In central and southern Florida Diaptomus dorsalis is the sole diaptomid in most eutrophic lakes whereas Diaptomus floridanus and Diaptomus mississippiensis co‐occur in oligotrophic and mesotrophic lakes. The importance of food availability and water quality in determining the species distributions of Diaptomus was ascertained by culturing the three species in water from a lake of each type with its natural phytoplankton present and with the natural phytoplankton removed and Chlamydomonas added at a concentration above feeding saturation. The experimental evidence indicated that neither food availability nor water quality is important in excluding D. floridanus and D. mississippiensis from the eutrophic lakes. Additional data suggested that strong predation pressure may prevent these two species from occupying lakes of this type. However, low food availability seemed of major importance in excluding D. dorsalis from the oligotrophic and mesotrophic lakes. Competition is likely because food levels are always limiting and a potential competitor is present in the form of D. floridanus—in the same subgenus and close to the same size. Additional evidence suggests that predation is probably of lesser importance to the zooplankton in lakes of these types.

IntroductionTwo experiments were conducted with a subtropical calanoid, Diaptomus dorsalis Marsh 1907, to determine the influence of food concentration and the volume of medium per copepod (one copepod in each of several containers of different volumes) on post-embryonic development rates, adult body size, clutch size, survivorship and sex ratio. Low concentrations of food (Chlamydomonas reinhardti) decreased development rates, body size, clutch size and survivorship; the sex ratio did not vary significantly from 1:1. Small container volumes had the same effects as low food concentrations, except that naupliar development time was not affected and survivorship showed greater variability. Because the copepod parameters exhibited maximum responses when food was abundant, even in the smallest container volume, it was concluded that container volume did not directly influence these parameters but exerted its effect through food availability.Larger life history stages were affected more than smaller life history stages by low food levels. In part, this was attributed to a laboratory artifact in which depletion of food by larger animals was greater than by smaller animals and, in part, to a real effect of low food concentration. A possible explanation of this real effect came from comparisons of these results to data from D. dorsalis fed phytoplankton from a Florida lake. The comparisons suggested that nauplii may be more efficient feeders on, or utilizers of, small food items such as Chlamydomonas.Numerous studies of natural zooplankton populations have correlated concentration of food with responses of various life history parameters. Although such studies have been useful in suggesting factors which may influence these parameters in nature, it has often been impossible to separate the effects of food from other factors, e.g., temperature, water quality and predation.For this reason, laboratory studies have been undertaken to elucidate the relationships between food concentration and zooplankton life history parameters. There have been many studies of the effects of food concentration on rotifers (e.g.

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Dissociative disorders have a lifetime prevalence of about 10%. Dissociative symptoms may occur in acute stress disorder, posttraumatic stress disorder, somatization disorder, substance abuse, trance and possession trance, Ganser's syndrome, and dissociative identity disorder, as well as in mood disorders, psychoses, and personality disorders. Dissociative symptoms and disorders are observed frequently among patients attending our rural South Carolina community mental health center. Given the prevalence of mental illness in primary care settings and the diagnostic difficulties encountered with dissociative disorders, such illness may be undiagnosed or misdiagnosed in primary care settings. We developed an intervention model that may be applicable to primary care settings or helpful to primary care physicians. Key points of the intervention are identification of dissociative symptoms, patient and family education, review of the origin of the symptoms as a method of coping with trauma, and supportive reinforcement of cognitive and relaxation skills during follow-up visits. Symptom recognition, Education of the family, Learning new skills, and Follow-up may be remembered by the mnemonic device SELF. We present several cases to illustrate dissociative symptoms and our intervention. Physicians and other professionals using the 4 steps and behavioral approaches will be able to better recognize and triage patients with dissociative symptoms. Behaviors previously thought to be secondary to psychosis or personality disorders may be seen in a new frame of reference, strengthening the therapeutic alliance while reducing distress and acting-out behaviors.

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