identity and body size on tolerance to hypoxia and low humidity. Desiccation resistance was tightly linked to water loss rates (R² = 0.96) and strongly resembled the interspecific pattern across 20 isopod species. However, our results did not support the postulated trade-off. Tolerance to hypoxia and low humidity covaried, both increasing with body size and being higher in P. scaber. Thermal preference was affected by both hypoxia and low humidity, but not by body size. Our study increases understanding of the ecophysiology of both species, which can be useful in explaining the geographical distribution and use of microhabitats of isopod species in a climate change context.
... To address the predictions of TOCS, we studied the effects of thermal and oxygen conditions during development on cell size in the common rough woodlice (Porcellio scaber), a species of terrestrial isopods. Typically, terrestrial isopods inhabit litter environments with intense decomposition and thus are likely to experience hypoxic conditions in their natural habitats (Wright & Ting, 2006). ...
... Having evolved various land adaptations, such as pleopodal lungs, water conducting systems, or conglobating behavior (Cloudsley-Thompson, 1988;Hornung, 2011), terrestrial isopods are sometimes regarded as the best land adapted order of crustaceans (Hornung, 2011). Previous studies of terrestrial isopods showed that oxygen deficiency in the air affects their mobility, thermal performance and thermal preferences (Antoł et al., 2019), respiration rate and hemolymph lactate level (Wright & Ting, 2006), lung size (Antoł et al., 2020), and the length of aquatic/air phases during marsupial development of offspring (Horváthová, Antoł, Czarnoleski, Kozłowski, & Bauchinger, 2017). In this study, we assessed the cell size of woodlice in the eye, hepatopancreas and hindgut and evaluated how it changes with developmental conditions. ...
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During development, cells may adjust their size to balance between the tissue metabolic demand and the oxygen and resource supply: Small cells may effectively absorb oxygen and nutrients, but the relatively large area of the plasma membrane requires costly maintenance. Consequently, warm and hypoxic environments should favor ectotherms with small cells to meet increased metabolic demand by oxygen supply. To test these predictions, we compared cell size (hindgut epithelium, hepatopancreas B cells, ommatidia) in common rough woodlice (Porcellio scaber) that were developed under four developmental conditions designated by two temperatures (15 or 22°C) and two air O2 concentrations (10% or 22%). To test whether small‐cell woodlice cope better under increased metabolic demand, the CO2 production of each woodlouse was measured under cold, normoxic conditions and under warm, hypoxic conditions, and the magnitude of metabolic increase (MMI) was calculated. Cell sizes were highly intercorrelated, indicative of organism‐wide mechanisms of cell cycle control. Cell size differences among woodlice were largely linked with body size changes (larger cells in larger woodlice) and to a lesser degree with oxygen conditions (development of smaller cells under hypoxia), but not with temperature. Developmental conditions did not affect MMI, and contrary to predictions, large woodlice with large cells showed higher MMI than small woodlice with small cells. We also observed complex patterns of sexual difference in the size of hepatopancreatic cells and the size and number of ommatidia, which are indicative of sex differences in reproductive biology. We conclude that existing theories about the adaptiveness of cell size do not satisfactorily explain the patterns in cell size and metabolic performance observed here in P. scaber. Thus, future studies addressing physiological effects of cell size variance should simultaneously consider different organismal elements that can be involved in sustaining the metabolic demands of tissue, such as the characteristics of gas‐exchange organs and O2‐binding proteins.
... A légzőszerv felépítése, szerkezeti bonyolultsága összefüggésben van az élőhely nedvességviszonyaival: szárazabb körülmények között a fajok légzőszerve strukturáltabb felépítést mutat (Paoli et al. 2002). A fejlettebb, szárazföldi életmódhoz jobban alkalmazkodott fajok, mint pl. a Porcellio és Armadillidium nem tagjainak fejlett, és fedett fehérszervük van a potrohlábaik külső ágán (Wright & Ting 2006). Az Armadillidium nem esetén két pár pszeudotrachea található a potrohlábak külső ágain, amelyek levegőtartalmuk miatt szembetűnő fehér foltként jelennek meg. ...
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A szárazföldi ászkarákok morfológiai, fiziológiai és viselkedésbeli adaptációik révén sokféle élőhelyen előfordulhatnak: a nedvestől a szárazig, a természetestől a zavartig. Mint talaj felszínén mozgó, röpképtelen, kisméretű gerincteleneknek igen nagy a helyhűségük. Így megjelenésük, túlélésük az élőhely adottságaitól és a fajok tűrőképességétől függ. Ökológiai jellemzőik (tolerancia viszonyaik) alapján fajaikat minősíthetjük, ami az egyes élőhelyek természetességi megítélésében segítségül szolgál. Vizsgálatainkat az Armadillidium nem négy hazai faján (Armadillidium zenckeri, A. nasatum, A. versicolor, A. vulgare) végeztük, melyek a földrajzi elterjedésükben található átfedések ellenére élőhelyi skálán jelentősen eltérnek. Az ászkarákok túlélésének szempontjából kulcsfontosságú a kiszáradás elleni védekezés. Vízháztartásuk szempontjából fontos tényező a kutikulájuk vastagsága, légzőszervük szerkezete. Kutatásunkban ezek különbségét vizsgáltuk a fajok élőhelyeinek változatossága szempontjából. Fénymikroszkópos vizsgálataink igazolták feltételezésünket: a négy faj karaktereik alapján egyértelműen elkülönül és sorrendbe állítható az élőhelygeneralista, szárazságtűrőbb A. vulgare fajtól a specialista, nagy nedvességtartalmat igénylő A. zenckeri fajig.
... This implies that high LDH activity in H. rubra is not because of unique enzyme characteristics, but instead likely due to high expression levels of LDH mRNA. The strategy hypothesized above may play a role in preparing shrimp for periodic bouts of hypoxia in anchialine habitats, similar to how terrestrial isopods with correspondingly high LDH activities (though those of H. rubra are still 4-fold higher) deal with the hypoxia occasionally encountered in their sand burrows (Wright and Ting, 2006). Another hypothesis is that H. rubra may utilize alternative anaerobic pathways independent of lactate formation, as has been hypothesized for the crustacean Upogebia pugettensis (Zebe, 1982), or may even utilize a terminal electron acceptor other than oxygen. ...
Article
Crustaceans generally act as oxy-regulators, maintaining constant oxygen uptake as oxygen partial pressures decrease, but when a critical low level is reached, ventilation and aerobic metabolism shut down. Cave-adapted animals, including crustaceans, often show a reduced metabolic rate possibly owing in part to the hypoxic nature of such environments. However, metabolic rates have not been thoroughly explored in crustaceans from anchialine habitats (coastal ponds and caves), which can experience variable oxygenic regimes. Here, an atypical oxy-conforming pattern of oxygen uptake is reported in the Hawaiian anchialine atyid Halocaridina rubra, along with other unusual metabolic characteristics. Ventilatory rates are near-maximal in normoxia and did not increase appreciably as PO2 declined, resulting in a decline in VO2 during progressive hypoxia. Halocaridina rubra maintained in anoxic waters survived for seven days (the duration of the experiment) with no measureable oxygen uptake, suggesting a reliance on anaerobic metabolism. Supporting this, lactate dehydrogenase activity was high, even in normoxia, and oxygen debts were quickly repaid by an unusually extreme increase in oxygen uptake upon exposure to normoxia. In contrast, four related anchialine shrimp species from the Ryukyus Islands, Japan, exhibited physiological properties consistent with previously studied crustaceans. The unusual respiratory patterns found in H. rubra are discussed in the context of a trade-off in gill morphology for osmoregulatory ion transport vs diffusion of respiratory gasses. A future focus on additional anchialine species may offer novel insight into the diversity of metabolic responses to hypoxia and other physiological challenges experienced by organisms from these habitats.
... Our experimental approach enabled us to disentangle the independent effects of temperature and oxygen, which are otherwise correlated in nature. Terrestrial isopods use a two-stage gas exchange system in which oxygen initially dissolves in the haemolymph and is subsequently delivered to the tissues (Wright and Ting 2006), which may lead to oxygen limitation at higher temperatures (Klok et al. 2004). Furthermore, early ontogenetic development in isopods takes place in an aqueous environment inside the brood pouch (Surbida and Wright 2001) where oxygen pressure is much lower than that of the ambient air (Strathmann 1990). ...
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According to the temperature-size rule (TSR), ectotherms developing under cold conditions experience slower growth as juveniles but reach a larger size at maturity. Whether temperature alone causes this phenomenon is unknown, but oxygen limitation can play a role in the temperature-size relationship. Oxygen may become limited under warm conditions when the resulting higher metabolism creates a greater demand for oxygen, especially in larger individuals. We examined the independent effects of oxygen concentration (10% and 22% O2) and temperature (15 °C and 22 °C) on duration of ontogenic development, which takes place within the maternal brood pouch (marsupium), and juvenile growth in the terrestrial isopod common rough woodlouse (Porcellio scaber). Individuals inside the marsupium undergo the change from the aqueous to the gaseous environment. Under hypoxia, woodlice hatched from the marsupium sooner, but their subsequent growth was not affected by the level of oxygen. Marsupial development and juvenile growth were almost three times slower at low temperature, and marsupial development was longer in larger females but only in the cold treatment. These results show that temperature and oxygen are important ecological factors affecting developmental time and that the strength of the effect likely depends on the availability of oxygen in the environment.
... Terrestrial isopods are strongly sensitive to microclimatic conditions and have developed morphological and behavioural traits, such as pleopodal lungs and aggregation, as adaptations to the terrestrial environments (Warburg 1968). The extent to which morphological traits have developed to reduce moisture loss varies between different families: for example members of the Oniscidae lack well developed pleopodal lungs in contrast to members of the Porcellionidae which do have elaborately developed pleopodal lungs with a large number of fine branched tubules, resulting in a greater surface area for absorbing oxygen with reduced loss of water vapour (Wright and Ting 2006). Oniscus asellus was chosen as a representative of the Oniscidae family while Porcellio scaber and Porcellio dilatatus were used, according to availability, as representatives of the Porcellionidae, both species having elaborate pleopodal lungs. ...
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The sensitivity of terrestrial isopods to changes in both temperature and moisture make them suitable models for examining possible responses of arthropod macro-decomposers to predicted climate change. Effects of changes in both temperature and relative humidity on aggregation, growth and survivorship of species of isopods contrasting in their morphological and physiological adaptations to moisture stress have been investigated in laboratory microcosms. All three traits were more sensitive to a reduction in relative humidity of 20–25% than they were to an increase in temperature of 5–6 °C. These results suggest that predicted changes in climate in south east England may reduce the extent to which soil animals stimulate microbial activity and hence carbon dioxide (CO2) emissions from soils in the future. This may help to mitigate the potential for a positive feedback between increased CO2 emissions from soils, and increased greenhouse effects causing an increase in soil temperatures.
... Klok and colleagues suggested that the additional binding step of oxygen to haemocyanin may delay oxygen delivery to the tissues in isopods and in other marine invertebrates with similar gas exchange systems. Indeed, gas exchange systems of the isopods Ligia occidentalis and Alloniscus perconvexus limited these animals in normoxia, since mild hyperoxia (25% O 2 ) caused increased oxygen uptake (Wright and Ting, 2006). Additionally, oxygen is known to diffuse faster through air than through water (Prosser, 1973), and thus probably faster to the tissues of beetles than to those of isopods. ...
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MSc Thesis presented in partial fulfilment of the requirements for the degree of Master of Science (zoology) at Stellenbosch University ENGLISH ABSTRACT: It has recently been suggested that physiological responses of animals to temperature change can be incorporated into climate change models. This has sparked renewed interest in ectotherm thermal physiology. Recent studies on marine species have suggested that critical thermal limits, that is, the temperature extremes at which animals lose control over motor activity, are coupled by a common mechanism: oxygen limitation of thermal tolerance. The theory of oxygen limitation suggests the failure of gas exchange systems to supply tissues with oxygen at animals’ critical thermal extremes as the primary mechanism setting thermal limits. It has been suggested that this mechanism applies to both aquatic and terrestrial ectotherms. This thesis investigates the applicability of oxygen limitation to the thermal tolerance of two representative terrestrial arthropod species, the beetle Tenebrio molitor (Insecta) and the terrestrial isopod Porcellio scaber (Crustacea). These species were selected to represent two groups with different gas exchange systems: the transport of gaseous oxygen along air-filled tracheae (T. molitor), or bound to haemocyanin in the fluid haemolymph (P. scaber). Oxygen availability appeared only to influence the critical thermal maxima (CTmax) of these two species, and not the critical thermal minima (CTmin). This agrees with previous studies on terrestrial arthropods that have suggested that CTmin and CTmax are decoupled, rather than being set by a common mechanism. Aerobic failure of T. molitor was estimated by measuring the critical partial pressure of oxygen (Pc) at five test temperatures (7, 14, 21, 28 and 35°C). Pc is the critical partial pressure of oxygen at which an animal’s gas exchange system fails to supply tissues with oxygen, and aerobic metabolism can no longer be maintained, forcing a switch to anaerobic metabolism. Aerobic failure was independent of test temperature, suggesting that oxygen limitation does not underlie temperature tolerance of these animals thus not supporting the oxygen limitation hypothesis. Methodological comparisons throughout the course of the above experiments highlighted the need for standard statistical and analytical methods to determine endpoints (CTmax, CTmin and Pc estimates). The different methods currently used in the published literature can yield substantially different endpoints. AFRIKAANSE OPSOMMING: Daar was onlangs voorgestel dat die fisiologiese reaksies van diere ten opsigte van temperatuur verandering, in klimaats veranderingmodelle geïnkorporeer moet word. Dit het hernude belangstelling in ektoterm temperatuur fisiologie gewek. Onlangse studies op mariene spesies stel voor dat die kritiese termiese limiete, dit wil sê, temperatuur uiterstes waar diere beheer oor motoriese aktiwiteit verloor, gekoppel is deur die algemene meganisme: suurstof beperking van temperatuur toleransie. Dié teorie van suurstof beperking behels die versuiming van gaswisselingssisteme om suurstof aan weefsels te voorsien, dit wil sê aërobiese mislukking by die kritiese temperatuur uiterstes. Dit word voorgestel dat hierdie meganisme toepaslik is op beide akwatiese en terrestriële ektoterme. Hierdie tesis ondersoek die toepaslikheid van suurstof beperking van temperatuur toleransie op twee verteenwoordigende terrestriële geleedpotige spesies, die kewer Tenebrio molitor (Insecta) en die terrestriële houtluis Porcellio scaber (Crustacea). Hierdie spesies was gekies om twee groepe met verskillende gaswisselingssisteme te verteenwoordig: die vervoer van suurstof in lugpype (T. molitor), of gebonde aan hemosianine in hemolimf (P. scaber). Suurstof beskikbaarheid blyk slegs om die kritiese temperatuur maksima (CTmax) van hierdie spesies te beïnvloed, en nie die kritiese temperatuur minima (CTmin) nie. Dit stem ooreen met vorige studies van terrestriële geleedpotiges wat bevind het dat CTmin en CTmax nie gekoppel is deur `n algemene meganisme nie. Aërobiese mislukking van T. molitor was bepaal deur die kritiese parsiële druk van suurstof (Pc) by vyf toets temperature (7, 14, 21, 28 en 35°C) te meet. Pc is die kritiese parsiële druk van suurstof waar `n dier se gaswisselingssisteem versuim om die weefsels van suurstof te voorsien, en aërobiese metabolisme nie behou kan word nie, wat `n oorskakeling na anaërobiese metabolisme bevorder. Aërobiese mislukking was onafhanklik van toets temperatuur, wat voorstel dat dit nie die onderliggende meganisme geassosieer met hierdie diere se temperatuur toleransie is nie. Dus word die suurstof limitasie hipotese nie ondersteun nie. Metodologiese vergelykings deur die loop van die bogenoemde eksperimente het getoon dat standaard statistiese en analitiese metodes wat eindpunte (CTmax, CTmin en Pc) bepaal, benodig word. Die verskillende metodes wat tans in die gepubliseerde literatuur gebruik word, kan `n verskeidenheid eindpunte tot gevolg hê.
... The assumption that mass-loss represents an accurate measure of water loss is valid only if respiratory carbon loss can be ignored. The mean mass of animals used for the mass-loss trials was 42 mg and the mass-specific catabolic rate for similar sized oniscideans is approximately 4 μl CO 2 min −1 g −1 (Wright and Ting, 2006), representing 0.17 μmol C min −1 g −1 , or 0.084 μg animal −1 min −1 . This is only about 1% of the measured mass-loss in dry air. ...
... The highest abundance of A. vulgare was in arid grasslands, which confirmed our original hypothesis. We conclude that A. vulgare is a typical and common species of drier areas (65,45,66). Miller & Cameron (67) showed that survivorship of A. vulgare in Texas was highest in grassland areas. ...
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Background and purpose: The impact of invasive species in ecosystems is an important problem worldwide and the spreading of invader species are affected exceedingly by linear infrastructure. Primarily the aim of our investigation was to studied how the invasion of the species impacts the isopod diversity of roadside verges. Secondly, we determined what attributes of linear infrastructure affect on mass occurrence by the species. Materials and methods: Double-glass pitfall traps were established 30 localities along highways and 4 localities along main roads in Hungary between 2011 and 2016. To studied what attributes of roads affect the abundance of A. vulgare we considered seasons, adjacent areas, road edge proximity, leaf-litter depth, the age of highway, vegetation type and mowing. Results: We collected a total of 18 isopod species. The A. vulgare was the most abundant and frequently encountered species in both road types, which represented 89% of the total isopod catches. The high abundance of the species negatively correlated with isopod diversity. The invasive nature of this species is promoted by summer season, the proximity of arable felds, intermediate distance from the road, leaf-litter at a depth of 0 cm and the young age of highways. On mainroad verges the highest abundance was in the non-mown sections of the arid grassland sites. Conclusions: Our results suggest that this species is likely to adversely impact ecosystem function of roadside verges in Hungary. Different land use, water supply, surrounding landscapes, habitat structure, vegetation, biogeographical context and human activities along road verges influence the invasiveness of A. vulgare.
... Patterns of CO 2 release have also been reported during thermolimit respirometry for two non-insects, the isopod species Armadillidium vulgare (Klok et al., 2004) and Porcellio scaber (Stevens et al., 2010). In isopods, gases are exchanged through pleopodal exopodites, and circulated to the tissues by respiratory pigments in the hemolymph (Wright and Ting, 2006). This differs markedly from insects, in which gases are delivered directly to the tissues via the air-filled tracheal system. ...
Article
Thermal limits to activity profoundly affect the abundance and distribution of ectothermic animals. Upper thermal limits to activity are typically reported as the critical thermal maximum (CT(max)), the temperature at which activity becomes uncontrolled. Thermolimit respirometry is a new technique that allows CT(max) to be quantified in small animals, such as insects, as the point of spiracular failure by measuring CO(2) release from the animal as temperature increases. Although prior studies have reported a characteristic pattern of CO(2) release for insects during thermolimit respirometry trials, no studies have been carried out to determine the universality of this pattern across development, or at what point death occurs along this pattern. Here, we compared the CT(max) and patterns of CO(2) release among three life stages of a beetle species, Tenebrio molitor, and mapped heat death onto these patterns. Our study is the first to report distinct patterns of CO(2) release in different life stages of an insect species during thermolimit respirometry. Our results show that CT(max) was significantly higher in adult beetles than in either larvae or pupae (P<0.001) and, similarly, death occurred at higher temperatures in adults than in larvae and pupae. We also found that death during heating closely follows CT(max) in these animals, which confirms that measuring the loss of spiracular control with thermolimit respirometry successfully identifies the point of physiological limitation during heat stress.
... Klok and colleagues suggested that the additional binding step of oxygen to haemocyanin may delay oxygen delivery to the tissues in isopods and in other marine invertebrates with similar gas exchange systems. Indeed, gas exchange systems of the isopods Ligia occidentalis and Alloniscus perconvexus limited these animals in normoxia, since mild hyperoxia (25% O 2 ) caused increased oxygen uptake (Wright and Ting, 2006). Additionally, oxygen is known to diffuse faster through air than through water (Prosser, 1973), and thus probably faster to the tissues of beetles than to those of isopods. ...
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Recent studies of marine invertebrates and fish have suggested that lower and upper critical temperatures (CT(min) and CT(max)) are coupled by a common mechanism: oxygen and capacity limitation of thermal tolerance (OCLT). Using thermolimit respirometry, we tested the predictions of this theory for terrestrial arthropods by measuring maxima and minima for both critical temperatures and metabolic rate in two arthropods, the isopod Porcellio scaber and the beetle Tenebrio molitor, at 40%, 21%, 10% and 2.5% ambient O(2). Critical temperatures were identified as particular points on both activity and traces in four ways. In the first two instances, we identified the inflection points in regressions of absolute difference sum (ADS) residuals calculated for activity (aADS) and (VI), respectively. In the third, we visually identified the lowest point before the post-mortal peak in CO(2) release (PMV). Finally, we pinpointed the sudden drop in at death, where fell outside the 95% confidence intervals of the 5 min period immediately preceding the drop-off (CI). Minimum and maximum metabolic rates were determined using CO(2) traces, and the temperatures corresponding to these identified as T(MetMin) and T(MetMax). For both species, ambient oxygen concentration did not influence CT(min), minimum metabolic rate, or T(MetMin). By contrast, severe hypoxia (2.5% O(2)) caused a 6.9 degrees C decline in activity-based CT(max) for T. molitor and a 10.6 degrees C decline for P. scaber, relative to normoxia (21% O(2)). The magnitude of this decrease differed between methods used to estimated critical thermal limits, highlighting the need for a standard method to determine these endpoints during thermolimit respirometry. Maximum metabolic rate also declined with decreasing ambient oxygen in both species. The combination of increasing metabolic rate and oxygen limitation affected upper thermal limits in these arthropods only in severe hypoxia (2.5% O(2)). In both species, CT(min) and CT(max) responded differently to oxygen limitation, suggesting that this is not a common mechanism coupling upper and lower limits in terrestrial arthropods.
... Ϫ9 0.6-3.3 # 10 These values are four orders of magnitude below typical massspecific metabolic rates documented for oniscideans (e.g., Taylor and Carefoot 1993;Wright and Ting 2006) and indicate that most CO 2 diffuses away from the egg in the nonionic form. It is possible that proton fluxes arise through the activity of a Figure 9. Chloride fluxes measured across the dorsal organ of three early stage 2 eggs incubated for 24 h in 10 mM Cl Ϫ saline and scanned in the same. ...
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The thin-walled, lecithotrophic eggs of land isopods (suborder Oniscidea) are brooded in a fluid-filled maternal marsupium until a few days following the second embryonic molt. Eggs of Armadillidium vulgare possess a well-developed dorsal organ underlying a broad silver-staining saddle on the vitelline membrane. Based on its chloride permeability and known transport functions in planktotrophic crustaceans, we hypothesized that the dorsal organ functions in passive or active ion movements. To study this, we employed the automated scanning electrode technique with self-referencing ion-selective microelectrodes to measure ion fluxes across the dorsal organ and adjacent egg poles. Stage 1 (chorionated) eggs revealed only small ion fluxes, indicating low permeability. Early stage 2 eggs--between the first embryonic molt and blastokinesis--showed evidence for active uptake of Ca(2+) and Cl(-) and possibly Na(+) against low bathing concentrations, and uptake fluxes were predominantly localized over the dorsal organ. Late stage 2 eggs revealed no capacity for ion uptake, consistent with the atrophy of the dorsal organ at blastokinesis, but high ion permeability. In all stages, the silver-staining saddle showed a sustained outward proton flux indicating that it is the primary site for metabolic acid/CO(2) excretion. The emerging picture is that the embryo dorsal organ in A. vulgare serves important functions in ion regulation, calcium provisioning, and acid excretion.
... The family Oniscidae, together with Porcellionidae and Armadillidiidae, are found in drier areas with increased morphological specialisation (Wright, Ting, 2006) and different ability to tolerate dry conditions. O. asellus as epigean clinger species (Schmalfuss, 1984 ...
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The present survey provides records on terrestrial isopods from southern and north-western parts of Lithuania. Isopods were sampled manually by checking substrates in eight habitats (several types of forest and anthropogenic environment) between 2014 and 2016. In total, seven species were recorded. The common European species Trachelipus rathkii was noted as the most frequent isopod in all studied habitats from southern Lithuania. Porcellionides pruinosus, found in the habitat of anthropogenic activity, was recorded for the first time from Lithuania. Based on the data of the present study and previous surveys, the 14 species of terrestrial isopods are recorded in Lithuania and the current state of knowledge about Lithuanian isopod is summarised.
... In the Gulf of California, T. punctatus burrowed until it reached sand moisture levels of at least 1 % (Holanov and Hendrickson 1980), and studies by Brusca (1966) showed that A. perconvexus burrowed down to sand moisture levels of 2.9-5.5 %. Both species are also relatively impermeable for Oniscidea (Wright and Ting 2006). Accordingly, they should be able to liberate ammonia at modest rates for extended periods, requiring smaller total ammonia accumulation than terrestrial species. ...
Article
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A key evolutionary development facilitating land colonization in terrestrial isopods (Isopoda: Oniscidea) is the intermittent liberation of waste nitrogen as volatile ammonia. Intermittent ammonia release exploits glutamine (Gln) as an intermediary nitrogen store. Here, we explore the relationship between temporal patterns of ammonia release and Gln accumulation in three littoral oniscideans from Southern California. Results are interpreted in terms of water availability, habitat, activity patterns, and ancestry. A two-way experimental design was used to test whether ammonia excretion and Gln accumulation follow a tidal or diel periodicity. Ammonia excretion was studied in the laboratory using chambers with or without available seawater and using an acid trap to collect volatile ammonia. Ligia occidentalis releases ammonia directly into seawater and accumulates Gln during low tide (48.9 ± 6.5 μmol g(-1) at low tide, 24.1 ± 3.0 μmol g(-1) at high tide), indicating that excretion is tidally constrained. Alloniscus perconvexus and Tylos punctatus can excrete ammonia directly into seawater or utilize volatilization. Both species burrow in sand by day and show a diel excretory pattern, accumulating Gln nocturnally (31.8 ± 2.7 μmol g(-1) at dawn and 21.8 ± 2.3 μmol g(-1) at dusk for A. perconvexus; 85.7 ± 15.1 μmol g(-1) at dawn and 25.4 ± 2.9 μmol g(-1) at dusk for T. punctatus) and liberating ammonia diurnally. Glutaminase shows higher activity in terrestrial (0.54-0.86 U g(-1)) compared to intertidal (0.25-0.31 U g(-1)) species, consistent with the need to generate high PNH(3) for volatilization. The predominant isoform in Armadillidium vulgare is phosphate dependent and maleate independent; phosphate is a plausible regulator in vivo.
Article
The complete mitochondrial (mt) genome sequence of the Australian fresh water isopod Eophreatoicus sp.-14 has been determined. The new species is a member of the taxon Phreatoicidea, a clade of particular interest, as it is often regarded as the sister group to all other Isopoda. Although the overall genome organization of Eophreatoicus sp.-14 conforms to the typical state of Metazoa--it is a circular ring of DNA hosting the usual 37 genes and one major non-coding region--it bears a number of derived characters that fall within the scope of "genome morphology". Earlier studies have indicated that the isopod mitochondrial gene order is not as conserved as that of other crustaceans. Indeed, the mt genome of Eophreatoicus sp.-14 shows an inversion of seven genes (including cox1), which is as far as we know unique. Even more interesting is the derived arrangement of nad1, trnL(CUN), rrnS, control region, cob, trnT, nad5 and trnF that is shared by nearly all available isopod mt genomes. A striking feature is the close proximity of the rearranged genes to the mt control region. Inferable gene translocation events are, however, more suitable to trace the evolution of mt genomes. Genes like nad1/trnL(CUN) and nad5/trnF, which retained their adjacent position after being rearranged, were most likely translocated together. A very good example for the need to understand the mechanisms of translocations is the remolding of trnL(UUR) to trnL(CUN). Both tRNA genes are adjacent and have a high sequence similarity, probably the result of a gene duplication and subsequent anticodon mutation. Modified secondary structures were found in three tRNAs of Eophreatoicus sp.-14, which are all characterized by the loss of the DHU-arm. This is common to crustaceans for tRNA Serine(AGY), while the arm-loss in tRNA Cysteine within Malacostraca is only shared by other isopods. Modification of the third tRNA, Isoleucine, is not known from any other related species. Nucleotide frequencies of genes have been found to be indirectly correlated to the orientation of the mitochondrial replication process. In Eophreatoicus sp.-14 and in other Isopoda the associated nucleotide bias is inversed to the state of other Malacostraca. This is a strong indication for an inversion of the control region that most likely evolved in the isopod ancestor.
Article
During evolution, various lineages of arthropods colonized land and independently acquired air-breathing organs. Some taxa of oniscidean isopods (Crustacea, Isopoda, Oniscidea) are the most successful crustacean lineages on land and possess organs called “lungs” or “pseudotrachea” for air-breathing in their abdominal appendages, i.e., in pleopods. Although these lungs are important for adapting to the terrestrial environment, their developmental process has not yet been elucidated. In the present study, we investigated the process of lung development in Porcellio scaber, the common rough woodlouse with pleopodal lungs in the first two pairs of pleopods. The lungs in the second pleopods developed at the manca 1 stage (immediately after hatching) and became functional at the manca 2 stage. In the first pleopods, which appear at the manca 3 stage, the lungs were gradually developed during the manca 3 stage and became functional in post-manca juveniles. In the second pleopods, epithelial invaginations led to lung development. These results suggest that some novel developmental mechanisms with epithelial invaginations and cuticle formation were acquired during terrestrialization, resulting in the development of functional lungs in the terrestrial isopod lineages.
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The 11 th International Symposium on Terrestrial Isopod Biology and this special issue of ZooKeys is dedicated to the memory of our colleague, Dr. Jonathan C. Wright, who passed away on December 16, 2019. Jonathan was a scientist, educator, musician, public servant, husband and father.
Article
The large radiation of terrestrial isopods (suborder Oniscidea) includes several families that are represented primarily in marine-littoral or riparian habitats. Among these are members of Ligiidae and Tylidae as well as several basal families within the section Crinocheta. Structural and physiological evidence supports a marine-littoral ancestry of the Oniscidea. We examined aerial and aquatic respiration (measured as VCO2) in six species of marine-littoral Oniscidea representing five families, as well as one riparian and one endogean species. Complimentary data were collected for immersion tolerance and whole-animal permeability in air, and structural specialization of the respiratory pleopods was examined using SEM. Ligia occidentalis Dana, 1853 (marine, littoral) and Ligidium lapetum Mulaik & Mulaik, 1942 (riparian) showed similar VCO2 in air and water. VCO2 in air for the other species was significantly higher than in water. Compared across species, aerial VCO2 scaled with mass in accordance with Kleiber’s law (β = 0.774) while aquatic VCO2 increased in approximate proportion to mass (β = 0.957). At least some specimens of the six marine-littoral species survived over 24 h immersion. Ligidium lapetum and the endogean trichoniscid Brackenridgia heroldi (Arcangeli, 1932) also tolerated prolonged immersion in freshwater but did not survive beyond 5–6 h, probably due to limited capacity for hyper-regulation. The upper shore sand-burrowers, Tylos punctatus Holmes & Gay, 1909 and Alloniscus perconvexus Dana, 1856 had the lowest permeability among the study species and are the only representatives with elaborated pleopodal respiratory fields (Alloniscus) and lungs (Tylos). The ventral lung spiracles of T. punctatus are surrounded by an extensive cuticle meshwork and we propose that this functions as a plastron field to enhance aquatic gas exchange. Collectively, the results show that littoral species tolerate significant periods of immersion, allowing them to withstand habitat inundation during spring high tides, storm swells and, in riparian species, rainstorms and snowmelt.
Article
Although scientists know that overheating kills many organisms, they do not agree on the mechanism. According to one theory, referred to as oxygen- and capacity-limitation of thermal tolerance, overheating occurs when a warming organism’s demand for oxygen exceeds its supply, reducing the organism’s supply of ATP. This model predicts that an organism’s heat tolerance should decrease under hypoxia, yet most terrestrial organisms tolerate the same amount of warming across a wide range of oxygen concentrations. This point is especially true for adult insects, who deliver oxygen through highly efficient respiratory systems. However, oxygen limitation at high temperatures may be more common during immature life stages, which have less developed respiratory systems. To test this hypothesis, we measured the effects of heat and hypoxia on the survival of South American locusts (Schistocerca cancellata) throughout development and during specific instars. We demonstrate that the heat tolerance of locusts depends on oxygen supply during the first instar but not during later instars. This finding provides further support for the idea that oxygen limitation of thermal tolerance depends on respiratory performance, especially during immature life stages.
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Crustaceans are often exposed to hypoxic stress in intensive aquaculture systems. Such stress leads to physiological, behavioural and biochemical changes, which can cause various metabolic disorders or even death. Crustacean response mechanisms to hypoxia stress are known to be complex, with their regulation involving multiple genes. In this review, after briefly exploring some known causes of hypoxic stress in aquaculture systems, we discuss the physiological adaptation strategies used by crustaceans in response to hypoxia and summarise recent information regarding the effects of hypoxia on the behaviour, survival, antioxidant ability, metabolic processes and innate immunity of crustaceans. In addition, we give particular emphasis to the known molecular mechanisms underlying hypoxia related to the hypoxia‐inducible factor 1 (HIF‐1) signalling pathway, the adenosine 5′‐monophosphate‐activated protein kinase signalling (AMPK) pathway, and apoptosis. Practically, it is clear that multiple measures need to be taken to prevent and regulate the adverse effects of hypoxic stress in intensive aquaculture systems, including development of hypoxia‐resistant breeds and nutritional regulation techniques. Overall, this review provides a theoretical basis for understanding the molecular mechanisms underlying hypoxic stress in crustaceans, while making conceptual connections with data from related study areas in other species.
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Marsupial embryos of Armadillidium vulgare (Isopoda: Oniscidea) were collected at different stages of development and assayed for products of nitrogen excretion. Stages were classified as early stage one, late stage one (clear embryo and somite differentiation), early stage two (chorion shed, prior to blastokinesis), late stage two (following blastokinesis), and mancae (vitelline membrane shed; second embryonic molt). Stage one and stage two embryos were primarily ammonotelic. Mancae showed a significant increase in stored uric acid and decrease in ammonia production, in most cases to undetectable levels. The increased metabolic rate of mancae, and the fact that they imbibe marsupial fluid prior to exiting the marsupium, may have favored a switch from ammonotely to uricotely to avoid ammonia toxicity. Protein metabolism, estimated from ammonia production, accounted for 7% of the measured catabolic rate in Stage 2 embryos. Newly emerged juveniles showed a >2-fold increase in metabolism relative to mancae, accompanying the transition from aquatic to aerial respiration. Following 48 h post-emergence, juveniles resumed ammonia excretion, volatilizing the base (NH3) as in later instars. Elevated ammonia excretion in early juveniles may derive from the catabolism of remaining yolk protein. A sharp increase in whole-animal glutamine in juveniles is consistent with its role as an intermediary nitrogen store during periodic ammonia excretion. Total ammonia concentration in the marsupial fluid fluctuated but did not increase significantly over time and ammonia was not volatilized across the oostegites, indicating that embryo ammonia is transported into the maternal hemolymph for excretion.
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At 1200-1250 m altitude at Finse, S Norway, both species show seasonal variation in cold hardiness. Gut evacuation and accumulation of cryoprotective substances during autumn result in an ability to supercool to temperatures below normal winter temperatures. The great ability of the 2 species to tolerate anaerobic conditions is important to survive periods in winter when the rock surface is enclosed by an ice crust. Adaptation to dry conditions was evident from the great ability of both species to survive drought stress. They also reproduce later in the season than most other collembolan species thus reducing the risk for the sensitive hatchlings to emerge during the driest periods of summer. In all these aspects X. maritima and A. laricis differ greatly from Collembola of climatically protected habitats. Tetracanthella wahlgreni inhabiting the surrounding lichen heath is also highly adapted to cold and anaerobic conditions, but is more susceptible to desiccation than the two rock species.-from Authors
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Summary Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92-0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplemen- tary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can be varied, allowing animals to balance water losses accurately over long periods. Blocking experiments have localised the ventral pleon as the uptake site. The pleopods display ventilatory cycling during WVA. Cycle frequency increases with humidity, compensating for changes in activity deficit between uptake fluid and air, and allowing uptake rate to be maximised. Freezing-point depression studies reveal hyperosmotic fluid in the ventral pleon. Osmolalities are compatible with prior uptake rates of the specimens studied. WVA would allow terrestrial isopods to regulate their water balance in external activities below the haemolymph activity (approximately 0.99) and above the uptake threshold. Liquid water - an alternative source for hydration - is rapidly absorbed across the hydrophilic cuticle, posing severe danger of drowning.
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The premier text in the field, Biometry provides both an elementary introduction to basic biostatistics as well as coverage of more advanced methods used in biological research. Students are shown how to think through research problems and understand the logic behind the different experimental situations. This book is designed to serve not only as a text to accompany a lecture course but is also a must-have reference text! NEW TO THIS EDITION • An Increased Focus on Computer-Based Statistical Methods. Computational formulas have also been replaced throughout with simpler structural formulas for ease of understanding. • Matrix methods. Matrix methods are introduced in new sections on multiple regression, general linear models, ancova, and curvilinear regression. A new appendix on matrix algebra is also included. • New Chapter on Statistical Power and Sample Size Estimation. The new edition features a new chapter that covers statistical power, measures of effect size, and the estimation of sample size required for tests and for confidence limits. • Up-to-Date Coverage of Key Developments in Biostatistics. This edition includes the most up-to-date coverage of key topics such as meta-analysis and trends in the discipline such as the use of resampling methods.
Chapter
The concept that insect respiration depends only on diffusion supplemented in larger species by ventilation is in need of an overhaul: the situation is much more complex. For example, ventilation appears in a variety of forms, and diffusion probably does not play the dominant role hitherto assigned to it. The insect respiratory system displays much refinement in its control systems, and there is a diversity of mechanisms which allows different species to inhabit environments ranging from the wettest to the driest, and to change abruptly from low rates to high rates of metabolism.
Article
The hypothesis of oxygen limitation of thermal tolerance proposes that critical temperatures are set by a transition to anaerobic metabolism, and that upper and lower tolerances are therefore coupled. Moreover, this hypothesis has been dubbed a unifying general principle and extended from marine to terrestrial ectotherms. By contrast, in insects the upper and lower limits are decoupled, suggesting that the oxygen limitation hypothesis might not be as general as proposed. However, no direct tests of this hypothesis or its predictions have been undertaken in terrestrial species. We use a terrestrial isopod ( Armadillidium vulgare ) and a tenebrionid beetle ( Gonocephalum simplex ) to test the prediction that thermal tolerance should vary with oxygen partial pressure. Whilst in the isopod critical thermal maximum declined with declining oxygen concentration, this was not the case in the beetle. Efficient oxygen delivery via a tracheal system makes oxygen limitation of thermal tolerance, at a whole organism level, unlikely in insects. By contrast, oxygen limitation of thermal tolerances is expected to apply to species, like the isopod, in which the circulatory system contributes significantly to oxygen delivery. Because insects dominate terrestrial systems, oxygen limitation of thermal tolerance cannot be considered pervasive in this habitat, although it is a characteristic of marine species.
Article
Adult females of the chrysomelid beetle Melasoma collaris emerged in August and collected in September do not develop mature eggs and have a lower O2-consumption at 20oC than beetles exposed to 0oC for 19 wk. After 19 wk at 0oC they accomplish vitellogenesis and oviposition within 10 d when transferred to 20oC. Adult females thus enter diapause after hatching in August and the diapause decreases in intensity with the time of exposure to low temperature and is broken after 19 wk at 0oC. When stored in 99.9% N2 at 0oC for 120 d, 60% of beetles survived. During anoxia lactate was accumulated in the haemolymph. Anaerobiosis is apparently an important factor in the overwintering biology.-from Author
Article
Tylos punctatus is an abundant oniscoid isopod on sheltered sandy beaches in southern California and in Baja California. It is strictly nocturnal, being buried in the sand or under wrack by day. During the winter it does not emerge onto the surface, remaining buried in the sand high up on the beach, the adults up to a meter deep and the juveniles shallower. From March to late October or November, however, it emerges at night to feed on stranded seaweeds and dead animals. When the high tide is early in the evening, T. punctatus emerges onto the surface only after the tide has begun to ebb from over the sand in which it is buried. Tylos moves seawards at first, but this strict seaward tendency diminishes the further down the beach it has walked. It apparently navigates by beach slope. Later in the night, having fed, Tylos moves back up the beach to bury itself at the previous night's high-water mark. T. punctatus is extremely abundant on El Estero Beach. Its reproductive rate is very low compared with that of other oniscoid isopods. Females breed once a year in summer. They incubate with that of other oniscoid isopods. Females breed once a year in summer. They incubate the embryos in their brood pouches in the sand above the high-tide line for about 9 weeks and produce an average of 13.6 young each. Larger females tend to produce more young. Very few if any females breed before they are 3 years old and most, if not all, die soon after. Some males, however, live for at least 4 years. T. punctatus only grows during a 5-month period in the summer. There is no significant difference between mean sizes or growth rates of males and females. Growth rate declines with age.
Article
Oxygen uptake and the influence of declining oxygen pressures ( $P_{O_{2}}'s$ ) were examined in a Brazilian spirostreptid millipede, Pseudonannolene tricolor. The data were obtained in a Warburg respirometer at 25° C from both male and female animals, sexually inactive, in the intermolt stage, and fasting for 24 h. In a sudden exposure to a decreased $P_{O_{2}}$ the millipedes regulated respiration down to at least 71 mmHg O₂. From a $P_{O_{2}}$ of 35 mmHg O₂ downward the animals started to show oxyconformity. When the millipedes were exposed to a stepwise declining $P_{O_{2}}$ the results indicated only conformation. After exposure to hypoxia, P. tricolor showed a pattern of "underrepayment" on return to normoxia, but larger millipedes accumulated more O₂ debt than smaller ones.
Article
The daytime distribution of Tylos punctatus Holmes and Gay was examined by coring on a sand beach in the northern Gulf of California. Moisture and temperature measurements in the cores indicated that the isopods burrow downward to reach sand with at least 1% moisture. Animals experimentally confined to sand with 0.1% moisture showed high mortality rates. We suggest burrowing depth is primarily controlled by a requirement for saturation humidity in the surrounding sand.
Article
The sandy-beach isopod Tylos granulatus Krauss burrows at the high tide mark, and has rhythms of nocturnal emergence coincident with the low tide period. Measurements of the respiration rate show that a low rate of oxygen consumption is maintained throughout the day but there is a circatidal rhythmic increase of between 300 and 700% during the nocturnal low tide. The height of this peak and the percentage of animals displaying a peak both increase from spring tide to neap tide suggesting a semi-lunar rhythm. The respiratory peaks have a 24.8 h periodicity, being later each night until low tide falls in the dawn, when there is a ‘switch-back’ so that peaks are then during the subsequent evening low tide. These respiratory rhythms are persistent under constant light and coincide with previously described activity rhythms. The respiratory rhythms considerably reduce metabolic energy losses, particularly as the activity rhythms ensure avoidance of high diurnal temperatures and activity during the cooler nocturnal period.
Article
1.Cirolana borealis utilises glycogen during anaerobiosis and shows a marked Pasteur effect. In 18h, 20–30 mg/g dry weight were converted, about half of the initial total glycogen content (Table 1).2.Lactate is the major end product, while succinate and alanine are minor end products. 27–52% of the lactate produced was excreted into the incubation water (Tables 2 and 3). A good stoichiometric relationship was obtained between the glycogen consumed and the accumulation of these end products.3.Small amounts of glutamate and aspartate contribute to the carbon flow, which could be of significance for obtaining redox balance (Table 3).4.ATP production during anoxia was 75% of that during the standard aerobic state.5.It is concluded that anaerobic fermentative metabolism ofC. borealis is adapted to maintain a high ATP output per unit time, which suits the high energy demand under natural anaerobic conditions.6.WhenC. borealis are subjected to experimental anoxia they expel their gut contents and the incubation water becomes enriched with acetate, propionate, and amino acids. Most of these compounds probably stem directly from the gut content, while some, like acetate, may be produced by microbial activity. Starvation and anaerobic preincubation resulted in a marked lowering of the amounts of these compounds in the incubation water.
Article
Relationship of body weight, imposed fasting, temperature, fight intensity, and oxygen concentration to oxygen consumption in Porcellio laevis and Armadillidium vulgare has been investigated in a series of laboratory experiments. It was observed that (1) the metabolic response in the two species to temperature change was a uniform increase of oxygen consumption with increasing temperature from 15°C to 30 °C. Beyond 30 °C, the oxygen consumption in each species fell, and the thermal death point was reached at about 40 °C. (2) The response to decreasing oxygen concentrations was a corresponding decrease in oxygen consumption. Armadillidium vulgare was a partial regulator while Porcellio laevis was able to conform its internal state to the changing oxygen levels. (3) In each species there was a decrease in metabolic rate with increasing body weight. (4) On the basis of their general activity level and oxygen consumption rate, Porcellio appeared to be a nocturnal species, while Armadillidium had a day active metabolism.
1.1. A respiratory overshoot or oxygen debt was found in Corystes cussivelaunus and Galathea strigosa after exposure to a hypoxic stress. This oxygen debt was dependent on the length and severity of the hypoxic period and the oxygen debt/deficit ratio was smaller in Corystes than in Galathea.2.2. Haemolymph lactate levels rose rapidly during hypoxia in both Corystes and Galathea but returned to control levels more rapidly in Corystes when returned to normoxia.3.3. Comparative studies of lactate levels in other crustaceans showed that lactate declined during recovery from hypoxia more rapidly in burrowing crustaceans compared to non-burrowing species.4.4. The problem of interpretation of oxygen debt/deficit ratios is discussed together with the possible role played by lactate during anaerobic periods.
Article
Little is known of the physiology of isopods, and although much work has been done on the osmoregulation of other crustacean groups in both marine and fresh- water environments, the isopods have been rarely studied. The occurrence of related isopod species in marine, fresh-water and terrestrial habitats should provide interesting material for comparative physiological study. Ligia oceanica (L.) is the largest of the endemic species and so a suitable subject for experimental work. The recent development of a micro-freezing-point determination of osmotic pressure (Ramsay, 1949) and the micro-analytical techniques of Robertson & Webb (1939) make possible the analysis of the small quantities of blood obtainable from these animals. This work was begun in order to find out if L. oceanica could control the con- centration of salts and water in the blood in aquatic and terrestrial conditions. To this end the osmotic pressure of the blood was measured in animals living in varied conditions of salinity and oxygenation, and in moist and dry terrestrial conditions. The influence of moulting on the concentration of salts in the blood was also followed, but without any clear-cut results. Previous measurements of the osmotic pressure of the blood in various isopod species have been made. Widmann (1935), using a cryoscopic method, gives a range of 2-2-2-5A0 C. for normal L. oceanica collected from the shore; Bateman (1933) with vapour pressure determinations in the same species living on moist seaweed gives A2-29° C. (recalculated from the mean molar concentration given). Blood calcium was determined in the related L. exotica by Numanoi, who found o-11 mg. calcium in o-i ml. blood (1934) and 0-97 mg. ± 0-06 in 1 ml. blood (1937). Of this total calcium, 75 % was found to be dialysable and 25 % bound to proteins.
Article
The 6j symbols of the exceptional group �7 are studied and evaluated explicitly for a number of important cases involving the fundamental and adjoint representations. These 6j symbols suffice to calculate all the 3jm factors (or isoscalar factors) involving the fundamental or adjoint representations of �7 at least twice, except in the latter case those involving the power-4 irreps (426) and (3 225).
Article
SUMMARY 1. Within a few hours of the lobsters being placed in the experimental chamber in normoxic water (POi, 130-135 mmHg), their heart rate, oxygen uptake (^Oj) and ventilation volume (Vu) were relatively high. The scaphog- nathites were simultaneously active on both sides (bilateral ventilation) for 50% of the time, active on one side only (unilateral ventilation) for 32% of the time and simultaneously inactive (respiratory pause) for 18% of the time. Percentage extraction of O2 (% Ext.) was relatively low. 48 h after having been set up, heart rate, VOi and Vg had decreased significantly, % Ext. had increased and bilateral ventilation occupied 25 % of the time. Heart rate was low and the beat irregular. 2. Upon subsequent exposure to hypoxia (POj, 50-55 mmHg), PQio, fell, there was initial hyperventilation, bilateral ventilation for 89 % of the time, heart beat was more regular but £'Oa did not change significantly. An initial increase in pHa caused the O2 affinity of the Hey to rise. After 72 h exposure to hypoxia j£ and pHa had declined, but *Vg was still higher than at the end of the period of normoxia. Blood lactate, POi and % Ext. were not significantly different from the values recorded after 48 h in normoxic water. Upon return to normoxic water, Vg and the time the animals spent ventilating both branchial chambers fell, but POt increased. 3. It is concluded that for settled lobsters, I^Oa could be maintained during moderate hypoxia by increasing J£, maintaining a regular heart beat, and at least initially by increasing the O2 affinity of the Hey.
1.1. Oxygen consumption and ammonia excretion were measured simultaneously in Ligia beaudiana, at 15, 25 and 35°C.2.2. Oxygen consumption is unaffected by substrate factors or by time of year (September vs. October), and there are no signs of acclimatization to acute temperature changes.3.3. Ammonia is excreted in sufficient quantities only when the animals are provided with a moist substrate (glass wool soaked in sea or tap water).4.4. In September ammonia production is three to eight times—according to temperature—higher than in October.5.5. It is shown that a pH of 8·6–8·8 would be required to volatilize as much ammonia from a 10 mM solution as can be trapped in gaseous form from terrestrial isopods.
Article
The morphology of the respiratory structures located in the pleopod exopodites of terrestrial Isopoda is described for representative species of different genera. Special emphasis is set on the evolution of these lungs in the context of phylogenetic relationships as revealed by other morphological characters. In the most primitive species of the Oniscidea, and still of subordinate taxa of the Crinocheta, respiration takes place in the thin ventral integument of the exopodites. The evolution of dorsal respiratory fields with a weakly wrinkled surface occurred at least six times within the Crinocheta. In five of these cases, a further development can be observed. The evolution of a partly covered respiratory field with strongly wrinkled surface may have taken place six times. It is assumed that completely internalized lungs with spiracles surrounded by a water-repellent surface microsculpture, evolved at least six times independently within the Oniscidea: in the Tylidae, Actaecia, Aphiloscia, the Eubelidae, the Armadillidae and in a taxon probably comprising Porcellionidae plus Armadillidiidae.
Article
At concentrations between 0 and 15 mM, L-lactate increases the oxygen affinity of the hemocyanin in hemolymph dialysates of the crabs Carcinus means and Cancer pagurus without changing the Bohr effect. A possible role of lactate and other anaerobic end products as cofactors regulating the oxygen transport function is suggested.
Article
During environmental anaerobiosis, when the whole organism is exposed to anoxic conditions caused by external, physical factors in the microhabitat, arginine phosphate, glycogen, and aspartate (only mollusks) are the substrates for the metabolism. Main end products formed are lactate (Crustacea, Xiphosura, some Gastropoda and Bivalvia), alanine, succinate, and the volatile fatty acids, propionate and acetate (most Gastropoda and most Bivalvia). Because of reduction of the overall metabolism in bivalves, utilization and production rates of substrates and end products, respectively, are low. They are generally faster in Crustacea, which do not reduce their metabolism. During functional anaerobiosis, when the muscle tissue becomes anoxic because of increased work done by the animal, energy is derived from arginine phosphate and glycogen. The main end products formed are lactate (Crustacea), octopine (active Gastropoda and Bivalvia), and strombine/alanopine (some gastropod species). Utilization rates of the phosphagen and production rate of lactate and opines are sometimes more than 500-fold higher than during environmental anaerobiosis. These strong variations in the glycolytic flux are probably regulated by the influence of the phosphagen and adenylates on regulatory enzymes and by the NADH/NAD ratio.
Abstract1.Oxygen consumption (MO2) may be independent or dependent upon environmental partial pressure of O2 (PIO2). The degree of regulation depends upon the species, the physiologic state of the individual, as well as temperature and salinity of the environment.2.A model of gas exchange is presented where MO2 depends upon the PO2 gradient between the environment and mitochondria and on the O2 conductance (GT) through the animal: MO2=Gr (PiO2−PmO2).3.Regulators compensate for a fall in PIO2 by increasing O2 conductance such as via increased ventilation (VG) or circulation. Different strategies are evident by examining changes in VG and O2 extraction and percent utilization.4.Three types of conformers are designated depending upon the extent to which they compensate anaerobically for a drop in P1O2.5.Five types of recovery patterns from hypoxia are designated depending upon the nature of the O2 debt.
Article
In crayfishOrconectes limosus and shrimpCrangon crangon abdominal muscle, lactate dehydrogenase (LDH, EC 1.1.1.27) is encoded by one locus. No polymorphism was detected. The enzymes were purified to homogeneity. The specific activities for purified crayfish and shrimp LDHs were 472 and 414 μmol NADH min−1 mg−1, respectively, at 30°C. Their physicochemical and kinetic properties did not resemble fish (Gadus morhua) LDH-A4 isoenzyme. Their amino acid composition indicated greater similarity to fish LDH-C4 isoenzymes.
Article
Using prawns, Palaemon elegans (Rathke) from intertidal pools on the Isle of Cumbrae, Scotland, and P. serratus (Pennant) from the subtidal at Plymouth, England, some metabolic responses to hypoxia and anoxia have been studied. P. elegans was found to have a greater tolerance of severe hypoxia than P. serratus. Tolerance of totally anoxic conditions, however, was limited to only 4 h in P. elegans and to approximately 1 h in P. serratus. exposure to moderate hypoxia (30 torr) resulted in little change in the concentration of L-lactate in the blood or in the tissues of either P. elegans or P. serratus. When exposed to extreme hypoxia (10 or 5 torr for P. elegans), however, there was a progressive increase in the concentration of L-lactate in the blood and in the tissues of both species. After normoxic conditions had been restored, the concentration of L-lactate in the blood and in the tissues returned to normal resting levels more rapidly in P. elegans than in P. serratus. Under hypoxic conditions, both P. elegans and P. serratus showed an increase in the concentration of blood glucose and a slight reduction in the glycogen content of the tissues. The concentrations of blood glucose and of tissue glycogen returned to normal levels within 6 h of the prawns being returned to normoxic conditions. The results of an in situ study in April and August 1986 to examine the metabolic responses of P. elegans to the hypoxic conditions normally experienced in high-shore rock pools are also presented. The ecological significance of the differing abilities of these species to survive hypoxic exposure is discussed.
Article
We investigated the accumulation of haemolymph L-lactate in response to anoxia, progressive hypoxia and activity, in a species that rarely encounters low PO2 in its natural environment, the freshwater amphipod Gammarus pulex (L.). Individuals survived –1 h–1. No lactate was excreted into the medium during this time. Despite the fact that most individuals of G. pulex were oxyconformers, exposure to acutely declining PO2s did not result in a switch to anaerobic pathways until PO2 < 4.4="" kpa.="" even="" then="" the="" concentrations="" accumulated="" remained="" very="" low="" until="">2 < 0.46="" kpa.="" there="" was="" no="" accumulation="" of="" l-lactate="" in="" the="" haemolymph="" as="" a="" result="" of="" exhaustive="" activity.="" consequently,="" it="" was="" suggested="" that="" (a)="" it="" cannot="" be="" automatically="" assumed="" that="" anaerobic="" metabolism="" is="" switched="" on="" only="" at="" the="" point="" at="" which="" oxyregulation="" breaks="" down,="" (b)="" that="" the="" poor="" anaerobic="" capacity="" observed="" plays="" little,="" if="" any,="" role="" in="" the="" metabolic="" response="" to="" hypoxia="" by="">Gammarus pulex.
Article
In terrestrial isopods there are two types of a water conducting system. The porcellio-type is a recycling system. Out of the maxillar-nephridium urine is secreted, which spreads through the ventral and dorsal structures of the water conducting system. It is then directed along the pleopods and is reabsorbed in the gut. Within this system only urine runs. The ligiatype is an open system. Here urine runs as well as water, which is absorbed by the sixth and seventh pereiopods. In all the species investigated incl. Ligia and Hemilepistus a water conducting system has been found. Apparently this system is constitutive for all terrestrial isopods. Concerning function (hypothesis): the water conducting system is multifunctional, but above all serving excretion. Isopods, also terrestrial isopods, are ammoniotelic. While the urine is spreading through the conducting structures ammonia is vapourizing off the increased surface. A special permeability of the integument needs not be assumed. After the urine having passed the anus, it is reabsorbed in the gut. The disadvantage of the ammoniotelism, the great demand of water, is avoided, the advantage, the economizing of energy, is preserved. Additionally the water conducting system allows an active thermoregulation to a certain extent. Furthermore it has functions in respiration, conducting of water and keeping the integument humid and clean.
Article
1. Die Lebensdauer von Porcellio scaber bei Submersion unter Wasser ist in hohem Grade abhngig von der Temperatur. 2. Verwundete Versuchstiere vermgen unter physiologischer Kochsalzlsung lnger zu leben als unter Wasser; bei intakten Tieren ist dieser Unterschied nicht vorhanden. 3. Durch Ausschaltung der Corpora alba mittels Paraffinum liquidum wird die Sauerstoffaufnahme stark beeintrchtigt, die Kohlensureabgabe jedoch nicht. 4. Durch Bestimmung der Lebensdauer von Tieren mit und ohne funktionierende Corpora alba in Gasgemischen von verschiedener Sauerstoffspannung wird bewiesen, da die Corpora alba wichtige Luftatmungsorgane sind.
1.1. The oxygen consumption of Talitrus pacificus, measured at 20°C and in normoxic conditions, varied with body weight according to the equation O2 = 1.245 W0.462 for N = 45(1.4–34.1 mg) and r = 0.725 (P < 0.05).2.2. The weight (mg) specific oxygen consumption (“respiratory rate”) of T. pacificus ranged from 1.171 (1.4 mg animal) to 0.148 (34.1 mg animal) in μ 102mg/hr.3.3. The respiratory rates of T. pacificus acclimated to 20°C increased with rising temperatures, particularly in the range 10–15°C (Q10 = 3.65); a Q10 = 1.09 indicated a zone of respiratory homeostasis between 25 and 30°C.4.4. In declining oxygen tensions, T. pacificus regulated the rate of oxygen consumption down to 105 or even 70 mm Hg of O2.5.5. No animals out of groups of 10 survived after 40–45 min in an anoxic condition (100% nitrogen).
1.1. During environmental anoxia glycogen was the sole substrate and l-lactate the only quantitatively important anaerobic end product in the crayfish Orconectes limosus.2.2. Muscle lactate concentration increased to 20 mM, Whereas blood lactate level accumulated to approx. 60 mM after 16hr of anoxia.3.3. A pronounced breakdown of arginine phosphate and a decrease of the energy charge value occurred only during prolonged anoxia.4.4. During recovery from anoxia venous Po2 was elevated, the phosphagen pool restored between 1 and 6hr and blood and muscle lactate levels were not back to control levels between 12 and 24 hr.5.5. During functional anoxia (swimming) muscle phosphagen level was diminished rapidly, some lactate was produced and the energy charge dropped from 0.94 to 0.79.6.6. During recovery after exercise venous hemolymph Po2 rose, the energy charge was fully restored and the phosphagen pool was restored to 70% (1 hr) and muscle and blood lactate levels were slightly elevated.
Article
Osmoregulation of the haemolymph during dehydration was investigated in a selection of temperate oniscidean isopods. Inulin tracer studies show that the haemolymph contributes approximately 69% of water losses in Porcellio scaber, significantly more than predicted from the volume of this compartment (42% of total water). Haemolymph osmolality increases linearly as a function of haemolymph dehydration but at a significantly lower rate than predicted from the change in haemolymph fluid volume. Similar results for Oniscus asellus show that both species display efficient osmoregulation until lethal dehydration. Osmoregulation is associated with significant hyporegulation of haemolymph sodium and chloride. These findings indicate that: (1) cell water is conserved at the expense of the haemolymph; and (2) haemolymph dehydration is associated with the removal of Na+ and Cl− contributing to net osmoregulation. During dehydration, accumulations of both Na+ and Cl− are seen in the hindgut, with significant accumulations of electrolytes also seen in the luminal fluid of the hepatopancreas. Low fluid volumes in the foregut and hindgut suggest macromolecular association as the most plausible mechanism of ion sequestration. Evidence refutes ion excretion and haemocyte sequestration as osmoregulatory mechanisms. Sequestration of Na+ as urate salts, as shown for Periplaneta and generally assumed for other insects, is insignificant in isopods.
The thalassinidean shrimp Calocaris macandreae inhabits complex burrows in marine muddy sediments which are subject to severe hypoxia. In the laboratory, C. macandreae was highly tolerant of anoxia (LT50 = 43 hr) and accumulated l-lactate as the major end-product of anaerobic metabolism. Metabolic recovery of C. macandreae from anoxia was slow; haemolymph lactate concentrations returned to normal levels after approximately 40 hr. Anaerobic metabolism appeared to be initiated only during exposure to severe hypoxia (PO2 < 7 Torr).
Article
The degree of hypoxia experienced by Carcinus maenas (L.) in littoral rock pools varies throughout the year. In summer, conditions may become extremely hypoxic or even anoxic at night. Crabs which remain in the pools utilize anaerobic metabolism for energy production as indicated by an increase in tissue lactate. In the laboratory, l-lactate was found to be the major end-product of anaerobic metabolism for although fumarate and alanine accumulated during anoxia, the amounts accumulated indicate that alternative metabolic pathways are of only very limited importance in C. maenas. Survival for long periods under anoxic conditions necessitates a considerable reduction in metabolic rate. Calorimetric measurements indicated that, during anoxia, the metabolic rate of C. maenas is reduced to <20% of the normoxic rate. Exposure to anoxia resulted in significant acid-base disturbances. Although a marked metabolic acidosis developed, there was no indication that exoskeletal carbonates were important in buffering these changes. Recovery from anoxia resulted in a pronounced increase in the rates of O2 consumption and heart rate. A transient but significant increase in tissue lactate concentration was observed during the initial stages of recovery suggesting that anaerobic glycolysis may also be important in meeting the high energy demands of the crabs at this time.