Thermal tolerance of larvae of Pollicipes elegans, a marine species with an antitropical distribution

For the antitropical gooseneck barnacle Pollicipes elegans, population-specific physiological temperature tolerance of larvae may serve as a barrier to larval dispersal across the warmest regions of the tropical Pacific Ocean. Thermal tolerance ranges of larvae of three different populations of P. elegans sampled in 2011 and 2012 (Mexico [MX], El Salvador [ES], and Peru [PE]) were investigated by measuring three indicators of physiological performance: swimming activity, oxygen consumption, and lethality or LT₅₀. The thermal tolerance profiles, which include measurable optimum (maximum aerobic performance), pejus (“getting worse”) and pessimum (worst aerobic performance) ranges, of larvae from the three populations were consistent with their characteristic environmental temperatures. In MX, larvae live close to the upper border of their optimum during warm months and so have a limited capacity to tolerate higher-than-normal temperatures. Larvae from the ES population likewise appear to live within their optimum temperature range, but these larvae lack a detectable pessimum range, suggesting they would be unable to cope with temperatures above their pejus range. Larvae from PE have a broad optimum but no pejus range. Different thermal tolerance ranges provide strong evidence for population-dependent physiological adaptations in P. elegans. For the southern (PE) and northern (MX) P. elegans populations, high tropical temperatures are likely to be a strong direct physiological barrier to larval survival and dispersal, which is in contrast to the more thermally tolerant ES population.     

Epilithic Lichen—Atmospheric Deposition Monitors of Trace Elements and Organohalogens?

ABSTRACT

Epilithic lichen (Xanthoria elegans in Canada, Lecanora muralis in Germany) were gathered from 17 locations in Ontario, Canada (from Lake Ontario to James Bay) and 43 locations in Germany (from the Alps to the North Sea and from the Baltic Sea to the Erzgebirge). Sample aliquots were digested in nitric acid and trace elements were analyzed by inductively coupled plasma-mass spectrom-etry techniques. The organohalogens were determined as absorbable organic halogens (AOXs) by coulometry. Concentration ranges from Germany for trace element samples and AOXs were determined. The lichen showed high spatial resolution in their element enrichment patterns. This allowed for differentiation between natural and anthropogenic dominance in ambient air concentrations. This biomonitoring method has proven to be very sensitive, fast, and reliable. No clear relationship could be found between trace element and AOX concentrations. The AOX values may reflect individual metabolic rates of the fungal partner in lichen symbionts.     

来自印度Adayar河的重金属:渗透进入相邻的地下水含水层

引言 Adayar河是一条很短的河流(40km长),向西南方向流去,流经Chennai(北纬13°05',东经80°15'),从这里蜿蜒曲折大约13km后汇入孟加拉湾(图1).在河口地带它变得很宽,河口宽达2km.汇水面积约有800km2,其中大多数地方地势平坦,有岩层的露头.     

Protective skin structures in shell-less marine gastropods

Skin and stomach epithelia of the four suborders of nudibranch gastropods (Mollusca, Opisthobranchia) are characterized by large intracellular ovoid disks, here called spindles. These spindles are an evolutionary novelty in the nudibranchs; in shell-less sacoglossan species they are missing. We here examined whether the distribution and occurrence of the spindles is consistent with the assumption of a protective role against discharging nematocysts of co-habiting and prey Cnidaria. Spindles were abundant in epidermal cells of regions exposed to nematocysts, such as the cerata, the lips, the edges of lamellate rhinophores, the surfaces of non-retractile gill-like organs, as well as in the stomach epithelium of eolid and dendronotacean species which feed on Cnidaria. While cells packed with spindles almost exclusively formed the epidermis of eolid and arminacean species, they were less numerous in the skin of dendronotacean and dorid species, where glandular cells predominated. The preponderance of either glandular or spindle cells suggests a dual complementary defense strategy, on the one side the production of mucus coats and aversive glandular secretions, on the other structural defensive devices that are cushion-like entities filled with inert grains.