scholarly journals Embryonic exposure to conspecific chemicals suppresses cane toad growth and survival

2011 ◽  
Vol 8 (2) ◽  
pp. 226-229 ◽  
Author(s):  
Michael R. Crossland ◽  
Richard Shine
Keyword(s):  
Chemical Cues ◽  
Ecological Impacts ◽  
Cane Toad ◽  
Growth And Survival ◽  
Rhinella Marina ◽  
Embryonic Exposure ◽  
Body Sizes ◽  
Tropical Australia ◽  
Survival And Growth ◽  
Invasive Taxa

Adaptations to suppress the viability of conspecifics may provide novel ways to control invasive taxa. The spread of cane toads ( Rhinella marina ) through tropical Australia has had severe ecological impacts, stimulating a search for biocontrol. Our experiments show that cane toad tadpoles produce waterborne chemical cues that suppress the viability of conspecifics encountering those cues during embryonic development. Brief (72 h) exposure to these cues in the egg and post-hatching phases massively reduced rates of survival and growth of larvae. Body sizes at metamorphosis (about three weeks later) were almost twice as great in control larvae as in tadpole-exposed larvae. The waterborne cue responsible for these effects might provide a weapon to reduce toad recruitment within the species' invaded range.

Habitat use of the introduced cane toad (Rhinella marina) and native frog species in tropical Australia

2015 ◽  
Vol 31 (6) ◽  
pp. 531-540 ◽  
Author(s):  
Martin Mayer ◽  
Gregory P. Brown ◽  
Barbara Zimmermann ◽  
Matthew J. Greenlees ◽  
Richard Shine
Keyword(s):  
Spatial Distribution ◽  
Habitat Selection ◽  
Habitat Use ◽  
Ecological Impacts ◽  
Northern Australia ◽  
Cane Toad ◽  
Rhinella Marina ◽  
Frog Species ◽  
Tropical Australia ◽  
Reducing Activity

Abstract:The ecological impacts of introduced species can reveal mechanisms underlying habitat selection and behaviour. We investigated the habitat use of native frog species and the invasive cane toads (Rhinella marina) in tropical northern Australia to measure overlap in habitat use, and to test if the presence of the cane toad influences frog behaviour. Native frog species and the cane toad both preferred habitats close to water and unvegetated holes. However, native frogs were found further from water (on average 19.4 m) than were toads (on average 12.6 m), and preferred areas with higher vegetation (8–50 cm) than did toads, which were more abundant in vegetation lower than 8 cm. For both types of anuran, the next neighbour was more often of the same type (89% in frogs, 52% in toads) than expected by chance (observed ratio: 75% frogs vs 25% toads), reflecting these differences in habitat use. Our counts of frog abundance increased on average 14.5% in areas from which we removed cane toads temporarily. This result suggests that cane toads inhibit the activity of native anurans either by inducing avoidance, or by reducing activity. By modifying the behaviour and spatial distribution of native taxa, invasive cane toads may curtail activities such as feeding and breeding.

Predation on toxic cane toads (Bufo marinus) may imperil bluetongue lizards (Tiliqua scincoides intermedia, Scincidae) in tropical Australia

2010 ◽  
Vol 37 (2) ◽  
pp. 166 ◽  
Author(s):  
Samantha J. Price-Rees ◽  
Gregory P. Brown ◽  
Richard Shine
Keyword(s):  
Population Decline ◽  
Bufo Marinus ◽  
Ecological Impacts ◽  
Laboratory Research ◽  
Direct Result ◽  
Population Declines ◽  
Cane Toad ◽  
Lizard Species ◽  
Stochastic Variation ◽  
Tropical Australia

Context. Detecting ecological impacts of invasive species can be extremely difficult. Even major population declines may be undetectable without extensive long-term data if the affected taxon is rare and/or difficult to census, and exhibits stochastic variation in abundance as a result of other factors. Our data suggest such a situation in an iconic Australian reptile species, the bluetongue lizard. Originally restricted to Central and South America, cane toads (Bufo marinus) are rapidly spreading through tropical Australia. Most native predators have no evolutionary history of exposure to the toads’ distinctive chemical defences (bufadienolides), and many varanid lizards, elapid snakes, crocodiles and marsupials have been killed when they have attempted to consume toads. Aims. Scincid lizards have not been considered vulnerable to toad invasion; however, one lineage (the bluetongues, genus Tiliqua) consists of large omnivores that may be affected. Our field and laboratory research aimed to elucidate this concern. Methods. Nightly surveys for bluetongue lizards (Tiliqua scincoides intermedia) and cane toads were conducted along two adjacent roadways on the Adelaide River floodplain of the Northern Territory. Scent discrimination trials in the laboratory assessed lizard responses to chemical cues from three food types (native frogs, cane toads and ‘preferred foods’) by counting tongue-flicks and biting elicited by cotton swabs. A subset of lizards was presented with live toads. Key results. Numbers of bluetongues encountered during standardised field surveys in the Darwin region declined soon after toads arrived, and we have not recorded a single lizard for the last 20 months. In the laboratory, foraging responses of bluetongues were as intense to cane-toad scent as to the scent of native frogs, and many of the lizards we tested attempted to consume toads, and were poisoned as a result. Conclusions and implications. The population decline of bluetongues in this region appears to have been the direct result of fatal ingestion of toxic cane toads. Our studies thus add a scincid lizard species to the list of native Australian predators imperilled by cane-toad invasion, and point to the difficulty of detecting invader impact even for an iconic species in a system subject to detailed survey work.

scholarly journals Chemical cues that attract cannibalistic cane toad (Rhinella marina) larvae to vulnerable embryos

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michael R. Crossland ◽  
Angela A. Salim ◽  
Robert J. Capon ◽  
Richard Shine
Keyword(s):  
Atpase Activity ◽  
Inhibitory Activity ◽  
Molecular Basis ◽  
Chemical Cues ◽  
Strongly Correlated ◽  
Cane Toad ◽  
Attraction Response ◽  
Rhinella Marina ◽  
Structure Activity ◽  
Relationship Study

AbstractChemical cues produced by late-stage embryos of the cane toad (Rhinella marina) attract older conspecific larvae, which are highly cannibalistic and can consume an entire clutch. To clarify the molecular basis of this attraction response, we presented captive tadpoles with components present in toad eggs. As previously reported, attractivity arises from the distinctive toxins (bufadienolides) produced by cane toads, with some toxins (e.g., bufagenins) much stronger attractants than others (e.g., bufotoxins). Extracts of frozen toad parotoid glands (rich in bufagenins) were more attractive than were fresh MeOH extracts of the parotoid secretion (rich in bufotoxins), and purified marinobufagin was more effective than marinobufotoxin. Cardenolide aglycones (e.g., digitoxigenin) were active attractors, whereas C-3 glycosides (e.g., digoxin, oubain) were far less effective. A structure–activity relationship study revealed that tadpole attractant potency strongly correlated with Na+/K+ ATPase inhibitory activity, suggesting that tadpoles monitor and rapidly react to perturbations to Na+/K+ ATPase activity.

Rhabdias pseudosphaerocephala infection in Bufo marinus: lung nematodes reduce viability of metamorph cane toads

Parasitology ◽  
2009 ◽  
Vol 136 (8) ◽  
pp. 919-927 ◽  
Author(s):  
C. KELEHEAR ◽  
J. K. WEBB ◽  
R. SHINE
Keyword(s):  
Experimental Studies ◽  
Bufo Marinus ◽  
Ecological Impacts ◽  
Locomotor Performance ◽  
Native Range ◽  
Cane Toad ◽  
Control Plan ◽  
Survival And Growth ◽  
Host Parasite ◽  
Rhabdias Pseudosphaerocephala

SUMMARYCane toads (Bufo marinus) were introduced to Australia in 1935 and have since spread widely over the continent, generating concern regarding ecological impacts on native predators. Most Australian cane toad populations are infected with lung nematodes Rhabdias pseudosphaerocephala, a parasite endemic to New World (native-range) cane toad populations; presumably introduced to Australia with its toad host. Considering the high intensities and prevalence reached by this parasite in Australian toad populations, and public ardour for developing a control plan for the invasive host species, the lack of experimental studies on this host-parasite system is surprising. To investigate the extent to which this lungworm influences cane toad viability, we experimentally infected metamorph toads (the smallest and presumably most vulnerable terrestrial phase of the anuran life cycle) with the helminth. Infected toads exhibited reduced survival and growth rates, impaired locomotor performance (both speed and endurance), and reduced prey intake. In summary, R. pseudosphaerocephala can substantially reduce the viability of metamorph cane toads.

scholarly journals Behavioural responses of cane toad (Rhinella marina) adults and tadpoles to chemical cues

2018 ◽  
Vol 45 (2) ◽  
pp. 149-157
Author(s):  
Takashi Haramura
Keyword(s):  
Chemical Cues ◽  
Control Method ◽  
Chemical Substance ◽  
Cane Toad ◽  
Specific Chemical ◽  
Chemical Substances ◽  
Rhinella Marina ◽  
Size At Metamorphosis ◽  
Pheromonal Communication ◽  
Species Specific

Pheromonal communication may be possible to control the invader animal. Pheromone-induced behavioural changes could be exploited to control invasive species such as the cane toad (Rhinella marina). Injured cane toad tadpoles are known to produce species-specific chemical cues that alert conspecific tadpoles to danger. These chemical cues reduce both the survival rate of other tadpoles and body size at metamorphosis, and suggest that cane toad tadpoles express chemical substances that control the behaviour of other tadpoles. Identification of the chemical substance(s) involving in tadpole could lead to the development of methods to control the behaviour of cane toad. Here, the behaviour of cane toad adults and tadpoles was characterized following exposure to chemical substances extracted from dead cane toad tadpoles using methanol (MeOH) or distilled water (H2O). Adult toads showed signs of avoiding water to which the H2O-extracted chemical cue had been added. By contrast, no differences were observed in the swimming behaviour of tadpoles (control, MeOHor H2O-extracted samples). These data indicate that development of a chemicalbased behaviour control method will require more detailed chemical analyses. We used dead tadpoles to extract chemical substrate, but in future studies, the potential behaviour-controlling chemical cues should be extracted from live cane toad tadpoles.Bangladesh J. Zool. 45(2): 149-157, 2017

The fauna fights back: invasive Cane Toads killed by native centipedes in tropical Australia

2021 ◽  
Author(s):  
John Pomeroy ◽  
Gregory P. Brown ◽  
Grahame J. W. Webb ◽  
Richard Shine
Keyword(s):  
Northern Territory ◽  
Cane Toad ◽  
Popular Opinion ◽  
Rhinella Marina ◽  
Tropical Australia

ABSTRACT We report two cases of Cane Toads Rhinella marina being killed by Australasian Giant Centipedes Ethmostigmus rubripes in the Northern Territory. At 1730 h on 12 November 2020, a centipede was found attacking a subadult Cane Toad near Larrimah, Northern Territory. At 2015 h on 26 April 2005, near Humpty Doo, a centipede that was seized by a subadult Cane Toad retaliated and killed its attacker (but did not consume it). These observations reinforce the fact that, contrary to popular opinion, Cane Toads are vulnerable to many species of native predators in Australia.

Cane toad ( Rhinella marina ) vitamin A, vitamin E, and carotenoid kinetics

Zoo Biology ◽  
2021 ◽  
Author(s):  
Tarra Freel ◽  
Elizabeth Koutsos ◽  
Larry J. Minter ◽  
Troy Tollefson ◽  
Frank Ridgley ◽  
...  
Keyword(s):  
Vitamin E ◽  
Vitamin A ◽  
Cane Toad ◽  
Rhinella Marina

scholarly journals Prunus Africana Provenances Growth and Survival Evaluation in the Highland of Awi zone, Amhara Region, North Western Ethiopia

2018 ◽  
Author(s):  
Abraham Demekristos
Keyword(s):  
Light Exposure ◽  
Seedling Survival ◽  
Block Design ◽  
Soil Water Potential ◽  
Mean Value ◽  
Good Growth ◽  
Growth And Survival ◽  
Prunus Africana ◽  
Survival And Growth ◽  
Establishment Rate

The aims of the study were to evaluate seedling growth and survival of Prunus africana provenances in awi highland based on ecological requirement of the tree. We measured survival and growth of three P.africana provenances seedlings found in Ethiopia (provenances sources namely: Gedeo, Jibat and Munnessa). Design of experiment with randomized complete block design (RCBD) with three replications. Seedlings planted at 2m, 2.5m and 3m distance between plants, plot, and blocks respectively. A plot size of 10mx10m and 25 plants are found per plot (0.01ha). We used ANOVA to test differences in survival, and growth among provenances over time. Results concluded that, provenances have no significant variation among in establishment rate, plant height and collar diameter growth. Of these provenances, Jibat was the first in establishment (56%), second in height (1.97m) and diameter (2.89cm). Gedeo was stood first in height (2.30m) but second in establishment rate (52%) and thickness(3.45cm), but Munessa with very good growth in diameter(3.59cm) might be prefreed for bark extraction followed by Gedeo, last in height (1.75m),but established second (52%). Contrary to expectations, seedlings were still at substantial risk of mortality ≥3 years after planting. Probably the plants survival rate and growth probably affected by altitude, soil water potential, light exposure, and wild animal presence in the surrounding. In steep slope sites, canopy shade, existing weed vegetation as well as wild animals such as apes is unlikely to enhance seedling survival after planting. Our results suggest that seedling mean growth increased with 0.008mm thickness and 0.41mm per day while 2.8mm thickness and 146.8mm tall increment recorded in 2560meter elevated high land or injibara with mean value of 18.5°C and rain fall is 1300mm.

Changes in urinary testosterone and corticosterone metabolites during short-term confinement with repeated handling in wild male cane toads (Rhinella marina)

2011 ◽  
Vol 59 (4) ◽  
pp. 264 ◽  
Author(s):  
Edward J. Narayan ◽  
Frank C. Molinia ◽  
John F. Cockrem ◽  
Jean-Marc Hero
Keyword(s):  
Adult Male ◽  
Reproductive Effort ◽  
Hormone Secretion ◽  
Reproductive Hormone ◽  
Cane Toad ◽  
Short Term ◽  
Rhinella Marina ◽  
Testosterone Secretion ◽  
Metabolite Concentrations ◽  
Corticosterone Metabolites

Stressors generally decrease testosterone secretion and inhibit reproduction in animals. Urinary testosterone and corticosterone metabolite concentrations were measured in adult male cane toads (Rhinella marina) at the time of capture from the wild and during 24 h of confinement with repeated handling. Mean urinary testosterone concentrations increased 2 h after capture, were significantly elevated above initial concentrations at 5 h, and then declined. Mean testosterone concentrations remained elevated 24 h after capture. Mean urinary corticosterone concentrations increased after capture, were significantly elevated above initial concentrations at 2 h, and remained elevated thereafter. This is the first report in amphibians of an increase in testosterone excretion after capture from the wild, with previous studies showing either no change or decline in testosterone. This finding may be associated with the mating strategy and maintenance of reproductive effort in the cane toad, a species that shows explosive breeding and agonistic male–male interactions during breeding. The finding that testosterone excretion increases rather than decreases after capture in male cane toads shows that it should not be generally assumed that reproductive hormone secretion will decrease after capture in amphibians.

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