Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fish Paramormyrops kingsleyae.

Communication signals serve crucial survival and reproductive functions. In Gabon, the widely distributed mormyrid fish Paramormyrops kingsleyae emits an electric organ discharge (EOD) signal with a dual role in communication and electrolocation that exhibits remarkable variation: populations of P. kingsleyae have either biphasic or triphasic EODs, a feature that characterizes interspecific signal diversity among the Paramormyrops genus. We quantified variation in EODs of 327 P. kingsleyae from nine populations and compared it to genetic variation estimated from microsatellite loci. We found no correlation between electric signal and genetic distances, suggesting that EOD divergence cannot be explained by drift alone. An alternative hypothesis is that EOD differences are used for mate discrimination, which would require P. kingsleyae be capable of differentiating between divergent EOD waveforms. Using a habituation-dishabituation assay, we found that P. kingsleyae can discriminate between biphasic and triphasic EOD types. Nonetheless, patterns of genetic and electric organ morphology divergence provide evidence for hybridization between these signal types. Although reproductive isolation with respect to signal type is incomplete, our results suggest that EOD variation in P. kingsleyae could be a cue for assortative mating.

Metabolic syndrome in small fiber sensory neuropathy.

OBJECTIVES: To determine the prevalence and risk of metabolic syndrome in patients with small fiber sensory neuropathy (SFSN). METHODS: We searched our skin biopsy database and identified 194 subjects for this retrospective study. Of these 194 subjects, 43 had normal skin biopsies and 151 had mild, moderate, or severe length-dependent SFSN with no large fiber involvement. Fifty-four subjects had diabetic or prediabetic SFSN and 97 had idiopathic SFSN. RESULTS: The mean age of the neuropathy group was older (54.1 ± 11.9 years) than the normal biopsy group (44.8 ± 13.0, P < 0.001). The prevalence of metabolic syndrome was higher in the neuropathy group (27.8%) than in the normal biopsy group (2.3%, P < 0.001). Age was not different among three neuropathy subgroups. The prevalence of metabolic syndrome was higher in the severe (38.1%) than in the moderate (26.0%) and mild (14.7%) neuropathy groups (P = 0.04). Multivariate analysis revealed that age (odds ratio [OR], 1.95; P < 0.001), metabolic syndrome (OR, 3.20; P < 0.001), hypertension (OR, 1.88; P = 0.04), and obesity (OR, 1.93; P = 0.004) were independent risk factors for SFSN. CONCLUSIONS: The prevalence of metabolic syndrome is increased in patients with SFSN and it correlates with the severity of SFSN. Metabolic syndrome may represent an independent risk factor for SFSN.