Male calling behavior,female discrimination and acoustic interference in the Neotropical treefrog Hyla microcephala under realistic acoustic conditions

Summary Anuran choruses are acoustically complex assemblages of calling males. Little is known about the behavior of males or females in such natural sound environments. I studied calling behavior of males of Hyla microcephala in nature by using an interactive computer-based system that allowed me to simulate call interruptions by a number of males. I also monitored the calling behavior of groups of four to six males. When a male is interrupted by the call of another frog, he increases the spacing between the notes of his call. Responses of this kind are strongest to the loudest neighbor, and some males may ignore interruptions by all but a single close male. Interruptions using synthetic calls with silent gaps indicated that males respond vocally to reductions in sound intensity as brief as 20 ms. This ability helps to explain how males can rapidly alternate notes during pairwise interactions. Amounts of acoustic overlap between pairs of males in the choruses were usually below 10% of an individual's total calling time during bouts. The time a male spent calling that was free of acoustic interference by any other male ranged from 34–92% of his total calling time. When group size was decreased, this unobstructed calling time increased. Previous research showed that females of H. microcephala discriminate against calls that overlap so that the call pulse-train structure is degraded. Here I show that a 6 dB difference in intensity between the overlapped calls is sufficient to reduce the degradative effect of call interference. Females were also given a choice between interfering calls broadcast from two adjacent and two widely separated speakers. An angular separation between speakers of 120° was insufficient to elicit a preference for the separated sources. Together, data on behavior of males and females indicated that males actively reduce acoustic interference with those loud individuals most likely to degrade seriously the temporal structure of their calls.     

Testing the presence of marine protected areas against their ability to reduce pressures on biodiversity

Marine protected areas (MPAs) are the preferred tool for preventing marine biodiversity loss, as reflected in international protected area targets. Although the area covered by MPAs is expanding, there is a concern that opposition from resource users is driving them into already low-use locations, whereas high-pressure areas remain unprotected, which has serious implications for biodiversity conservation. We tested the spatial relationships between different human-induced pressures on marine biodiversity and global MPAs. We used global, modeled pressure data and the World Database on Protected Areas to calculate the levels of 15 different human-induced pressures inside and outside the world's MPAs. We fitted binomial generalized linear models to the data to determine whether each pressure had a positive or negative effect on the likelihood of an area being protected and whether this effect changed with different categories of protection. Pelagic and artisanal fishing, shipping, and introductions of invasive species by ships had a negative relationship with protection, and this relationship persisted under even the least restrictive categories of protection (e.g., protected areas classified as category VI under the International Union for Conservation of Nature, a category that permits sustainable use). In contrast, pressures from dispersed, diffusive sources (e.g., pollution and ocean acidification) had positive relationships with protection. Our results showed that MPAs are systematically established in areas where there is low political opposition, limiting the capacity of existing MPAs to manage key drivers of biodiversity loss. We suggest that conservation efforts focus on biodiversity outcomes and effective reduction of pressures rather than prescribing area-based targets, and that alternative approaches to conservation are needed in areas where protection is not feasible.     

Allopaternal care in the fathead minnow,Pimephales promelas: stepfathers discriminate against their adopted eggs

Summary Some species of fishes with exclusive male parental care exhibit the phenomena of allopaternal care and female preference for males with eggs. In these species, newly reproductive males adopt and care for the eggs of other males, apparently as a part of their mating strategy. Assuming that adoption is adaptive, I would expect males to discriminate between adopted eggs and eggs that they sired themselves. Specifically, I predicted that adopted eggs would receive less care and suffer heavier mortality than sired eggs. I examined the allocation of care and egg survival for adopted and sired eggs in the fathead minnow, Pimephales promelas, and corroborated both predictions.     

Population differences in predation on Batesian mimics in allopatry with their model: selection against mimics is strongest when they are common

Batesian mimicry evolves when a palatable species, the “mimic,” resembles a dangerous species, the “model,” because both receive protection from predation. Yet, this protection should break down where the model is absent, because predators in such areas would not be under selection to avoid the model. Here, we test this prediction in a coral snake mimicry complex. We exposed plasticine replicas of milk snakes that closely mimic coral snakes to natural predators to determine if good mimetic milk snakes are preferentially attacked in allopatry with their model. Moreover, we evaluated whether attack rates on these replicas varied among three different allopatric regions that differed in the type of mimic found locally (i.e., good mimic, poor mimic, or no mimic). When all three regions were considered together, mimics were not preferentially attacked. When regions were analyzed separately, however, attacks on mimics were significantly greater than randomness only where good mimics were found. These variable levels of predation on good mimics might reflect frequency-dependent (i.e., apostatic) predation. In allopatric regions where good mimics are present, predators might have learned or evolved preferences for conspicuous, palatable prey that they encounter frequently. By contrast, in allopatric regions where good mimics are absent, predators might not have learned or evolved preferences for novel phenotypes. Thus, when predation is frequency-dependent, as long as good mimics are rare, they might not experience elevated levels of predation in allopatry with their model as predicted by the Batesian mimicry hypothesis.     

Comparative changes in absorption,distribution and toxicity of copper and cadmium chloride in toads during the hibernation and the role of vitamin C against their toxicity

The aim of this study was to determine the bioavailability and adverse effects of cadmium (Cd) and copper (Cu) on hibernating Egyptian toads and whether ascorbic acid (vitamin C) blocked Cd- and Cu-induced effects during hibernation. The oxidative status of liver, kidney, and intestine of Bufo regularis to Cd, Cu, and/or a combination of both metals administered orally for 2 weeks was determined. In the protection studies, vitamin C was given for 1?h prior to administration of Cu, Cd, and/or metal combination for 2 weeks. Treatment with Cu, Cd, and a combination of both metals produced a reduction in red blood count cells and hemoglobin content, while white blood count cells showed an increase in numbers during these treatments. After 2 weeks exposure, Cd and Cu increased significantly in all the tissues studied. Cu storage presented the following sequence: liver?>?intestine?>?kidney. Cd storage presented the following sequence: intestine?>?kidney?>?liver. When exposed to both metals, Cu and Cd storage presented the following sequence: liver?>?intestine?>?kidney. Histopathological examination of the liver revealed marked alterations including loss of hepatic cell architecture, and some cells exhibited distinct cytoplasmic vacuoles. The majority of blood vessels exhibited a marked dilatation and congestion with infiltration of blood cells, prominent hyperemia of hepatic veins, and significant proliferation of bile ductules. Histopathological changes in the kidney showed destruction and degeneration of both renal tubule cells and glomerular with infiltration of leukocytes and inflammatory cells. Histopathological alterations in the intestine were restricted to the innermost mucosal epithelium with marked degeneration of the villi and submucosa and an extensive fragmentation of mucosal epithelium as well as atrophy of goblet cells. The administration of vitamin C 1?h prior to administration of Cd, Cu, and metal combination did not protect against hepatic, renal, and intestinal damage. However, parental vitamin C given alone increased tissue toxicity.