Overexposure to ultraviolet radiation (UVR) emitted by the sun can damage and kill living cells in animals, plants, and microorganisms. In aquatic environments, UVR can penetrate nearly 47 m into the water column, severely impacting many marine organisms. Jellyfish are often considered resilient to environmental stressors, potentially explaining their success in environmentally disturbed areas, but the extent of their resilience to UVR is not well known. Here, we tested resiliency to UVR by exposing benthic polyps of the moon jellyfish,
Ecologists and evolutionary biologists have been looking for the key(s) to the success of scyphomedusae through their long evolutionary history in multiple habitats. Their ability to generate young medusae (ephyrae) via two distinct reproductive strategies, strobilation or direct development from planula into ephyra without a polyp stage, has been a potential explanation. In addition to these reproductive modes, here we provide evidence of a third ephyral production which has been rarely observed and often confused with direct development from planula into ephyra. Planulae of
- NSF-PAR ID:
- 10306167
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Claudia Pogoreutz (Ed.)more » « less
Aurelia sp., to UVA and UVB—the two types of UVR that reach Earth’s surface—both separately and in combination. We quantified asexual reproduction rates and polyp attachment to hard substrate, in addition to qualitative observations of polyp health. There were no differences in asexual reproduction rates between polyps exposed to isolated UVA and polyps that received no UVR. Polyps reproduced when exposed to short term (∼7–9 days) isolated UVB, but long-term exposure limited reproduction and polyp attachment to the substrate. When exposed to both UVA and UVB, polyps were unable to feed and unable to remain attached to the substrate, did not reproduce, and ultimately, experienced 100% mortality within 20 days. Although many studies only examine the effects of UVB, the combination of UVA and UVB here resulted in greater negative impacts than either form of UVR in isolation. Therefore, studies that only examine effects of UVB potentially underestimate environmentally relevant effects of UVR. These results suggest that polyps are unsuccessful under UVR stress, so the planula larval stage must settle in low-UVR environments to establish the success of the polyp stage. -
more » « less
Abstract Evolutionary and behavioural ecologists have long been interested in factors shaping the variation in mating behaviour observed in nature. Although much of the research on this topic has focused on the consequences of mate choice and mate change on annual reproductive success, studies of a potential positive link between mate fidelity and adult demographic rates have been comparatively rare. This is particularly true for long‐lived birds with multi‐year, socially monogamous pair bonds.
We used a 26‐year capture–mark–recapture dataset of 3,330 black brent
Branta bernicla nigricans to test whether breeding with a familiar mate improved future breeding propensity and survival. We predicted that experienced breeders nesting with a new partner would have rates of survival similar to familiar pairs because long‐lived species avoid jeopardizing survival since their lifetime fitness is sensitive to this vital rate. In contrast, we expected that any costs of breeding with a new partner would be paid through skipping the subsequent breeding attempt.We found that unfamiliar pairs had lower subsequent breeding propensity than faithful partners. However, contrary to our expectations, individuals breeding with a new mate also suffered reduced survival.
These results add to a small number of studies indicating that a positive relationship between mate retention and adult demographic rates may exist in a diverse array of avian species. Given these results, researchers should consider costs of mate change that extend beyond within‐season reproductive success to fully understand the potential adaptive basis for perennial social monogamy. We caution that if mate retention enhances survival prospects, improvements in annual reproductive success with pair‐bond length could be a secondary factor favouring perennial social monogamy, particularly in species with slower life‐history strategies. Furthermore, some cases where annual reproductive success does not improve with pair‐bond duration, yet multi‐year pair bonds are common, could be explained by benefits afforded by mate fidelity to adult vital rates.
-
more » « less
Abstract Many tropical species show declining populations. The pantropical order Trogoniformes has 76% of its species ranked as declining, reflecting a worldwide problem. Here, we report on the reproductive ecology and life history traits of the declining and near‐threatened old world Whitehead's Trogon (
Harpactes whiteheadi ), the declining new world Collared Trogon (Trogon collaris ), and the stable Masked Trogon (T. personatus ). We also reviewed the literature on reproductive ecology and life history traits of trogons to assess possible commonalities that might help explain population declines. We found that the declining Whitehead's and Collared Trogons had reasonable nest success (32% and 25%, respectively), while the stable Masked Trogon had poor reproductive success (9%), all contrary to population trends. However, the limited literature data suggested that poor reproductive success may be common among trogons, which may contribute to population declines. Parents fed young at a low rate and had long on‐bouts for incubation and nestling warming that reduced activity at the nest, as favored by high nest predation risk over evolutionary time. We found that young fledged from the nest with poorly developed wings, as also favored by high nest predation risk. Evolved nestling periods among trogon species suggests that poor wing development is likely common. Wing development has been shown to affect juvenile survival after leaving the nest. The poor wing development may be an important contributor to population declines that deserves more attention. Evolved life history traits are important to recognize as creating population vulnerabilities in a changing world. -
more » « less
Abstract We used fluorescently labeled phalloidin to examine the subumbrellar musculature of the scyphozoan jellyfish
Aurelia aurita in a developmental series from ephyra to adult medusa. In the ephyra, the swim musculature includes a disc‐like sheet of circular muscle, in addition to two radial bands of muscle in each of the eight ephyral arms. The radial muscle bands join with the circular muscle, and both circular and radial muscle act together during each swim contraction. As the ephyra grows into a juvenile medusa, arms tissue is resorbed as the bell tissue grows outward, so eventually, the ephyral arms disappear. During this process, the circular muscle disc also grows outward and the radial muscle bands of the arms also disappear. At this time, a marginal gap appears at the bell margin, which is devoid of circular muscle cells, but has a loose arrangement of radial muscle fibers. This marginal gap is preserved as the medusa grows, and contributes to the floppy nature of the bell margin. Radial distortions in the circular muscle layer involve muscle fibers that run in random directions, with a primarily radial orientation. These are believed to be remnants of the radial muscle of the ephyral arms, and the distortions decrease in number and extent as the medusa grows. Since the mechanics of swimming changes from drag‐based paddling in the ephyra to marginal rowing in the adult medusa, the development of the marginal gap and the presence of radial distortions should be considered in terms of this mechanical transition. -
more » « less
Abstract Cnidarians display a wide diversity of life cycles. Among the main cnidarian clades, only Medusozoa possesses a swimming life cycle stage called the medusa, alternating with a benthic polyp stage. The medusa stage was repeatedly lost during medusozoan evolution, notably in the most diverse medusozoan class, Hydrozoa. Here, we show that the presence of the homeobox gene
Tlx in Cnidaria is correlated with the presence of the medusa stage, the gene having been lost in clades that ancestrally lack a medusa (anthozoans, endocnidozoans) and in medusozoans that secondarily lost the medusa stage. Our characterization ofTlx expression indicate an upregulation ofTlx during medusa development in three distantly related medusozoans, and spatially restricted expression patterns in developing medusae in two distantly related species, the hydrozoanPodocoryna carnea and the scyphozoanPelagia noctiluca . These results suggest thatTlx plays a key role in medusa development and that the loss of this gene is likely linked to the repeated loss of the medusa life cycle stage in the evolution of Hydrozoa.
