Influence of ambient temperature on efficacy of signals produced by female Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae)
Melissa Campbell and J. Andrew Roberts. 2015. Journal of Arachnology 43(3):422-424. doi: http://dx.doi.org/10.1636/0161-8202-43.3.422
The ambient temperature of an environment has potential to influence many aspects of the behavior and physiology of small-bodied ectotherms, including brush-legged wolf spiders Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae). Temperature varies significantly, and often unpredictably, in their habitat throughout the spring breeding season, and is known to influence male Schizocosa courtship behavior. Currently unknown is what effect fluctuations in ambient temperature alone might have on critical, non-behavioral sexual signals such as female silk and chemical cues. We collected cues from mature, virgin females and subjected each sample to one of three thermal treatments (40°C, 20°C, or -12°C), at constant humidity. We presented treated female cues to mature males and recorded male response across treatment types as a behavioral indicator of signal degradation. There were no significant differences across treatments in the frequency or duration of male behaviors, including critical courtship and exploratory behaviors. Our results suggest that thermally induced degradation of female sexual signals is negligible for this species and likely has little or no influence on male behavior.
Anonymous nuclear markers data supporting species tree phylogeny and divergence time estimates in a cactus species complex in South America
Supportive data related to the article “Anonymous nuclear markers reveal taxonomic incongruence and long-term disjunction in a cactus species complex with continental-island distribution in South America” (Perez et al., 2016) . Here, we present pyrosequencing results, primer sequences, a cpDNA phylogeny, and a species tree phylogeny.
Organization of lipids in avian stratum corneum: Changes with temperature and hydration
Chemistry and Physics of Lipids 195:47–57. doi:10.1016/j.chemphyslip.2015.12.001, , ,
In response to increases in ambient temperature (Ta), many animals increase total evaporative water loss (TEWL) through their skin and respiratory passages to maintain a constant body temperature, a response that compromises water balance. In birds, cutaneous water loss (CWL) accounts for approximately 65% of TEWL at thermoneutral temperatures. Although the proportion of TEWL accounted for by CWL decreases to only 25% at high Ta, the magnitude of CWL still increases, suggesting changes in the barrier function of the skin. The stratum corneum (SC) is composed of flat, dead cells called corneocytes embedded in a matrix of lipids, many of which arrange in layers called lamellae. The classes of lipids that comprise these lamellae, and their attendant physical properties, determine the rate of CWL. We measured CWL at 25, 30, 35, and 40 °C in House Sparrows (Passer domesticus) caught in the winter and summer, and in sparrows acclimated to warm and cold lab environments. We then used Fourier transform infrared spectroscopy to measure lipid–lipid and lipid–water interactions in the SC under different conditions of temperature and hydration, and correlated these results with lipid classes in the SC. As CWL increased at higher temperatures, the amount of gauche defects in lipid alkyl chains increased, indicating that lipid disorder is partially responsible for higher CWL at high temperatures. However, variation in CWL between groups could not be explained by the amount of gauche defects, and this remaining variation may be attributed to greater amounts of cerebrosides in birds with low CWL, as the sugar moieties of cerebrosides lie outside lipid lamellae and form strong hydrogen bonds with water molecules.
Can heterotrophic uptake of dissolved organic carbon and zooplankton mitigate carbon budget deficits in annually bleached corals?
Annual coral bleaching events due to increasing sea surface temperatures are predicted to occur globally by the mid-century and as early as 2025 in the Caribbean, and severely impact coral reefs. We hypothesize that heterotrophic carbon (C) in the form of zooplankton and dissolved organic carbon (DOC) is a significant source of C to bleached corals. Thus, the ability to utilize multiple pools of fixed carbon and/or increase the amount of fixed carbon acquired from one or more pools of fixed carbon (defined here as heterotrophic plasticity) could underlie coral acclimatization and persistence under future ocean-warming scenarios. Here, three species of Caribbean coral—Porites divaricata, P. astreoides, and Orbicella faveolata—were experimentally bleached for 2.5 weeks in two successive years and allowed to recover in the field. Zooplankton feeding was assessed after single and repeat bleaching, while DOC fluxes and the contribution of DOC to the total C budget were determined after single bleaching, 11 months on the reef, and repeat bleaching. Zooplankton was a large C source for P. astreoides, but only following single bleaching. DOC was a source of C for single-bleached corals and accounted for 11–36 % of daily metabolic demand (CHARDOC), but represented a net loss of C in repeat-bleached corals. In repeat-bleached corals, DOC loss exacerbated the negative C budgets in all three species. Thus, the capacity for heterotrophic plasticity in corals is compromised under annual bleaching, and heterotrophic uptake of DOC and zooplankton does not mitigate C budget deficits in annually bleached corals. Overall, these findings suggest that some Caribbean corals may be more susceptible to repeat bleaching than to single bleaching due to a lack of heterotrophic plasticity, and coral persistence under increasing bleaching frequency may ultimately depend on other factors such as energy reserves and symbiont shuffling.
Portfolio theory as a management tool to guide conservation and restoration of multi-stock fish populations
Identification of the nutritional resources of larval sea lamprey in two Great Lakes tributaries using stable isotopes
The sea lamprey (Petromyzon marinus) is an important invasive parasitic species in the Laurentian Great Lakes, but the nutritional subsidies supporting the protracted filter feeding ammocoete stage are not well established. We used stable isotope ratios (δ13C and δ15N) to determine the major sources of autochthonous (aquatically produced) and allochthonous (terrestrially produced) organic matter (OM) to the nutrition of ammocoetes collected in 2010 from the Pigeon and Jordan Rivers in Michigan (USA). Ammocoete δ13C was positively correlated with animal length and C:N ratio, but δ15N was not correlated with either, suggesting that ammocoetes are primary consumers. We used a Bayesian model (MixSIR) to estimate the contributions of potential nutritional sources to ammocoetes. Estimates suggest that aquatic sediments were most important to ammocoete nutrition (median contributions ranged from 49–51%). Aquatic plants, including macrophytes and algae, were also important to ammocoete nutrition with a median contribution of 29%. Terrestrial plants were generally of lesser but still significant importance to ammocoetes, with a median contribution of 19–39%. Our findings generally agree with those of previous studies that have found that inputs of detrital and recently living OM from aquatic primary producers both provide an important source of nutrition for ammocoetes. The present study provides more quantitative estimates of the different forms of OM supporting ammocoete nutrition and biomass.
Using stable isotopes and C:N ratios to examine the life-history strategies and nutritional sources of larval lampreys.
Evans TM, Bauer JE. 2015. Journal of Fish Biology.
Natural abundance stable-isotope analysis (δ(13) C and δ(15) N) and C:N ratios were used to study the ammocoete phase of two common non-parasitic lamprey species (least brook lamprey Lampetra aepyptera and American brook lamprey Lethenteron appendix) in two tributaries of the Ohio River (U.S.A.). The C:N ratios suggest that each species employs different lipid accumulation strategies to support its metamorphosis and recruitment into an adult animal. Ammocoete δ(13) C values generally increased with increasing C:N values. In contrast to δ(13) C, ammocoete δ(15) N values were weakly related to the total length (LT ) in L. aepyptera, but positively correlated to both LT and C:N ratios in L. appendix. In L. appendix, C:N also correlated positively with LT , and presumably age. A Bayesian mixing model using δ(13) C and δ(15) N was used to estimate nutritional subsidies of different potential food resources to ammocoetes at each site. The models suggested that although nutritional subsidies to ammocoetes varied as a function of site, ammocoetes were generally reliant on large contributions (42-62% at three sites) from aquatic plants. Contributions from aquatic sediment organic matter were also important at all sites (32-63%) for ammocoetes, with terrestrially derived plant materials contributing smaller amounts (4-33%). These findings provide important insights into the feeding ecology and nutrition of two species of lampreys. They also suggest that similar and other quantitative approaches are required to (1) fully understand how the observed stable-isotopes ratios are established in ammocoetes and (2) better assess ammocoete nutritional subsidies in different natal streams.