The effects of temperature on walking and righting in temperate and Antarctic crustaceans

Antarctic marine invertebrates live in a cold, thermally stable environment and cannot tolerate large changes in body temperature (i.e. they are stenothermal). Their temperate relatives, by contrast, are eurythermal, living in warmer and thermally more variable environments. Have these different environments influenced how specific behaviours are affected by changes of temperature? This question was addressed in two temperate crustaceans, the decapod Carcinus maenas and isopod Ligia oceanica, and two Antarctic crustaceans, the isopod Glyptonotus antarcticus and amphipod Paraceradocus gibber. The thermal dependence of walking speed was analysed by contrasting the slopes of the linear part of each species’ behavioural curve. Over the temperature ranges analysed, the temperature sensitivity of walking speed in the stenotherms was 13–23% that of the eurytherms when measured in body lengths s^?1. There was a linear relationship between walking speed and temperature up to +4.5°C in the Antarctic species G. antarcticus and P. gibber. Elevating temperature by up to 3.5°C above the maximum temperature experienced in the Antarctic (+1°C), does not lead to an acute breakdown of motor coordination. We describe for the first time the righting behaviour of G. antarcticus. The mean time-to-right tended to a minimum on warming from ?2 to+5°C, but this trend was not statistically significant. Our results suggest that the physiological adaptations which permit continued activity at low Antarctic temperatures have resulted in a lower thermal dependence of activity in Antarctic species, compared to related temperate species.     

Proteasome properties of hemocytes differ between the whiteleg shrimp <Emphasis Type="Italic">Penaeus vannamei</Emphasis> and the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (Crustacea,Decapoda)

Crustaceans are intensively farmed in aquaculture facilities where they are vulnerable to parasites, bacteria, or viruses, often severely compromising the rearing success. The ubiquitin-proteasome system (UPS) is crucial for the maintenance of cellular integrity. Analogous to higher vertebrates, the UPS of crustaceans may also play an important role in stress resistance and pathogen defense. We studied the general properties of the proteasome system in the hemocytes of the whiteleg shrimp, Penaeus vannamei, and the European brown shrimp Crangon crangon. The 20S proteasome was the predominant proteasome population in the hemocytes of both species. The specific activities of the trypsin-like (Try-like), chymotrypsin-like (Chy-like), and caspase-like (Cas-like) enzymes of the shrimp proteasome differed between species. P. vannamei exhibited a higher ratio of Try-like to Chy-like activities and Cas-like to Chy-like activities than C. crangon. Notably, the Chy-like activity of P. vannamei showed substrate or product inhibition at concentrations of more than 25 mmol L^?1. The K _M values ranged from 0.072 mmol L^?1 for the Try-like activity of P. vannamei to 0.309 mmol L^?1 for the Cas-like activity of C. crangon. Inhibition of the proteasome of P. vannamei by proteasome inhibitors was stronger than in C. crangon. The pH profiles were similar in both species. The Try-like, Chy-like, and Cas-like sites showed the highest activities between pH 7.5 and 8.5. The proteasomes of both species were sensitive against repeated freezing and thawing losing ~80–90% of activity. This study forms the basis for future investigations on the shrimp response against infectious diseases, and the role of the UPS therein.     

Interannual variability in the feeding of ice fish (Notothenioidei, Channichthyidae) in the southern Scotia Arc and the Antarctic Peninsula region (CCAMLR Subareas 48.1 and 48.2)

We have studied the annual variation in food intake of three sub-Antarctic ice fish species (Champsocephalus gunnari, Chaenocephalus aceratus, and Pseudochaenichthys georgianus) and three high-Antarctic ice fish species (Chionodraco rastrospinosus, Cryodraco antarcticus, and Chaenodraco wilsoni). Stomach content analyses were conducted during bottom trawl surveys around the South Shetland Islands in 1998, 2001, 2002, 2003, and 2007, the South Orkney Islands in 1999 and 2009, and off the north-western Antarctic Peninsula in 2002, 2006, and 2006/2007 in order to obtain further insight into the amount of food of Antarctic demersal fish consume during summer. Annual variation in food intake was comparatively low within an area in the krill-feeding species C. gunnari and C. wilsoni. Food intake was much more variable, by a factor of 2 or 3 among years and areas, in larger C. aceratus and C. antarcticus, which rely heavily on fish as their dietary source. Food consumption was intermediate in the two species P. georgianus and C. rastrospinosus, which rely on both krill and fish.     

A comparative study of the respiratory properties and physiological function of haemocyanin in two burrowing and two non-burrowing crustaceans

• 1.1. Oxygen dissociation curves were constructed for the haemolymph of two non-burrowing, Galathea strigosa and Eupagurus bernhardus, and two burrowing crustaceans, C. cassivelaunus and Nephrops norvegicus. The p₅₀ at in vivo pH values and 10°C was 12.6 Torr in G. strigosa, 23 Torr in E. bernhardus, 3.1 Torr in C. cassivelaunus and 11.5 Torr in N. norvegicus.
• 2.2. The Bohr values (Δlogp₅₀/ΔpH) were high in all species ranging between −0.96 and −1.48. Cooperativity expressed as P₅₀ averaged 3.3, 3.8 and 3.8 in G. strigosa, E. bernhardus and N. norvegicus. respectively. A lower value of 2.2 was observed in C. cassivelaunus.
• 3.3. The oxygen affinity of the haemocyanin was relatively temperature independent, the values for ΔH at pH7.9 ranging between −5.1 and −18.1 kJmol⁻¹.
• 4.4. Haemolymph respiratory gas analysis showed values similar to those previously reported in crustaceans: p_aO₂ ranging between 44 and 107 Torr and p_vO₂ values between 18 and 24 Torr.
• 5.5. Pre-/post-branchial pH differences were small in G. strigosa, E. bernhardus and N. Norvegicus, but averaged 0.09 of a pH unit in C. cassivelaunus. p_aCO₂ and P_vCO₂ values ranged between 1.4 and 2.3 Torr.
• 6.6. In buried C. cassivelaunus both pre- and post-branchial oxygen tensions decreased, as did oxygen tension overall during respiratory pauses.
• 7.7. Cardiac output values were low, ranging between 59 and 71 ml kg⁻¹ min⁻¹ for all four species and calculated stroke volumes were realistic in terms of animal size.
• 8.8. In the non-burrowing species physically dissolved oxygen accounted for 5–21% of the oxygen transported to the tissues. In the burrowing species values of 40–77% were found.

     

Investigation of blood parasites of pygoscelid penguins at the King George and Elephant Islands, South Shetlands Archipelago, Antarctica

Parasites may adversely affect the breeding success and survival of penguins, potentially hampering the viability of their populations. We examined 161 pygoscelid penguins (3 Pygoscelis adeliae, 98 Pygoscelis antarcticus, and 60 Pygoscelis papua) at the South Shetlands Archipelago during the 2010–2011 summer; blood smears were examined for 64 penguins (2 P. adeliae, 18 P. antarcticus, and 44 P. papua), and a PCR test targeting Haemoproteus sp. and Plasmodium sp. was applied for 37 penguins (2 P. adeliae, 17 P. antarcticus, 19 P. papua). No blood parasites were observed, and all PCR tests were negative, leukocyte profiles were similar to those reported in other studies for wild pygoscelid penguins, and all penguins were in good body condition and had no external signs of disease. One specimen of chewing lice (Austrogoniodes sp.) was recorded in one P. antarcticus at King George Island. Ticks (Ixodes uriae) were not observed on the penguins, but were found on the ground near P. antarcticus nests at King George Island. The absence of avian blood parasites in Antarctic penguins is thought to result from the absence of competent invertebrate hosts in the climatic conditions. Predicted climate changes may redefine the geographic distribution of vector-borne pathogens, and therefore, the occurrence of blood parasites and their invertebrate hosts should be monitored regularly in Antarctic birds, particularly in the northernmost Antarctic Peninsula.     

Reproductive biology of caridean decapods from the Weddell Sea

Summary Data on reproductive biology are presented for five benthic caridean shrimps from the high Antarctic (Chorismus antarcticus, Notocrangon antarcticus, Nematocarcinus lanceopes, Lebbeus antarcticus and Eualus kinzeri). The first three species were very common on the Weddell Sea shelf and upper slope, whereas only a few individuals of the other two species were caught-but these did include some ovigerous females. Our measurements include size at first maturity, fecundity (total number and mass of eggs), individual egg mass, egg length, ovary indices, maximum size encountered and documentation of the reproductive cycle in spring and summer. Egg number generally increases with female size, and the largest species (N. lanceopes) also carries the highest number of eggs. The eggs of all high Antarctic species are large, the extreme being L. antarcticus with an egg length of up to 3.3 mm. For C. antarcticus and N. antarcticus, which have wide geographic distributions, a comparison is made with older published and unpublished data from the Subantarctic (South Georgia). High Antarctic representatives of these two species grow to a larger maximum size, attain sexual maturity later in their life cycle, and produce fewer and larger eggs in relation to both carapace length and female mass, than their Subantarctic counterparts.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Chemotactic attraction between hemocytes of the oyster,Crassostrea virginica,and bacteria

Experiments were conducted to ascertain whether there is chemotactic attraction by Bacillus megaterium and Micrococcus varians, both Gram-positive species, and Escherichia coli and Vibrio parahaemolyticus, both Gram-negative species, for hemocytes of the American oyster, Crassostrea virginica. It was ascertained quantitatively that oyster hemocytes are attracted to live E. coli, B. megaterium, and M. varians but not to heat-killed bacteria. Furthermore, oyster cells are not attracted to either live or heat-killed V. parahaemolyticus. It is concluded that the chemoattractant is some molecule emitted by living vegetative cells of certain Gram-positive as well as Gramnegative bacteria.     

Profiles of soluble carbohydrates and their adaptive role in maritime Antarctic terrestrial arthropods

The existence of seasonal changes in concentrations of water-soluble carbohydrates in arthropods (both freezing-tolerant and intolerant species) from Signy Island was demonstrated. Seasonal patterns of variation, imposed by seasonality of the maritime Antarctic environment, in the production of soluble carbohydrates in response to low temperatures and/or dehydration for a range of terrestrial arthropods were confirmed. The freshwater copepod Pseudoboeckellapoppei exhibited much lower levels of soluble carbohydrates, with glycerol as the main component, and smaller seasonal fluctuations relative to the four terrestrial species. The two Antarctic mites (Alaskozetes antarcticus and Gamasellus racovitzai) accumulated glycerol (as a single-component cryoprotective system), in agreement with previous work reporting increased glycerol levels and lowering of the supercooling point in A. antarcticus. In the case of G. racovitzai, increased levels of glycerol may function in a different manner. The larval dipteran Eretmoptera murphyi and the collembolan Cryptopygus antarcticus have complex multi-component cryoprotective systems involving trehalose that may be related to low temperature acclimation and dehydration. These findings are discussed in relation to published work on single and multiple cryoprotective systems, supercooling points and the involvement of dehydration as a complementary stress in overwintering insects. Received: 28 February 1997 / Accepted: 20 October 1997     

In vitro bacteridical capacity of Blaberus craniifer hemocytes

Blaberus craniifer hemocytes, maintained in short-term culture, are capable of phagocytosing and destroying Staphylococcus aureus, Staphylococcus albus, Streptococcus faecalis, Serratia marcescens, and Proteus mirabilis. The observed bactericidal activity of the hemocyte suspensions was entirely a function of the phagocytes; the medium, the hemolymph, and cell products elaborated during incubations were not bactericidal. No humoral opsonic factors were required for, or facilitated, bacterial phagocytosis in vitro. Washed hemocyte monolayers bathed by hemolymph-free medium were capable of phagocytosing bacteria. The addition of hemolymph concentrated by ultrafiltration did not increase the bactericidal capacity of the hemocytes. Bacteria opsonized with concentrated hemolymph were not killed more efficiently than were untreated bacteria.A partial blockage of bactericidal capacity was induced by prior exposure of the hemocytes to bacteria or to latex particles. The functional blockade was more complete with bacteria than with latex particles.Pseudomonas aeruginosa, Escherichia coli, Salmonella typhosa, and Diplococcus pneumoniae were phagocytosed but not killed by the hemocytes. This lack of bactericidal activity suggests that roaches may encounter difficulty in eliminating these organisms from the hemocoel. However, deficient bactericidal capacity probably does not entirely correlate with pathogenicity since the known insect pathogens, Staphylococcus albus, Serratia marcescens, and Proteus mirabilis, are killed by the hemocytes. Pathogenicity seems to depend on a complex of factors including bacterial strain, dose received, and intracellular survival of ingested bacteria. A possible connection between the lack of hemocytic bactericidal capacity and the role of roaches as potential disease vectors warrants further investigation.     

Heat tolerance and physiological plasticity in the Antarctic collembolan, Cryptopygus antarcticus, and mite, Alaskozetes antarcticus

Polar amplification of global warming has led to an average 2 °C rise in air temperatures in parts of the polar regions in the last 50 years. Poikilothermic ectotherms that are found in these regions, such as Collembola and mites, may therefore be put under pressure by changing environmental conditions. However, it has also been suggested that the thermal sensitivity of invertebrates declines with higher latitudes and, therefore, that polar ectotherms may not be at risk. In the current study, the heat tolerance and physiological plasticity to heat stress of two well-studied Antarctic invertebrates, the collembolan, Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus, were investigated. Both species showed considerable heat tolerance, with each having an Upper Lethal Temperature (ULT) above 35 °C (1 h exposure). These species were also able to survive for over 43 d at 10 °C and for periods of 5–20 min at 40 °C. Across all experimental procedures, A. antarcticus possessed a somewhat greater level of heat tolerance than C. antarcticus. Water loss during short duration exposures did not differ between the two species at 30, 35 and 40 °C, suggesting that the greater tolerance of A. antarcticus over this timescale was not due to higher desiccation resistance. Physiological plasticity was investigated by testing for Rapid Heat Hardening (RHH) and long-term acclimation. RHH was observed to a small degree in both species at a warming rate of 0.5 °C min⁻¹, and also 0.2 °C min⁻¹ in A. antarcticus alone. Longer-term acclimation (1 week at 10 °C) did not enhance the heat tolerance of either species. Even with this limited physiological plasticity, the results of this study indicate that C. antarcticus and A. antarcticus have capacity in their heat tolerance to cope with current and future environmental extremes of high temperature.     

Microscopic anatomy and ultrastructure of the digestive system of three Antarctic shrimps (Crustacea: Decapoda: Caridea)

Mandibles and stomachs of three Antarctic shrimp species (Nematocarcinus lanceopes, Notocrangon antarcticus, and Chorismus antarcticus) were investigated by means of scanning electron microscopy. Transmission electron microscopy of the midgut glands was applied to find out the nutritional status of the animals, which contained a broad variety of food items in their stomachs. In contrast to the Antarctic krill, the three carideans possess a dual filter system; primary filters in the cardia and secondary filters in the pyloric chamber. Morphologically, the mandibles and stomachs of the three species vary considerably; however, their food items are similar. We conclude that stomach contents do not really reflect the different modes of life or habitat preferences of the investigated species.     

Phagocytosis as a cellular immune response mechanism in the American lobster, Homarus americanus.

Procedures to quantitate accurately the in vitro phagocytosis of sheep erythrocytes and Aerococcus viridans var. homari (formerly Gaffkya homari) bacteria by hemocytes of the American lobster were utilized to assess the effect of various vaccines on the humoral and cellular defense mechanisms of the lobster. Both the percent of hemocytes showing phagocytosis and the number of particles phagocytosed increased markedly in many of the animals injected with Pseudomonas perolens cells or endotoxin. A lesser response was elicited by A. viridans cellular vaccines. In vivo phagocytosis was observed in the circulatory system of lobsters infected with A. viridans var. homari.Natural hemolymph agglutinins for sheep or rabbit erythrocytes were not affectd by any vaccines. Hemocyte numbers dropped initially after administration of P. perolens endotoxin or cells. The bactericidin level was enhanced in samples taken from vaccinated animals.     

Salt tolerance and survival thresholds for two species of Antarctic soil nematodes

We evaluated the response of the Antarctic soil nematodes Scottnema lindsayae and Plectus antarcticus to various salts (NaCl, MgSO₄, KNO₃ and NaCl + MgSO₄) and salt concentrations in prepared salt solutions ranging from 0.1 to 3 M, and in saturation paste extracts of soils collected from multiple locations where nematode abundance varied from zero to numerous, and where electrical conductivity ranged from 108 to >12,000 μS/cm. Nematode salt tolerance was salt specific; both nematode species survived in low-experimental concentrations of NaCl and MgSO₄, and neither species survived in KNO₃ solutions of any concentration. There was no survival of nematodes in the saturation paste extracts of highly saline soils (4,100 μS/cm), while survival was over 80–97% in less saline soils (1,945 μS/cm). A 1:1 dilution of these highly saline saturation paste extracts increased S. lindsayae survival to 80%, while survival of P. antarcticus was not observed until dilutions of greater than 200%. The results complement previous studies demonstrating niche partitioning of S. lindsayae and P. antarcticus across salinity gradients and strengthen interpretations of the physiological mechanisms underlying previously reported spatial correlation between soil salinity and nematodes abundance in the Antarctic Dry Valleys.     

Comparison of antibacterial activity in the hemolymph of marine bivalves from Galicia (NW Spain)

A screening study of in vitro antibacterial activity was conducted in marine bivalves with economical importance and widespread along the coast of Galicia (NW Spain). Hemocyte lysate supernatant (HLS) and plasma of Mytilus galloprovincialis, Ostrea edulis, Crassostrea gigas, Ruditapes decussatus, Ruditapes philippinarum, and Cerastoderma edule were incubated with Vibrio splendidus and Micrococcus sp. HLS and plasma for all the species demonstrated antibacterial activity, and C. edule had the highest activity per unit of protein in these hemolymph fractions. Significant differences were not found between HLS and plasma activities. Furthermore, antibacterial activity against Micrococcus sp. (Gram-positive) was stronger than against V. splendidus (Gram-negative).     

Morphology,egg cocoons,and transmission paths of the Antarctic leech Glyptonotobdella antarctica Sawyer and White, 1969 (Hirudinea: Rhynchobdelliformes: Piscicolidae)

The biology of piscicolids which move between different host species is poorly understood. Very little is known about leeches of Antarctic waters, though they are not uncommon in that region. This paper adds to the fundamental knowledge of the Antarctic piscicolid leech Glyptonotobdella antarctica Sawyer and White, 1969. According to the new findings the distribution of the species has to be extended to the geographical latitude of 76°08.1′S and to a depth of 665 m. Besides Glyptonotus antarcticus Eights 1853, sea urchins of the genus Sterechinus (Meissner 1900), and the benthic octopus Pareledone (charcoti?) (Joubin 1905) serve as hosts. Hitherto there were only two records on piscicolids from Octopus dofleini and none from sea urchins. Egg cocoons on the ventral side of the isopod Glyptonotus antarcticus were attributed to the leech. Most likely Glyptonotobdella antarctica moves between different hosts, i.e. Antarctic octopuses and their potential prey. Surface structures of the leech are studied by light and scanning electron microscope. The observations complement the basic knowledge on Antarctic leeches and provide arguments for phylogenetic discussions.     

Adaptations for the maintenance of water balance by three species of Antarctic mites

Three species of Antarctic mites, Alaskozetes antarcticus, Hydrogamasellus antarcticus and Rhagidia gerlachei, are abundant in the vicinity of Palmer Station, Antarctica. No single mechanism for reducing water stress was shared by all three species. A. antarcticus and R. gerlachei (both ca. 200 μg) are over twice as large as H. antarcticus (ca. 90 μg), but all had similar body water content (67%) and tolerated a loss of up to 35% of their body water before succumbing to dehydration. All imbibed free water and had the capacity to reduce water loss behaviorally by forming clusters. Alaskozetes antarcticus was distinct in that it relied heavily on water conservation (xerophilic classification) that was largely achieved by its thick cuticular armor, a feature shared by all members of this suborder (Oribatida), and abundant cuticular hydrocarbons. In comparison to the other two species, A. antarcticus was coated with 2–3× the amount of cuticular hydrocarbons, had a 20-fold reduction in net transpiration rate, and had a critical transition temperature (CTT) that indicates a pronounced suppression in activation energy (E _a) at temperatures below 25°C. In contrast, H. antarcticus and R. gerlachei lack a CTT, have lower amounts of cuticular hydrocarbons and have low E _as and high net transpiration rates, classifying them as hydrophilic. Only H. antarcticus was capable of utilizing water vapor to replenish its water stores, but it could do so only at relative humidities close to saturation (95–98 %RH). Thus, H. antarcticus and R. gerlachei require wet habitats and low temperature to counter water loss, and replace lost water behaviorally through predation. Compared to mites from the temperate zone, all three Antarctic species had a lower water content, a feature that commonly enhances cold tolerance.     

Molecular data support the existence of two species of the Antarctic fish genus <Emphasis Type="Italic">Cryodraco</Emphasis> (Channichthyidae)

Antarctic notothenioids represent one of the few strongly supported examples of adaptive radiation in marine fishes. The extent of population connectivity and structure is unknown for many species, thereby limiting our understanding of the factors that underlie speciation dynamics in this radiation. Here, we assess the population structure of the widespread species Cryodraco antarcticus and its sister species Cryodraco atkinsoni, whose taxonomic status is currently debated. Combining both population genetic and phylogenetic approaches to species delimitation, we provide evidence that C. atkinsoni is a distinct species. Our analyses show that C. atkinsoni and C. antarcticus are recently diverged sister lineages, and the two species differ with regard to patterns of population structure. A systematic and accurate account of species diversity is a critical prerequisite for investigations into the complex processes that underlie the history of speciation in the notothenioid adaptive radiation.     

2,5-Diketopiperazines Produced by Bacillus pumilus During Bacteriolysis of Arthrobacter citreus

We report the detection by gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry analyses of the secreted 2,5-diketopiperazines (DKPs) cyclo(-Ala-Pro), cyclo(-Gly-Pro), cyclo(-Val-Pro), cyclo(-Ile-Pro), cyclo(-Leu-Pro), cyclo(-Pro-Pro), cyclo(-HyP-Pro), cyclo(-Met-Pro), and cyclo(-Phe-Pro) produced by Bacillus pumilus. The study focuses on a marine isolate and a laboratory test strain of B. pumilus with capabilities to lyse pregrown living cell lawns of different bacterial species, among them Arthrobacter citreus. Chromatographic methods were used to analyze induced bioactive compounds. At least 13 different DKPs are produced by B. pumilus. Both strains respond with an increased production of the DKPs cyclo(-Gly-Pro), cyclo(-Ala-Pro), and cyclo(-Val-Pro) to the presence of pasteurized A. citreus cells after 4 h in a nutrient-poor liquid medium. In agar diffusion assays, these DKPs did not cause lysis zones in living cell lawns, but they did inhibit further growth of several pregrown test bacteria in microplates even at concentrations as low as 1 μg ml^?1. Antibiotic substances produced by B. pumilus after 20 h of cultivation in a special lysis medium showed lytic activity in cell-free extracts of B. pumilus culture supernatants.     

Morphology and diet are decoupled in nearshore notothenoids from King George Island,West Antarctica

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.     

Antarctic Collembolans Use Chemical Signals to Promote Aggregation and Egg Laying

Terrestrial arthropods that reside in Antarctica are exposed to considerable periods of environmental stress, thus factors that promote identification of favorable microhabitats are extremely important. In this study, we report the presence of chemical cues that induce oviposition and aggregation in two species of Antarctic collembolans, Cryptopygus antarcticus and Friesea grisea. Responses of the Collembola were enhanced by low temperatures but were not altered by humidity. One of the major physiological benefits derived from an aggregation was a substantial reduction in water loss rates. Although F. grisea and C. antarcticus were commonly found in cross-species aggregations, we found no evidence to suggest cross-species attraction. When individuals were exposed to areas previously occupied by groups of Collembola, more eggs were laid. Thus, chemicals released by the collembolans appear to induce both aggregation and oviposition in these Antarctic species.