Biomedical subjects

Shelley A Adamo

Publications and source records attributed to Shelley A Adamo.

10 recordsLinked to original sources

PubMed2006

Illness-induced anorexia and its possible function in the caterpillar, Manduca sexta.

Although many animals exhibit illness-induced anorexia when immune-challenged, the adaptive significance of this behavior remains unclear. Injecting Manduca sexta larvae (caterpillars) with live bacteria (Serratia marcescens), heat-killed bacteria or bacterial lipopolysaccharides resulted in a decline in feeding, demonstrating illness-induced anorexia in this species. We used M. sexta to test four commonly suggested adaptive functions for illness-induced anorexia. (1) Food deprivation did not reduce the iron content of the hemolymph. (2) Immune-challenged M. sexta were not more likely to move to a different part of the plant. Therefore, the decline in feeding is unlikely to be an adaptive response allowing the animal to move away from a patch of contaminated food. (3) M. sexta force-fed S. marcescens bacteria were not more susceptible to a S. marcescens systemic infection than were M. sexta force-fed nutrient broth. (4) Force-feeding infected M. sexta during illness-induced anorexia did not increase mortality and short-term food deprivation did not enhance survival. However, force-feeding M. sexta with a high lipid diet (linseed oil and water) resulted in an increase in mortality when challenged with S. marcescens. Force-feeding sucrose or water did not reduce resistance. Force-feeding a high lipid diet into healthy animals did not reduce weight gain, suggesting that it was not toxic. We hypothesize that there is a conflict between lipid metabolism and immune function, although whether this conflict has played a role in the evolution of illness-induced anorexia remains unknown. The adaptive function of illness-induced anorexia requires further study in both vertebrates and invertebrates.

Adaptation, Physiological↗

PubMed2006

Response of female cuttlefish Sepia officinalis (Cephalopoda) to mirrors and conspecifics: evidence for signaling in female cuttlefish.

Cuttlefish have a large repertoire of body patterns that are used for camouflage and interspecific signaling. Intraspecific signaling by male cuttlefish has been well documented but studies on signaling by females are lacking. We found that females displayed a newly described body pattern termed Splotch toward their mirror image and female conspecifics, but not to males, prey or inanimate objects. Female cuttlefish may use the Splotch body pattern as an intraspecific signal, possibly to reduce agonistic interactions. The ability of females to produce a consistent body pattern in response to conspecifics and mirrors suggests that they can recognize same-sex conspecifics using visual cues, despite the lack of sexual dimorphism visible to human observers.

Analysis of Variance↗

PubMed2006

Comparative psychoneuroimmunology: evidence from the insects.

Interactions between immune systems, nervous systems, and behavior are well established in vertebrates. A comparative examination of these interactions in other animals will help us understand their evolution and present adaptive functions. Insects show immune-behavioral interactions similar to those seen in vertebrates, suggesting that many of them may have a highly conserved function. Activation of an immune response in insects results in illness-induced anorexia, behavioral fever, changes in reproductive behavior, and decreased learning ability in a broad range of species. Flight-or-fight behaviors result in a decline in disease resistance. In insects, illness-induced anorexia may enhance immunity. Stress-induced immunosuppression is probably due to physiological conflicts between the immune response and those of other physiological processes. Because insects occupy a wide range of ecological niches, they will be useful in examining how some immune-behavioral interactions are sculpted by an animal's behavioral ecology.

Animals↗

PubMed2006

The ventilatory, cardiac and behavioural responses of resting cuttlefish (Sepia officinalis L.) to sudden visual stimuli.

When startled, some animals reduce ventilation rate and heart rate, and become motionless. The function of this response, if any, remains unknown. We used non-invasive ultrasound imaging to monitor the ventilatory, cardiac and postural responses of cuttlefish exposed to sudden visual stimuli. Simultaneously, we recorded cuttlefish behaviour using an overhead video camera. Upon presentation of the sudden visual stimulus (rapidly approaching bird cut-out), cuttlefish rapidly changed the colour and the texture of their skin, taking on characteristics of the Deimatic Display. Cuttlefish also became motionless (behavioural freezing), hyperinflated their mantles, and decreased their ventilation rate and heart rate. We found no evidence of a relationship between the intensity of the Deimatic Display and the intensity of any other measured parameter. Ventilation rate decreased during behavioural freezing. Hyperinflation of the mantle was most intense in preparation for and during behavioural freezing. Heart rate decreases occurred during mantle hyperinflation and were greatest in animals showing the most hyperinflation. Decreased heart rate may not be adaptive per se. Instead, it might be a product of the unusual arrangement of the cuttlefish peripheral vasculature, which could be compressed during mantle hyperinflation. By filling the mantle with water (hyperinflation), this response to sudden stimuli may help cuttlefish prepare for possible flight by jet propulsion, which often follows the Deimatic Display.

Animals↗

PubMed2006

Signaling to the enemy? Body pattern expression and its response to external cues during hunting in the cuttlefish Sepia officinalis (Cephalopoda).

Cuttlefish can rapidly alter their appearance by using neurally controlled chromatophore organs. This ability may provide a window into their cognitive capacity. We test whether the changes in body pattern that occur during hunting depend on context. If they do, then it may be possible to use these changes to study cephalopod cognition while the animal is engaged in ecologically relevant tasks. We found consistent individual differences in the tendency of cuttlefish to hunt with the first two arms raised. We also found that cuttlefish usually darken their skin after they seize a prey item. This darkening is observed regardless of the identity of the prey (fish, crab, or shrimp), prey context (buried in sand, in a bare tank, or on top of a rock pile), or the presence of a sudden stimulus. The sudden stimulus was created by presenting an overhead model bird to the cuttlefish. The model induced components of the Deimatic Display, which is a form of antipredator behavior, suggesting that the model was perceived as a potential threat. Passing Cloud displays and the Darkening of the arms were significantly reduced after exposure to the model bird. The effect of a potential predator on body pattern expression during hunting suggests it may be possible to use these changes as a sensitive indicator of ecologically relevant learning.

Animal Communication↗

PubMed2005

Parasitic suppression of feeding in the tobacco hornworm, Manduca sexta: parallels with feeding depression after an immune challenge.

The parasitic wasp, Cotesia congregata, suppresses feeding in its host Manduca sexta. Feeding suppression in the host coincides with the emergence of the wasps through the host's cuticle. During wasp emergence, host hemocyte number declined, suggesting that the host mounts a wound/immune response against the exiting parasitoids and/or resulting tissue damage. Eliciting a different type of immune response by injecting heat-killed Serratia marcescens also resulted in a decline in feeding and a reduction in hemocyte number. Both the emerging wasps and the bacteria induced an increase in hemolymph octopamine concentration and a decrease in foregut peristalsis in M. sexta. The emerging parasitoids produced the largest changes. The source of the additional octopamine appeared to be the host in both cases. S. marcescens was found to contain no detectable amounts of octopamine. The parasitoids had insufficient octopamine to account for the amount found in host hemolymph and they did not secrete octopamine in vitro. One cause for the high concentration of octopamine in parasitized M. sexta was that octopamine was removed from the hemolymph approximately 23 times more slowly after the wasps emerged than prior to wasp emergence. The striking similarity between the effects of parasitoids and bacteria on M. sexta feeding, hemocyte number, hemolymph octopamine concentration, and foregut peristalsis supports the possibility that the immune/wound reaction induced by the emerging wasps could play a role in the suppression of host feeding. These results also support the hypothesis that M. sexta exhibit an immune-activated anorexia.

Animals↗

PubMed2005

Using ultrasound to understand vascular and mantle contributions to venous return in the cephalopod Sepia officinalis L.

Using ultrasound imaging, we investigated the roles of the potentially contractile veins and of the mantle (the powerful body wall that moves water over the gills, and also encloses the large veins and the hearts) in returning the blood of cuttlefish to its hearts. Ultrasound provided the first non-invasive observations of vascular function in an unanaesthetized, free-moving cephalopod. The large veins (anterior vena cava, lateral venae cavae and efferent branchial vessels) contracted in live, intact cuttlefish (Sepia officinalis L.). The anterior vena cava contracted at the same rate as the mantle, but it often expanded during mantle contraction. Furthermore, the anterior vena cava contracted peristaltically in vivo, suggesting that it actively aids venous return. The lateral venae cavae and efferent branchial vessels contracted at the same rate as the branchial and systemic hearts, but at a different rate from the mantle. A peristaltic wave appeared to travel along the lateral venae cavae to the branchial hearts, potentially aiding venous return. We found a muscular valve between the anterior and lateral venae cavae, which ensured that blood flowed only one way between these unsynchronized vessels. The mantle appears to have an unclear connection with cardiovascular function. We conclude that, when cuttlefish are at rest, the mantle does not compress any of the large veins that we imaged (including the anterior vena cava), and that peristaltic contractions of the large veins might be important in returning cephalopod blood to the hearts.

Animals↗

PubMed2004

Cuttlefish (Sepia officinalis: Cephalopoda) hunting behavior and associative learning.

Because most learning studies in cephalopods have been performed on octopods, it remains unclear whether such abilities are specific to octopus, or whether they correlate with having a larger and more centrally organized brain. To investigate associative learning in a different cephalopod, six sexually mature cuttlefish (Sepia officinalis) participated in a counterbalanced, within-subjects, appetitive, classical conditioning procedure. Two plastic spheres (conditioned stimuli, CSs), differing in brightness, were presented sequentially. Presentation of the CS+ was followed 5 s later by a live feeder fish (unconditioned stimulus, US). Cuttlefish began to attack the CS+ with the same type of food-acquisition seizures used to capture the feeder fish. After seven blocks of training (42 presentations of each CS) the difference in seizure probability between CS+ and CS- trials more than doubled; and was found to be significantly higher in late versus early blocks. These results indicate that cuttlefish exhibit autoshaping under some conditions. The possible ecological significance of this type of learning is briefly discussed.

Animals↗

PubMed2002

Modulating the modulators: parasites, neuromodulators and host behavioral change.

Neuromodulators can resculpt neural circuits, giving an animal the behavioral flexibility it needs to survive in a complex changing world. This ability, however, provides parasites with a potential mechanism for manipulating host behavior. This paper reviews three invertebrate host-parasite systems to examine whether parasites can change host behavior by secreting neuromodulators. The parasitic wasp, Cotesia congregata, suppresses host feeding partly by inducing the host (Manduca sexta) to increase the octopamine concentration in its hemolymph. The increased octopamine concentration disrupts the motor pattern produced by the frontal ganglion, preventing the ingestion of food. Polymorphus paradoxus (Acanthocephalan) alters the escape behavior of its host, Gammarus lacustris (Crustacea), possibly through an effect on the host's serotonergic system. The trematode Trichobilharzia ocellata inhibits egg-laying in its snail host (Lymnaea stagnalis), partly by inducing the host to secrete schistosomin. Schistosomin decreases electrical excitability of the caudodorsal cells. The parasite also alters gene expression for some neuromodulators within the host's central nervous system. In at least two of these three examples, it appears that the host, not the parasite, produces the neuromodulators that alter host behavior. Producing physiologically potent concentrations of neuromodulators may be energetically expensive for many parasites. Parasites may exploit indirect less energetically expensive methods of altering host behavior. For example, parasites may induce the host's immune system to produce the appropriate neuromodulators. In many parasites, the ability to manipulate host behavior may have evolved from adaptations designed to circumvent the host's immune system. Immune-neural-behavioral connections may be pre-adapted for parasitic manipulation.

Animals↗

PubMedDate not supplied

Estimating disease resistance in insects: phenoloxidase and lysozyme-like activity and disease resistance in the cricket Gryllus texensis.

An animal's ability to resist disease is usually estimated by measuring one or more components of the immune system. There is an assumption that these assays of immunity measure an animal's ability to mount an effective immune response. This paper tests this assumption by examining the relationship between two common estimates of insect immunocompetence, phenoloxidase and lysozyme-like enzyme activity, and resistance to three common insect bacterial pathogens: Serratia marcescens, Serratia liquefaciens, and Bacillus cereus. There was a correlation (Spearman's rs=0.33, p<0.001, n=190 pairs) between total phenoloxidase and baseline lysozyme-like activity within individuals. However, total phenoloxidase and baseline lysozyme-like activity levels did not predict which male crickets would survive any of the three bacterial challenges. Lysozyme-like activity increased after an immune challenge (Friedman, 33.72, p<0.001), and the greater the increase, the greater the chance that the cricket would survive S. marcescens (slope=0.15, chi 2=8.2, p=0.005) or B. cereus (slope=0.8, chi 2=6.4, p=0.01). The crickets with a greater total hemolymph protein concentration were also more likely to survive a challenge with any of the three bacterial pathogens than the crickets with lower total hemolymph protein concentrations (S. liquefaciens: slope=0.02, chi 2=9.2, p=0.002; B. cereus: slope=0.02, chi 2=6.5, p=0.01; S. marcescens: slope=0.03, chi 2=7.8, p=0.005). Because of the complexity of the immune system, empirical tests of the relationship between assays of immunity and resistance to a range of actual pathogens are important for correctly interpreting these measures.

Animals↗