Sex Differences in Spotted Hyenas.

The apparent virilization of the female spotted hyena raises questions about sex differences in behavior and morphology. We review these sex differences to find a mosaic of dimorphic traits, some of which conform to mammalian norms. These include space-use, dispersal behavior, sexual behavior, and parental behavior. By contrast, sex differences are reversed from mammalian norms in the hyena's aggressive behavior, social dominance, and territory defense. Androgen exposure early in development appears to enhance aggressiveness in female hyenas. Weapons, hunting behavior, and neonatal body mass do not differ between males and females, but females are slightly larger than males as adults. Sex differences in the hyena's nervous system are relatively subtle. Overall, it appears that the "masculinized" behavioral traits in female spotted hyenas are those, such as aggression, that are essential to ensuring consistent access to food; food critically limits female reproductive success in this species because female spotted hyenas have the highest energetic investment per litter of any mammalian carnivore. Evidently, natural selection has acted to modify traits related to food access, but has left intact those traits that are unrelated to acquiring food, such that they conform to patterns of sexual dimorphism in other mammals.

Tissue and salinity specific Na+/Cl- cotransporter (NCC) orthologues involved in the adaptive osmoregulation of sea lamprey (Petromyzon marinus).

Two orthologues of the gene encoding the Na+-Cl- cotransporter (NCC), termed ncca and nccb, were found in the sea lamprey genome. No gene encoding the Na+-K+-2Cl- cotransporter 2 (nkcc2) was identified. In a phylogenetic comparison among other vertebrate NCC and NKCC sequences, the sea lamprey NCCs occupied basal positions within the NCC clades. In freshwater, ncca mRNA was found only in the gill and nccb only in the intestine, whereas both were found in the kidney. Intestinal nccb mRNA levels increased during late metamorphosis coincident with salinity tolerance. Acclimation to seawater increased nccb mRNA levels in the intestine and kidney. Electrophysiological analysis of intestinal tissue ex vivo showed this tissue was anion absorptive. After seawater acclimation, the proximal intestine became less anion absorptive, whereas the distal intestine remained unchanged. Luminal application of indapamide (an NCC inhibitor) resulted in 73% and 30% inhibition of short-circuit current (Isc) in the proximal and distal intestine, respectively. Luminal application of bumetanide (an NKCC inhibitor) did not affect intestinal Isc. Indapamide also inhibited intestinal water absorption. Our results indicate that NCCb is likely the key ion cotransport protein for ion uptake by the lamprey intestine that facilitates water absorption in seawater. As such, the preparatory increases in intestinal nccb mRNA levels during metamorphosis of sea lamprey are likely critical to development of whole animal salinity tolerance.

Species diversity and mycotoxin production by members of the Fusarium tricinctum species complex associated with Fusarium head blight of wheat and barley in Italy.

Fusarium head blight (FHB) is a global cereal disease caused by a complex of Fusarium species. In Europe, the main species responsible for FHB are F. graminearum, F. culmorum and F. poae. However, members of the F. tricinctum species complex (FTSC) have become increasingly important. FTSC fusaria can synthesize mycotoxins such as moniliformin (MON), enniatins (ENNs) and several other biologically active secondary metabolites that could compromise food quality. In this study, FTSC isolates primarily from Italian durum wheat and barley, together with individual strains from four non-graminaceous hosts, were collected to assess their genetic diversity and determine their potential to produce mycotoxins in vitro on rice cultures. A multilocus DNA sequence dataset (TEF1, RPB1 and RPB2) was constructed for 117 isolates from Italy and 6 from Iran to evaluate FTSC species diversity and their evolutionary relationships. Phylogenetic analyses revealed wide genetic diversity among Italian FTSC isolates. Among previously described FTSC species, F. avenaceum (FTSC 4) was the most common species in Italy (56/117 = 47.9%) while F. tricinctum (FTSC 3), and F. acuminatum (FTSC 2) accounted for 11.1% (13/117) and the 8.5% (10/117), respectively. The second most detected species was a new and unnamed Fusarium sp. (FTSC 12; 32/117 = 19%) resolved as the sister group of F. tricinctum. Collectively, these four phylospecies accounted for 111/117 = 94.9% of the Italian FTSC collection. However, we identified five other FTSC species at low frequencies, including F. iranicum (FTSC 6) and three newly discovered species (Fusarium spp. FTSC 13, 14, 15). Of the 59 FTSC isolates tested for mycotoxin production on rice cultures, 54 and 55 strains, respectively, were able to produce detectable levels of ENNs and MON. In addition, we confirmed that the ability to produce bioactive secondary metabolites such as chlamydosporol, acuminatopyrone, longiborneol, fungerin and butanolide is widespread across the FTSC.

Effects of long-term cortisol treatment on growth and osmoregulation of Atlantic salmon and brook trout.

Cortisol is the final product of the hypothalamic-pituitary-interrenal (HPI) axis and acts as a gluco- and mineralo-corticoid in fish. Long-term elevations of cortisol have been linked to reduced growth in fishes, but the mechanism(s) and relative sensitivities of species are still unclear. We carried out experiments to examine the relative effects of cortisol on growth and gill NKA activity in two salmonids: Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis). Treatment with intraperitoneal cortisol implants for 30 days resulted in reduced growth in both species, but with greater sensitivity to cortisol in brook trout. Gill NKA activity was strongly upregulated by cortisol in Atlantic salmon, and weakly upregulated in brook trout but with no statistically significant effect. Cortisol treatment resulted in reduced plasma levels of insulin-like growth factor I and increased plasma growth hormone levels in Atlantic salmon. Our results demonstrate that there are species differences in the sensitivity of growth and osmoregulation to cortisol, even among species in the same family (Salmonidae).

Macrophage-derived Wnt signaling increases endothelial permeability during skeletal muscle injury.

OBJECTIVE: The inflammatory response and the presence of macrophages are reported to be necessary for proper muscle regeneration. However, our understanding of the molecular mechanisms governing how macrophages signal to promote muscle regeneration is incomplete. METHODS AND RESULTS: Here we conditionally deleted Wls, which is required for Wnt secretion, from macrophages and examined the impact on endothelial permeability following muscle injury. The expression of Wnt ligands and Wls was increased in the tibialis anterior (TA) of mice 2 days following BaCl2 injury. Loss of macrophage Wls inhibited the loss of endothelial barrier function, as measured by transendothelial resistance and Evans blue dye permeability assays. Interestingly, the blockade in endothelial permeability correlated with reduced VEGF levels and pretreatment of wild type endothelial cells with a VEGFR2 blocking antibody was sufficient to reduce endothelial permeability induced by stimulated macrophage supernatant. We also found that macrophage Wls-null TAs had myocytes with reduced cross-sectional area 7 day post-injury suggesting a delay in muscle regeneration. CONCLUSION: Our results indicate that macrophage-derived Wnt signaling increases endothelial permeability in a VEGF-dependent fashion following muscle injury. Our findings implicate macrophages as a primary source of Wnt ligands following muscle injury and highlight the Wnt pathway as a therapeutic target following injury.

Cortisol regulates insulin-like growth-factor binding protein (igfbp) gene expression in Atlantic salmon parr.

The growth hormone (Gh)/insulin-like growth-factor (Igf)/Igf binding protein (Igfbp) system regulates growth and osmoregulation in salmonid fishes, but how this system interacts with other endocrine systems is largely unknown. Given the well-documented consequences of mounting a glucocorticoid stress response on growth, we hypothesized that cortisol inhibits anabolic processes by modulating the expression of hepatic igfbp mRNAs. Atlantic salmon (Salmo salar) parr were implanted intraperitoneally with cortisol implants (0, 10, and 40 µg g-1 body weight) and sampled after 3 or 14 days. Cortisol elicited a dose-dependent reduction in specific growth rate (SGR) after 14 days. While plasma Gh and Igf1 levels were unchanged, hepatic igf1 mRNA was diminished and hepatic igfbp1b1 and -1b2 were stimulated by the high cortisol dose. Plasma Igf1 was positively correlated with SGR at 14 days. Hepatic gh receptor (ghr), igfbp1a, -2a, -2b1, and -2b2 levels were not impacted by cortisol. Muscle igf2, but not igf1 or ghr, levels were stimulated at 3 days by the high cortisol dose. As both cortisol and the Gh/Igf axis promote seawater (SW) tolerance, and particular igfbps respond to SW exposure, we also assessed whether cortisol coordinates the expression of branchial igfbps and genes associated with ion transport. Cortisol stimulated branchial igfbp5b2 levels in parallel with Na+/K+-ATPase (NKA) activity and nka-α1b, Na+/K+/2Cl--cotransporter 1 (nkcc1), and cystic fibrosis transmembrane regulator 1 (cftr1) mRNA levels. The collective results indicate that cortisol modulates the growth of juvenile salmon via the regulation of hepatic igfbp1s whereas no clear links between cortisol and branchial igfbps previously shown to be salinity-responsive could be established.

How repeatable is CTmax within individual brook trout over short- and long-time intervals?

As stream temperatures increase due to factors such as heated runoff from impervious surfaces, deforestation, and climate change, fish species adapted to cold water streams are forced to move to more suitable habitat, acclimate or adapt to increased thermal regimes, or die. To estimate the potential for adaptation, a (within individual) repeatable metric of thermal tolerance is imperative. Critical thermal maximum (CTmax) is a dynamic test that is widely used to measure thermal tolerance across many taxa and has been used in fishes for decades, but its repeatability in most species is unknown. CTmax tests increase water temperature steadily over time until loss of equilibrium (LOE) is achieved. To determine if CTmax is a consistent metric within individual fish, we measured CTmax on the same lab-held individually-marked adult brook trout Salvelinus fontinalis at three different times (August & September 2016, September 2017). We found that CTmax is a repeatable trait (Repeatability ±â€¯S.E.: 0.48 ±â€¯0.14). CTmax of individuals males was consistent over time, but the CTmax of females increased slightly over time. This result indicates that CTmax is a robust, repeatable estimate of thermal tolerance in a cold-water adapted fish.

Genetic bases for variation in structure and biological activity of trichothecene toxins produced by diverse fungi.

Trichothecenes are sesquiterpene toxins produced by diverse but relatively few fungal species in at least three classes of Ascomycetes: Dothideomycetes, Eurotiomycetes, and Sordariomycetes. Approximately 200 structurally distinct trichothecene analogs have been described, but a given fungal species typically produces only a small subset of analogs. All trichothecenes share a core structure consisting of a four-ring nucleus known as 12,13-epoxytrichothec-9-ene. This structure can be substituted at various positions with hydroxyl, acyl, or keto groups to give rise to the diversity of trichothecene structures that has been described. Over the last 30 years, the genetic and biochemical pathways required for trichothecene biosynthesis in several species of the fungi Fusarium and Trichoderma have been elucidated. In addition, phylogenetic and functional analyses of trichothecene biosynthetic (TRI) genes from fungi in multiple genera have provided insights into how acquisition, loss, and changes in functions of TRI genes have given rise to the diversity of trichothecene structures. These analyses also suggest both divergence and convergence of TRI gene function during the evolutionary history of trichothecene biosynthesis. What has driven trichothecene structural diversification remains an unanswered question. However, insight into the role of trichothecenes in plant pathogenesis of Fusarium species and into plant glucosyltransferases that detoxify the toxins by glycosylating them point to a possible driver. Because the glucosyltransferases can have substrate specificity, changes in trichothecene structures produced by a fungus could allow it to evade detoxification by the plant enzymes. Thus, it is possible that advantages conferred by evading detoxification have contributed to trichothecene structural diversification. KEY POINTS : • TRI genes have evolved by diverse processes: loss, acquisition and changes in function. • Some TRI genes have acquired the same function by convergent evolution. • Some other TRI genes have evolved divergently to have different functions. • Some TRI genes were acquired or resulted from diversification in function of other genes. • Substrate specificity of plant glucosyltransferases could drive trichothecene diversity.

Osmoregulatory role of the intestine in the sea lamprey (Petromyzon marinus).

Lampreys are the most basal vertebrates with an osmoregulatory strategy. Previous research has established that the salinity tolerance of sea lamprey increases dramatically during metamorphosis, but underlying changes in the gut have not been examined. In the present work, we examined changes in intestinal function during metamorphosis and seawater exposure of sea lamprey (Petromyzon marinus). Fully metamorphosed juvenile sea lamprey had 100% survival after direct exposure to 35 parts per thousand seawater (SW) and only slight elevations in plasma chloride (Cl-) levels. Drinking rates of sea lamprey juveniles in seawater were 26-fold higher than juveniles in freshwater (FW). Na+-K+-ATPase (NKA) activity in the anterior and posterior intestine increased 12- and 3-fold, respectively, during metamorphosis, whereas esophageal NKA activity was lower than in the intestine and did not change with development. Acclimation to SW significantly enhanced NKA activity in the posterior intestine but did not significantly change NKA activity in the anterior intestine, which remained higher than that in the posterior intestine. Intestinal Cl- and water uptake, which were observed in ex vivo preparations of anterior and posterior intestine under both symmetric and asymmetric conditions, were higher in juveniles than in larvae and were similar in magnitude of those of teleost fish. Inhibition of NKA by ouabain in ex vivo preparations inhibited intestinal water absorption by 64%. Our results indicate drinking and intestinal ion and water absorption are important to osmoregulation in SW and that preparatory increases in intestinal NKA activity are important to the development of salinity tolerance that occurs during sea lamprey metamorphosis.

[Reversible cerebral vasoconstriction syndrome associated with anastrozole: an unusual cause of high impact]. / Sindrome de vasoconstriccion cerebral reversible asociado a anastrozol: una causa inusual de alto impacto.

INTRODUCTION: Reversible cerebral vasoconstriction syndrome (RCVS) is a low incidence disability with a multifactorial etiology and a wide array of symptoms. The main symptom is a thunderclap headache, accompanied sometimes with various neurological deficits that can lead to death. RCVS is usually diagnosed through radiological imaging technology. The treatment includes adopting general measures of monitoring, symptomatic management, identifying the etiology and acting on it to avoid recurrence. CASE REPORT: A 71-year-old woman with a history of breast cancer originally treated with tamoxifen. Due to urticaria, the anastrozole management was staggered. She was admitted for aphasia, drowsiness and a thunderclap headache. The patient reported a similar event two weeks prior admission. In brain resonance, there was evidence of small sub-arachnoidal haemorrhage (SAH) of the left parietal temporal convexity and cerebral angiography. As well as documented vasospasm in the posterior parietal region confirming the diagnosis of RCVS plus SAH. During the stay, she presented three events with the same characteristics, requiring intensive monitoring and two therapeutic panangiographies with intra-arterial nimodipine with subsequent resolution of the vessel spasm. The patient remains asymptomatic six months later. CONCLUSION: RCVS is difficult to diagnose given its wide array of symptoms and multifactorial etiology. In this case, RCVS plus SAH is associated with the use of anastrozole. So far there are no reported cases of aromatase inhibitors associated with this pathology and should be reported in the literature for pharmacovigilance.

TITLE: Sindrome de vasoconstriccion cerebral reversible asociado a anastrozol: una causa inusual de alto impacto.Introduccion. El sindrome de vasoconstriccion cerebral reversible (SVCR) es una entidad de baja incidencia, de etiologia multifactorial y amplio espectro de presentacion. El principal sintoma es la cefalea de tipo trueno. Puede estar acompañado de focalizacion neurologica y cursar con desenlaces clinicos variable que incluso pueden llevar a la muerte. El diagnostico es clinico e imaginologico, y el tratamiento incluye adoptar medidas generales de monitorizacion, manejo sintomatico, identificar la etiologia y actuar sobre ella para evitar recurrencia. Caso clinico. Mujer de 71 años con antecedente de cancer de seno, tratada inicialmente con tamoxifeno; por presentar urticaria, se escalono tratamiento con anastrozol. Ingreso por cefalea de tipo trueno, afasia anterior y somnolencia. La paciente refirio un evento similar una semana antes del ingreso. En la resonancia magnetica cerebral evidencio una hemorragia subaracnoidea (HSA) pequeña de la convexidad temporoparietal izquierda, y la panangiografia documento vasoespasmo en la region parietal posterior, lo que confirmo el diagnostico de SVCR mas HSA. Durante el ingreso presento tres eventos de iguales caracteristicas, que requirieron monitorizacion intensiva y dos panangiografias terapeuticas con nimodipino intraarterial, con posterior resolucion del vasoespasmo. Permanece asintomatica seis meses despues. Conclusion. El SVCR constituye un reto diagnostico dada su presentacion variable y su etiologia multifactorial. En este caso, el SVCR mas HSA esta asociado al uso de anastrozol. Hasta el momento no hay casos descritos de inhibidores de la aromatasa asociados a esta patologia, que debe comunicarse para su farmacovigilancia.

Proximate composition, lipid utilization and validation of a non-lethal method to determine lipid content in migrating American shad Alosa sapidissima.

Lipid content forms the most important energy reserve in anadromous fish and can limit survival, migration and reproductive success. A fat meter was evaluated and compared with a traditional extractive method of measuring available lipid for migrating American shad Alosa sapidissima in the Connecticut River, U.S.A. The fat meter gives rapid (<10 s) and non-lethal lipid measurements, whereas traditional methods require lethal sampling that is both time consuming and expensive. The fat-meter readings had a strong relationship to traditional lipid extractions for 60 fish, 30 whole body (R2 = 0·72) and 30 fillet only (R2 = 0·81). Additional validation showed that fat-meter readings captured the gradual decrease of lipid in individual fish over time, were not affected by removal of gonads or scales and were stable for fish exposed to water or air for 24 h after death. These experiments indicate that the fat meter can be used as a reliable tool for future A. sapidissima energetic studies, allowing for larger sample sizes and non-lethal sampling.

A cytosolic carbonic anhydrase molecular switch occurs in the gills of metamorphic sea lamprey.

Carbonic anhydrase plays a key role in CO2 transport, acid-base and ion regulation and metabolic processes in vertebrates. While several carbonic anhydrase isoforms have been identified in numerous vertebrate species, basal lineages such as the cyclostomes have remained largely unexamined. Here we investigate the repertoire of cytoplasmic carbonic anhydrases in the sea lamprey (Petromyzon marinus), that has a complex life history marked by a dramatic metamorphosis from a benthic filter-feeding ammocoete larvae into a parasitic juvenile which migrates from freshwater to seawater. We have identified a novel carbonic anhydrase gene (ca19) beyond the single carbonic anhydrase gene (ca18) that was known previously. Phylogenetic analysis and synteny studies suggest that both carbonic anhydrase genes form one or two independent gene lineages and are most likely duplicates retained uniquely in cyclostomes. Quantitative PCR of ca19 and ca18 and protein expression in gill across metamorphosis show that the ca19 levels are highest in ammocoetes and decrease during metamorphosis while ca18 shows the opposite pattern with the highest levels in post-metamorphic juveniles. We propose that a unique molecular switch occurs during lamprey metamorphosis resulting in distinct gill carbonic anhydrases reflecting the contrasting life modes and habitats of these life-history stages.

Evidence for episodic acidification effects on migrating Atlantic salmon Salmo salar smolts.

Field studies were conducted to determine levels of gill aluminium as an index of acidification effects on migrating Atlantic salmon Salmo salar smolts in the north-eastern U.S.A. along mainstem river migration corridors in several major river basins. Smolts emigrating from the Connecticut River, where most (but not all) tributaries were well buffered, had low or undetectable levels of gill aluminium and high gill Na(+) /K(+) -ATPase (NKA) activity. In contrast, smolts emigrating from the upper Merrimack River basin where most tributaries are characterized by low pH and high inorganic aluminium had consistently elevated gill aluminium and lower gill NKA activity, which may explain the low adult return rates of S. salar stocked into the upper Merrimack catchment. In the Sheepscot, Narraguagus and Penobscot Rivers in Maine, river and year-specific effects on gill aluminium were detected that appeared to be driven by underlying geology and high spring discharge. The results indicate that episodic acidification is affecting S. salar smolts in poorly buffered streams in New England and may help explain variation in S. salar survival and abundance among rivers and among years, with implications for the conservation and recovery of S. salar in the north-eastern U.S.A. These results suggest that the physiological condition of outmigrating smolts may serve as a large-scale sentinel of landscape-level recovery of atmospheric pollution in this and other parts of the North Atlantic region.

Trichodiene Production in a Trichoderma harzianum erg1-Silenced Strain Provides Evidence of the Importance of the Sterol Biosynthetic Pathway in Inducing Plant Defense-Related Gene Expression.

Trichoderma species are often used as biocontrol agents against plant-pathogenic fungi. A complex molecular interaction occurs among the biocontrol agent, the antagonistic fungus, and the plant. Terpenes and sterols produced by the biocontrol fungus have been found to affect gene expression in both the antagonistic fungus and the plant. The terpene trichodiene (TD) elicits the expression of genes related to tomato defense and to Botrytis virulence. We show here that TD itself is able to induce the expression of Botrytis genes involved in the synthesis of botrydial (BOT) and also induces terpene gene expression in Trichoderma spp. The terpene ergosterol, in addition to its role as a structural component of the fungal cell membranes, acts as an elicitor of defense response in plants. In the present work, using a transformant of T. harzianum, which is silenced in the erg1 gene and accumulates high levels of squalene, we show that this ergosterol precursor also acts as an important elicitor molecule of tomato defense-related genes and induces Botrytis genes involved in BOT biosynthesis, in both cases, in a concentration-dependent manner. Our data emphasize the importance of a balance of squalene and ergosterol in fungal interactions as well as in the biocontrol activity of Trichoderma spp.

Effects of Trichothecene Production on the Plant Defense Response and Fungal Physiology: Overexpression of the Trichoderma arundinaceum tri4 Gene in T. harzianum.

Trichothecenes are fungal sesquiterpenoid compounds, the majority of which have phytotoxic activity. They contaminate food and feed stocks, resulting in potential harm to animals and human beings. Trichoderma brevicompactum and T. arundinaceum produce trichodermin and harzianum A (HA), respectively, two trichothecenes that show different bioactive properties. Both compounds have remarkable antibiotic and cytotoxic activities, but in addition, trichodermin is highly phytotoxic, while HA lacks this activity when analyzed in vivo. Analysis of Fusarium trichothecene intermediates led to the conclusion that most of them, with the exception of the hydrocarbon precursor trichodiene (TD), have a detectable phytotoxic activity which is not directly related to the structural complexity of the intermediate. In the present work, the HA intermediate 12,13-epoxytrichothec-9-ene (EPT) was produced by expression of the T. arundinaceum tri4 gene in a transgenic T. harzianum strain that already produces TD after transformation with the T. arundinaceum tri5 gene. Purified EPT did not show antifungal or phytotoxic activity, while purified HA showed both antifungal and phytotoxic activities. However, the use of the transgenic T. harzianum tri4 strain induced a downregulation of defense-related genes in tomato plants and also downregulated plant genes involved in fungal root colonization. The production of EPT by the transgenic tri4 strain raised levels of erg1 expression and reduced squalene accumulation while not affecting levels of ergosterol. Together, these results indicate the complex interactions among trichothecene intermediates, fungal antagonists, and host plants.

Temporal dynamics and population genetic structure of Fusarium graminearum in the upper Midwestern United States.

Fusarium graminearum sensu stricto causes Fusarium head blight (FHB) in wheat and barley, and contaminates grains with several trichothecene mycotoxins, causing destructive yield losses and economic impact in the United States. Recently, a F. graminearum strain collected from Minnesota (MN) was determined to produce a novel trichothecene toxin, called NX-2. In order to determine the spatial and temporal dynamics of NX-2 producing strains in MN, North Dakota (ND) and South Dakota (SD), a total of 463 F. graminearum strains were collected from three sampling periods, 1999-2000, 2006-2007 and 2011-2013. A PCR-RFLP based diagnostic test was developed and validated for NX-2 producing strains based on polymorphisms in the Tri1 gene. Trichothecene biosynthesis gene (Tri gene)-based polymerase chain reaction (PCR) assays and ten PCR-restriction fragment length polymorphism (RFLP) markers were used to genotype all strains. NX-2 strains were detected in each sampling period but with a very low overall frequency (2.8%) and were mainly collected near the borders of MN, ND and SD. Strains with the 3ADON chemotype were relatively infrequent in 1999-2000 (4.5%) but increased to 29.4% in 2006-2007 and 17.2% in 2011-2013. The distribution of 3ADON producing strains also expanded from a few border counties between ND and MN in 1999-2000, southward toward the border between SD and MN in 2006-2007 and westward in 2011-2013. Genetic differentiation between 2006-2007 and 2011-2013 populations (3%) was much lower than that between 1999-2000 and 2006-2007 (22%) or 1999-2000 and 2011-2013 (20%) suggesting that most change to population genetic structure of F. graminearum occurred between 1999-2000 and 2006-2007. This change was associated with the emergence of a new population consisting largely of individuals with a 3ADON chemotype. A Bayesian clustering analysis suggested that NX-2 chemotype strains are part of a previously described Upper Midwestern population. However, these analyses also suggest that the NX-2 isolates could represent a distinct population, but that interpretations of population assignment are influenced by the small number of NX-2 strains available for analysis.

Migratory patterns of hatchery and stream-reared Atlantic salmon Salmo salar smolts in the Connecticut River, U.S.A.

The timing of downstream migration and detection rates of hatchery-reared Atlantic salmon Salmo salar smolts and stream-reared smolts (stocked 2 years earlier as fry) were examined in the Connecticut River (U.S.A.) using passive integrated transponder (PIT) tags implanted into fish and then detected at a downstream fish bypass collection facility at Turners Falls, MA (river length 192 km). In two successive years, hatchery-reared smolts were released in mid-April and early May at two sites: the West River (river length 241 km) or the Passumpsic (river length 450 km). Hatchery-reared smolts released higher in the catchment arrived 7 to 14 days later and had significantly lower detection rates than smolts stocked lower in the catchment. Hatchery-reared smolts released 3 weeks apart at the same location were detected downstream at similar times, indicating that early-release smolts had a lower average speed after release and longer residence time. The size and gill Na(+) /K(+) -ATPase (NKA) activity of smolts at the time of release were significantly greater for detected fish (those that survived and migrated) than for those that were not detected. Stream-reared pre-smolts (>11·5 cm) from four tributaries (length 261-551 km) were tagged in autumn and detected during smolt migration the following spring. Stream-reared smolts higher in the catchment arrived later and had significantly lower detection rates. The results indicate that both hatchery and stream-reared smolts from the upper catchment will arrive at the mouth of the river later and experience higher overall mortality than fish from lower reaches, and that both size and gill NKA activity are related to survival during downstream migration.

Photoperiod control of downstream movements of Atlantic salmon Salmo salar smolts.

This study provides the first direct observations that photoperiod controls the initiation of downstream movement in Atlantic salmon Salmo salar smolts. Under simulated natural day length (LDN) conditions and seasonal increases in temperature, smolts increased their downstream movements five-fold for a period of 1 month in late spring. Under the same conditions, parr did not show changes in downstream movement behaviour. When given a shortened day length (10L:14D) beginning in late winter, smolts did not increase the number of downstream movements. An early increase in day length (16L:8D) in late winter resulted in earlier initiation and termination of downstream movements compared to the LDN group. Physiological status and behaviour were related but not completely coincident: gill Na(+) /K(+) -ATPase activity increased in all treatments and thyroid hormone was elevated prior to movement in 16L:8D treatment. The most parsimonious model describing downstream movement of smolts included synergistic effects of photoperiod treatment and temperature, indicating that peak movements occurred at colder temperatures in the 16L:8D treatment than in LDN, and temperature did not influence movement of smolts in the 10L:14D treatment. The complicated interactions of photoperiod and temperature are not surprising since many organisms have evolved to rely on correlations among environmental cues and windows of opportunity to time behaviours associated with life-history transitions. These complicated interactions, however, have serious implications for phenological adjustments and persistence of S. salar populations in response to climate change.