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The feline infectious peritonitis virus (FIPV) is a mutated form of the feline enteric coronavirus (FeCV) that can present with a variety of clinical signs. The purpose of this retrospective study was to analyze abdominal ultrasonographic findings associated with cats with confirmed FIPV infection. Sixteen cases were included in the study from a review of medical records at two academic institutions; inclusion was based either on necropsy lesions (n=13) or a combination of histopathological, cytological, and clinicopathological findings highly suggestive of FIPV infection (n=3). The liver was judged to be normal in echogenicity in 11 (69%) cats, diffusely hypoechoic in three cats, focally hyperechoic in one cat, and focally hypoechoic in one cat. Five cats had a hypoechoic subcapsular rim in one (n=3) or both (n=2) kidneys. Free fluid was present in the peritoneal cavity in seven cats and in the retroperitoneal space in one cat. Abdominal lymphadenopathy was noted in nine cats. The spleen was normal in echogenicity in 14 cats and was hypoechoic in two. One cat had bilateral orchitis with loss of normal testicular architecture. Although none of these ultrasonographic findings are specific for FIPV infection, a combination of these findings should increase the index of suspicion for FIPV infection when considered along with appropriate clinical signs.

Abstract.-Host plant-associated fitness trade-offs are central to models of sympatric speciation proposed for certain phytophagous insects. But empirical evidence for such trade-offs is scant, which has called into question the likelihood of nonallopatric speciation. Here, we report on the second in a series of studies testing for host-related selection on pupal life-history characteristics of apple-(Malus pumila L.) and hawthorn-(Crataegus mol/is L. spp.) infesting races of the Tephritid fruit fly, Rhagoletis pomonel/a (Walsh). In particular, we examine the effects of winter length on the genetics of these flies.We have previously found that the earlier fruiting phenology of apple trees exposes apple-fly pupae to longer periods of warm weather preceding winter than hawthorn-fly pupae. Because R. pomonel/a has a facultative diapause, we hypothesized that this selects for pupae with more recalcitrant pupal diapauses (or slower metabolic/development rates) in the apple-fly race. A study in which we experimentally manipulated the length of the prewintering period for hawthorn-origin pupae supported this prediction.If the period preceding winter is important for apple-and hawthorn-fly pupae, then so too should be the length (duration) of winter; the rationale for this prediction is that "fast developing" pupae that break diapause too early will deplete their energy reserves and disproportionately die during long winters. To test this possibility, we chilled apple-and hawthorn-origin pupae collected from a field site near Grant, Michigan, in a refrigerator at 4°C for time periods ranging from one week to two years. Our a priori expectation was that longer periods of cold storage would select against allozyme markers that were associated with faster rates of development in our earlier study. Since these electromorphs are typically found at higher frequencies in hawthorn flies, extending the overwintering period should favor "apple-fly alleles" in both races.The results from this "overwinter" experiment supported the diapause hypothesis. The anticipated genetic response was observed in both apple and hawthorn races, as allele frequencies became significantly more "apple-fly-like" in eclosing adults surviving longer chilling periods. This indicates that it is the combination of environmental conditions before and during winter that selects on the host races. Many tests for trade-offs fail to adequately consider the interplay between insect development, host plant phenology, and local climatic conditions. Our findings suggest that such oversight may help to explain the paucity of reported fitness trade-offs.

Several aquatic invertebrates with free-swimming larvae have paradoxically demonstrated fine-scale genetic heterogeneity. In this study, we tested for genetic heterogeneity in an exotic freshwater bivalve, the zebra mussel, Dreissena polymorpha (Pallas), which like many marine molluscs has a free-swimming larval stage. Zebra mussels were collected from 22 sites in the Great Lakes and from a small inland lake complex in southwestern Michigan and scored for 13 allozyme loci. Sites were sampled in a hierarchical fashion to assess the spatial scale of genetic variation. Zebra mussel populations exhibited significant genetic heterogeneity on a local scale within lakes, even though populations remained homogenous on a larger regional scale between lakes or lake complexes. The allozyme loci that exhibited heterogeneity differed from lake to lake. Populations also displayed significant heterozygote deficiencies from Hardy-Weinberg expectations for a majority of loci, implying population subdivision and (or) inbreeding on a fine scale. Our results suggest that local genetic differentiation for zebra mussels is both spatially and temporally fluid and is the product of stochastic processes, such as spawning asynchrony and uneven mixing of larval cohorts, rather than natural selection.

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