John Christy
Smithsonian Tropical Research Institute, Naos Marine Lab, Department Member
Synopsis Pair-living is a common social system found across animal taxa, and the relationship between pair-living and reproduction varies greatly among species. Siphonaria gigas, hermaphroditic pulmonate gastropods, often live in pairs in... more
Synopsis Pair-living is a common social system found across animal taxa, and the relationship between pair-living and reproduction varies greatly among species. Siphonaria gigas, hermaphroditic pulmonate gastropods, often live in pairs in the rocky intertidal zone of the tropical Eastern Pacific. Combining genetic parentage analysis using four polymorphic microsatellite loci with behavioral observations from a 10-week field study, we provide the first description of the mating system of a Siphonaria species incorporating genetic data. S. gigas mated both within-pair and extra-pair and three out of four paired S. gigas individuals produced egg masses with extra-pair paternity. Multiple paternity was detected, but at a relatively low frequency (19% of egg masses) compared to other marine gastropods. Behavioral data indicate one potential advantage of pair-living: paired S. gigas produced almost twice as many egg masses as their solitary counterparts over four reproductive cycles. Thes...
Research Interests: Zoology, Biology, Medicine, Gastropoda, Mating, and 3 moreHermaphrodite, Intertidal Zone, and Limpet
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Plankton live under the countervailing selective pressures of predation and ultraviolet radiation (UVR). In lakes, zooplankton are transparent reducing visibility to predatory fishes but are pigmented in the absence of fishes,... more
Plankton live under the countervailing selective pressures of predation and ultraviolet radiation (UVR). In lakes, zooplankton are transparent reducing visibility to predatory fishes but are pigmented in the absence of fishes, hypothetically reducing UVR damage. In the sea, planktivorous fishes are widespread, so plankton typically are transparent and ascend to productive surface waters at night to forage and descend during the day to reduce visibility to predators. However, larvae of some species face the unique constraint of traveling in surface currents in the daytime during migrations between adult and larval habitats. We would expect these larvae to be transparent since companion studies demonstrated increased predation risk of pigmented larvae under strong sunlight. Paradoxically, larvae range from being darkly to lightly pigmented. We hypothesize that some larvae are more heavily pigmented to reduce UVR damage, while other species travelling in subsurface currents with low UV...
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Research Interests: Science, Biology, Medicine, Multidisciplinary, Lizards, and 3 moreAnimals, Lizard, and Predatory Behavior
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Animal communication theory predicts that low-frequency cheating should be common in generally honest signalling systems. However, perhaps because cheats are designed to go undetected, there are few examples of dishonest signals in... more
Animal communication theory predicts that low-frequency cheating should be common in generally honest signalling systems. However, perhaps because cheats are designed to go undetected, there are few examples of dishonest signals in natural populations. Here we present what we believe is the ¢rst example of a dishonest signal which is used commonly by males to attract mates and ¢ght sexual rivals. After losing their large claw, male ¢ddler crabs (Uca annulipes) grow a new one which has less mass, is a less e¡ective weapon and costs less to use in signalling than an equivalent-length claw of the original form. Males with original claws do not di¡erentially ¢ght males with regenerated claws even though they are likely to win. Regenerated claws e¡ectively blu ¡ ¢ghting ability and deter potential opponents before they ¢ght. During mate searching, females do not discriminate against males with low-mass, regenerated claws, indicating that they are deceived as to the true costs males pay t...
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Many animals are considered to be specialists because they have feeding structures that are fine-tuned for consuming specific prey. For example, "smasher" mantis shrimp have highly specialized predatory appendages that generate... more
Many animals are considered to be specialists because they have feeding structures that are fine-tuned for consuming specific prey. For example, "smasher" mantis shrimp have highly specialized predatory appendages that generate forceful strikes to break apart hard-shelled prey. Anecdotal observations suggest, however, that the diet of smashers may include soft-bodied prey as well. Our goal was to examine the diet breadth of the smasher mantis shrimp, Neogonodactylus bredini, to determine whether it has a narrow diet of hard-shelled prey. We combined studies of prey abundance, feeding behavior, and stable isotope analyses of diet in both seagrass and coral rubble to determine if N. bredini's diet was consistent across different habitat types. The abundances of hard-shelled and soft-bodied prey varied between habitats. In feeding experiments, N. bredini consumed both prey types. N. bredini consumed a range of different prey in the field as well and, unexpectedly, the sta...
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Research Interests: Geography, Climate Change, Atmospheric Science, Animal Behavior, Climatology, and 15 moreBiology, Ecology, Benthic Ecology, Behavioral Ecology, Fiddler Crabs, Biological Sciences, Intertidal ecology, Crabs, Female, Animals, Courtship, Crab Biology and Taxonomy, Brachyura, Coastal Ecology, and Fiddler crab
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The polarisation of light is used by many species of cephalopods and crustaceans to discriminate objects or to communicate. Most visual systems with this ability, such as that of the fiddler crab, include receptors with photopigments that... more
The polarisation of light is used by many species of cephalopods and crustaceans to discriminate objects or to communicate. Most visual systems with this ability, such as that of the fiddler crab, include receptors with photopigments that are oriented horizontally and vertically relative to the outside world. Photoreceptors in such an orthogonal array are maximally sensitive to polarised light with the same fixed e-vector orientation. Using opponent neural connections, this two-channel system may produce a single value of polarisation contrast and, consequently, it may suffer from null points of discrimination. Stomatopod crustaceans use a different system for polarisation vision, comprising at least four types of polarisation-sensitive photoreceptor arranged at 0°, 45°, 90° and 135° relative to each other, in conjunction with extensive rotational eye movements. This anatomical arrangement should not suffer from equivalent null points of discrimination. To test whether these two sys...
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When females search for mates and their perceived risk of predation increases, they less often express preferences for males that use conspicuous courtship signals, relaxing sexual selection on production of these signals. Here, we report... more
When females search for mates and their perceived risk of predation increases, they less often express preferences for males that use conspicuous courtship signals, relaxing sexual selection on production of these signals. Here, we report an apparent exception to this general pattern. Courting male fiddler crabs Uca beebei sometimes build pillars of mud at the openings to their burrows in which crabs mate. Females visit several males before they choose a mate by staying and breeding in their burrows, and they preferentially visit males with pillars. Previous studies suggested that this preference is based on a visual orientation behaviour that may reduce females' risk of predation while searching for a mate. We tested this idea by determining whether the female preference for males with pillars increases with perceived predation risk. We attracted avian predators to where crabs were courting and measured the rates that sexually receptive females visited courting males with and w...
Research Interests: Animal Behavior, Mate Choice, Biology, Medicine, Natural Selection, and 15 moreBiological Sciences, Perceived Risk, Predation, Female, Animals, Male, Courtship, Mate Preference, Brachyura, Predation Risk, Passeriformes, Predatory Behavior, Female Preference, Fiddler crab, and Medical and Health Sciences
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Research Interests: Vision Science, Visual perception, Biology, Medicine, Fiddler Crabs, and 14 moreCrustacean Biology, Biological Sciences, Visual Ecology, Animals, Cell, Male, Light, Polarization, Brachyura, Agricultural and Biological Sciences, Contrast Enhancement, Psychology and Cognitive Sciences, Fiddler crab, and Medical and Health Sciences
Fiddler crabs are abundant, semi-terrestrial crustaceans inhabiting tropical, subtropical and warm temperate coasts worldwide. Some species build above-ground sedimentary structures at or near the opening to their burrows. The functions... more
Fiddler crabs are abundant, semi-terrestrial crustaceans inhabiting tropical, subtropical and warm temperate coasts worldwide. Some species build above-ground sedimentary structures at or near the opening to their burrows. The functions and shapes of these constructions vary interspecifically and according to the sex of the builder. Here, we compile the dispersed reports on these structures, suggest uniform naming for different shapes, review explanations for their functions and explore associations between the attributes of builders and their structures. We found that 47 fiddler crab species build at least one type (or subtype) of structure, including chimneys, hoods, pillars, semidomes, mudballs, and rims. Sedimentary structures show a strong association with sediment type as well as builder front type, genus and sex, but not with fiddler crab clade. Experimental studies have revealed distinct, sometimes multiple functions for some of these structures (e.g., female attraction, red...
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Vol. 57: 259-265, 1989 MARINE ECOLOGY PROGRESS SERIES Mar. Ecol. Prog. Ser. Published November 10 Rapid development of megalopae of the fiddler crab Uca pugilator reared over sediment: implications for models of larval recruitment* John... more
Vol. 57: 259-265, 1989 MARINE ECOLOGY PROGRESS SERIES Mar. Ecol. Prog. Ser. Published November 10 Rapid development of megalopae of the fiddler crab Uca pugilator reared over sediment: implications for models of larval recruitment* John H. Christy Smithsonian ...