Growth rates of dominant planktonic ciliates in two freshwater bodies of different trophic degree

The in situ growth rates of dominant ciliate species were studiedduring and shortly after phytoplankton peaks in two water bodies:the eutrophic Rímov Reservoir (South Bohemia, Czech Republic)and the oligo-mesotrophic Piburger See (Tyrol, Austria). Growthrate estimates based on changes in ciliate abundances in incubatedpre-screened samples (E_N) were compared with those derived fromthe ciliate cell volume and ambient temperatures (E_T). The valuesof E_N were always rather lower than those of E_T. During thestudies, the food supply limited the ciliate growth dependingon the ciliate feeding mode. An ecological grouping into filterfeeding versus raptorial feeding (‘hunting’) species,on the one hand, and attached/crawling (browsing) versus freeswimming species, on the other hand, clearly affected experimentalestimation. Both fine filter feeders (namely attached) and browsersexhibited a calculated E_N closer to the theoretical (maximum)E_T than did hunters and coarse filter feeders. It was apparent,for example, comparing E_N and E_T (day^–1) of the followingspecies: filter feeders Halteria grandinella (E_N = 0.42; E_T>1.4), Strobilidium hexakinetum (0.34;>1.9), Pelagohalteriaviridis (0.27;>0.9), Vorticella aquadulcis complex (0.75;>1.0);raptorial Balanion planctonicum (0.65;>1.5), Urotricha furcata(in Rímov Reservoir 0.65;>2.1; in Piburger See 0.20;>1.5),Rhabdoaskenasia minima (0.22;>1.0), Askenasia acrostomia(0.12;>0.6); opportunistic Cyrtolophosis mucicola (0.42;>1.6)and Cinetochilum margaritaceum (0.86;>1.4). Predation byrotifers apparently affected measurements in several samplescontaining {small tilde}400 rotifers l^–1 however, it seemedto be of little importance in the water column.     

Can freshwater planktonic ciliates survive on a diet of picoplankton?

Ciliate picoplanktivory was studied in two different freshwatersystems with abundant autotrophic picoplankton (APP): the eutrophic     

Relative Sensitivity of the Ocular Trigeminal, Nasal Trigeminal and Olfactory Systems to Airborne Chemicals

We measured thresholds for eye irritation and odor in homologousseries of alcohols (ethanol, 1-butanol, 1-hexanol and 1-octanol),ketones (2-propanone, 2-pentanone, 2-heptanone and 2-nonanone),and alkylbenzenes (toluene, ethyl benzene and propyl benzene).Eye irritation thresholds were well above odor thresholds forall series. Both sensory thresholds declined with carbon chainlength, a trend that has implicated lipophilicity in the potencyof these and related stimuli. Eye irritation thresholds wereremarkably close to nasal pungency thresholds obtained previouslyin persons lacking olfaction (i.e. anosmics). The agreementbetween the two thresholds implies that, despite differencesin the mucus layer at the two sites and in the epithelial tissueitself, there is remarkable similarity at the site of stimulation.As a practical matter, the eyes could serve as the sites toassess potency for induction of nasal pungency, an assessmentpreviously limited to testing anosmics. Presumably, for ourbrief stimulus presentations (1–3 s), the differencesbetween ocular and nasal mucosae have little relevance to chemicalsensitivity. Studies of the ability of homologous chemical seriesto evoke threshold eye irritation, nasal pungency and odor notonly have practical value, but also can help to define the physicochemicalproperties of the receptor and perireceptor biophases. ¹Present address: Department of Surgery (Otolaryngology), UCSDMedical Center, University of California, San Diego, USA     

Tit for Tat: sticklebacks (Gasterosteus aculeatus) 'trusting' a cooperating partner

Individual three-spined sticklebacks (Gasterosteus aculeatus)moved closer to a predatory trout when a ‘cooperator’stickleback, which the test fish could see through a one-waymirror, swam up to the predator than when a ‘defector’stickleback appeared to swim only half as close to the predator.After four training runs with both types of partners, the formercooperator also defected. The test fish continued to move closerto the predator in the presence of the former cooperator eventhough both the former cooperator and the defector now appearedto stop in their approach to the predator at the same distance.This shows that probable partners build up trust.     

Protein assay in reversed micelle solutions

Summary An adaptation of the Lowry (1951) method has been developed for quantifying proteins in organic reversed micellar solutions. Ethanol is added to improve the re-extraction of the proteins from the micelles and a centrifugation step is included to separate the organic phase.