Leech removal is not the primary driver of basking behavior in a freshwater turtle

Leaving the water to bask (usually in the sun) is a common behavior for many freshwater turtles, with some species also engaging in “nocturnal basking.” Ectoparasite removal is an obvious hypothesis to explain nocturnal basking and has also been proposed as a key driver of diurnal basking. However, the efficacy of basking, day or night, to remove leeches has not been experimentally tested. Therefore, we examined the number of leeches that were removed from Krefft''s river turtles (Emydura macquarii krefftii) after experimentally making turtles bask at a range of times of day, durations, and temperatures. Turtles had high initial leech loads, with a mean of 32.1 leeches per turtle. Diurnal basking under a heat lamp for 3 hr at ~28°C significantly reduced numbers of leeches relative to controls. In diurnal trials, 90.9% of turtles lost leeches (mean loss of 7.1 leeches per turtle), whereas basking for 30 min under the same conditions was not effective (no turtles lost leeches, and all turtles were still visibly wet). Similarly, “nocturnal basking” at ~23°C for 3 hr was not effective at removing leeches. Only 18% of turtles lost leeches (one turtle lost one leech and another lost four leeches). Diurnal basking outdoors under direct sunlight for 20 min (mean temp = 34.5°C) resulted in a small reduction in leeches, with 50% of turtles losing leeches and an average loss of 0.7 leeches per turtle. These results indicate basking can remove leeches if temperatures are high or basking durations are long. However, it was only effective at unusually long basking durations in this system. Our data showed even the 20‐min period was longer than 70.1% of natural diurnal basking events, many of which took place at cooler temperatures. Therefore, leech removal does not appear to be the purpose of the majority of basking events.     

Reduced sialylation status in UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE)-deficient mice

Sialic acids are widely expressed as terminal carbohydrates on glycoconjugates of eukaryotic cells. They are involved in a variety of cellular functions, such as cell adhesion or signal recognition. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), which catalyzes the first two steps of sialic acid biosynthesis in the cytosol. Previously, we have shown that inactivation of the GNE by gene targeting causes early embryonic lethality in mice, whereas heterozygous GNE-deficient mice are vital. In this study we compared the amount of membrane-bound sialic acids of wildtype mice with those of heterozygous GNE-deficient mice. For that we quantified membrane-bound sialic acid concentration in various organs of wildtype- and heterozygous GNE-deficient mice. We found an organ-specific reduction of membrane-bound sialic acids in heterozygous GNE-deficient mice. The overall reduction was 25%. Additionally, we analyzed transferrin and polysialylated neural cell adhesion molecule (NCAM) by one- or two-dimensional gel electrophoresis. Transferrin-expression was unchanged in heterozygous GNE-deficient mice; however the isoelectric point of transferrin was shifted towards basic pH, indicating a reduced sialylation. Furthermore, the expression of polysialic acids on NCAM was reduced in GNE-deficient mice. Daniel Gagiannis and André Orthmann have contributed equally to this work.     

Epizootiology of blood parasites in an Australian lizard: a mark-recapture study of a natural population

The dynamics of a naturally endemic blood parasite (Hepatozoon hinuliae) were studied in a lizard (Eulamprus quoyii) host population, using 2 years of longitudinal data. We investigated how parasite abundance in the population varied over time, examined whether certain host sub-populations were more prone to infection, and compared parasite loads in relation to host reproductive behaviour. We recorded blood parasite infections of 331 individuals, obtained in 593 captures. Prevalence (the proportion of the host population infected) of blood parasites was high; approximately 66% of the lizard population was infected. Probability of infection increased with host age and size, but did not differ between the sexes. Within individuals, parasite load (the intensity of infection within individuals) did not vary over time, and was independent of host reproductive behaviour. Parasite load was significantly higher in males compared to females.     

Enzymic glucosylation of gibberellins

Starting from the well-known conversion of exogenously applied free gibberellic acid (GA₃) to its 3(O)-glucoside by intact immature fruits of runner beans (Phaseolus coccineus L.), a protein fraction has been prepared from this plant material possessing glucosylating activity towards GAs. This glucosyltransferase is located in the pericarp only and utilizes preferably UDP-glucose as a sugar donor. The product formed enzymically from GA₃ and UDP-glucose could be identified by derivatization and comparison with the authentic compound to be GA₃-3(O)-glucoside. Among 15 native or chemically modified GAs, the enzyme glucosylates only GA₃ and to a lower extent GA₇ and GA₃₀, indicating a high enzyme specificity with regard to the A ring of gibberellins. The physiological significance of the enzymic GA₃-3(O)-glucoside formation inPhaseolus coccineus is not clear, since this glucoside is not known to be endogenous in this plant. The enzyme preparation did not glucosylate substances of phenolic structure, such as hydroquinone, aesculetin, and quercetin. Glucosylation of GA₃ was achieved also by enzyme preparations fromVigna sinensis and from cell suspension cultures ofDigitalis purpurea. A number of other plant materials showed no activity.Gibberellins 100. For part 99 see Liebisch et al. 1984a.     

In vitro glucosylation of gibberellins

In maturing fruits ofPhaseolus coccineus a soluble glucosyltransferase activity occurs which converts gibberellins into their O-glucosides. The enzyme glucosylates GA₃ and structurally closely related gibberellins (GA₇ and GA₃₀) to their 3-O-glucosides by transfer of glucose preferentially from UDP-glucose. From cell suspension cultures ofLycopersicon peruvianum cytosolic glucosyltransferases were isolated which in the presence of UDP-glucose converted GA₇ and GA₉ to the corresponding glucosyl esters. In both cases numerous other gibberellins failed to serve as substrates. Thus, the enzymes are UDP-glucose: gibberellin glucosyltransferases of considerable substrate specificity.     

Behavioural responses of an Australian colubrid snake (<Emphasis Type="Italic">Dendrelaphis punctulatus</Emphasis>) to a novel toxic prey item (the Cane Toad <Emphasis Type="Italic">Rhinella marina</Emphasis>)

The invasion of a toxic prey type can differentially affect closely related predator species. In Australia, the invasive Cane Toad (Rhinella marina) kills native anurophagous predators that cannot tolerate the toad’s toxins; but predators that are physiologically resistant (i.e., belong to lineages that entered Australia recently from Asia, where toads of other species are common) have been more resilient. In the current study, we examine the case of an Asian-derived predator lineage that relies on behavioural not physiological adaptations to deal with toads. Despite their Asian origins, Common Tree Snakes (Dendrelaphis punctulatus) are highly sensitive to toad toxins; yet this snake has not declined in abundance due to toads. We exposed captive (field-collected) snakes to toads of different sizes and ontogenetic stages, to quantify feeding responses and outcomes. Tree Snakes were less likely to attack toads than to attack native frogs, and rarely retained their hold on large toads. Tree Snakes ingested frogs of a wide range of body sizes but only ingested very small toads (<?1 g vs. up to 30 g for frogs). Behavioural responses were virtually identical between Tree Snakes from invaded versus yet-to-be-invaded areas, suggesting that preadaptation (from Asia) rather than adaptation (within Australia) is the key to successful utilisation of this novel but potentially toxic prey resource. Nonetheless, a previously-documented shift in relative head sizes of Tree Snakes coincident with toad invasion suggests that the ancestral behavioural tactic may have been reinforced by a recent morphological shift that further reduces maximal prey size, and hence the risk of fatal poisoning.     

Benthic communities along a littoral of the Central Adriatic Sea (Italy)

Bacteria, meio- and macrofauna were investigated at different depths in a coastal area of the Central Adriatic Sea, yielding information about the composition and abundance of the benthic community. In particular, 14 nematode genera were recorded for the first time in the Upper Adriatic Sea. All communities resulted as being significantly different between inshore and offshore stations, especially when the season interaction was considered. Sediment grain size seemed to be the main natural variable, along with trophic resources, affecting the distribution and composition of these benthic components, whilst there was no clear evidence of competition for food sources and predatory pressure between the communities. Meiofauna appeared the most useful community for detecting disturbances and river influences. In particular, the lowest copepod abundance in the shallow waters seemed to be related to a greater anthropogenic disturbance inshore, whilst meiofaunal abundance and diversity together with the nematode maturity index suggest the influence of the Foglia and Metauro rivers and the small stream Arzilla.     

Adaptation or preadaptation: why are keelback snakes (<Emphasis Type="Italic">Tropidonophis mairii</Emphasis>) less vulnerable to invasive cane toads (<Emphasis Type="Italic">Bufo marinus</Emphasis>) than are other Australian snakes?

Biological invasions can expose native predators to novel prey which may be less nutritious or detrimental to predators. The introduction and subsequent spread of cane toads (Bufo marinus) through Australia has killed many anuran-eating snakes unable to survive the toad’s toxins. However, one native species, the keelback snake (Tropidonophis mairii), is relatively resistant to toad toxins and remains common in toad-infested areas. Is the keelback’s ability to coexist with toads a function of its ancestral Asian origins, or a consequence of rapid adaptation since cane toads arrived in Australia? And does the snake’s feeding preference for frogs rather than toads reflect an innate or learned behaviour? We compared keelback populations long sympatric with toads with a population that has encountered toads only recently. Unlike toad-vulnerable snake species, sympatry with toads has not affected keelback toxin tolerances or feeding responses: T. mairii from toad-sympatric and toad-naïve populations show a similar sensitivity to toad toxin, and a similar innate preference for frogs rather than toads. Feeding responses of neonatal keelbacks demonstrate that learning plays little or no role in the snake’s aversion to toads. Thus, behavioural aversion to B. marinus as prey, and physiological tolerance to toad toxins are pre-existing innate characteristics of Australian keelbacks rather than adaptations to the cane toad’s invasion of Australia. Such traits were most likely inherited from ancestral keelbacks that adapted to the presence of bufonids in Asia. Our results suggest that the impact of invasive species on native taxa may be strongly influenced by the biogeographic histories of the species involved.