Sex change and spatial distribution pattern in an intertidal holothurian Polycheira rufescens in the reproductive season

The patterns of sex change and spatial distribution in an intertidal holothurian, Polycheira rufescens (Chiridotidae; Echinodermata), were investigated on a stony beach in Amakusa, western Kyushu. Field caging experiments revealed that some individuals of P. rufescens underwent a sequential sex change from male to female via hermaphrodite stages and back to male again within a single reproductive season. The sex ratio of the population gradually changed from male dominance at first to equal proportions of males and females as the reproductive season progressed. Toward the end of the reproductive season, immature or spent individuals increased in proportion. Stone size appeared to be an important factor affecting the occurrence of P. rufescens individuals on a stony beach. Analysis of spatial distribution by means of Morisita's index of dispersion and nearest neighbor distances indicated that (i) males showed a slightly stronger tendency to aggregate than females, while females had a tendency toward uniform distribution; (ii) females tended to attract males, as shown by relatively short female-to-male distances; and (iii) there was a substantial variation in male-to-female distances, such that some males were positioned close to females while others were not. It may be suggested that spatial distribution of P. rufescens individuals during the reproductive period is partly dictated by the differential needs of individuals of different sexual states. Received: January 25, 1999 / Accepted: June 10, 1999     

Comorbidities as predictors of incidental prostate cancer after Holmium laser enucleation of the prostate: diabetes and high-risk cancer

Prostate cancer can be diagnosed as an incidental finding during the pathological examination of benign prostatic hyperplasia (BPH) specimens by Holmium laser enucleation of the prostate (HoLEP). BPH and comorbidities such as hypertension, diabetes, and dyslipidemia often coexist in elderly people. We identified which comorbidities can be used to predict the presence of incidental prostate cancer, particularly high-risk cancer, in men who had undergone HoLEP. On the basis of pathological findings of HoLEP specimens, patients with incidental cancer were categorized as low-risk (Gleason ≤6 and T1a) or high-risk (all others). Of the 654 patients who underwent HoLEP, 41 patients (6.3%) were identified as having incidental cancer (25 low-risk and 16 high-risk). There were no significant factors for overall prostate cancers. However, a significantly higher frequency of diabetes was observed in patients with high-risk cancer compared to those with BPH (31% vs. 13%; p?=?.033). Logistic regression analysis using prostate-specific antigen (PSA) and prostate volume (PV), and smoking showed that diabetes was an independent predictor of high-risk cancer (odds ratio, 3.15; 95% confidence interval, 1.06–9.43). Diabetes may be an important predictor of the presence of high-risk prostate cancer in men with BPH who have undergone HoLEP.     

Competitive habitat utilization in the damselfly,Mnais nawai (Zygoptera: Calopterygidae) coexisting with a related species,Mnais pruinosa

Reproductive behaviors related to habitat utilization were studied in males of the damsefly,Mnais nawai, which has two male forms, territorial orange-winged males (nawai) and non-territorial pale-orange-winged males (sahoi), at the upper part of a mountain stream where they partiallycoexist with a related species,Mnais pruinosa, which also has two male forms, territorial orange-winged males (esakii) and non-territorial hyaline-winged males (strigata). These two species showed parapatric distribution; the lower part of the stream was occupied byM. nawai, and the upper part byM. pruinosa. In the present study, cross-matings occurred between bothMnais species, although normal intraspecific matings occurred more frequently than cross-matings. Territorial males of both species copulated with conspecific females that entered their territory and guarded the ovipositing females, probably to avoid sperm displacement resulting from subsequent copulations. Severe competition for oviposition sites by territorial males even occurred between the two species. On the other hand, non-territorial males of both species have alternative mating strategies (including several tactics such as sneaking, takeover and interception). The possible benefits from conflict among territorial males of both species is discussed.