Search results for "Single species"
showing 7 items of 27 documents
Macroalgal responses to ocean acidification depend on nutrient and light levels
2015
Ocean acidification may benefit algae that are able to capitalize on increased carbon availability for photosynthesis, but it is expected to have adverse effects on calcified algae through dissolution. Shifts in dominance between primary producers will have knock-on effects on marine ecosystems and will likely vary regionally, depending on factors such as irradiance (light vs. shade) and nutrient levels (oligotrophic vs. eutrophic). Thus experiments are needed to evaluate interactive effects of combined stressors in the field. In this study, we investigated the physiological responses of macroalgae near a CO2 seep in oligotrophic waters off Vulcano (Italy). The algae were incubated in situ …
Effects of ocean acidification on embryonic respiration and development of a temperate wrasse living along a natural CO2 gradient
2016
Volcanic CO2 seeps provide opportunities to investigate the effects of ocean acidification on organisms in the wild. To understand the influence of increasing CO2 concentrations on the metabolic rate (oxygen consumption) and the development of ocellated wrasse early life stages, we ran two field experiments, collecting embryos from nesting sites with different partial pressures of CO2 [pCO2; ambient (400 µatm) and high (800-1000 µatm)] and reciprocally transplanting embryos from ambient- to high-CO2 sites for 30 h. Ocellated wrasse offspring brooded in different CO2 conditions had similar responses, but after transplanting portions of nests to the high-CO2 site, embryos from parents that sp…
Cyanophyte calcification morphotypes and depositional environments (Alenquer oncolite, upper Kimmeridgian?, Portugal)
1985
Terrigenous red siliciclastics of Upper Kimmeridgian(?) to Portlandian age around Alenguer, Portugal, comprise a narrow level of oncoid-bearing limestones. Oncoid cortices are composed of cyanophytes which appear in different calcification morphotypes according to changing physico-chemical parameters. Recent examples reveal that in most cases each calcification morphotype is related to one single species or one defined association. Hence, the characteristic calcification patterns are mostly biologically rather than abiogenetically controlled. Oncoid shapes, sizes and arrangement, on the other hand, are mainly determined by the hydraulic parameter within the depositional environment.
Dynamics of a Single Species in a Fluctuating Environment under Periodic Yield Harvesting
2013
We discuss the effect of a periodic yield harvesting on a single species population whose dynamics in a fluctuating environment is described by the logistic differential equation with periodic coefficients. This problem was studied by Brauer and Sánchez (2003) who attempted the proof of the existence of two positive periodic solutions; the flaw in their argument is corrected. We obtain estimates for positive attracting and repelling periodic solutions and describe behavior of other solutions. Extinction and blow-up times are evaluated for solutions with small and large initial data; dependence of the number of periodic solutions on the parameterσassociated with the intensity of harvesting i…
<p><strong>Towards resolving a problem of the identity of the <em>Aethus</em> species (Hemiptera: Heteroptera: Cydnidae) occu…
2014
The genus Aethus in Cambodia is known only from a single species collected in the 1950s that was originally identified as A. indicus. However, what was regarded as A. indicus in the Oriental and Australian regions appeared to consist of three sibling species, recognizable only on the basis of male genital structures, i.e., A. philippinensis, A. pseudindicus, and true A. indicus. To date, the lack of males representing this genus from Cambodia made it impossible to verify which species actually occur in this country. The present study, based on eight males collected at the same locality in Cambodia where the specimens were originally identified as A. indicus more than 50 years ago (i.e., Sie…
The nasus gland: A new gland in soldiers of Angularitermes (Termitidae, Nasutitermitinae)
2015
Termites have developed many exocrine glands, generally dedicated to defence or communication. Although a few of these glands occur in all termite species, or represent synapomorphies of larger clades, others are morphological innovations of a single species, or a few related species. Here, we describe the nasus gland, a new gland occurring at the base of the nasus of Angularitermes soldiers. The nasus gland is composed of class 1, 2, and 3 secretory cells, a rare combination that is only shared by the sternal and tergal glands of some termites and cockroaches. The ultrastructural observations suggest that the secretion is produced by class 2 and 3 secretory cells, and released mostly by cl…
Helminth Infection of the Loggerhead Sea Turtle Caretta caretta along the Coasts of Sicily and the North West Adriatic Sea
2021
We provide new data on the presence of helminth parasites in 64 individual loggerhead sea turtles Caretta caretta stranded along the coasts of Sicily and the northwest Adriatic Sea between June 2014 and August 2016. The necropsy examination revealed 31 individuals (48.4%) positive for endoparasites, showing a greater prevalence of trematodes than nematodes. In particular, seven species and a single genus of Trematoda (Hapalotrema) and a single species and genus of Nematoda (Kathlania) were identified. Among the Digenea flukes the species with the highest prevalence of infection were Rhytidodes gelatinosus (34.6%) and Hapalotrema sp. (33.3%), while among the Nematoda they were Kathlania sp. …