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PubMed1992

Roles for secondary metabolites in plants.

More than about 20,000 secondary metabolites have now been identified and their isolation and characterization continues at an undiminishing rate. Although the production of most secondary metabolites is under genetic control, in relatively few cases have convincing arguments been put forward to rationalize their occurrence in terms of primary metabolic functions. Whatever the initial reason for their evolution, secondary metabolites are now an essential part of the armamentaria used by plants in the battle to survive and propagate, to the extent where the expenditure of energy, photosynthate and nutrients for their production can be demonstrated to be 'cost effective' for that. Their role may centre on defence of the producer against predators (herbivores), pathogens or competitors, on aid to pollination or seed dispersal, or on protection against or adaptation to extrinsic abiotic factors, or on combinations of these functions. Various examples are given in support of this argument.

Alleles↗

PubMed2003

Colors of primate pelage and skin: objective assessment of conspicuousness.

We present a quantitative means of assessing the conspicuousness of animal coats or other objects in terms of the color vision of each possible observer. We measured reflectance spectra from the fur and skin of many primate species in order to provide an objective survey of the possibilities of pelage coloration found in extant primates. We show that the orange coloration displayed by many platyrrhine and some strepsirhine primates, while being conspicuous to humans, would be cryptic amongst foliage to all males and many females of their own species. In relation to this finding, we briefly review what is known of the color vision of birds that prey on primates, and assess how conspicuous the orange pelage would be to these predators.

Adaptation, Physiological↗

PubMed2006

Predation of arthropods by southern bearded sakis (Chiropotes satanas) in Eastern Brazilian Amazonia.

Bearded sakis are seed predators, but are also known to consume arthropods. This is the first detailed report of arthropod predation in southern bearded sakis (Chiropotes satanas). Two groups were monitored-one in continuous forest, and one on a small island-between January 2003 and February 2004. The arthropod prey included spiders and six insect orders. Island group members spent more time foraging for arthropods (3.8% vs. 2.6% of activity time) but ingested less prey (3.7% vs. 4.6% of feeding time). Arthropods accounted for a small proportion of feeding records in most months, but there were occasional sharp peaks due to the exploitation of temporary agglomerations of insects. In November, arthropods accounted for 26.6% and 14.2% of the feeding records of the mainland and island groups, respectively. The results suggest that bearded sakis actively seek arthropods as a dietary supplement, but that they represent a minor resource during most of the year, even under conditions of intense habitat fragmentation (island group).

Animals↗

PubMed2006

Brief communication: predatory bird damage to the Taung type-skull of Australopithecus africanus Dart 1925.

In this issue of the Journal, McGraw et al. ([2006] Am. J. Phys. Anthropol. 000:00-00) present new data on the taphonomic signature of bone assemblages accumulated by crowned hawk eagles (Stephanoaetus coronatus), including characteristic talon damage to the inferior orbits of primates preyed upon by these birds. Reexamination of the Taung juvenile hominin specimen (the type specimen of Australopithecus africanus Dart 1925) reveals previously undescribed damage to the orbital floors that is nearly identical to that seen in the crania of monkeys preyed upon by crowned hawk eagles (as reported by McGraw et al., this issue). This new evidence, along with previously described aspects of the nonhominin bone assemblage from Taung and damage to the neurocranium of the hominin specimen itself, strongly supports the hypothesis that a bird of prey was an accumulating agent at Taung, and that the Taung child itself was the victim of a bird of prey.

Animals↗

PubMed2006

Primate remains from African crowned eagle (Stephanoaetus coronatus) nests in Ivory Coast's Tai Forest: implications for primate predation and early hominid taphonomy in South Africa.

Understanding the initial processes of deposition can help with interpretations of fossil assemblages. Here we discuss the taphonomy of primate remains collected under 16 nests of African crowned eagles (Stephanoaetus coronatus) in the Tai Forest, Ivory Coast. From 1,200 bones collected, including 669 primate bones, we calculated minimum number of individuals (MNI), survivability profiles, and damage profiles using methods identical to those employed by Sanders et al. (2003 J. Hum. Evol. 44:87-105) in their analysis of bones from eagle nests in Uganda. Crowned eagles leave a consistent taphonomic signature on their prey remains; hence, results from our analysis of the Tai assemblage are similar to those from the Ugandan sample. Hindlimb and cranial bones are relatively abundant in the sample, while ribs, vertebrae, carpals, and tarsals do not survive well. Primate crania typically display puncture marks around the eye, long bones remain largely intact, and scapulae exhibit raked breakage. These data have implications for understanding the dynamic between extant primates and one of their principle predators, as well as the taphonomy of hominid-bearing caves in South Africa. We concur with Berger and Clarke (1995 J. Hum. Evol. 29:275-299) that a large raptor could have been responsible for the death of the Taung child, Australopithecus africanus.

Animals↗

PubMed2003

Nutritional plasticity of the predatory ladybeetle Harmonia axyridis (Coleoptera: Coccinellidae): comparison between natural and substitution prey.

The predatory coccinellid Harmonia axyridis is a polyphagous species, efficient at controlling certain aphid species and already commercialized in Europe for that purpose. The complete development of this predator can be accomplished using the aphid Acyrthosiphon pisum or Ephestia kuehniella eggs as substitution prey. Biochemical analyses were conducted on the proteins, lipids, and carbohydrates of these two different prey species. E. kuehniella eggs were 2 times richer in amino acids than A. pisum adults (12% of the fresh weight vs. 6%). E. kuehniella eggs were 3 times richer in lipids than the aphids but, on the contrary, the aphids were 1.5 times richer in glycogen. The impact of these two kinds of food on the body composition of the coccinellid was evaluated to appreciate the degree of nutritional plasticity of the coccinellid. The composition of the coccinellids feeding either on E. kuehniella eggs or on aphids was compared for amino acid, fatty acid and glycogen contents, revealing a good capability of H. axyridis to develop on foods that are very different in their biochemical composition. Nevertheless, when fed on aphids, the crude protein content of the predator was reduced and the lipid content decreased by a factor of two, with a change in amino and fatty acid patterns. Some biological parameters, such as larval mortality, adult weight, and fecundity, were modified according to the food eaten.

Adaptation, Physiological↗

PubMed2005

Carcass analysis to improve a meat-based diet for the artificial rearing of the predatory mirid bug Dicyphus tamaninii.

Improvement of an existing meat-based diet has been obtained for rearing the generalist predator Dicyphus tamaninii (Heteroptera: Miridae). The approach followed, different from the classical addition/deletion method, was performing biochemical analysis of adult carcasses in order to have information about the nutritional status of the predator. Comparison of total, free amino acids and lipid composition of meat-reared and conventionally reared females allowed detecting some nutritional deficiencies. A reformulated diet with new sources of proteins and lipids was tested again with the predator. Some biological parameters of bugs that were inferior in the initial meat diet when compared with those of the conventionally reared insects, such as nymphal development time and fresh weight, have been improved with the reformulated diet.

Amino Acids↗

PubMed1980

Effect of psychological stress on the induction of arthritis in rats.

To determine whether emotional states could influence susceptibility to type II collagen-induced arthritis in rats, we studied the effects of experimentally produced psychological stress on the clinical, histologic, and immunologic manifestations of this autoimmune disease. Stress, induced by exposure to a cat, abrogated the development of arthritis in rats immunized with type II collagen. The incidence of arthritis was also decreased in rats subjected to transportation and handling. These environmental factors dissociated the development of humoral and cellular sensitivity to collagen from the occurrence of arthritis. This study provides a unique demonstration that psychosomatic processes can influence an animal mode of autoimmunity.

Animals↗

PubMed2004

Plant coloration undermines herbivorous insect camouflage.

The main point of our hypothesis "coloration undermines camouflage" is that many color patterns in plants undermine the camouflage of invertebrate herbivores, especially insects, thus exposing them to predation and causing them to avoid plant organs with unsuitable coloration, to the benefit of the plants. This is a common case of "the enemy of my enemy is my friend" and a visual parallel of the chemical signals that plants emit to call wasps when attacked by caterpillars. Moreover, this is also a common natural version of the well-known case of industrial melanism, which illustrates the great importance of plant-based camouflage for herbivorous insects and can serve as an independent test for our hypothesis. We claim that the enormous variations in coloration of leaves, petioles and stems as well as of flowers and fruits undermine the camouflage of invertebrate herbivores, especially insects. We assume that the same principle might operate in certain animal-parasite interactions. Our hypothesis, however, does not contrast or exclude other previous or future explanations of specific types of plant coloration. Traits such as coloration that have more than one type of benefit may be selected for by several agents and evolve more rapidly than ones with a single type of advantage.

Animals↗

PubMed2005

Diatom/copepod interactions in plankton: the indirect chemical defense of unicellular algae.

Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that chemical signals and chemical defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use chemical defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a chemical defense for the plankton community structure are also discussed.

Aldehydes↗

PubMed2006

Influence of predator stress on the consolidation versus retrieval of long-term spatial memory and hippocampal spinogenesis.

We have studied the influence of predator stress (30 min of cat exposure) on long-term (24 h) spatial memory and the density of spines in basilar dendrites of CA1 neurons. Predator stress occurred either immediately before water maze training (Stress Pre-Training) or before the 24 h memory test (Stress Pre-Retrieval). The Control (nonstress) group exhibited excellent long-term spatial memory and a robust increase in the density of stubby, but not mushroom, shaped spines. The Stress Pre-Training group had impaired long-term memory and did not exhibit any changes in spine density. The Stress Pre-Retrieval group was also impaired in long-term memory performance, but this group exhibited an increase in the density of stubby, but not mushroom, shaped spines, which was indistinguishable from the control group. These findings indicate that: (1) A single day of water maze training under control conditions produced intact long-term memory and an increase in the density of stubby spines in CA1; (2) Stress before training interfered with the consolidation of information into long-term memory and suppressed the training-induced increase in spine density; and (3) Stress immediately before the 24 h memory test trial impaired the retrieval of the stored memory, but did not reverse the training-induced increase in CA1 spine density. Overall, this work provides evidence of structural plasticity in dendrites of CA1 neurons which may be involved in the consolidation process, and how spinogenesis and memory are modulated by stress.

Amnesia↗

PubMed2005

Influence of body reserves and eye opacity on foraging behaviours of tiger snakes.

Physiological states such as reproductive stage, parasite load, body condition, and environmental conditions, influence behaviours in complex ways. According to the Clark's asset-protection principle (Clark, 1994. Behav Ecol 5:159-170), individuals in good body condition take fewer predation risks than conspecifics in lesser condition. In many ectotherms, foraging, digestion, and moulting require an elevation of the metabolism achieved through intensive basking, thereby increasing the risk of being detected by predators. Using four experimental groups of snakes, we showed that two independent physiological states, (1) the presence of prey in the stomach and (2) eye opacity associated with moulting, increase predator vulnerability. In a parallel experiment, two groups of snakes were maintained on contrasting diets (high food intake vs. low food intake) for 6 months. Apart from sloughing periods, most individuals (89%) accepted their meal irrespective of food treatment. Consequently, well-fed snakes exhibited higher body condition (one third physiological state) relative to less-fed individuals. During sloughing events, however, well-fed individuals often refused (78%) to eat while the less-fed individuals readily accepted (86%) their meal despite eye opacity. Individuals with less body reserves accepted the cumulative risks owing to eye opacity and stomach fullness. By contrast, well-fed snakes remained more "prudent" (i.e., exhibited behaviours that depended on their internal state). Our results show that snakes can adjust their foraging "decision" by combining different physiological informations.

Analysis of Variance↗

PubMed2006

Modulation and variability of prey capture kinematics in clariid catfishes.

Species with narrow or limited diets (trophic specialists) are expected to be less flexible in their feeding repertoire compared to species feeding on a wide range of different prey (trophic generalists). The ability to modulate prey capture kinematics in response to different prey types and prey position, as well as the overall variability in prey capture kinematics, is evaluated in four clariid species ranging from trophic generalist (Clarias gariepinus) to species with morphological specializations and a narrow diet (Channallabes apus and Gymnallabes typus). High-speed video recordings were made of prey captures on two prey that differ in shape, attachment strength and hardness. While the observed amount of strike-to-strike variability in prey capture kinematics is similar for all species and not influenced by prey type, only the two less specialized species showed the ability to modulate their prey capture kinematics in function of the presented prey types. All species did, however, show positional modulation during the strike by adjusting the magnitude of neurocranial elevation. These results indicate that the narrow dietary breadth of trophic specialists is indeed indicative of functional stereotypy in this group of fishes. Although most studies focussing on prey processing found a similar result, the present study is one of the few that was able to demonstrate this relationship when focussing on prey capture mechanics. Possibly, this relationship is less frequently observed for prey capture compared to prey processing because, regardless of prey type, the initial capture of prey requires a higher amount of variability.

Animals↗

PubMed2007

Pregnant female lizards Iberolacerta cyreni adjust refuge use to decrease thermal costs for their body condition and cell-mediated immune response.

Lizards often respond to increased predation risk by increasing refuge use, but this strategy may entail a loss of thermoregulatory opportunities, which may lead to a loss of body condition. This may be especially important for pregnant oviparous female lizards, because they need to maintain optimal body temperatures as long as possible to maximize developmental embryos rate until laying. However, little is known about how increased time spent at low temperatures in refuges affects body condition and health state of pregnant female lizards. Furthermore, it is not clear how initial body condition affects refuge use. Female Iberian rock lizards forced to increase time spent at low temperatures showed lower body condition and tended to show lower cell-mediated immune responses than control females. Therefore, the loss of thermoregulatory opportunities seems to be an important cost for pregnant females. Nevertheless, thereafter, when we simulated two repeated predatory attacks, females modified refuge use in relation to their body condition, with females with worse condition decreasing time hidden after attacks. In conclusion, female lizards seemed able to compensate increased predation risk with flexible antipredatory strategies, thus minimizing costs for body condition and health state.

Analysis of Variance↗

PubMed2004

Inducible reproductive plasticity of the guppy Poecilia reticulata in response to predation cues.

Predation has long been described as one of the major driving forces in evolution. Guppies (Poecilia reticulata) from natural populations exposed to different predation pressures, were found to have different life history traits. Reproductive plasticity in response to direct predation cues has mainly been reported for invertebrates. The goals of the present study were to determine whether exposure to predation cues would induce reproductive phenotypic plasticity in female guppies and to determine whether the effective cues are visual, chemical, or a combination of both. In our first experiment, female guppies exposed to predation cues of the african cichlids Aulonocara nyassae increased their reproductive output by almost two fold, having larger brood-sizes and shorter brood-interval at the first spawn. This effect disappeared in the second spawn in the absence of predators. In the second experiment we found that exposure to the predators induced an increase in the brood-size regardless of whether the cue was: only visual, only chemical, visual and chemical or visual, chemical and tactile. The impacts of these cues were equally powerful on the tested variables and they did not have any cumulative effect. Similar to the results of the first experiment, this effect disappeared in the second spawn, in the absence of predation cues. The present study demonstrates a direct immediate and reversible effect of predation cues on guppy reproduction.

Adaptation, Physiological↗

PubMed2001

Aquatic prey capture in ray-finned fishes: a century of progress and new directions.

The head of ray-finned fishes is structurally complex and is composed of numerous bony, muscular, and ligamentous elements capable of intricate movement. Nearly two centuries of research have been devoted to understanding the function of this cranial musculoskeletal system during prey capture in the dense and viscous aquatic medium. Most fishes generate some amount of inertial suction to capture prey in water. In this overview we trace the history of functional morphological analyses of suction feeding in ray-finned fishes, with a particular focus on the mechanisms by which suction is generated, and present new data using a novel flow imaging technique that enables quantification of the water flow field into the mouth. We begin with a brief overview of studies of cranial anatomy and then summarize progress on understanding function as new information was brought to light by the application of various forms of technology, including high-speed cinematography and video, pressure, impedance, and bone strain measurement. We also provide data from a new technique, digital particle image velocimetry (DPIV) that allows us to quantify patterns of flow into the mouth. We believe that there are three general areas in which future progress needs to occur. First, quantitative three-dimensional studies of buccal and opercular cavity dimensions during prey capture are needed; sonomicrometry and endoscopy are techniques likely to yield these data. Second, a thorough quantitative analysis of the flow field into the mouth during prey capture is necessary to understand the effect of head movement on water in the vicinity of the prey; three-dimensional DPIV analyses will help to provide these data. Third, a more precise understanding of the fitness effects of structural and functional variables in the head coupled with rigorous statistical analyses will allow us to better understand the evolutionary consequences of intra- and interspecific variation in cranial morphology and function.

Animals↗

PubMed2001

Evolution and mechanics of long jaws in butterflyfishes (family Chaetodontidae).

We analyzed the functional morphology and evolution of the long jaws found in several butterflyfishes. We used a conservative reanalysis of an existing morphological dataset to generate a phylogeny that guided our selection of seven short- and long-jawed taxa in which to investigate the functional anatomy of the head and jaws: Chaetodon xanthurus, Prognathodes falcifer (formerly Chaetodon falcifer), Chelmon rostratus, Heniochus acuminatus, Johnrandallia nigrirostris, Forcipiger flavissimus, and F. longirostris. We used manipulations of fresh, preserved, and cleared and stained specimens to develop mechanical diagrams of how the jaws might be protruded or depressed. Species differed based on the number of joints within the suspensorium. We used high-speed video analysis of five of the seven species (C. xanthurus, Chel. rostratus, H. acuminatus, F. flavissimus, and F. longirostris) to test our predictions based on the mechanical diagrams: two suspensorial joints should facilitate purely anteriorly directed protrusion of the lower jaw, one joint should allow less anterior protrusion and result in more depression of the lower jaw, and no joints in the suspensorium should constrain the lower jaw to simple ventral rotation around the jaw joint, as seen in generalized perciform fishes. We found that the longest-jawed species, F. longirostris, was able to protrude its jaws in a predominantly anterior direction and further than any other species. This was achieved with little input from cranial elevation, the principal input for other known lower jaw protruders, and is hypothesized to be facilitated by separate modifications to the sternohyoideus mechanism and to the adductor arcus palatini muscle. In F. longirostris the adductor arcus palatini muscle has fibers oriented anteroposteriorly rather than medial-laterally, as seen in most other perciforms and in the other butterflyfish studied. These fibers are oriented such that they could rotate the ventral portion of the quadrate anteriorly, thus projecting the lower jaw anteriorly. The intermediate species lack modification of the adductor arcus palatini and do not protrude their jaws as far (in the case of F. flavissimus) or in a purely anterior fashion (in the case of Chel. rostratus). The short-jawed species both exhibit only ventral rotation of the lower jaw, despite the fact that H. acuminatus is closely related to Forcipiger.

Animals↗

PubMed2004

Embryological aspects of inducible morphological defenses in Daphnia.

Many cases of predator-induced morphological plasticity in daphnids are well studied examples of inducible defenses. However, little is known about the early development of these sometimes conspicuous traits. We compared for the first time in five different Daphnia species the embryonic development of predator-induced and noninduced animals using scanning electron microscopy (SEM). We observed significant morphological changes in the last embryonic stage in helmet formation in Daphnia cucullata and in neck-pedestal development in Daphnia pulex. In contrast, no morphological changes could be found during embryogenesis between induced and noninduced Daphnia lumholtzi, D. longicephala, and D. ambigua. Strategies for initiating the defensive traits differ among Daphnia species because of trade-offs between environmental requirements and developmental constraints. Some general features of Daphnia embryonic development are described using SEM. All Daphnia embryos have to shed at least three different membranes before leaving the brood pouch of the mother. After the embryos shed the third membrane, chemosensillae that are likely able to detect predator-released chemicals are exposed to the olfactory environment.

Animals↗