In vitro human skin absorption of linalool: Effects of vehicle composition, evaporation and occlusion on permeation and distribution.

In vitro human skin permeation and distribution of the fragrance material linalool (3,7-dimethyl-1,6-octadien-3-ol, CAS No. 78-70-6) following application in a range of single and mixed vehicles was determined, under unoccluded and occluded conditions, using human epidermal membranes. Vehicles were (70/30 v/v) ethanol[EtOH]/water, dipropyleneglycol [DPG], diethyl phthalate [DEP], (25/75 v/v) EtOH/DEP, (25/75 v/v) EtOH/DPG and petrolatum. Worst case absorbed dose values (% applied dose) for linalool under unoccluded conditions varied from 1.84% (DPG) to 4.08% (EtOH/water) and under occluded conditions from 5.9% (DEP) to 14.7% (EtOH/water). Occlusion always increased absorption but the magnitude of the effect varied with the vehicle from 2 to 6-fold. This study demonstrated that in vitro human skin permeation of linalool varied quite widely between test vehicles and that the magnitude of the effect of occlusion was also vehicle dependent. This was particularly significant in view of the reported variations in biological responses using different vehicles (Lalko et al., 2004; Politano et al., 2006).

The contact structure of Great Britain's salmon and trout aquaculture industry.

We analyse the network structure of the British salmonid aquaculture industry from the perspective of infectious disease control. We combine for the first time live fish transport (or movement) data covering England and Wales with data covering Scotland and include network layers representing potential transmission by rivers, sea water and local transmission via human or animal vectors in the immediate vicinity of each farm or fishery site. We find that 7.2% of all live fish transports cross the England-Scotland border and network analysis shows that 87% of English and Welsh nodes and 72% of Scottish nodes are reachable from cross-border connections via live fish transports alone. Consequently, from a disease-control perspective, the contact structures of England and Wales and of Scotland should not be considered in isolation. We also show that large epidemics require the live fish movement network and so control strategies targeting movements can be very effective. While there is relatively low risk of widespread epidemics on the live fish transport network alone, the potential risk is substantially amplified by the combined interaction of multiple network layers.

Identifying genotype specific elevated-risk areas and associated herd risk factors for bovine tuberculosis spread in British cattle.

Bovine tuberculosis (bTB) is a chronic zoonosis with major health and economic impact on the cattle industry. Despite extensive control measures in cattle and culling trials in wildlife, the reasons behind the expansion of areas with high incidence of bTB breakdowns in Great Britain remain unexplained. By balancing the importance of cattle movements and local transmission on the observed pattern of cattle outbreaks, we identify areas at elevated risk of infection from specific Mycobacterium bovis genotypes. We show that elevated-risk areas (ERAs) were historically more extensive than previously understood, and that cattle movements alone are insufficient for ERA spread, suggesting the involvement of other factors. For all genotypes, we find that, while the absolute risk of infection is higher in ERAs compared to areas with intermittent risk, the statistically significant risk factors are remarkably similar in both, suggesting that these risk factors can be used to identify incipient ERAs before this is indicated by elevated incidence alone. Our findings identify research priorities for understanding bTB dynamics, improving surveillance and guiding management to prevent further ERA expansion.

Heterogeneous responses of temperate-zone amphibian populations to climate change complicates conservation planning.

The pervasive and unabated nature of global amphibian declines suggests common demographic responses to a given driver, and quantification of major drivers and responses could inform broad-scale conservation actions. We explored the influence of climate on demographic parameters (i.e., changes in the probabilities of survival and recruitment) using 31 datasets from temperate zone amphibian populations (North America and Europe) with more than a decade of observations each. There was evidence for an influence of climate on population demographic rates, but the direction and magnitude of responses to climate drivers was highly variable among taxa and among populations within taxa. These results reveal that climate drivers interact with variation in life-history traits and population-specific attributes resulting in a diversity of responses. This heterogeneity complicates the identification of conservation 'rules of thumb' for these taxa, and supports the notion of local focus as the most effective approach to overcome global-scale conservation challenges.

Male infertility in long-term survivors of pediatric cancer: a report from the childhood cancer survivor study.

PURPOSE: The purpose of this study was to assess the prevalence of male infertility and treatment-related risk factors in childhood cancer survivors. METHODS: Within the Childhood Cancer Survivor Study, 1,622 survivors and 274 siblings completed the Male Health Questionnaire. The analysis was restricted to survivors (938/1,622; 57.8 %) and siblings (174/274; 63.5 %) who tried to become pregnant. Relative risks (RR) and 95 % confidence intervals (CI) for the prevalence of self-reported infertility were calculated using generalized linear models for demographic variables and treatment-related factors to account for correlation among survivors and siblings of the same family. All statistical tests were two-sided. RESULTS: Among those who provided self-report data, the prevalence of infertility was 46.0 % in survivors versus 17.5 % in siblings (RR = 2.64, 95 % CI 1.88-3.70, p < 0.001). Of survivors who met the definition for infertility, 37 % had reported at least one pregnancy with a female partner that resulted in a live birth. In a multivariable analysis, risk factors for infertility included an alkylating agent dose (AAD) score ≥3 (RR = 2.13, 95 % CI 1.69-2.68 for AAD ≥3 versus AAD <3), surgical excision of any organ of the genital tract (RR = 1.63, 95 % CI 1.20-2.21), testicular radiation ≥4 Gy (RR = 1.99, 95 % CI 1.52-2.61), and exposure to bleomycin (RR = 1.55, 95 % CI 1.20-2.01). CONCLUSION: Many survivors who experience infertility father their own children, suggesting episodes of both fertility and infertility. This and the novel association of infertility with bleomycin warrant further investigation. IMPLICATIONS FOR CANCER SURVIVORS: Though infertility is common, male survivors reporting infertility often father their own children. Bleomycin may pose some fertility risk.

Well-differentiated liposarcoma of the epiglottis.

OBJECTIVE: Liposarcomas of the larynx and its sub-sites are rare. Within this group of tumours, well-differentiated liposarcomas of the epiglottis have been only sporadically reported. In view of its infrequent presentation, difficulty still exists over the diagnosis of this pathological entity, together with uncertainty over its exact accepted management. METHOD: We present the case of a well-differentiated liposarcoma of the epiglottis, and we review the associated English-language literature. RESULTS: The reported patient underwent multiple attempts at surgical treatment prior to establishment of a firm diagnosis. In light of the diagnosis and other mitigating factors, a conservative approach was adopted. CONCLUSION: A high index of clinical suspicion and detailed histological analysis are required when encountering a recurrent soft tissue lesion of the larynx. In the presented case, a multidisciplinary approach and conservative management plan were adopted, based on a holistic management approach and a review of the published literature.

Differential characterization of emerging skin diseases of rainbow trout--a standardized approach to capturing disease characteristics and development of case definitions.

Farmed and wild salmonids are affected by a variety of skin conditions, some of which have significant economic and welfare implications. In many cases, the causes are not well understood, and one example is cold water strawberry disease of rainbow trout, also called red mark syndrome, which has been recorded in the UK since 2003. To date, there are no internationally agreed methods for describing these conditions, which has caused confusion for farmers and health professionals, who are often unclear as to whether they are dealing with a new or a previously described condition. This has resulted, inevitably, in delays to both accurate diagnosis and effective treatment regimes. Here, we provide a standardized methodology for the description of skin conditions of rainbow trout of uncertain aetiology. We demonstrate how the approach can be used to develop case definitions, using coldwater strawberry disease as an example.

Content variability of active drug substance in compounded oral 3,4-diaminopyridine products.

WHAT IS KNOWN AND OBJECTIVE: 3,4-diaminopyridine (3,4-DAP; amifampridine) is used for symptomatic treatment of Lambert-Eaton myasthenic syndrome. Until recently, it was only available as a compounded product, which raises safety concerns because of possible high variability in active drug substance content. The objective of this study was to evaluate the variability in dosage form weight, active content variability and impurity of compounded oral 3,4-DAP drug products. METHODS: Ten samples each of 9 oral 3,4-DAP compounded products were weighed, extracted with water and the 3,4-DAP content determined by ultra high-performance liquid chromatography. RESULTS AND DISCUSSION: Variability in dosage form weight ranged from 0·81% relative standard deviation (RSD) to 4·82% RSD. In the 90 samples tested, 3,4-DAP content ranged from 22·2% to 125·2% of declared label content. All 10 samples of one compounded product had active drug substance content well below the declared label content (35·0%, 51·7% RSD). No compounded product achieved the Good Manufacturing Practice (GMP) standard of 95-105% range limit of declared label content; one achieved 90-110%, and four others achieved 80-120% of declared content for all 10 samples. There was no evidence of a significant presence of degradation products or related substances in any compounded product. WHAT IS NEW AND CONCLUSION: Compounded 3,4-DAP products are subject to considerable variability in active drug substance content. This variability seems to be principally because of heterogeneous formulated material rather than variation in dosage form weight.

The potential for targeted surveillance of live fish movements in Scotland.

The network structure of the movements of live fish in the Scottish aquaculture industry has recently been demonstrated for 2003. In this paper, we enlarge this analysis to a longer 3-year period from 2002 to 2004, the new data allowing complete coverage of at least one production cycle. The resulting network contains slightly more sites than that for a single year and is denser with more arcs (directed site-to-site connections) present, but otherwise features recognizable in the 1-year network are still recognizable in the 3-year network. Arc-removal algorithms (a proxy for targeted surveillance) were identified that could successfully reduce the portion of the network reachable from a node (a proxy for potential epidemic size) by approximately one-third by removing as few as four arcs. This results from the high centrality of particular nodes and arcs. A strong community structure was identified in the network, corresponding with species farmed, but only weakly geographical, with a high proportion of arcs occurring between management areas and catchments.

Seasonality and heterogeneity of live fish movements in Scottish fish farms.

Movement of live animals is a key contributor to disease spread. Farmed Atlantic salmon Salmo salar, rainbow trout Onchorynchus mykiss and brown/sea trout Salmo trutta are initially raised in freshwater (FW) farms; all the salmon and some of the trout are subsequently moved to seawater (SW) farms. Frequently, fish are moved between farms during their FW stage and sometimes during their SW stage. Seasonality and differences in contact patterns across production phases have been shown to influence the course of an epidemic in livestock; however, these parameters have not been included in previous network models studying disease transmission in salmonids. In Scotland, farmers are required to register fish movements onto and off their farms; these records were used in the present study to investigate seasonality and heterogeneity of movements for each production phase separately for farmed salmon, rainbow trout and brown/sea trout. Salmon FW-FW and FW-SW movements showed a higher degree of heterogeneity in number of contacts and different seasonal patterns compared with SW-SW movements. FW-FW movements peaked from May to July and FW-SW movements peaked from March to April and from October to November. Salmon SW-SW movements occurred more consistently over the year and showed fewer connections and number of repeated connections between farms. Therefore, the salmon SW-SW network might be treated as homogeneous regarding the number of connections between farms and without seasonality. However, seasonality and production phase should be included in simulation models concerning FW-FW and FW-SW movements specifically. The number of rainbow trout FW-FW and brown/sea trout FW-FW movements were different from random. However, movements from other production phases were too low to discern a seasonal pattern or differences in contact pattern.

The effectiveness of fallowing strategies in disease control in salmon aquaculture assessed with an SIS model.

Salmon production is an important industry in Scotland, with an estimated retail value >£1 billion. However, this salmon industry can be threatened by the invasion and spread of diseases. To reduce this risk, the industry is divided into management areas that are physically separated from each other. Pathogens can spread between farms by local processes such as water movement or by long-distance processes such as live fish movements. Here, network modelling was used to investigate the importance of transmission routes at these two scales. We used different disease transmission rates (ß), where infected farms had the probability of 0.10, 0.25 or 0.50 per month to infect each contacted farm. Interacting farms were modelled in such a way that neighbours within a management area could infect each other, resulting in two contacts per farm per month. In addition, non-local transmission occurred at random. Salmon are input to marine sites where they are raised to harvest size, the site is then fallowed; in the model the effects of different fallowing strategies (synchronised, partial synchronised and unsynchronised fallowing at the management area level) on the emergence of diseases were investigated. Synchronised fallowing was highly effective at eradicating epidemics when transmission rate is low (ß=0.10) even when long distance contacts were fairly common (up to 1.5farm(-1)month(-1)). However for higher transmission rates, long distance contacts have to be kept at much lower levels (0.15contactsmonth(-1) where ß=0.25) when synchronised fallowing was applied. If fallowing was partially synchronised or unsynchronised then low rates of long-distance contact are required (0.75 or 0.15farm(-1)month(-1)) even if ß=0.10. These results demonstrate the potential benefits of having epidemiologically isolated management areas and applying synchronised fallowing.

Data quality of the Cattle Tracing System in Great Britain.

The Cattle Tracing System (cts) of Great Britain was examined to investigate the quality of its data in terms of known errors and omissions, and their distribution. The proportions of erroneous or missing data have decreased steadily over time, with a marked improvement in the quality of the data since 2001, when recording became mandatory. There is little variation between regions in the quality of the data, but there are potentially important variations between the types of agricultural premises that cattle move to and from, and in other factors correlated with the type of premises, such as the age of the animals and the number of animal movements associated with the premises.

In-vitro human skin penetration of the fragrance material geranyl nitrile.

In-vitro human skin permeation and distribution of geranyl nitrile (GN) was determined using epidermal membranes following application (5 microl/cm(2)) in 70% ethanol, under non-occlusive conditions, at maximum in-use concentration (1%). Permeation was measured (12 time-points over 24 h) using 6% (w/v) Oleth-20 in pH 7.4 phosphate buffered saline as receptor. Permeation of reference benzoic acid was assessed using the same skin donors. Overall recovery of GN at 24 h was low (14.1+/-0.4%) due to evaporation. Evaporative loss of GN from polytetrafluoroethylene (PTFE) sheet, under the same conditions was rapid (93% over 24h) although this overestimated loss during permeation where evaporation competed with uptake. At 24 h, 1.89+/-0.15 microg/cm(2) GN, (3.74+/-0.30% of applied dose) (mean+/-standard error, SE, n=12), had permeated. Following rapid initial permeation, the absorption plateaued due to depletion. Levels of GN in the epidermis (plus any remaining stratum corneum after tape stripping), filter paper membrane support and receptor fluid were combined (as per SCCNFP guidelines) to produce a total absorbed dose value of 4.72+/-0.32%. Systemic exposure resulting from the use of GN as a fragrance ingredient, under unoccluded conditions, would be low based on the currently reported use levels.

Modelling the initial spread of foot-and-mouth disease through animal movements.

Livestock movements in Great Britain (GB) are well recorded and are a unique record of the network of connections among livestock-holding locations. These connections can be critical for disease spread, as in the 2001 epidemic of foot-and-mouth disease (FMD) in the UK. Here, the movement data are used to construct an individual-farm-based model of the initial spread of FMD in GB and determine the susceptibility of the GB livestock industry to future outbreaks under the current legislative requirements. Transmission through movements is modelled, with additional local spread unrelated to the known movements. Simulations show that movements can result in a large nationwide epidemic, but only if cattle are heavily involved, or the epidemic occurs in late summer or early autumn. Inclusion of random local spread can considerably increase epidemic size, but has only a small impact on the spatial extent of the disease. There is a geographical bias in the epidemic size reached, with larger epidemics originating in Scotland and the north of England than elsewhere.

Effect of early full weight-bearing after joint injury on inflammation and cartilage degradation.

BACKGROUND: Early full weight-bearing after an acute osteochondral injury avoids problems associated with immobility but may also be harmful by amplifying the inflammatory response. To investigate these effects, we developed an in vivo model of subchondral trauma. METHODS: After an impact injury to the femoral condyle, fourteen dogs were randomized to immediate full weight-bearing or to four weeks of minimal weight-bearing before full weight-bearing. Synovial fluid was sampled by aspiration at one, two, four, eight, twelve, sixteen, twenty, and twenty-four weeks. Neutrophils, monocytes, and lymphocytes were enumerated, and the concentrations of tumor necrosis factor-alpha, interleukin-10, nitric oxide, matrix metalloproteinases, and glycosaminoglycans were measured. RESULTS: Compared with the findings for uninjured joints, the synovial fluid from the impacted joints of full-weight-bearing dogs had significantly higher peak concentrations of neutrophils (p = 0.0006 at one week), mononuclear leukocytes (p = 0.001 at four weeks), tumor necrosis factor-alpha (p = 0.001 at one week), nitric oxide (p = 0.001 at one week), matrix metalloproteinases (p = 0.008 at one week), and glycosaminoglycans (p = 0.002 at four weeks and p = 0.001 at six months). The size of the bone bruise correlated with the peak concentrations of tumor necrosis factor-alpha (r2= 0.89, p = 0.007; Spearman rank test), matrix metalloproteinases (r2= 0.96, p = 0.0004), and glycosaminoglycans (r2= 0.96, p = 0.0004). However, restriction to minimal weight-bearing for four weeks after the injury led to a significant reduction in the synovial fluid concentrations of neutrophils (p = 0.007 at one week and p = 0.01 at two weeks), tumor necrosis factor-alpha (p = 0.0006 to 0.02 during the first four weeks), nitric oxide (p = 0.001 to 0.04 during the first four weeks), and matrix metalloproteinases (p = 0.007 to 0.01 from the second week to the eighth week). In contrast, interleukin-10 concentrations were significantly higher (p = 0.002 at one week) and glycosaminoglycan levels remained at normal levels in animals that were restricted from immediate full weight-bearing after the injury. CONCLUSIONS: The magnitude of the inflammatory response is proportional to the size of the bone bruise. Restriction to minimal weight-bearing for four weeks reduces the magnitude of the inflammatory response and the cartilage degradation following articular cartilage impact injury. CLINICAL RELEVANCE: Strategies to minimize mechanical stress during the early postinjury period may help to preserve cartilage integrity and forestall the development of osteoarthritis.

Demographic structure and pathogen dynamics on the network of livestock movements in Great Britain.

Using a novel interpretation of dynamic networks, we analyse the network of livestock movements in Great Britain in order to determine the risk of a large epidemic of foot-and-mouth disease (FMD). This network is exceptionally well characterized, as there are legal requirements that the date, source, destination and number of animals be recorded and held on central databases. We identify a percolation threshold in the structure of the livestock network, indicating that, while there is little possibility of a national epidemic of FMD in winter when the catastrophic 2001 epidemic began, there remains a risk in late summer or early autumn. These predictions are corroborated by a non-parametric simulation in which the movements of livestock in 2003 and 2004 are replayed as they occurred. Despite the risk, we show that the network displays small-world properties which can be exploited to target surveillance and control and drastically reduce this risk.

Cellular events leading to chondrocyte death after cartilage impact injury.

OBJECTIVE: We undertook this study to test our postulate that leukocytes extend the zone of injury in cartilage after acute mechanical trauma. METHODS: Fresh cadaveric canine femoral condyles were subjected to 20-25-MPa impact injury. Condyle explants or dispersed chondrocytes were cultured with autologous blood mononuclear leukocytes (MNLs). Viability of chondrocytes at varying distances from the impact site was assessed by trypan blue exclusion. RESULTS: Mechanical injury caused a significant loss of viable chondrocytes over 7 days, even in cartilage >10 mm from the impact site. After biomechanical stress, death of cells within 10 mm of the impact could be largely prevented by addition of N(G)-monomethyl-L-arginine to inhibit nitric oxide (NO) generation. Chondrocytes within 10 mm of the impact were also susceptible to killing by living MNLs, but not by incubation with the supernatants of endotoxin-activated MNLs. Chondrocytes in this vulnerable zone expressed intercellular adhesion molecule 1 (ICAM-1) (CD54), facilitating attachment of MNLs that localized adjacent to the chondrocytes. Leukocytes killed dispersed chondrocytes harvested from the impact zone by generation of reactive oxygen species. Leukocyte-mediated killing could be blocked by desferoxamine or by antibodies to CD18, which prevent attachment of leukocytes to ICAM-1-expressing chondrocytes. CONCLUSION: Our data suggest that after mechanical injury, chondrocytes distant from the site may be killed through the generation of NO. Inflammatory leukocytes further extend the zone of chondrocyte death by adhering to chondrocytes expressing ICAM-1 and by inducing the accumulation of free oxygen radicals in the chondrocyte cytoplasm. Patients may benefit from therapies that reduce infiltration of inflammatory leukocytes into acutely injured cartilage.

The role of menthol in skin penetration from topical formulations of ibuprofen 5% in vivo.

In vivo plasma profiles from formulations containing 5% ibuprofen were compared after a single topical application in a randomised, double-blind, cross-over trial. Ibuleve gel (Dermal Laboratories, UK) contained only ibuprofen whilst Deep Relief gel (Mentholatum, UK) also contained 3% menthol. In contrast to results obtained when these products were compared under in vitro conditions, there was no statistically significant difference in vivo between delivery of ibuprofen. Estimated relative bioavailability fraction (Deep Relief gel/Ibuleve gel) from log-transformed AUC((0-24h)) was 0.99 (95% CI: 0.94-1.04), estimated C(max )ratio was 0.96 (95% CI: 0.91-1.00) and estimated t(max) ratio was 1.01 (95% CI: 0.81-1.20). Menthol produces local vasodilation, which reduces skin barrier function, and these data demonstrate that it is inappropriate to extrapolate from in vitro data where formulation components produce biologically-mediated enhancement of permeation which cannot be modelled ex vivo. In clinical use, these products deliver comparable amounts of ibuprofen, but only Deep Reliefgel provides the secondary immediate benefit of the direct analgesic action of menthol.

Percutaneous penetration of diethanolamine through human skin in vitro: application from cosmetic vehicles.

Concern has been raised over the safety of diethanolamine (DEA) which may be present as a minor component of alkanolamide ingredients of cosmetic formulations. Skin penetration data were therefore generated for a range of typical formulations under in-use conditions. Seven rinse-off formulations (A-E, G and H), a leave-on emulsion (F), representing prototype cosmetic formulations and containing representative levels of DEA were prepared. Target levels of DEA were attained by inclusion of DEA as either (14)C-DEA or a combination of (14)C-DEA and unlabeled DEA. Skin permeation and distribution were evaluated using human skin in vitro, static diffusion cells and phosphate buffered saline (pH 7.4) as the receptor phase. At least 12 replicate epidermal membranes were prepared from a minimum of four donors for each test group. Receptor phase samples were taken at appropriate time intervals. At the end of the test period, radioactivity remaining on the skin surface and on the diffusion cell donor cap was determined before the skin samples were tape-stripped. The remaining tissue was solubilized and radioactivity determined. Permeation was very low from all vehicles applied under in-use conditions (range 1-48 ng/cm(2) over 24 h). Comparison was also made between permeation and distribution of DEA from an infinite dose of a simple aqueous solution and the leave-on formulation (F) through paired samples of fresh and frozen full thickness skin from the same donors. When applied as an infinite dose in aqueous solution DEA permeation at 24 h was greater through frozen than through fresh skin. From the leave-on formulation, permeation was similar and very low for both fresh and frozen skin. Recovery of DEA after application of the aqueous solution to fresh human skin and subsequent aqueous and organic extraction of the epidermal and dermal tissue indicated that the majority (>98%) of DEA was in the aqueous extract, suggesting that DEA was in the free state and not associated with the lipid fraction. These data provide a basis for the estimation of the potential systemic exposure and safety margins for DEA in representative cosmetic formulations.

Dispersal, habitat differences, and comparative phylogeography of Southeast Asian seahorses (Syngnathidae: Hippocampus).

Four distinct phylogeographical patterns across Southeast Asia were observed for four species of seahorse (genus Hippocampus) with differing ecologies. For all species, genetic differentiation (based on cytochrome b sequence comparisons) was significantly associated with sample site (Phi(ST) = 0.190-0.810, P < 0.0001) and with geographical distance (Mantel's r = 0.37-0.59, P < 0.019). Geographic locations of genetic breaks were inconsistent across species in 7/10 comparisons, although some similarities across species were also observed. The two shallow-water species (Hippocampus barbouri and Hippocampus kuda) have colonized the Sunda Shelf to a lesser degree than the two deeper-water species (Hippocampus spinosissimus and Hippocampus trimaculatus). In all species the presence of geographically restricted haplotypes in the Philippines could indicate past population fragmentation and/or long-distance colonization. A nested clade analysis (NCA) revealed that long-distance colonization and/or fragmentation were likely the dominant forces that structure populations of the two shallow-water species, whereas range expansion and restricted dispersal with isolation by distance were proportionally more important in the history of the two deeper-water species. H. trimaculatus has the most widespread haplotypes [average clade distance (D(c)) of nonsingleton haplotypes = 1169 km], indicating potentially high dispersal capabilities, whereas H. barbouri has the least widespread haplotypes (average D(c) = 67 km) indicating potentially lower dispersal capabilities. Pleistocene separation of marine basins and postglacial flooding of the Sunda Shelf are extrinsic factors likely to have contributed to the phylogeographical structure observed, whereas differences among the species appear to reflect their individual ecologies.