Characterization of three pro-inflammatory cytokines,TNFα1, TNFα2 and IL-1β, in cage-reared Atlantic bluefin tuna Thunnus thynnus

Atlantic bluefin tuna (BFT) (Thunnus thynnus) is of great economic significance for world aquaculture and therefore it is necessary to ensure optimal and sustainable conditions for the farming of this species. Intensive culture of fish may be limited by infectious diseases that can impact on growth performance and cause heavy losses. However, to date there are no reports of cloning and expression analysis of any major immune genes of Atlantic BFT although some immune genes are known in other BFT species. Therefore the aim of this study was to characterize the first cytokine molecules in Atlantic BFT, through: 1) Isolation of full-length cDNA and gene sequences of TNFα1, TNFα2 and IL-1β, 2) comparison of these molecules to known sequences in other vertebrates, especially teleost fish, by multiple sequence alignment, phylogenetic tree analysis and homology modeling; 3) Quantification of in vivo expression of these cytokines in selected tissues in reared BFT over the duration of the farming process. The results indicated that these three cytokines could have value for monitoring Atlantic BFT health status. Curiously, the liver seemed to be an important site of cytokine production during poor health conditions in this species, perhaps reflecting its role as an important organ involved in fish defenses.     

Do eosinophils have a role in the killing of helminth parasites?

Eosinophils have been shown to be potent effector cells for the killing of helminth parasites in in vitro cultures. However, an in vivo role for eosinophils has been more difficult to establish. Early data showed close associations between eosinophils and damaged or dead parasites in histological sections, and significant correlations between resistance to parasites and the capacity to induce eosinophilia after infection. However, more recent studies, using mice that have reduced or increased eosinophil levels through targeting of the eosinophil-specific cytokine interleukin 5, have not unanimously supported an in vivo role for eosinophils in resistance to parasites. Here, Els Meeusen and Adam Balic review these studies and suggest a major role for the innate immune response in unnatural mouse-parasite models to explain some of the findings. They conclude that the data so far are consistent with a role for eosinophils in the killing of infective larval stages, but not adults, of most helminth parasites.     

Do ovarian steroid hormones control the resumption of embryonic growth following the period of diapause in roe deer (Capreolus capreolus)?

Embryonic diapause in the European roe deer includes a period of five months from August to December in which embryonic development is extremely decelerated. Following exit from diapause, the embryo rapidly elongates and subsequently implants. In diapausing carnivores and marsupials, resumption of embryonic growth is regulated by ovarian steroid hormones. In the roe deer, the role of steroid hormones is not known to date. In the present study, progesterone (P4), estradiol-17β (E2) and total estrogens (E_tot) were determined in blood plasma and endometrium of roe deer shot in the course of regular huntings between September and December. Steroid hormone concentrations were correlated to the corresponding size of the embryo derived from ex vivo uterine flushing and to the date of sampling. The mean plasma concentrations of P4 (5.4 ± 0.2 ng/ml, mean ± SE, N = 87), E2 (24.3 ± 2.6 pg/ml, N = 86) and E_tot (21.7 ± 2.6 pg/ml, N = 78) remained constant over the sampling period and were not correlated to embryonic size. Likewise, endometrial concentrations of P4 (66.1 ± 6.5 ng/ml), E2 (284.0 ± 24.43 pg/ml) and, E_tot (440.9 ± 24.43 pg/ml) showed no changes over time. Therefore, it was concluded that ovarian steroid hormones do not play a determining role in resumption of embryonic growth following the period of diapause in the roe deer.     

Delayed Phenotypic Expression of Growth Hormone Transgenesis during Early Ontogeny in Atlantic Salmon (Salmo salar)?

Should growth hormone (GH) transgenic Atlantic salmon escape, there may be the potential for ecological and genetic impacts on wild populations. This study compared the developmental rate and respiratory metabolism of GH transgenic and non-transgenic full sibling Atlantic salmon during early ontogeny; a life history period of intense selection that may provide critical insight into the fitness consequences of escaped transgenics. Transgenesis did not affect the routine oxygen consumption of eyed embryos, newly hatched larvae or first-feeding juveniles. Moreover, the timing of early life history events was similar, with transgenic fish hatching less than one day earlier, on average, than their non-transgenic siblings. As the start of exogenous feeding neared, however, transgenic fish were somewhat developmentally behind, having more unused yolk and being slightly smaller than their non-transgenic siblings. Although such differences were found between transgenic and non-transgenic siblings, family differences were more important in explaining phenotypic variation. These findings suggest that biologically significant differences in fitness-related traits between GH transgenic and non-transgenic Atlantic salmon were less than family differences during the earliest life stages. The implications of these results are discussed in light of the ecological risk assessment of genetically modified animals.     

Do root hydraulic properties change during the early vegetative stage of plant development in barley (Hordeum vulgare)?

Background and Aims

As annual crops develop, transpirational water loss increases substantially. This increase has to be matched by an increase in water uptake through the root system. The aim of this study was to assess the contributions of changes in intrinsic root hydraulic conductivity (Lp, water uptake per unit root surface area, driving force and time), driving force and root surface area to developmental increases in root water uptake.

Methods

Hydroponically grown barley plants were analysed during four windows of their vegetative stage of development, when they were 9–13, 14–18, 19–23 and 24–28 d old. Hydraulic conductivity was determined for individual roots (Lp) and for entire root systems (Lp_r). Osmotic Lp of individual seminal and adventitious roots and osmotic Lp_r of the root system were determined in exudation experiments. Hydrostatic Lp of individual roots was determined by root pressure probe analyses, and hydrostatic Lp_r of the root system was derived from analyses of transpiring plants.

Key Results

Although osmotic and hydrostatic Lp and Lp_r values increased initially during development and were correlated positively with plant transpiration rate, their overall developmental increases (about 2-fold) were small compared with increases in transpirational water loss and root surface area (about 10- to 40-fold). The water potential gradient driving water uptake in transpiring plants more than doubled during development, and potentially contributed to the increases in plant water flow. Osmotic Lp_r of entire root systems and hydrostatic Lp_r of transpiring plants were similar, suggesting that the main radial transport path in roots was the cell-to-cell path at all developmental stages.

Conclusions

Increase in the surface area of root system, and not changes in intrinsic root hydraulic properties, is the main means through which barley plants grown hydroponically sustain an increase in transpirational water loss during their vegetative development.     

Do propagation methods affect the fine root architecture of African plum (Dacryodes edulis)?

Belowground tree growth attributes determine whether associations will be complementary or competitive in an agroforestry context. A study on fine root (d?≤?2?mm) distribution patterns of Dacryodes edulis based on root density (RD), root length density (RLD) and root weight density (RWD) was conducted to evaluate the effect of propagation methods on rooting distribution. Results showed that D. edulis trees of seed origin had greater RD (P?≤?0.001) than trees of vegetative origin (cuttings and marcots) in the upper soil stratum (0–30?cm). Similarly, in the uppermost soil stratum (0–10?cm), RLD and RWDs varied significantly (P?<?0.01). Trees of seed origin had an exponential distribution pattern for fine RD, RLD and RWD with depth to 80?cm. In contrast, the distribution pattern of fine roots of trees of vegetative origin (cuttings and marcots) were quadratic for the same variables which increased in the 20–30?cm soil depth stratum before declining steadily to a depth of 80?cm. The findings of this study suggest that D. edulis trees of vegetative origin (cuttings and marots) are likely to be less competitive than trees of seed origin when intercropped with shallow-rooted annual plants in an agroforestry system for belowground resources.     

What Role Do Mothers Play in the Gestural Acquisition of Bonobos (Pan paniscus) and Chimpanzees (Pan troglodytes)?

Contemporary research hypothesizes that biological inheritance and ontogenetic factors shape the development of gestural communication in nonhuman great apes. However, little is known about the specific role that mothers play in the acquisition of their infants’ gestures. We observed 6 bonobo (Pan paniscus) and 4 chimpanzee (Pan troglodytes) mother–infant dyads and recorded their gesture types and frequency. We analyzed all behavioral contexts in which gestures occurred as well as the play context alone. Infants of both species were unlikely to share gestures with their mother or unrelated adult females. However, gestural sharing was prevalent within age groups. Within and across species, infant–infant and mother–mother groups were homogeneous regarding the types of gestures they shared, although there was individual variation in the frequency of gesture use. Our findings provide limited evidence that infants learned their gestures by imitating their mothers. Phylogenetic influences seem to be vital in gestural acquisition but, we suggest, repertoire development cannot be disentangled from individual social encounters during life.     

Do environmental differences between lakes in northwestern Argentinean Patagonia affect the infection of Philureter trigoniopsis (monogenea) in Galaxias maculatus (osmeriformes)?

Philureter trigoniopsis is the only parasite found in the ureters and urinary bladder of Galaxias maculatus in Patagonian Andean lakes. The dynamics of this endoparasitic monogenean were studied in Lake Gutiérrez, a body of water with scarce shoreline vegetation, where the host has an annual cycle of migration to the deep pelagic zone of the lake. To compare variations of the infection related to differences between lakes, G. maculatus specimens were sampled monthly with baited traps from September 1998 to November 1999 in Lake Moreno, which is an oligotrophic body of water with emergent shoreline vegetation and where the fish do not migrate to the deep pelagic areas of the lake. In addition, data for summer infections of P. trigoniopsis from 10 Andean Patagonian lakes that differ in aquatic vegetation, depth, and area were compared. In Lake Moreno prevalence of P. trigoniopsis showed a seasonal pattern, with 1-yr-old fish exhibiting the highest values of prevalence and mean intensity. Negative correlations between water temperature and prevalence and between age of fish and abundance were found. Our results suggest that age of fish may be the main factor structuring the distribution of P. trigoniosis in populations of G. maculatus. At the regional level the relationship between the infection and the characteristics of the lakes was also observed, with prevalence and mean intensity of P. trigoniopsis in G. maculatus higher in large deep lakes without macrophytes.     

Does zinc concentration in the substrate influence the onset of flowering in Arabidopsis arenosa (Brassicaceae)?

We investigated the impact of low zinc (Zn) concentrations in the substare on the onset of flowering in Arabidopsis arenosa (Brassicaceae). Experiments were carried out in controlled conditions using plants from four different populations. The research was aimed to verify experimentally the following hypotheses: (1) Zn content in the growth medium promote the onset of flowering in A. arenosa, (2) Changes in the onset of flowering induced by Zn depend on Zn concentration employed; (3) Zn-induced early onset of flowering is an universal plant response present within the species and is not an effect of stress or physiological adaptation to high Zn content in the environment. Investigated plants were subjected to four different Zn concentrations: 0.4 (control), 155, 775 and 1,550???M Zn²⁺. To asses stress level in investigated plants we calculated biomass accumulation and employed fluorometric methods. Zn content was estimated in shoots using atomic absorption spectroscopy. Differences in the onset of flowering were assessed using Kaplan?CMeier curves. Our results showed that Zn was transported form growth medium to roots and shoots of investigated plants and that the content of Zn increased with the increase of Zn concentration in the growth medium. We evidenced that apart from one (1,550???M Zn²⁺) applied Zn concentrations did not caused stress in investigated plants what was confirmed by two independent experimental approaches: measurement of biomass accumulation and chlorophyll a fluorescence. Flowering curves obtained on the basis of calculation of Kaplan?CMeier estimator showed that: (1) control plants originating from four different populations did not differ in terms of the onset of flowering, (2) plants from each population tested tends to enter flowering phase earlier in response to applied Zn concentrations than control plants, (3) plants treated with the lowest tested Zn concentration (155???M Zn²⁺) tend to flower earlier than plants treated with the higher concentration (775???M Zn²⁺), (4) the impact of Zn on the onset of flowering did not depend on the origin on the plant material used (Zn-rich or Zn-poor soils). Our results indicate that Zn ions present in the growth medium promote early flowering in A.arenosa and that this effect may depend on Zn concentration used. Zn-induced early flowering in A. arenosa seems to be an universal plant response present within the species and is not an effect of stress or physiological adaptation to high Zn content in the environment.     

Under how wide a set of conditions will nonrandom mating occur in Raphanus sativus (Brassicaceae)?

Studies of the weedy annual Raphanus sativus have demonstrated that nonrandom mating, a prerequisite for sexual selection, can occur in greenhouse plants. To determine whether this nonrandom mating pattern can occur under a wide range of conditions, including conditions that might occur in the field, we considered variation in both maternal condition and pollen load size. Maternal condition was varied by altering the watering regime. Pollen load size was varied from approximately 26 to 343 pollen grains per stigma. At the smallest pollen load size, patterns of seed paternity were altered in two of the three pollen donor pairs; seed paternity became more equal among donors. For one of three pollen donor pairs, seed paternity was more divergent among donors on stressed maternal plants. Finally, for one pollen donor pair, rank order of pollen donor performance changed from the medium to the small pollen loads on stressed vs. control maternal plants. Thus, some field conditions may alter patterns of nonrandom mating in wild radish.     

Does long-term storage of spermatozoa occur in the adder (Vipera berus)?

In the adder ( Vipera berus) multiple inseminations during the spring mating season have been demonstrated, with fertilization taking place several weeks after mating activities have ceased. Subsequent sperm competition in the female reproductive tract can result in within-season mixed paternity. Prolonged sperm storage between mating seasons has been suggested as another mechanism of sperm competition in the adder. Competition between new and old spermatozoa would obstruct efforts to reveal reproductive strategies that correlate observed behaviour to paternity in natural populations. In the present study, controlled breeding experiments with adders were performed and DNA fingerprinting was used to determine paternity among all offspring of a total of 15 litters. The offspring of 11 large females, that had most probably also mated in a previous season, were sired exclusively by enclosure males. This result and earlier empirical data support the hypothesis that long-term sperm storage, over one or several reproductive cycles, does not occur in the adder.     

Do abandoned nests of leaf‐cutting ants enhance plant recruitment in the Atlantic Forest?

The role played by abandoned nests of leaf‐cutting ants (Atta spp.) as a small‐scale disturbance regime that affects plant recruitment, species coexistence and forest regeneration remains poorly investigated. Here we examine whether abandoned nests of Atta cephalotes serve as regeneration niches and operate as particular plant recruitment habitats, favouring forest regeneration after ant activities cease and leading to the establishment of taxonomically/ecologically distinct plant assemblages. Soil properties, canopy openness, light availability and regenerating plant assemblages were evaluated across 18 nests and adjacent control plots in a large remnant of Atlantic Forest in north‐east Brazil from December 2004 to December 2005. Surprisingly, nests and control plots exhibited very similar light environments irrespective of nest age, but nest soils exhibited substantial reductions in carbon content (1.45 ± 0.24 vs. 1.79 ± 0.13%) and organic matter (2.50 ± 0.41 vs. 3.08 ± 0.23%), and proved to be much more resistant to penetration (30.57 ± 6.08 vs. 39.48 ± 7.53 mm). Functional signature of regenerating plant assemblages exhibited little variation across both habitat types, as they were dominated by pioneer, small‐seeded and vertebrate‐dispersed species. However, abandoned nests exhibited less dense, impoverished and more homogeneous regenerating plant assemblages at local and landscape scale; they clearly lacked nest‐dependent plant species and represented floristic subsets of the flora inhabiting the undisturbed forest. This recruitment bottleneck was transient in the long term because nest‐related effects ameliorated in older nests. Our results suggest that, unlike treefall gaps, abandoned nests represent temporary (relatively long‐lasting) islands of unsuitable substrate that reduce plant recruitment, retard forest regeneration, and fail in providing a special regeneration niche able to promote species coexistence and plant diversity.     

Do sterile females affect the sexual performance of sterile males of Anastrepha ludens (Diptera: Tephritidae)?

The release of sterile males to suppress the Mexican fruit fly Anastrepha ludens (Loew) population was simulated in field cages to compare the sexual performance of sterile males with wild females in the presence and absence of sterile females. Using different release ratios of sterile and wild individuals, this study showed that the presence of sterile females negatively affected the sexual performance of sterile males in mating with wild females. We found that the sterility induced was proportional to the magnitude of the sterile/fertile ratio. These results indicate that the release of sterile males without sterile females can significantly improve the efficiency of the sterile insect technique for the control of A. ludens.     

Do seasonal changes in light availability influence the inverse leafing phenology of the neotropical dry forest understory shrub Bonellia nervosa (Theophrastaceae)?

In tropical dry forests most plants are deciduous during the dry season and flush leaves with the onset of the rains. In Costa Rica, the only species displaying the opposite pattern is Bonellia nervosa. To determine if seasonal changes in light availability are associated with the leaf and reproductive phenology of this species, we monitored leaf production, survival, and life span, as well as flower and fruit production from April 2000 to October 2001 in Santa Rosa National Park. Leaf flushing and flower bud production took place shortly after the autumnal equinox when day length starts to decrease. Leaves began expansion at the end of the wet season, and plants reached 70 % of their maximum leaf area at the beginning of the dry season, maintaining their foliage throughout the entire dry period. Leaf shedding occurred gradually during the first three months of the wet season. Leaf flushing and shedding showed high synchrony, with leaf numbers being related to light availability. Maximum leaf production coincided with peaks in radiation during the middle of the dry season. Decreasing day length induces highly synchronous flower bud emergence in dry forest species, but this is the first study indicating induction of leaf flushing by declining day length.     

The occurrence of some metazoan parasites of Atlantic cod, Gadus morhua L., in relation to age and sex of the host in Balsfjord (70°N), North Norway

Age and sex differences in the occurrence of some metazoan parasites were investigated in 243 cod (Gadus morhua L.) from Balsfjord, a subarctic fjord in northern Norway. Thirteen species of parasite were studied, comprising seven nematodes, three parasitic copepods, one acanthocephalan, one cestode and one digenean. The nematode Anisakis simplex showed significant increases in both prevalence and mean abundance with host age, while the digenean Hemiurus levinseni showed a significant increase in mean abundance with age. The increases probably result from a long parasite life-span for A. simplex and changes in the feeding pattern of cod with age for H. levinseni. Prevalence of the nematode Contracaecum sp. and mean abundance of the acanthocephalan Echinorhynchus gadi were significantly higher in male than in female cod, whereas mean abundance of H. levinseni was significantly higher in female cod. These results suggest that there may be differences in feeding behaviour between male and female cod in Balsfjord. Accepted: 14 November 1999     

Ecological impacts of invading species: Do parasites of the cane toad imperil Australian frogs?

Parasite transfer to native fauna is a potentially catastrophic impact of invasive species. Introduced cane toads in Australia frequently host the nematode lungworm Rhabdias pseudosphaerocephala, which reduces viability of metamorph toads. If native frogs are vulnerable to this South American parasite, cane toad invasion may affect native species via this route; but if the native taxa are not vulnerable, we may be able to exploit the parasites for managing toads. Our laboratory experiments show that infective larvae can penetrate the body of all seven species of Australian frogs (five hylids: Cyclorana longipes, Litoria caerulea, Litoria dahlii, Litoria nasuta, Litoria rothii, one myobatrachid: Opisthodon ornatus, and one limnodynastid: Limnodynastes convexiusculus) we tested, but most did not host the adult worms at the end of the trials, and none showed major impairment of growth, survival or locomotor performance. One native tree‐frog (L. caerulea) retained high infection levels with few ill effects, suggesting that we might be able to use this taxon as a reservoir species to build up local parasite densities for toad management. However, the interspecific variation in lungworm retention suggests that generalizations about parasite effects on native frogs will be elusive.