Interspecific mating of the introduced bumblebee <Emphasis Type="Italic">Bombus terrestris</Emphasis> and the native Japanese bumblebee <Emphasis Type="Italic">Bombus hypocrita sapporoensis</Emphasis> results in inviable hybrids

The bumblebee Bombus terrestris is not only an effective pollinator, but also a potential invasive alien species outside its native range. Recently, nearly 30% of queens of the Japanese native species Bombus hypocrita sapporoensis and B. hypocrita hypocrita were estimated to copulate with B. terrestris males in the field, suggesting that indigenous bumblebees could be genetically deteriorated through hybrid production with the introduced species. In this study, we evaluated hybrid production between the introduced B. terrestris and the indigenous B. hypocrita sapporoensis under laboratory conditions. The hatching rate of eggs derived from interspecific matings was 0% and 8.6% depending on the direction of the cross, which was significantly lower than that from intraspecific matings of B. terrestris (76.9%) and B. hypocrita sapporoensis (78.9%). Genetic studies using microsatellite markers revealed that both haploid and diploid individuals were present in the egg stage, whereas all hatched larvae were haploid. In addition, histological studies revealed that eggs derived from interspecific matings terminated development 2 days after oviposition. These results strongly suggested that eggs derived from interspecific matings are inviable due to post-mating isolation mechanisms. Mass release of exotic pollinators could cause serious population declines of native bumblebee species.     

Bee-hawking by the wasp, <Emphasis Type="BoldItalic">Vespa velutina</Emphasis>, on the honeybees <Emphasis Type="BoldItalic">Apis cerana</Emphasis> and <Emphasis Type="BoldItalic">A</Emphasis>. <Emphasis Type="BoldItalic">mellifera</Emphasis>

The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively.     

Conspecific flowers of <Emphasis Type="Italic">Sinapis arvensis</Emphasis> are stronger competitors for pollinators than those of the invasive weed <Emphasis Type="Italic">Bunias orientalis</Emphasis>

Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species (Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from native species.     

<Emphasis Type="Italic">Gnamptogenys hartmani</Emphasis> Wheeler (Ponerinae: Ectatommini): an agro-predator of<Emphasis Type="Italic"> Trachymyrmex</Emphasis> and<Emphasis Type="Italic"> Sericomyrmex</Emphasis> fungus-growing ants

The fungus gardens of fungus-growing ants are a potentially valuable resource for exploitation by natural enemies, but few of these antagonistic interactions have been studied. Here we describe key aspects of the behavioral ecology of Gnamptogenys hartmani (Ponerinae: Ectatommini), a specialized agro-predator of Trachymyrmex and Sericomyrmex fungus-growing ants in Panama. Raiding columns of G. hartmani attack and usurp nests with remarkably little effort: a few intruding workers are sufficient to cause panic among the attine ants and make them abscond from the nest. Both G. hartmani larvae and adults consume the fungus and the host brood, after which the colony migrates to a new fungus-growing ant nest discovered by scouting workers. The morphology of the G. hartmani larval mouthparts is similar to that of Gnamptogenys species with a non-fungal diet. However, we suggest that the presence of long spinules on the larval mandibles in the genus Gnamptogenys, comparable to those found in attine larvae, may have pre-adapted G. hartmani to fungus eating. G. hartmani workers do not actively maintain or modify fungus gardens, which makes them less efficient exploiters than Megalomyrmex, the only other agro-predatory ant species known so far.     

<Emphasis Type="BoldItalic">Osedax</Emphasis> borings in fossil marine bird bones

The bone-eating marine annelid Osedax consumes mainly whale bones on the deep-sea floor, but recent colonization experiments with cow bones and molecular age estimates suggesting a possible Cretaceous origin of Osedax indicate that this worm might be able grow on a wider range of substrates. The suggested Cretaceous origin was thought to imply that Osedax could colonize marine reptile or fish bones, but there is currently no evidence that Osedax consumes bones other than those of mammals. We provide the first evidence that Osedax was, and most likely still is, able to consume non-mammalian bones, namely bird bones. Borings resembling those produced by living Osedax were found in bones of early Oligocene marine flightless diving birds (family Plotopteridae). The species that produced these boreholes had a branching filiform root that grew to a length of at least 3 mm, and lived in densities of up to 40 individuals per square centimeter. The inclusion of bird bones into the diet of Osedax has interesting implications for the recent suggestion of a Cretaceous origin of this worm because marine birds have existed continuously since the Cretaceous. Bird bones could have enabled this worm to survive times in the Earth’s history when large marine vertebrates other than fish were rare, specifically after the disappearance of large marine reptiles at the end-Cretaceous mass extinction event and before the rise of whales in the Eocene.     

<Emphasis Type="Italic">Tenebrio</Emphasis> beetles use magnetic inclination compass

Animals that guide directions of their locomotion or their migration routes by the lines of the geomagnetic field use either polarity or inclination compasses to determine the field polarity (the north or south direction). Distinguishing the two compass types is a guideline for estimation of the molecular principle of reception and has been achieved for a number of animal groups, with the exception of insects. A standard diagnostic method to distinguish a compass type is based on reversing the vertical component of the geomagnetic field, which leads to the opposite reactions of animals with two different compass types. In the present study, adults of the mealworm beetle Tenebrio molitor were tested by means of a two-step laboratory test of magnetoreception. Beetles that were initially trained to memorize the magnetic position of the light source preferred, during the subsequent test, this same direction, pursuant geomagnetic cues only. In the following step, the vertical component was reversed between the training and the test. The beetles significantly turned their preferred direction by 180 degrees. Our results brought until then unknown original findings that insects, represented here by the T. molitor species, use-in contrast to another previously researched Arthropod, spiny lobster-the inclination compass.     

Tail loss and thermoregulation in the common lizard<Emphasis Type="Italic"> Zootoca vivipara</Emphasis>

Tail autotomy in lizards is an adaptive strategy that has evolved to reduce the risk of predation. Since tail loss reduces body mass and moving ability—which in turn are expected to influence thermal balance—there is potential for a trade-off between tail autotomy and thermoregulation. To test this hypothesis, we studied a common lizard (Zootoca vivipara) population at high latitude, inhabiting a high-cost thermal environment. Z. vivipara is a small, non-territorial lizard known as a very accurate thermoregulator. We made two predictions: (1) the reduced body weight due to tail loss results in faster heating rate (a benefit), and (2) the reduction in locomotor ability after tail loss induces a shift to the use of thermally poorer microhabitats (a cost), thus decreasing the field body temperatures of active lizards. We did not find any effect of tail loss on heating rate in laboratory experiments conducted under different thermal conditions. Likewise, no significant relationship between tail condition and field body temperatures, or between tail condition and thermal microhabitat use, were detected. Thus, our results suggest that tail autotomy does not influence the accuracy of thermoregulation in small-bodied lizards.Electronic Supplementary Material  Supplementary material is available in the online version of this article at     

Heterospecific pairing and hybridization between <Emphasis Type="Italic">Nasutitermes corniger</Emphasis> and <Emphasis Type="Italic">N. ephratae</Emphasis>

The sympatric neotropical termites Nasutitermes corniger and Nasutitermes ephratae are clearly distinguishable based on morphology, nest architecture, defensive secretion composition, and molecular markers. However, given the extensive ecological, geographical, and behavioral overlap of these closely related species, the potential for interbreeding may exist. To explore this possibility, heterospecific pairs were formed experimentally to examine courtship and colony-establishment behaviors, and reproductive potential. Courtship and nest construction behavior occurred in heterospecific pairs in a similar manner to that of conspecific pairs. Survival of pairs depended upon the species of the female partner. N. ephratae females paired with N. corniger males produced as many offspring as conspecific pairs. N. corniger females mated to N. ephratae males, however, produced significantly fewer offspring at 60 days post-establishment than the reciprocal cross or conspecific N. ephratae or N. corniger pairs. This was also the only pairing in which any aggression was observed. Heterospecific pairs and groups formed in mate choice mesocosms, suggesting that species recognition between these two termites is not an important aspect of mate choice. Overall, species mismatch tolerance and hybrid offspring viability are high. The present data, together with previous evidence from defensive secretions and isozyme analysis, suggest that hybridization may periodically occur in nature, and that reproductive barriers between these two species may be incomplete. Hybridization could provide a rare but important source of genetic diversity and may ensure mating opportunities for the more abundant sex of alates in each species.     

Alternative mating behaviors of the queen polymorphic ant <Emphasis Type="Italic">Temnothorax longispinosus</Emphasis>

Mating behaviors of ants fall into two categories: female calling, in which a female alate releases pheromones that attract males, and male swarming, in which large male aggregations attract females. Female calling is common in species with queens that return to their natal nest to found colonies dependently after mating, while male swarming is common in species with queens that disperse to found independently. In some species that display both founding strategies, a queen-size polymorphism has evolved in which dependent-founding queens are smaller than independent-founding queens. Dependent founding is likely difficult if gynes (virgin queens) are mating in distant swarms. Therefore, a queen may adopt one or the other mating strategy based on its size and founding behavior. We investigated mating behaviors in the queen-polymorphic ant, Temnothorax longispinosus. Observations in laboratory mating arenas indicated that small gynes exhibited significantly lower flight activity than large gynes. Both forms mated in male swarms, and neither form exhibited female calling. The reduced flight activity of the small morph may facilitate returning to the natal nest after mating, provided the mating swarm is located nearby. Therefore, alternative colony-founding behaviors may be possible without the evolution of female-calling behavior; however, the reduced flight activity of small morphs may require that mating swarms are not distant from the natal nest.     

Classification and ordination of understory vegetation using multivariate techniques in the <Emphasis Type="Italic">Pinus wallichiana</Emphasis> forests of Swat Valley,northern Pakistan

An understory vegetation survey of the Pinus wallichiana-dominated temperate forests of Swat District was carried out to inspect the structure, composition and ecological associations of the forest vegetation. A quadrat method of sampling was used to record the floristic and phytosociological data necessary for the analysis using 300 quadrats of 10 × 10 m each. Some vegetation parameters viz. frequency and density for trees (overstory vegetation) as well as for the understory vegetation were recorded. The results revealed that in total, 92 species belonging to 77 different genera and 45 families existed in the area. The largest families were Asteraceae, Rosaceae and Lamiaceae with 12, ten and nine species, respectively. Ward’s agglomerative cluster analysis for tree species resulted in three floristically and ecologically distinct community types along different topographic and soil variables. Importance value indices (IVI) were also calculated for understory vegetation and were subjected to ordination techniques, i.e. canonical correspondence analysis (CCA) and detrended correspondence analysis (DCA). DCA bi-plots for stands show that most of the stands were scattered around the centre of the DCA bi-plot, identified by two slightly scattered clusters. DCA for species bi-plot clearly identified three clusters of species revealing three types of understory communities in the study area. Results of the CCA were somewhat different from the DCA showing the impact of environmental variables on the understory species. CCA results reveal that three environmental variables, i.e. altitude, slope and P (mg/kg), have a strong influence on distribution of stands and species. Impact of tree species on the understory vegetation was also tested by CCA which showed that four tree species, i.e. P. wallichiana A.B. Jackson, Juglans regia Linn., Quercus dilatata Lindl. ex Royle and Cedrus deodara (Roxb. ex Lamb.) G. Don, have strong influences on associated understory vegetation. It is therefore concluded that Swat District has various microclimatic zones with suitable environmental variables to support distinct flora.     

Gamergates in the myrmicine genus <Emphasis Type="Italic">Metapone</Emphasis> (Hymenoptera:Formicidae)

Gamergates (i.e. mated reproductive workers) are mostly known from ant species within the Ponerinae. We report here the discovery of gamergates in two species of the subfamily Myrmicinae. Until now, mated reproductive females in colonies of myrmicine species have been considered morphologically distinct from the worker caste. However, in two species of the myrmicine Metapone (Metapone madagascarica and a newly discovered, not yet described Metapone species) all workers have six ovarioles and a spermatheca; and some of them are mated. There are no morphological differences between mated and non-mated workers. Field observations and laboratory studies indicate that colonies of the Metapone species can reproduce with gamergates only.     

Great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo</Emphasis>) can detect auditory cues while diving

In-air hearing in birds has been thoroughly investigated. Sound provides birds with auditory information for species and individual recognition from their complex vocalizations, as well as cues while foraging and for avoiding predators. Some 10% of existing species of birds obtain their food under the water surface. Whether some of these birds make use of acoustic cues while underwater is unknown. An interesting species in this respect is the great cormorant (Phalacrocorax carbo), being one of the most effective marine predators and relying on the aquatic environment for food year round. Here, its underwater hearing abilities were investigated using psychophysics, where the bird learned to detect the presence or absence of a tone while submerged. The greatest sensitivity was found at 2 kHz, with an underwater hearing threshold of 71 dB re 1 μPa rms. The great cormorant is better at hearing underwater than expected, and the hearing thresholds are comparable to seals and toothed whales in the frequency band 1–4 kHz. This opens up the possibility of cormorants and other aquatic birds having special adaptations for underwater hearing and making use of underwater acoustic cues from, e.g., conspecifics, their surroundings, as well as prey and predators.     

Inter and intra-population variation in shoaling and boldness in the zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Population differences in anti-predator behaviour have been demonstrated in several species, although less is known about the genetic basis of these traits. To determine the extent of genetic differences in boldness (defined as exploration of a novel object) and shoaling within and between zebrafish (Danio rerio) populations, and to examine the genetic basis of shoaling behaviour in general, we carried out a study that involved laboratory-raised fish derived from four wild-caught populations. Controlling for differences in rearing environment, significant inter-population differences were found in boldness but not shoaling. A larger shoaling experiment was also performed using one of the populations as the basis of a North Carolina type II breeding design (174 fish in total) to estimate heritability of shoaling tendency. A narrow-sense heritability estimate of 0.40 was obtained, with no apparent dominance effects.     

Female sex pheromone and male behavioral responses of the bombycid moth <Emphasis Type="Italic">Trilocha varians</Emphasis>: comparison with those of the domesticated silkmoth <Emphasis Type="Italic">Bombyx mori</Emphasis>

Analysis of female sex pheromone components and subsequent field trap experiments demonstrated that the bombycid moth Trilocha varians uses a mixture of (E,Z)-10,12-hexadecadienal (bombykal) and (E,Z)-10,12-hexadecadienyl acetate (bombykyl acetate) as a sex pheromone. Both of these components are derivatives of (E,Z)-10,12-hexadecadienol (bombykol), the sex pheromone of the domesticated silkmoth Bombyx mori. This finding prompted us to compare the antennal and behavioral responses of T. varians and B. mori to bombykol, bombykal, and bombykyl acetate in detail. The antennae of T. varians males responded to bombykal and bombykyl acetate but not to bombykol, and males were attracted only when lures contained both bombykal and bombykyl acetate. In contrast, the antennae of B. mori males responded to all the three components. Behavioral analysis showed that B. mori males responded to neither bombykal nor bombykyl acetate. Meanwhile, the wing fluttering response of B. mori males to bombykol was strongly inhibited by bombykal and bombykyl acetate, thereby indicating that bombykal and bombykyl acetate act as behavioral antagonists for B. mori males. T. varians would serve as a reference species for B. mori in future investigations into the molecular mechanisms underlying the evolution of sex pheromone communication systems in bombycid moths.     

The mimetic repertoire of the spotted bowerbird <Emphasis Type="Italic">Ptilonorhynchus maculatus</Emphasis>

Although vocal mimicry in songbirds is well documented, little is known about the function of such mimicry. One possibility is that the mimic produces the vocalisations of predatory or aggressive species to deter potential predators or competitors. Alternatively, these sounds may be learned in error as a result of their acoustic properties such as structural simplicity. We determined the mimetic repertoires of a population of male spotted bowerbirds Ptilonorhynchus maculatus, a species that mimics predatory and aggressive species. Although male mimetic repertoires contained an overabundance of vocalisations produced by species that were generally aggressive, there was also a marked prevalence of mimicry of sounds that are associated with alarm such as predator calls, alarm calls and mobbing calls, irrespective of whether the species being mimicked was aggressive or not. We propose that it may be the alarming context in which these sounds are first heard that may lead both to their acquisition and to their later reproduction. We suggest that enhanced learning capability during acute stress may explain vocal mimicry in many species that mimic sounds associated with alarm.     

First evidence of regular common cuckoo, <Emphasis Type="Italic">Cuculus canorus</Emphasis>, parasitism on eastern olivaceous warblers, <Emphasis Type="Italic">Hippolais pallida elaeica</Emphasis>

Coevolution is defined as specialized relationships between species that lead to a reciprocal evolutionary change. A particularly suitable model system for studying coevolution is the interactions between obligate avian brood parasites and their hosts. The common cuckoo (Cuculus canorus, hereafter cuckoo) is a well-known brood parasite, which utilizes a range of smaller passerines as hosts. However, warblers of the genus Hippolais have rarely been reported as being victims of cuckoos, and furthermore, few data exist on the occurrence of antiparasite defenses in these hosts. In this study, we examined possible host–parasite coevolution between cuckoos and eastern olivaceous warblers (Hippolais pallida elaeica, hereafter olivaceous warblers) in three closely situated areas in northwestern Bulgaria. The olivaceous warbler has never been reported to be a regular cuckoo host. However, the present study, carried out in 2001–2003 shows that the olivaceous warbler is regularly and heavily parasitized by the cuckoo in this area. Parasitism rate was high (26.6%, 34/128) and consistent among years, with some variation between areas. The cuckoo egg mimicry was moderately good, and olivaceous warbler rejection rate of such eggs was 50%. Cuckoo eggs laid in olivaceous warbler nests had a whitish to whitish-green ground color, and the majority appeared to be distinctly different from cuckoo eggs found in other host species in the area. The olivaceous warbler proved to be a rather good host for cuckoos as 20.6% (7/34) of cuckoo eggs laid produced fledglings, a breeding success comparable to other suitable hosts in Europe. This is the first in-depth study of brood parasitism in a warbler of the genus Hippolais, and cuckoos parasitizing olivaceous warblers probably represent a previously unknown gens.     

Taxonomy of oxalotrophic <Emphasis Type="Italic">Methylobacterium</Emphasis> strains

Most of the oxalotrophic bacteria are facultative methylotrophs and play important ecological roles in soil fertility and cycling of elements. This study gives a detailed picture of the taxonomy and diversity of these bacteria and provides new information about the taxonomical variability within the genus Methylobacterium. Twelve mesophilic, pink-pigmented, and facultatively methylotrophic oxalate-oxidizing strains were included in this work that had been previously isolated from the soil and some plant tissues by the potassium oxalate enrichment method. The isolates were characterized using biochemical tests, cellular lipid profiles, spectral characteristics of carotenoid pigments, G+C content of the DNA, and 16S rDNA sequencing. The taxonomic similarities among the strains were analyzed using the simple matching (S _SM) and Jaccard (S _J) coefficients, and the UPGMA clustering algorithm. The phylogenetic position of the strains was inferred by the neighbor-joining method on the basis of the 16S rDNA sequences. All isolates were Gram-negative, facultatively methylotrophic, oxidase and catalase positive, and required no growth factors. Based on the results of numerical taxonomy, the strains formed four closely related clusters sharing ≥85% similarity. Analysis of the 16S rDNA sequences demonstrated that oxalotrophic, pink-pigmented, and facultatively methylotrophic strains could be identified as members of the genus Methylobacterium. Except for M. variabile and M. aquaticum, all of the Methylobacterium type strains tested had the ability of oxalate utilization. Our results indicate that the capability of oxalate utilization seems to be an uncommon trait and could be used as a valuable taxonomic criterion for differentiation of Methylobacterium species.     

Evidence for a male-produced pheromone in <Emphasis Type="Italic">Tetropium fuscum</Emphasis> (F.) and <Emphasis Type="Italic">Tetropium cinnamopterum</Emphasis> (Kirby) (Coleoptera: Cerambycidae)

(E)-6,10-dimethyl-5,9-undecadien-2-ol (geranyl acetol), termed here fuscol, was identified as a male-produced pheromone emitted by Tetropium fuscum (F.) and Tetropium cinnamopterum Kirby. In field experiments, traps baited with synthetic fuscol alone were not significantly attractive, but the combination of fuscol plus host volatiles (a synthetic blend of monoterpenes plus ethanol) attracted significantly more male and female T. fuscum and female T. cinnamopterum than did host volatiles alone. This is the first homoterpenoid alcohol to be described in the Cerambycidae, and the first pheromone reported from the sub-family Spondylidinae.     

The emergence of collective foraging in the arboreal<Emphasis Type="Italic"> Gnamptogenys menadensis</Emphasis> (Hymenoptera: Formicidae)

Gnamptogenys menadensis is an arboreal nester that forages opportunistically almost exclusively on vegetation, sometimes recruiting others to participate in prey retrieval. The three-dimensional characteristics of vegetation suggest that functions describing recruitment decision thresholds or the pattern of recruitment in arboreal species may differ from those predicted by optimal foraging theory. To examine the effects of prey abundance and distance on the recruitment dynamics of G. menadensis, we baited nests with one termite, five termites or a number of termites between 20 and 40 either near to or far from the entrance and observed the ensuing behaviors. G. menadensis recruited others when encountering multiple termites regardless of the termite pile's distance from the nest, although a few individuals remained at the site and defended the resource. The pattern of arrivals at the site indicates that the majority and sometimes all arrivals were recruited from the branch trails. In combination, these results suggest that the architecture of the foraging habitat, which limits available return routes to the nest and thus increases encounter probabilities with potential recruits, shaped the process of information transfer and generated a collective pattern of foraging and prey retrieval.     

Body mass dependence of glycogen stores in the anoxia-tolerant crucian carp (<Emphasis Type="Italic">Carassius carassius</Emphasis> L.)

Glycogen is a vital energy substrate for anaerobic organisms, and the size of glycogen stores can be a limiting factor for anoxia tolerance of animals. To this end, glycogen stores in 12 different tissues of the crucian carp (Carassius carassius L.), an anoxia-tolerant fish species, were examined. Glycogen content of different tissues was 2–10 times higher in winter (0.68–18.20% of tissue wet weight) than in summer (0.12–4.23%). In scale, bone and brain glycogen stores were strongly dependent on body mass (range between 0.6 and 785 g), small fish having significantly more glycogen than large fish (p < 0.05). In fin and skin, size dependence was evident in winter, but not in summer, while in other tissues (ventricle, atrium, intestine, liver, muscle, and spleen), no size dependence was found. The liver was much bigger in small than large fish (p < 0.001), and there was a prominent enlargement of the liver in winter irrespective of fish size. As a consequence, the whole body glycogen reserves, measured as a sum of glycogen from different tissues, varied from 6.1% of the body mass in the 1-g fish to 2.0% in the 800-g fish. Since anaerobic metabolic rate scales down with body size, the whole body glycogen reserves could provide energy for approximately 79 and 88 days of anoxia in small and large fish, respectively. There was, however, a drastic difference in tissue distribution of glycogen between large and small fish: in the small fish, the liver was the major glycogen store (68% of the stores), while in the large fish, the white myotomal muscle was the principal deposit of glycogen (57%). Since muscle glycogen is considered to be unavailable for blood glucose regulation, its usefulness in anoxia tolerance of the large crucian carp might be limited, although not excluded. Therefore, mobilization of muscle glycogen under anoxia needs to be rigorously tested.