No abstract

Sequential polygyny is a reproductive strategy that allows males to continue to mate and compensates for the loss of future breeding opportunities incurred by parental care (i.e. egg attendance). Using the frog Kurixalus eiffengeri, we tested predictions that (1) attending males fathered two, overlapping clutches; and (2) that double clutching leads to improved offspring numbers. Using five microsatellite DNA markers, we genotyped 15 pairs of overlapping clutches, which differed slightly in developmental stage at a single egg‐laying site. Parentage analyses showed at least 12 of 15 pairs of overlapping egg clutches were sired by the attending male mated with different females, providing the first genetic evidence to support an earlier prediction that attending males sired both egg clutches. Field surveys found a low incidence of overlapping clutches (4.9% of 263 egg‐occupied stumps), suggesting sequential polygyny is uncommon. Stumps with multiple clutches contained significantly more eggs than stumps with single clutches but hatched similar number of tadpoles. Results suggest that continuous calling that attracts females during egg attendance is a reproductive tactic that maximizes mating opportunities. However, adoption of the sequential polygyny tactic may only result in marginal fitness gains for males that are traded off against average higher egg mortality in larger egg clutches.

Overlapping offspring occurs when eggs are laid in a nest containing offspring from earlier reproduction. Earlier studies showed that the parentage is not always obvious due to difficulties in field observation and/or alternative breeding tactics. To unveil the parentage between overlapping offspring and parents is critical in understanding oviposition site selection and the reproductive strategies of parents. Amplectant pairs of an arboreal-breeding frog, Kurixalus eiffingeri, lay eggs in tadpole-occupied nests where offspring of different life stages (embryos and tadpoles) coexist. We used five microsatellite DNA markers to assess the parentage between parents and overlapping offspring. We also tested the hypothesis that the male or female frog would breed in the same breeding site because of the scarcity of nest sites. Results showed varied parentage patterns, which may differ from the phenomenon of overlapping egg clutches reported earlier. Parentage analyses showed that only 58 and 25% of the tadpole-occupied stumps were reused by the same male and female respectively, partially confirming our prediction. Re-nesting by the same individual was more common in males than females, which is most likely related to the cost of tadpole feeding and/or feeding schemes of females. On the other hand, results of parentage analyses showed that about 42 and 75% of male and female respectively bred in tadpole-occupied stumps where tadpoles were genetically unrelated. Results of a nest-choice experiment revealed that 40% of frogs chose tadpole-occupied bamboo cups when we presented identical stumps, without or with tadpoles, suggesting that the habitat saturation hypothesis does not fully explain why frogs used the tadpole-occupied stumps. Several possible benefits of overlapping offspring with different life stages were proposed. Our study highlights the importance of integrating molecular data with field observations to better understand the reproductive biology and nest site selection of anuran amphibians.

SummaryBackgroundThe index of hemoglobin (IHb) has not been applied in colonoscopy to correlate the histological features of colon polyps. This study tested whether the net change of IHb values between polyp and normal mucosa correlates with the pathological features of colon polyps.Patients and methodsThis study consecutively enrolled patients who underwent colonoscopy during September 2011–August 2012 in a single tertiary referral colorectal unit. Endoscopic pictures and IHb values of each part of the colon were taken at the levels of cecum, ascending colon, transverse colon, sigmoid colon, and rectum. The net change of IHb values was calculated as follows: IHb value of colon polyp minus that of the surrounding mucosa.ResultsA total of 117 patients (32 with hyperplastic polyp, 5 with sessile serrated adenoma, 53 with tubular adenoma, 10 with villotubular adenoma, and 3 with adenocarcinoma) were recruited. The net change of IHb values increased in following order: hyperplastic polyp, tubular adenoma, sessile serrated adenoma, villotubular adenoma, and adenocarcinoma (−3.8 ± 6.3, −1.2 ± 1.7, −1.2 ± 5.7, 2.9 ± 8.1, and 12.7 ± 9.3, respectively; p < 0.001). Alcohol drinking and serum hemoglobin level were two independent factors related to the IHb values of non‐polyp colon mucosa. Using a cutoff value of 2.4 for the net change of IHb values, selected based on the receiver operating characteristic curve analysis, the optimal sensitivity (52.9%) and specificity (75.6%) could be achieved for defining the polyp histology as an advanced colon lesion.ConclusionThe net change of IHb values between colon polyp and nonpolyp mucosa can correlate with the pathological features of colon polyps. A positive net change of IHb values may indicate a more adverse histological pattern with a higher malignant potential.