This study examines the barnacle symbionts on 168 blue crabs, Callinectes sapidus, taken from both shallow and deep estuarine environments in the area of Beaufort, North Carolina. The purpose of the study was to quantify the prevalence, intensity, abundance, and spatial distribution of the ectosymbiotic barnacle Chelonibia patula on blue crabs. The proportion of blue crabs fouled was 67%. There was no difference in the prevalence of barnacles on crabs from the shallow versus the deep environment. Results indicate female crabs were significantly more fouled than males. This suggests that the prevalence and intensity of barnacles are dominantly controlled by the migratory habits of the host, since female crabs spend more time in deeper waters of higher salinity, where they are more likely to be fouled by barnacle larvae. The spatial distribution of barnacles on the crab carapaces was controlled by the surface topography of the carapace with more barnacles on the lateral regions than medial. The orientation of the carinal to rostral axes of the barnacles on the carapaces of the host crabs was measured, but no preferred orientation was found. The costs and benefits of epibiosis are reviewed and the barnacle/blue crab relationship appears to be more beneficial to the barnacles than to the host blue crabs.

alpha 2-Adrenoceptors were first described pharmacologically ten years ago. Within three years their capacity to inhibit adenylate cyclase had been demonstrated in many tissues. They were demonstrated biochemically in the kidneys in 1981 even before any renal physiological effects of their activation were known. They predominate numerically over alpha 1-adrenoceptors in renal membranes and their density is increased in genetic forms of rat hypertension. alpha 1-Adrenoceptors normally mediate the vasoconstriction and sodium- and water-retaining effects of sympathetic neuronally released norepinephrine. Norepinephrine or epinephrine must be infused to activate alpha 2-adrenoceptors, suggesting that renal alpha 2-adrenoceptors are extrajunctional, whereas alpha 1-adrenoceptors are postjunctional. When alpha 1-adrenoceptors are chronically blocked, renal alpha 2-adrenoceptor density increases and they assume a location at postjunctional sites, the otherwise exclusive domain of alpha 1-adrenoceptors. Results from microdissection studies have established that alpha 2-adrenoceptors are present on most segments of the nephron and that their activation can suppress adenosine 3,'5'-cyclic monophosphate (cAMP) accumulation induced by most renal hormones. However, failure of alpha 2-adrenoceptor activation to suppress cAMP accumulation in some tubular segments induced by certain hormones suggests compartmentalization of adenylate cyclase regulation that is hormone-function specific. In view of the potent inhibitory effects of alpha 2-adrenoceptor stimulation on hormone activated cAMP accumulation in several discrete areas of the nephron, we suggest that alpha 2-adrenoceptors fulfill important regulatory role(s) in renal function. To date, alpha 2-adrenoceptor activation has been shown to reverse vasopressin-induced sodium and water retention, and arachidonic acid- and furosemide-induced cAMP, sodium, and water excretion in the isolated perfused kidney. Thus the effects are qualitatively and quantitatively dependent in these studies on the hormone being infused and are therefore hormone-function specific. Physiological effects of alpha 2-adrenoceptor activation of thyrocalcitonin and on parathyroid hormone-induced effects have not been studied. alpha 2-Adrenoceptor activation can inhibit renin release in some model systems and can activate a sodium-hydrogen antiporter system in proximal tubules. The physiological roles of these actions are unknown.

Cyprid larvae of the lepadomorph Octolasmis colonize the gill chambers of the edible mangrove crab, Scylla serrata (Forskaal, 1755), sometimes in debilitating numbers. We set out to determine when, in the life cycle of the host, barnacle infestation begins. A total of 856 mangrove crabs, ranging in size from 10.9 to 132.3 mm carapace width (instars 5 to 18), were collected from natural populations in Phuket, Thailand, and examined for these barnacles. Almost a third harbored one or more barnacles. The smallest crab to host a barnacle was 34.3 mm (instar 10); 233 smaller crabs, representing instars 5-9, had none. Infestations by more than one barnacle were uncommon among crabs of less than 70 mm carapace width (instar 13). The percentage of crabs hosting barnacles increased as the crabs approached sexual maturity, and the magnitude of infestation on individual crabs increased with their size. The distribution of octolasmids on the gills of immature crabs differed from that on mature crabs. In the former, all barnacles were on the inside of the gill surfaces and none were on the outside, whereas in the latter, 11% were on the outside of the gills. The numbers of barnacles on the inside and the outside of the gills is a function of the number of barnacles in the gill chamber. The major inhalant aperture size, and gill chamber size were eliminated as possible factors limiting infestation. Instars 10 and 11 may be suboptimal for infestation by octolasmids because the intermolt time between instars does not allow sufficient time for production of barnacle nauplii. Current data do not permit us to distinguish the relative influences of microhabitat use, host hormonal changes, and behavioral changes on infestation.

Despite evidence of a relationship among obstructive sleep apnea (OSA), metabolic dysregulation, and diabetes, it is uncertain whether OSA treatment can improve metabolic parameters. We sought to determine effects of long-term continuous positive airway pressure (CPAP) treatment on glycemic control and diabetes risk in patients with cardiovascular disease (CVD) and OSA. RESEARCH DESIGN AND METHODSBlood, medical history, and personal data were collected in a substudy of 888 participants in the Sleep Apnea cardioVascular Endpoints (SAVE) trial in which patients with OSA and stable CVD were randomized to receive CPAP plus usual care, or usual care alone. Serum glucose and glycated hemoglobin A 1c (HbA 1c ) were measured at baseline, 6 months, and 2 and 4 years and incident diabetes diagnoses recorded. RESULTSMedian follow-up was 4.3 years. In those with preexisting diabetes (n 5 274), there was no significant difference between the CPAP and usual care groups in serum glucose, HbA 1c , or antidiabetic medications during follow-up. There were also no significant between-group differences in participants with prediabetes (n 5 452) or new diagnoses of diabetes. Interaction testing suggested that women with diabetes did poorly in the usual care group, while their counterparts on CPAP therapy remained stable. CONCLUSIONSAmong patients with established CVD and OSA, we found no evidence that CPAP therapy over several years affects glycemic control in those with diabetes or prediabetes or diabetes risk over standard-of-care treatment. The potential differential effect according to sex deserves further investigation.Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper-airway collapse during sleep that causes intermittent hypoxemia, sleep fragmentation, and daytime sleepiness. The standard therapy for OSA is continuous positive airway pressure (CPAP) to prevent airway obstruction (1).OSA is common in the population and strongly associated with obesity (2). Prospective cohort studies have found associations between moderate to severe OSA and

(1) IMCDi and IMCDt cells are both subject to vasopressin and alpha 2- and beta-adrenergic regulation of adenylyl cyclase activity; (2) the relative influence of beta-adrenergic, alpha 2-adrenergic and V2 receptors to affect cAMP accumulation is altered in primary culture versus freshly dissected IMCD segments, suggesting that caution must be exercised in the extrapolation of data from cultured IMCD cells to in vivo models.