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SUMMARYBackground Structural abnormalities of the anterior cingulate cortex (ACC) may interfere with the interaction of cortical and limbic networks involved in emotional regulation and contribute to chronic depressive syndromes in the elderly. This study examined the relationship of regional anterior cingulate cortical volumes with treatment remission of elderly depressed patients. We hypothesized that patients who failed to remit during a 12-week controlled treatment trial of escitalopram would exhibit smaller anterior cingulate gray matter volumes than patients who remitted. Methods The participants were 41 non-demented individuals with non-psychotic major depression. After a 2-week singleblind placebo period, subjects who still had a Hamilton Depression Rating Scale (HDRS) of 18 or greater received escitalopram 10 mg daily for 12 weeks. Remission was defined as a HDRS score of 7 or below for at least 2 consecutive weeks. The patient sample consisted of 22 depressed patients who achieved remission during the study and 19 depressed patients who remained symptomatic. High-resolution magnetization-prepared rapidly acquired gradient echo (MPRAGE) sequences were acquired on a 1.5 T scanner and regional ACC volumes were manually outlined (dorsal, rostral, anterior subgenual, and posterior subgenual). Results Repeated measure analyses revealed that patients who failed to remit following escitalopram treatment had smaller dorsal and rostral anterior cingulate gray matter volumes than patients who remitted, whereas subgenual cortical volumes did not differ between the groups. Conclusions Structural abnormalities of the dorsal and rostral anterior cingulate may perpetuate late-life depression.

Excirolana braziliensis is a dioecious marine isopod that lives in the high intertidal zone on both sides of tropical America. It lacks a dispersal phase and displays a remarkable degree of genetic divergence even between localities less than 1 km apart. Nine populations of this nominal species from both sides of the Isthmus of Panama and one population of the closely allied species, Excirolana chamensis, from the eastern Pacific were studied for 2 yr for allozymic temporal variation in 13 loci and for 3 to 4 yr for morphological variation in nine characters. The genetic and morphological constitution of 9 out of 10 populations remained stable. Allele frequencies at two loci and overall morphology in a tenth beach occupied by E. braziliensis changed drastically and significantly between 1986 and 1988. The change in gene frequency is too great to explain by genetic drift occurring during a maximum of 14 generations regardless of assumed effective population size; drift is also unlikely to have caused observed changes in morphology. Selective survival of a previously rare genotype is more plausible but still not probable. The most credible explanation is that the resident population at this locality became extinct and that the beach was recolonized by immigrants from another locality. Such infrequent episodes of extinction and recolonization from a single source may account for the large amount of genetic divergence between local populations of E. braziliensis. However, the low probability of large temporal genetic change even in a species such as this, in which gene flow between local demes is limited and generation time is short, suggests that a single sample through time is usually adequate for reconstructing the genetic history of populations.

Weinberg, J. R. 2005. Bathymetric shift in the distribution of Atlantic surfclams: response to warmer ocean temperature. e ICES Journal of Marine Science, 62: 1444e1453.Standard research vessel surveys during the 1980s and early 1990s demonstrated that Atlantic surfclams (Spisula solidissima solidissima) were common in the southern portion of their range (37e38(N) along the east coast of North America in the Delmarva region. Based on data from these surveys, the probability of capturing surfclams in shallow water (i.e. 20 m) tows of the Delmarva region was 75e85% in 1994. In 1999 this probability declined to 40e55%. The probability of capturing surfclams in survey tows from deeper waters (40e50 m) also declined, but this change was relatively small compared with that in shallower water. These changes were not the result of commercial clam fishing. Unusually warm water, which induces thermal stress in S. s. solidissima, was prevalent within the period from 1999 to 2002 over the Delmarva continental shelf during fall when annual bottom temperature was peaking. The combined effects of poor physiological condition and thermal stress likely resulted in mortality of Atlantic surfclams in shallow water habitats in the Delmarva region. This resulted in a shift in the bathymetric distribution of the population to deeper water. Between 1982 and 1997, most of the surfclams in the Delmarva region occurred at depths between 25 and 35 m, whereas in 1999 and 2002, most of the Delmarva population occurred at 35e40 m.