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Despite advances in cardiac surgery and anesthesia, the rates of brain injury remain high in aortic arch surgery requiring circulatory arrest. The mechanisms of brain injury, including permanent and temporary neurologic dysfunction, are multifactorial, but intraoperative brain ischemia is likely a major contributor. Maintaining optimal cerebral perfusion during cardiopulmonary bypass and circulatory arrest is the key component of intraoperative management for aortic arch surgery. Various brain monitoring modalities provide different information to improve cerebral protection. Electroencephalography gives crucial data to ensure minimal cerebral metabolism during deep hypothermic circulatory arrest, transcranial Doppler directly measures cerebral arterial blood flow, and near-infrared spectroscopy monitors regional cerebral oxygen saturation. Various brain protection techniques, including hypothermia, cerebral perfusion, pharmacologic protection, and blood gas management, have been used during interruption of systemic circulation, but the optimal strategy remains elusive. Although deep hypothermic circulatory arrest and retrograde cerebral perfusion have their merits, there have been increasing reports about the use of antegrade cerebral perfusion, obviating the need for deep hypothermia. With controversy and variability of surgical practices, moderate hypothermia, when combined with unilateral antegrade cerebral perfusion, is considered safe for brain protection in aortic arch surgery performed with circulatory arrest. The neurologic outcomes of brain protection in aortic arch surgery largely depend on the following three major components: cerebral temperature, circulatory arrest time, and cerebral perfusion during circulatory arrest. The optimal brain protection strategy should be individualized based on comprehensive monitoring and stems from well-executed techniques that balance the major components contributing to brain injury.

Understanding why some individuals are more prone to carry parasites and spread diseases than others is a key question in biology. Although epidemiologists and disease ecologists increasingly recognize that individuals of the same species can vary tremendously in their relative contributions to the emergence of diseases, very few empirical studies systematically assess consistent individual differences in parasite loads within populations over time. Two species of fleas (Oropsylla montana and Hoplopsyllus anomalous) and their hosts, California ground squirrels (Otospermophilus beecheyi), form a major complex for amplifying epizootic plague in the western United States. Understanding its biology is primarily of major ecological importance and is also relevant to public health. Here, we capitalize on a long-term data set to explain flea incidence on California ground squirrels at Briones Regional Park in Contra Costa County, USA. In a 7 year study, we detected 42,358 fleas from 2,759 live trapping events involving 803 unique squirrels from two free-living populations that differed in the amount of human disturbance in those areas. In general, fleas were most abundant and prevalent on adult males, on heavy squirrels, and at the pristine site, but flea distributions varied among years, with seasonal conditions (e.g., temperature, rainfall, humidity), temporally within summers, and between flea species. Although on-host abundances of the two flea species were positively correlated, each flea species occupied a distinctive ecological niche. The common flea (O. montana) occurred primarily on adults in cool, moist conditions in early summer whereas the rare flea (H. anomalous) was mainly on juveniles in hot, dry conditions in late summer. Beyond this, we uncovered significantly repeatable and persistent effects of host individual identity on flea loads, finding consistent individual differences among hosts in all parasite measures. Taken together, we reveal multiple determinants of parasites on free-living mammals, including the underappreciated potential for host heterogeneity – within populations – to structure the emergence of zoonotic diseases such as bubonic plague.

Mast cells are an exceptionally rich source of prostaglandin D2 (PGD2). PGD2 is pro-inflammatory and can cause bronchoconstriction. The enzyme cyclooxygenase (COX) is central to the generation of prostanoids such as PGD2. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit COX. COX exists as two isoforms, COX-1 and COX-2. The principal aim of this study was to establish whether COX-1 and/or COX-2 mediates PGD2 generation from human lung mast cells. Mast cells were isolated from human lung tissue and purified by flotation over Percoll and immunomagnetic bead separations. The cells were activated with anti-IgE or Stem Cell Factor (SCF). The generation of PGD2 was determined by ELISA. The effects of NSAIDs (aspirin, ibuprofen, diclofenac, naproxen, indomethacin), COX-1 selective (FR122047), and COX-2 selective (celecoxib) inhibitors on PGD2 generation were determined. The expression of COX-1 and COX-2 in mast cells was determined by Western blotting. All the NSAIDs tested abrogated stimulated PGD2 generation from mast cells except aspirin which was only weakly effective. FR122047 was an effective inhibitor of PGD2 generation (EC50 ~25nM) from mast cells whereas celecoxib was ineffective. Immunoblotting indicated that COX-1 was strongly expressed in all mast cell preparations while COX-2 expression was weak. No induction of COX-2 was observed following activation of mast cells. These findings indicate that COX-1 is the principal isoform involved in generating PGD2 from human lung mast cells. These studies provide insight into the potential behaviour of NSAIDs in the context of respiratory diseases.

Ocean acidification (OA) is likely to differentially affect the biology and physiology of calcifying and non-calcifying taxa, thereby potentially altering key ecological interactions (e.g., facilitation, competition, predation) in ways that are difficult to predict from single-species experiments. We used a two-factor experimental design to investigate how multispecies benthic assemblages in southern California kelp forests respond to OA and grazing by the purple sea urchin , Strongylocentrotus purpuratus . Settlement tiles accrued natural mixed assemblages of algae and invertebrates in a kelp forest off San Diego, CA for one year before being exposed to OA and grazing in a laboratory experiment for two months. Space occupying organisms were identified and pooled into six functional groups: calcified invertebrates, non-calcified invertebrates, calcified algae, fleshy algae, sediment, and bare space for subsequent analyses of community structure. Interestingly, communities that developed on separate tile racks were unique, despite being deployed close in space, and further changes in community structure in response to OA and grazing depended on this initial community state. On Rack 1, we found significant effects of both pCO2 and grazing with elevated pCO2 increasing cover of fleshy algae, but sea urchin grazers decreasing cover of fleshy algae. On Rack 2, we found a ~ 35% higher percent cover of sediment on tiles reared in ambient pCO2 but observed ~27% higher cover of bare space in the high pCO2 conditions. On Rack 3, we found an average of 45% lower percent cover of calcified sessile invertebrates at ambient pCO2 than in high pCO2 treatments on Rack 3. Net community calcification was 137% lower in elevated pCO2 treatments. Kelp sporophyte densities on tiles without urchins were 74% higher than on tiles with urchins and kelp densities were highest in the elevated pCO2 treatment. Urchin growth and grazing rates were 49% and 126% higher under ambient than high pCO2 conditions. This study highlights consistent negative impacts of OA on community processes such as calcification and grazing rates, even though impacts on community structure were highly context-dependent.

The relative contributions of grazing versus microbial food webs to the production of mesozooplankton communities in coral reef ecosystems remains an important and understudied field of inquiry. Here, we investigated the biomass and production of component organisms within these two food webs, and compared them to those of mesozooplankton on a coral reef in Okinawa, Japan throughout four seasons in 2011–2012. The relative production of grazing (phytoplankton) and microbial (nano and microzooplankton) food webs were on average 39% (7–77%) and 37% (19–57%), respectively, of the food requirements of particle-feeding mesozooplankton. Carbon flows within this planktonic food web suggested that primary production from the grazing food web could not satisfy the nutritional demands of mesozooplankton, and that the microbial food web contributed a significant amount of nutrition to their diets. These results also show that the heterotrophic components of the microbial food web (nano and microzooplankton) and mesozooplankton consume the equivalent of the entire phytoplankton production (particulate net production) each day, while the microzooplankton were almost entirely eaten by higher trophic levels (mesozooplankton) each day. However, even the combined production from both the grazing and microbial food webs did not fulfill mesozooplankton food requirements in some seasons, explaining 26–53%, suggesting that detritus was used to compensate for nutritional deficiencies during these periods. Understanding the flow of energy throughout coral reefs requires a detailed accounting of pelagic sources and sinks of carbon. Our results provide such an assessment and indicate that detailed investigation on the origin and production of detritus is necessary to better understand pelagic trophodynamics in coral ecosystems.

The accuracy and precision of ion sensitive field effect transistor (ISFET) pH sensors have been well documented, but primarily by ocean chemistry specialists employing the technology at single locations. Here we examine their performance in a network context through comparison to discrete measurements of pH, using different configurations of the Honeywell DuraFET pH sensor deployed in six coastal settings by operators with a range of experience. Experience of the operator had the largest effect on performance. The average difference between discrete and ISFET pH was 0.005 pH units, but ranged from −0.030 to 0.083 among operators, with more experienced operators within ± 0.02 pH units of the discrete measurement. In addition, experienced operators achieved a narrower range of variance in difference between discrete bottle measurements and ISFET sensor readings compared to novice operators and novice operators had a higher proportion of data failing quality control screening. There were no statistically significant differences in data uncertainty associated with sensor manufacturer or deployment environment (pier-mounted, flowthrough system, and buoy-mounted). The variation we observed among operators highlights the necessity of best practices and training when instruments are to be used in a network where comparison across data streams is desired. However, while opportunities remain for improving the performance of the ISFET sensors when deployed by less experienced operators, the uncertainty associated with their deployment and validation was several-fold less than the observed natural temporal variability in pH, demonstrating the utility of these sensors in tracking local changes in acidification.

Based on the National Highway Traffic Safety Association's (NHTSA) Report, fatalities due to distracted driving are on the rise and the highest proportion of fatalities by age group is the 20-29 year old category. To date little has been done to educate college students about the dangers of distracted driving and engage these students in promoting a safe driving culture. Intervening among college students has the potential for making real-time behavior change, can foster a lifetime of safe driving habits among these students, and can help contribute to a culture of safe driving that can be created and sustained through positive messages from peers. The goals of this study were to develop, implement and evaluate a distracted driving presentation for college students to change knowledge, attitude and behavior on distracted driving. A 30-min, multi-media presentation on distracted driving was presented to 19 colleges and universities, totaling 444 college students (mean age 23.7±7.0 years of age, 61% females, 39% males). Students completed three surveys: prior to the workshop (interview 1), immediately after the workshop (interview 2), and 3 months following the workshop (interview 3). We assessed changes between interview 1 and interview 2 and found 15 of the 15 attitude-knowledge based questions significantly improved after the course. In addition, we assessed changes from interviews 1 and 3, and found 11 of the 15 attitude-knowledge based questions maintained their significance. Responses to behavior related questions at three months were also compared to baseline, and significant improvements were found for 12 of the 14 questions. While this study was successful in improving the short-term attitude-knowledge and behaviors on distracted driving, work is needed to sustain (and evaluate) long-term effects.

The effects of social and ecological stressors on female reproductive success vary among species and, in mammals, previous reviews have identified no clear patterns. However, few studies have simultaneously examined the relation between social rank and stressors and the relationships among rank, stressors and reproductive success. We used a long-term data set to study free-living facultatively social yellow-bellied marmots, Marmota flaviventris, to isolate the relationship between female social dominance rank and faecal glucocorticoid metabolite (FGM) levels (our measure of basal stress) in adult females. In addition, we examined whether rank and FGM levels were associated with reproductive success by quantifying the probability of an individual successfully weaning a litter and, for those who did, litter size. High-ranking females had lower FGM levels and larger litters. However, females with the highest FGM levels were significantly more likely to wean a litter. Importantly, body condition (as measured by previous year's mass) was also positively associated with breeding and with weaning larger litters. Thus, although low-ranking females probably experienced more social stressors than high-ranking females and although adult females often delayed their first reproduction until they were of a sufficient mass, our results suggest that elevated baseline FGM levels failed to mediate reproductive suppression. Perhaps, in species like marmots that have only a single chance per year to reproduce, reproductive suppression should be rare. These results highlight the importance of social status, body condition and predator abundance on determining reproductive success in highly seasonal breeders.

Because collective movements have fitness consequences for all participants, group travel can impose conflicts of interest when group-mates vary. Challenges associated with coordinating activities of group-mates, such as during travel, may potentially be mitigated through the use of simple rules governing leadership and other behaviours to minimize conflict. Although individuals living in groups with fission–fusion dynamics may temporarily separate, leadership determination at subsequent reunions, and events occurring during reunions, are poorly understood. Here we investigate leadership during travel prior to reunions of spotted hyaenas, Crocuta crocuta, living in one large social group in the Masai Mara National Reserve, Kenya. Whereas individuals often arrived at dens or joined hunting parties alone, those joining others to participate in group defence of shared resources typically did so when accompanied by group-mates. Although most hyaenas led processions, the attributes of members within each travelling party consistently predicted leadership roles. The highest-ranking adult within each travelling subgroup, often a lactating female, typically assumed the vanguard position prior to reunions. Reunions promoted conflict, particularly at kills. However, as predicted by the conflict mitigation hypothesis, individuals that greeted conspecifics were significantly less likely to fight at reunions than were hyaenas that failed to greet at reunions. Thus, whereas temporary separations may reduce immediate conflicts of interest in fission–fusion societies, hyaenas pay consensus costs at subsequent reunions, particularly in the context of feeding competition, and greetings appear to reduce such costs. Finally, we propose a novel scheme for leadership categorization in which leadership depends on whether or not leadership is based on specific attributes of individual group members. We apply this attribute-based framework to quantify the patterns and mechanisms of leadership during group travel for 52 species of mammals, including the spotted hyaenas studied here, and place findings in a broad evolutionary context.

In 1964, W. D. Hamilton proposed a novel solution to the long-standing evolutionary puzzle: why do individuals cooperate? Hamilton predicted that, if individuals possess the ability to discriminate on the basis of kinship, then they should gain inclusive fitness benefits by biasing helpful behaviour towards relatives and harmful behaviour away from them. The possibility that kin selection might favour social evolution has now inspired five decades of active research. Here, I synthesize this evidence for social mammals. First, I report on the methodological advances that allow for pedigree construction, and review the evidence for maternal and paternal kin discrimination. Second, I recognize that a substantial body of evidence for the evolution of cooperative breeding via kin selection exists, and then focus on the potential for kin selection to favour less well understood, yet equally salient, targets of selection: social partner choice, coalition formation and social tolerance (withholding aggression). I find that kin selection favours remarkably similar patterns of nepotism in primate and nonprimates with respect to these short-lived social acts. Although social alliances among maternal and paternal kin are common in mammalian societies, kinship largely fails to protect individuals from aggression. Thus, an individual's closest associates and allies, many of whom are kin, are most often an individual's closest competitors within mammalian social groups. Taken together, these findings highlight the value of Hamilton's holistic approach in simultaneously considering the direct benefits of competition and the indirect fitness benefits of cooperation. Despite major empirical advances since the inception of kin selection theory, future tests using newly available molecular and statistical methods in combination with longitudinal behavioural data are required to partition the relative contributions of direct and indirect fitness on the lifetime inclusive fitness. Such approaches will elucidate the relative influences of evolutionary and ecological forces favouring social evolution across the mammalian lineage of social mammals.

Affiliative interactions have important fitness consequences for individuals. Yet, precisely how social roles emerge across ontogeny outside of the context of agonistic interactions is largely unknown, particularly in free-living species of nonprimates. Here we used longitudinal data on yellow-bellied marmots, Marmota flaviventris, residing around the Rocky Mountain Biology Laboratory in Colorado, U.S.A., to investigate the development of social partner choice in free-living rodents. We first characterized the symmetry of affiliative interactions between mother–offspring pairs and within cohorts of individuals as they developed across discrete life history stages. Affiliative behaviours generally increased in symmetry such that exchanges became more reciprocal as individuals matured. We then evaluated the extent to which individuals biased their affiliative behaviour towards, and agonistic behaviour away from, genetic relatives. As predicted by kin selection theory, rates of affiliation increased with the degree of relatedness among individuals at all three life history stages. Thus, nepotism emerged within cohorts of newly weaned pups and persisted into adulthood despite prolonged annual separations due to hibernation. Surprisingly, close relatives also exchanged the highest rates of agonistic behaviour. After accounting for the degree of relatedness, rates of affiliative behaviours given and agonistic behaviours received remained positively correlated, suggesting that close affiliates are each other's closest competitors. Thus, although reciprocity of affiliative exchanges within cohorts increased as individuals matured, competition among genetic relatives emerged early in ontogeny and persisted into adulthood. Taken together, these results highlight changes in social roles shown by individuals across ontogeny and shed light on theories of life history and social evolution.

Natural selection is expected to shape phenotypic traits that permit organisms to respond appropriately to the environments in which they live. One important mechanism by which animals cope with changes in their environment is through physiological responses to stressors mediated by glucocorticoid hormones. Here we perform biological and physiological validations of a minimally-invasive technique for assessing fecal corticosterone metabolites (FCMs) in captive and wild groups of yellow-bellied marmots (Marmota flaviventris). Then we draw from ten years of data on these obligate hibernators at the Rocky Mountain Biological Laboratory in Colorado, USA to assess the extent to which seasonal and daily changes explain naturalistic variation in baseline levels of FCMs. Interestingly, beyond important population-level variation with respect to year, season, time of day, sex, age and reproductive state, we found repeatable inter-individual differences in FCMs, suggesting this hormonal trait might be a meaningful target of selection. FCM levels were 68% lower in captive than wild marmots, suggesting that the natural environment in which these animals occur is generally more challenging or less predictable than life in captivity. Most live-trapping events failed to represent stressors for wild marmots such that repeated measurements of traits were possible with minimal "stress" to subjects. We also document the natural ranges of annual and seasonal variation necessary for understanding the extent to which anthropogenic assaults represent stressors for wild mammals. Taken together, this study provides a foundation for understanding the evolution of hormonal traits and has important welfare and conservation implications for field biologists.

Summary Honaucins A−C were isolated from the cyanobacterium Leptolyngbya crossbyana which was found overgrowing corals on the Hawaiian coast. Honaucin A consists of ( S )-3-hydroxy-γ-butyrolactone and 4-chlorocrotonic acid, which are connected via an ester linkage. Honaucin A and its two natural analogs exhibit potent inhibition of both bioluminescence, a quorum-sensing-dependent phenotype, in Vibrio harveyi BB120 and lipopolysaccharide-stimulated nitric oxide production in the murine macrophage cell line RAW264.7. The decrease in nitric oxide production was accompanied by a decrease in the transcripts of several proinflammatory cytokines, most dramatically interleukin-1β. Synthesis of honaucin A, as well as a number of analogs, and subsequent evaluation in anti-inflammation and quorum-sensing inhibition bioassays revealed the essential structural features for activity in this chemical class and provided analogs with greater potency in both assays.

Macroalgal blooms of Ulva lactuca and Hypnea musciformis have been problematic in shallow coastal waters around agricultural and urbanized regions of Maui, Hawai‘i for decades. Observations have highlighted the correspondence between these blooms and elevated nutrient levels from the adjacent land-use, however little evidence exists regarding the effects of nutrient enrichment on the blooming and non-blooming macroalgae in the area. To determine if elevated nutrient levels influence H. musciformis physiology, we conducted a nutrient enrichment (+N, +P, and +N+P) experiment and measured growth, photosynthetic status, and pigment absorbance. Phycobilin pigments were significantly reduced in the no addition and +P treatment and maintained in those with N additions, suggesting that H. musciformis can use phycobilins to store N. We conducted a second, larger experiment with additions of secondarily-treated wastewater effluent on the bloom forming species Acanthophora spicifera, H. musciformis, and U. lactuca and the common non-bloom forming species, Dictyota acutiloba. All samples were initially depleted of potential N stores and measured for growth, photosynthetic status, and N uptake rates; H. musciformis and U. lactuca were also assessed for micro nutrient uptake, % tissue N, and δ15N values. Growth rates of D. acutiloba, H. musciformis, and U. lactuca increased with increasing % wastewater effluent addition and concentrations of TN and NO3− and those of the bloom forming species were 2-fold higher. All species increased photosynthetic capacity and saturation irradiance with increasing % wastewater effluent addition and concentrations of TN and NO3−. U. lactuca was the most sensitive to low N conditions, evidenced by declines in light capturing efficiency. All species utilized a substantial amount of N over 24 h. H. musciformis and U. lactuca also (1) utilized micro nutrients: iron, manganese, molybdenum, and zinc, (2) decreased % tissue N in low N conditions, (3) increased % tissue N in response to elevated N conditions, and (4) expressed elevated δ15N values with increasing additions of wastewater effluent. These results demonstrate that in Hawai‘i, the bloom forming species H. musciformis and U. lactuca, have similar physiological responses to decreased and increased nutrient levels.

Societies characterized by fission–fusion dynamics consist of subgroups that frequently change in size and composition. Although this flexible lifestyle permits individuals to reduce conflicts of interest, it simultaneously imposes a unique set of challenges on group members that are regularly subject to prolonged separation. Theory predicts animals should evolve ritualized and risky displays to quickly update relationships at reunions. Here we investigated the function of nonconciliatory greetings among adult female spotted hyaenas, Crocuta crocuta, belonging to a single, large female-dominated social group in Kenya. We tested three hypotheses forwarded to explain the occurrence of these multimodal signals: formal submission, tension reduction and social bonding hypotheses. In contrast to predictions of the formal submission hypothesis, rank distance and relative rank were excluded from our best model predicting greetings among adult females. Moreover, directional consistency of greetings was low (0.65) compared to that of submissive behaviours during dyadic agonistic interactions (0.97). Instead, our data revealed that adult females greeted coalition partners and close associates, including kin, most often per opportunity, and they did so in neutral contexts more frequently than in situations characterized by social tension. Although these findings are in direct contrast to the predictions of the tension reduction and formal submission hypotheses, they strongly support the social bonding hypothesis. Importantly, the immediate act of greeting promoted cooperation among allies during intragroup and intergroup coalition formation. Thus, these risky, multimodal signals permit hyaenas to effectively communicate cooperative affiliations within a continuously shifting social milieu.

Summary Mixotrophy is among the most successful nutritional strategies in terrestrial and marine ecosystems. The ability of organisms to supplement primary nutritional modes along continua of autotrophy and heterotrophy fosters trophic flexibility that can sustain metabolic demands under variable or stressful conditions. Symbiotic, reef-building corals are among the most broadly distributed and ecologically important mixotrophs, yet we lack a basic understanding of how they modify their use of autotrophy and heterotrophy across gradients of food availability. Here, we evaluate how one coral species, Pocillopora meandrina, supplements autotrophic nutrition through heterotrophy within an archipelago and test whether this pattern holds across species globally. Using stable isotope analysis (δ13C) and satellite-derived estimates of nearshore primary production (chlorophyll-a, as a proxy for food availability), we show that P. meandrina incorporates a greater proportion of carbon via heterotrophy when more food is available across five central Pacific islands. We then show that this pattern is consistent globally using data from 15 coral species across 16 locations spanning the Caribbean Sea and the Indian and Pacific Oceans. Globally, surface chlorophyll-a explains 77% of the variation in coral heterotrophic nutrition, 86% for one genus across 10 islands, and 94% when controlling for coral taxonomy within archipelagos. These results demonstrate, for the first time, that satellite-derived estimates of nearshore primary production provide a globally relevant proxy for resource availability that can explain variation in coral trophic ecology. Thus, our model provides a pivotal step toward resolving the biophysical couplings between mixotrophic organisms and spatial patterns of resource availability in the coastal oceans.

Macroalgal blooms of Hypnea musciformis and Ulvafasciata in coastal waters of Maui only occur in areas of substantial anthropogenic nutrient input, sources of which include wastewater effluent via injection wells, leaking cesspools and agricultural fertilizers. Algal delta(15)N signatures were used to map anthropogenic nitrogen through coastal surveys (island-wide and fine-scale) and algal deployments along nearshore and offshore gradients. Algal delta(15)N values of 9.8 per thousand and 2.0-3.5 per thousand in Waiehu and across the north-central coast, respectively, suggest that cesspool and agricultural nitrogen reached the respective adjacent coastlines. Effluent was detected in areas proximal to the Wastewater Reclamation Facilities (WWRF) operating Class V injection wells in Lahaina, Kihei and Kahului through elevated algal delta(15)N values (17.8-50.1 per thousand). From 1997 to 2008, the three WWRFs injected an estimated total volume of 193 million cubic meters (51 billion gallons) of effluent with a nitrogen mass of 1.74 million kilograms (3.84 million pounds).

Theory predicts that individuals living in fission–fusion societies, in which group members frequently change subgroups, should modify grouping patterns in response to varying social and environmental conditions. Spotted hyaenas, Crocuta crocuta, are long-lived carnivores that reside in permanent social groups called clans. Clans are complex, fission–fusion societies in which individual members travel, rest and forage in subgroups that frequently change composition. We studied two clans in Kenya to provide the first detailed description of fission–fusion dynamics in this species. Because social and ecological circumstances can influence the cohesiveness of animal societies, we evaluated the extent to which specific circumstances promote the formation of subgroups of various sizes. We found that cooperative defence of shared resources during interclan competition and protection from lions were cohesive forces that promoted formation of large subgroups. We also tested hypotheses suggesting factors limiting subgroup size. Mothers with small cubs avoided conspecifics, thereby reducing infanticide risk. Victims of aggression either reconciled fights or separated from former opponents to reduce the immediate costs of escalated aggression in the absence of food. As predicted by the ecological constraints hypothesis, hyaenas adjusted their grouping patterns over both short and long time scales in response to feeding competition. Crocuta were most gregarious during periods of abundant prey, joined clanmates at ephemeral kills in numbers that correlated with the energetic value of the prey and gained the most energy when foraging alone because cooperative hunting attracted numerous competitors. Overall, our findings indicate that resource limitation constrains grouping in this species.

Summary The adaptor protein SLP76 directs signaling downstream of the T cell receptor (TCR) and is essential for thymocyte development. SLP76 contains three N-terminal tyrosines that are critical for its function. To define the role of these residues in thymocyte development, we generated two lines of "knock-in" mice, one expressing a mutation in tyrosine 145 (Y145F) and a second harboring two point mutations at tyrosines 112 and 128 (Y112-128F). We show here that although thymocyte development requires both Y145- and Y112-128-generated signals, selection was more dependent upon Y145. Although several proximal TCR signaling events were defective in both mutant mice, phosphorylation of the guanine nucleotide exchange factor, Vav1, and activation of Itk-dependent pathways were differentially affected by mutations at Y112-128 and Y145, respectively. Analysis of mice expressing one Y145F and one Y112-128F allele revealed that these mutants could complement one another in trans, demonstrating cooperativity between two or more SLP76 molecules. Thus, the N-terminal tyrosines of SLP76 are required for thymocyte selection but can function on separate molecules to support TCR signaling.

The clearance rate of natural planktonic assemblages was measured for the blue mussel Mytilus edulis (L.) and a co-occurring fouling community from mussel rope cultures using flow cytometry. Blue mussels had significantly higher clearance rates for all particle types and size classes. In addition, blue mussels showed selective feeding in favor of small phytoplankton (3–5 μm), whereas the solitary ascidian Ciona intestinalis (L.) and the suspension-feeding gastropod Crepidula fornicata (L.) showed preferential selection for large phytoplankton (> 16 μm). Clearance rates for large phytoplankton by these members of the fouling community were, however, always lower than blue mussels. Under conditions where food is not a limiting factor, interspecific competition for food by the associated fouling community should not significantly limit the yield of mussels.

An unusual case is presented of a peripheral ameloblastoma arising on the buccal mucosa, which brings the total number of such cases to three. The occurrence and pathogenesis of peripheral ameloblastomas in general, are reviewed, especially with reference to the basal cell carcinoma.