Cannibalism by large tadpoles of Rhinophrynus dorsalis (Anura: Rhinophrynidae)

In June 2014, we captured approximately 100 R. dorsalis tadpoles in a net from a seasonal wetland in Palo Verde National Park (10.3428 N, 85.3375 W) in N, 85.3375 W) in northwestern Costa Rica. While rearing the tadpoles in the laboratory, we observed five events in which larger tadpoles (Stage 26; Gosner, 1960) fed on conspecifics at earlier stages. At first, we interpreted this behaviour as scavenging. However, after observing more closely during two subsequent events, we noticed that the predated individuals were still alive. We were not able to observe interactions with tadpoles in older stages at this time due to tadpole mortality. Then, during the first week of the rainy season (May to November annually) on 23 May 2018, we collected approximately 300 Rhinophrynus dorsalis tadpolesUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Evidence of maternal provisioning of alkaloid-based chemical defenses in the strawberry poison frog Oophaga pumilio

Many organisms use chemical defenses to reduce predation risk. Aposematic dendrobatid frogs sequester alkaloid-based chemical defenses from a diet of arthropods, but research on these defenses has been limited to adults. Herein, we investigate chemical defense across development in a dendrobatid frog, Oophaga pumilio. This species displays complex parental care: at hatching, mothers transport tadpoles to phytotelmata, and then return to supply them with an obligate diet of nutritive eggs for about six weeks. We collected eggs, tadpoles, juveniles, and adults of O. pumilio, and detected alkaloids in all life stages. The quantity and number of alkaloids increased with frog and tadpole size. We did not detect alkaloids in the earliest stage of tadpoles, but alkaloids were detected as trace quantities in nutritive eggs and as small quantities in ovarian eggs. Tadpoles hand-reared with eggs of an alkaloid-free heterospecific frog did not contain alkaloids. Alkaloids that are sequestered from terrestrial arthropods were detected in both adults and phytotelm-dwelling tadpoles that feed solely on nutritive eggs, suggesting that this frog may be the first animal known to actively provision post-hatch offspring with chemical defenses. Finally, we provide experimental evidence that maternally derived alkaloids deter predation of tadpoles by a predatory arthropod.Ministerio del Ambiente, Energía y Technologia/[10CR000024]/MINAET/Costa RicaThe Convention on International Trade in Endangered Species/[10CR000024]/CITES/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP

How to move and when to escape: quantifying intraspecific exploratory and anti-predator behavior in an aposematic poison frog

Aposematic animals are chemically defended and tend to have bright and conspicuous color patterns that warn predators of the costs of attack. Most research on aposematism focuses on the role that predator cognition has on the evolution of aposematic defenses. Although the behavior of aposematic organisms is likely to be crucial in affecting their survival, it has been less thoroughly investigated. Bolder and more active movement decisions, and a reduced likelihood to respond to perceived threats of predation, should increase the conspicuousness and distinctiveness of aposematic prey to predators, which in turn should enhance their fitness. Here, we developed a laboratory-based framework to study the behavior of poison frogs, which are both conspicuously colored and defended by toxic alkaloids. We designed experiments to quantify boldness, exploratory behavior, movement patterns, and escape behavior (flight initiation distance from an incoming avian predator model) in the strawberry poison frog, Oophaga pumilio, from northeastern Costa Rica. We tested females, non-vocalizing males, and calling males to measure the intraspecific variability in their behavior. Calling males had a larger flight initiation distance than females, and varied more in directional change when moving compared to females. Non-vocalizing males varied more in sinuosity when moving compared to females. We found no differences in boldness or exploratory behavior between the three groups. Our results indicate movement variability within intraspecific groups of a single population in O. pumilio. Additionally, our results suggest plasticity in the escape behavior of calling males, which contrasts with findings from field-based studies. Our framework allowed us to quantify intraspecific differences in some anti-predator behaviors. Combining individual behavioral profiles with field data can provide a standardized comparative approach to understand the ecological and evolutionary consequences of anti-predator behavior within and among species of poison frogs (Abstract in Spanish in the Online Appendix 1)

Integrating tropical research into biology education is urgently needed

Understanding tropical biology is important for solving complex problems such as climate change, biodiversity loss, and zoonotic pandemics, but biology curricula view research mostly via a temperatezone lens. Integrating tropical research into biology education is urgently needed to tackle these issues. The tropics are engines of Earth systems that regulate global cycles of carbon and water, and are thus critical for management of greenhouse gases. Compared with higher-latitude areas, tropical regions contain a greater diversity of biomes, organisms, and complexity of biological interactions. The tropics house the majority of the world’s human population and provide important global commodities from species that originated there: coffee, chocolate, palm oil, and species that yield the cancer drugs vincristine and vinblastine. Tropical regions, especially biodiversity hotspots, harbor zoonoses, thereby having an important role in emerging infectious diseases amidst the complex interactions of global environmental change and wildlife migration [1]. These well-known roles are oversimplified, but serve to highlight the global biological importance of tropical systems. Despite the importance of tropical regions, biology curricula worldwide generally lack coverage of tropical research. Given logistical, economic, or other barriers, it is difficult for undergraduate biology instructors to provide their students with field-based experience in tropical biology research in a diverse range of settings, an issue exacerbated by the Coronavirus Disease 2019 (COVID-19) pandemic. Even in the tropics, field-based experience may be limited to home regions. When tropical biology is introduced in curricula, it is often through a temperate- zone lens that does not do justice to the distinct ecosystems, sociopolitical histories, and conservation issues that exist across tropical countries and regions [2]. The tropics are often caricatured as distant locations known for their remarkable biodiversity, complicated species interactions, and unchecked deforestation. This presentation, often originating from a colonial and culturally biased perspective, may fail to highlight the role of tropical ecosystems in global environmental and social challenges that accompany rising temperatures, worldwide biodiversity loss, zoonotic pandemics, and the environmental costs of ensuring food, water, and other ecosystem services for humans [3]

Heterologous hyperimmune polyclonal antibodies against SARS-COV-2: A broad coverage, affordable, and scalable potential immunotherapy for Covid-19

The emergence and dissemination of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting COVID-19 pandemic triggered a global public health crisis. Although several SARS-CoV-2 vaccines have been developed, demand far exceeds supply, access to them is inequitable, and thus, populations in low- and middle-income countries are unlikely to be protected soon (1). Furthermore, there are no specific therapies available, which is a challenge for COVID-19 patient care (2). Thus, the appearance of SARS-CoV-2 variants and reports of reinfections associated with immune escape (3, 4) highlight the urgent need for effective and broad coverage COVID-19 therapeutics. Intravenous administration of human or heterologous antibodies is a therapy successfully used in patients with viral respiratory diseases (5). Accordingly, formulations containing SARS-CoV-2 specific antibodies are an attractive therapeutic option for COVID-19 patients (6). SARS-CoV-2 specific antibodies could limit infection by direct virion neutralization and/or by targeting infected cells for elimination via complement or antibody-mediated cytotoxicity (6). Specific SARS-CoV-2 antibody-based therapeutics include convalescent plasma (CP), monoclonal antibodies (mAbs), human polyclonal IgG formulations purified from CP or transgenic animals, and heterologous hyperimmune polyclonal antibodies (pAbs) (6). Although the window for using antibody-based therapeutics varies, clinical data show that they are mainly effective if administered early after symptoms onset (6).Universidad de Costa Rica/[741-C0-198]/UCR/Costa RicaCaja Costarricense del Seguro Social/[]/CCSS/Costa RicaBanco Centroamericano de Integración Económica/[]/BCIE/Costa RicaGerman academic exchange services/[57592642]/DAAD/AlemaniaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de MedicinaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET

Sexual dimorphism of the second-to-fourth digit length ratio (2D : 4D) in the Strawberry Poison Dart Frog (Oophaga pumilio) in Costa Rica

Chang (Stynoski), Jennifer LynnThe second-to-fourth digit ratio (2D : 4D) is a well-studied sexual dimorphism that likely arises as a result of prenatal androgenic effects on homeobox gene expression. This dimorphism has been found to exhibit interesting phylogenetic patterns in which females have larger ratios than males among most mammalian species and males have larger ratios than females in most avian and reptilian species. Digit ratio has not been measured in more basal taxa such as amphibians. In this study, 2D : 4D and snout–vent length (SVL) were measured in 40 male and 44 female adult Oophaga [=Dendrobates] pumilio frogs to investigate the existence and patterning of sexual dimorphism. The 2D : 4D of the rear feet varied significantly by sex with males having a larger ratio than females. The digit ratio of the front feet did not differ between the sexes. SVL or its interaction with sex did not affect 2D : 4D on any of the feet. These results indicate that 2D : 4D in an anuran is both sexually dimorphic and follows a pattern between the sexes similar to that of diapsid species. A potential application of 2D : 4D to environmental monitoring is also discussed.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Behavioral Ecology of Parental Care in a Dendrobatid Frog (Oophaga pumilio)

Parental care is essential to the success of both parents and offspring in many species, and plays an important role in the evolution of animal mating systems and life histories. The mechanisms that regulate the intensity and form of parental care in a species are determined by many factors and are highly variable across taxa. However, our understanding of the behavioral ecology of parental care is built on research that is highly taxonomically biased to birds, with some studies also in mammals, arthropods, and fish. Amphibians display an impressive diversity of form in parental care, yet few studies of parental care have explained the mechanisms behind parental behaviors in this vertebrate class. Accordingly, the research in this dissertation tested four hypotheses about parental care in a species of dendrobatid frog that displays complex parental behavior, the strawberry poison frog (Oophaga pumilio). In this species, father frogs guard egg clutches in the leaf litter for approximately one week. When eggs hatch into tadpoles, mother frogs return to transport tadpoles individually to small terrestrial water pools such as those in the axils of a bromeliad plant. For approximately six weeks, mother frogs continue to visit tadpoles. When mother frogs visit, tadpoles display a vibration behavior. Then, mother frogs supply unfertilized eggs to their tadpoles as their principal source of food. To develop a thorough understanding of the behavioral mechanisms at play between mother and offspring O. pumilio, this dissertation tests hypotheses related to offspring discrimination, the use of multimodal sensory cues, honest signaling, and provisioning of potential chemical defenses. Studies mostly made use of behavioral tests and observations in the laboratory and in the field at the La Selva Biological Station in the lowland wet forest of Costa Rica. To facilitate observation of the interactions between mothers and tadpoles in a natural setting as well as easy access to large quantities of tadpoles, an extensive setup of 1000 artificial tadpole-rearing sites (“cups”) was installed on the trees in abandoned plantations adjacent to primary forest. Mother frogs used cups to deposit and feed tadpoles just as they would the natural phytotelmata in their habitat. Furthermore, motion-activated IR video cameras were installed at the site to permit 24-hour observation of mother-offspring interactions. Findings demonstrated that mother frogs use indirect recognition to locate tadpoles, and rely on honest signals of hunger from tadpoles to allocate nutritive eggs. Tadpole begging signals are likely reliable because of a significant cost of signal production via reduction in growth and as a result of a differential benefit of maternal eggs. Tadpoles use visual and tactile cues to discriminate between mother frogs and other visitors such as other species of frogs and potential predators when deciding whether to signal their level of need or to avoid predation. The eggs that mother frogs provide tadpoles as nourishment may also be provisioned with alkaloids that could provide chemical defenses for offspring. Thus, the behavioral mechanisms described in this research explain how mother O. pumilio determine who, when, and how much to feed, as well as how both tadpoles and mothers contribute to reducing the risk of predation to offspring

Maternally derived chemical defenses are an effective deterrent against some predators of poison frog tadpoles (Oophaga pumilio)

Parents defend their young in many ways, including provisioning chemical defences. Recent work in a poison frog system offers the first example of an animal that provisions its young with alkaloids after hatching or birth rather than before. But it is not yet known whether maternally derived alkaloids are an effective defence against offspring predators. We identified the predators of Oophaga pumilio tadpoles and conducted laboratory and field choice tests to determine whether predators are deterred by alkaloids in tadpoles. We found that snakes, spiders and beetle larvae are common predators of O. pumilio tadpoles. Snakes were not deterred by alkaloids in tadpoles. However, spiders were less likely to consume mother-fed O. pumilio tadpoles than either alkaloid-free tadpoles of the red-eyed treefrog, Agalychnis callidryas, or alkaloid-free O. pumilio tadpoles that had been hand-fed with A. callidryas eggs. Thus, maternally derived alkaloids reduce the risk of predation for tadpoles, but only against some predators.University of Miami/[NSF-OISE1114218]/UM/Estados UnidosUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Discrimination of offspring by indirect recognition in an egg-feeding dendrobatid frog, Oophaga pumilio

Offspring discrimination, the differential treatment of offspring and unrelated young, functions in numerous animal taxa to ensure that vital and costly parental care behaviours are appropriately directed. Discrimination can be facilitated either by direct (phenotypic) recognition of offspring or by indirect (nonphenotypic) recognition of offspring location. Offspring discrimination and recognition mechanisms have not been identified in an amphibian. In the strawberry poison frog, Oophaga pumilio, a dendrobatid frog with obligatory maternal provisioning behaviour, I tested whether mothers discriminate between offspring and unrelated young, whether they use direct or indirect recognition cues, and whether prior parental investment plays a contextual role in the differential treatment of young. Mother frogs utilized tadpole-rearing cups attached to tree trunks in wet tropical forest. After manipulating the identity, location and/or age of tadpoles in cups, I determined whether maternal provisioning behaviour was maintained by measuring tadpole growth and development. Mothers provisioned young regardless of tadpole identity, but were sensitive to location and did not provision tadpoles that were moved 2 cm to an adjacent cup. When given a choice between related and unrelated tadpoles in originally chosen or adjacent cups, mothers discriminated by location, but not by relatedness. Maternal provisioning behaviour persisted when a tadpole provisioned for 10 days was replaced with either an age-matched or newly hatched unrelated tadpole, so direct offspring recognition does not appear to be dependent on prior parental investment. Together, these results provide strong evidence that mother O. pumilio use indirect recognition cues to discriminate between offspring and unrelated offspring.Organization of Tropical Studies/[]/OTS/Estados UnidosInstitutional Animal Care and Use Committee/[]/IACUC/Estados UnidosUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Developmental morphology of granular skin glands in pre-metamorphic egg-eating poison frogs

Parents in many taxa, including insects, mol- luscs, fish, snakes, and amphibians provision chemical defences, such as peptides, steroids, or alkaloids to their offspring to reduce the risk of predation. In most cases, those defences are transferred to offspring in the egg and gradually diminish throughout the larval period. Adult poi- son frogs sequester alkaloid-based defences from arthro- pod prey in granular skin glands. In at least one poison frog, Oophaga pumilio, mother frogs intermittently feed tadpoles until metamorphosis with nutritive eggs contain- ing those alkaloid-based defences. However, alkaloids are not detected in tadpoles until they reach the middle stages of larval development. Here, we investigate the histology of a developmental series of O. pumilio tadpoles to deter- mine whether their ontogenetic alkaloid profile coincides with granular gland development. Our findings suggest that alkaloid sequestration in tadpoles is delineated by the dif- ferentiation of rudimentary granular skin glands in epithe- lial tissue. The timing of differentiation of granular glands in this species coincides with other anurans. Thus, provisioning of chemical defences to offspring is likely constrained by developmental timing of derived structures that can effectively store those toxic or noxious compounds.National Science Foundation/[IOS-1528866]/NSF/Estados UnidosUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí