Interactive effects of ocean acidification and temperature on two scleractinian corals from Moorea,French Polynesia

This study tested the hypothesis that the response of corals to temperature and pCO ₂ is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3 °C and 25.6 °C) and pCO ₂ (41.6 Pa and 81.5 Pa) at an irradiance of 599 μmol quanta m^?2 s^?1. Using microcosms and CO₂ gas mixing technology, treatments were created in a partly nested design (tanks) with two between‐plot factors (temperature and pCO ₂), and one within‐plot factor (taxon); calcification was used as a dependent variable. pCO ₂ and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3 °C compared with 25.6 °C, and 28% slower at 81.5 Pa vs. 41.6 Pa CO₂. A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO₃ ^?], and [CO₃ ^2?]. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO₃ cm^?2 h^?1. The compilation revealed a high degree of variation in calcification as a function of pH, [HCO₃ ^?], and [CO₃ ^2?], and supported three conclusions: (1) studies of the effects of ocean acidification on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO₃ ^?], and [CO₃ ^2?], and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO ₂, similar to that expected within 100 y.     

Semi-continuous culture and monitoring system for temperature-synchronized Euglena

A temperature-synchronized, semi-continuous culture and monitoring system is described, with results from use of the system for autotrophically growing Euglena. Outflow from the culture vessel consists of measured samples taken automatically at 2-hour intervals and fixed for later counting. Inflow is by siphon feed, which restores the culture level after each sampling. The interpretation of growth curves obtained from such cultures is discussed from the viewpoint, of division synchrony and cell cycle studies, and some general comparisons are made between batch and continuous cultures for such studies.     

Phasing effects of light on cell division in exponentially increasing cultures of Tetrahymena grown at low temperatures

Cultures of Tetrahymena pyriformis (W) grown at 10 ° ± 0.05 °C on proteose peptone-liver extract either in darkness or in relatively low light intensities exhibit marked differences in generation times during the exponential growth phase: about 20 h and 30 h, respectively. If a diurnal LD: 12, 12 or LD: 6, 18 light cycle was imposed on cultures that had been growing in the dark, cell division was phased so that the division bursts (each resulting in an approximate doubling of cell number) occurred once every 24 h and were confined primarily to the dark periods. Microscopic determination of the division index demonstrated that divisions virtually ceased during at least a portion of the light periods; indeed, a decrease in the index often anticipated the actual onset of light. Long trains of 24 h oscillations in apparent cell number could also be obtained in semicontinuous culture in LD: 6, 18. Furthermore, these entrained rhythmic division bursts persisted for at least 6 days with a circadian period if the culture was placed in constant darkness. These results are consistent with the hypothesis that an endogenous, self-sustaining circadian clock mechanism may underlie the observed persisting division rhythmicity as it does in many other microorganisms.     

Reversal of renovascular hypertension: role of the renal medulla

The fall in blood pressure, which occurs when renovascular hypertension is corrected surgically, offers a means of elucidating the factors responsible for blood pressure control. When Goldblatt two-kidney, one-clip hypertension in the rat is reversed by unclipping the renal artery, or by removal of the ischaemic kidney, restoration of normal blood pressure is due to a fall in peripheral resistance. This is associated with sodium retention and cannot be modified by inhibition of the renin-angiotensin system. The fall is, however, partially inhibited by chemical removal of the renal medulla by means of 2-bromo-ethylamine hydrobromide. When normal rats are chemically medullectomized, moderate hypertension is produced, which cannot be attributed to the renin-angiotensin system or sodium retention. It is concluded that a renomedullary vasodepressor system is ablated by chemical medullectomy: further, this system plays a role in the surgical correction of Goldblatt hypertension.