Innovative methods for analysis of reproduction may provide more information that can be used to conserve species of concern. We present data on oocyte development, batch size, and batch number of anadromous Alewives Alosa pseudoharengus in a lake-spawning population located in Connecticut. We sampled female Alewives as they arrived at the spawning habitat (uprunners) and females as they were leaving (downrunners). We estimated batch size by weighing all oocytes and performed image analysis on oocytes in subsamples of some ovaries, thereby estimating oocyte size-frequency distribution to define the number of batches. We performed both whole-mount and histological analysis on other ovaries to compare gravimetric and stereological estimates of batch size and to precisely characterize oocyte developmental stages. Uprunners had advanced oocytes at the ultimate stage of vitellogenesis and usually three additional less-developed batches. Postovulatory follicles and oocytes that were being resorbed were prevalent in downrunners but were absent in uprunners. Females spawned at least three batches in a season; however, downrunners had nearly as many batches as uprunners in their ovaries, indicating there was continuing recruitment and maturation of fresh batches. A numerical model of oocyte growth indicated that there is sufficient time for batches recruited at the beginning of the spawning season to develop and be spawned in the same season, indicating that fecundity is indeterminate. Accurate assessments of individual reproductive performance will require detailed consideration of within-season oocyte dynamics as opposed to relying on enumerating oocytes in prespawners.
Divino JN, Tonn WM. Effects of reproductive timing and hatch date on fathead minnow recruitment.Abstract -Timing of reproduction can be an important determinant of recruitment success for fish in strongly seasonal environments, both for individuals hatching at different times over extended spawning seasons and for entire cohorts, if the spawning period is accelerated or delayed among years. To examine potential demographic consequences of delayed spawning, we staggered dates that fathead minnow (Pimephales promelas) were introduced into experimental ponds in Alberta, Canada, by 3 weeks and compared growth and survival of offspring from early-and latestocked fish. By autumn, size and mass were consistently greater in earlyhatched minnows, regardless of cohort density. Size differences between treatments persisted through the second summer, which likely contributed to a higher proportion of early-hatched fish reaching sexual maturity as yearlings compared with late-hatched counterparts. Because late spawning can limit growth and subsequent maturation of progeny, temporal variability in reproductive timing should be considered when assessing recruitment potential of new year-classes.
Divino JN, Tonn WM. Effects of reproductive timing and hatch date on fathead minnow recruitment.Abstract -Timing of reproduction can be an important determinant of recruitment success for fish in strongly seasonal environments, both for individuals hatching at different times over extended spawning seasons and for entire cohorts, if the spawning period is accelerated or delayed among years. To examine potential demographic consequences of delayed spawning, we staggered dates that fathead minnow (Pimephales promelas) were introduced into experimental ponds in Alberta, Canada, by 3 weeks and compared growth and survival of offspring from early-and latestocked fish. By autumn, size and mass were consistently greater in earlyhatched minnows, regardless of cohort density. Size differences between treatments persisted through the second summer, which likely contributed to a higher proportion of early-hatched fish reaching sexual maturity as yearlings compared with late-hatched counterparts. Because late spawning can limit growth and subsequent maturation of progeny, temporal variability in reproductive timing should be considered when assessing recruitment potential of new year-classes.
Traumatic brain injury (TBI), caused by repeated concussive head trauma can induce chronic traumatic encephalopathy (CTE), a neurodegenerative disease featuring behavioral symptoms ranging from cognitive deficits to elevated aggression. In a Drosophila model, we used a high-impact trauma device (Katzenberger et al., 2013, 2015) to induce TBI-like symptoms and to study post-TBI behavioral outcomes. Following TBI, aggression in banged male flies was significantly elevated as compared with that in unbanged flies. These increases in aggressive behavior were not the result of basal motility changes, as measured by a negative geotaxis assay. In addition, the increase in post-TBI aggression appeared to be specific to concussive trauma: neither cold exposure nor electric shock—two alternate types of trauma—significantly elevated aggressive behavior in male-male pairs. Various forms of dietary therapy, especially the high-fat, low-carbohydrate ketogenic diet (KD), have recently been explored for a wide variety of neuropathies. We thus hypothesized that putatively neuroprotective dietary interventions might be able to suppress post-traumatic elevations in aggressive behavior in animals subjected to head-trauma-inducing strikes, or “bangs”. We supplemented a normal high-carbohydrate Drosophila diet with the KD metabolite beta-hydroxybutyrate (β-HB)—a ketone body (KB). Banged flies raised on a KB-supplemented diet exhibited a marked reduction in aggression, whereas aggression in unbanged flies was equivalent whether dieted with KB supplements or not. Pharmacological blockade of the ATP-sensitive potassium (KATP) channel abrogated KB effects reducing post-TBI aggression while pharmacological activation mimicked them, suggesting a mechanism by which KBs act in this model. KBs did not significantly extend lifespan in banged flies, but markedly extended lifespan in unbanged flies. We have thus developed a functional model for the study of post-TBI elevations of aggression. Further, we conclude that dietary interventions may be a fruitful avenue for further exploration of treatments for TBI- and CTE-related cognitive-behavioral symptoms.
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