The age and growth of weatherfish (Misgurnus fossilis), an endangered and protected freshwater fish with a poorly known life history, was studied in two watercourses (the River Ner and the Nowy Rów canal, Poland). The weight, length and sagittal otoliths of 166 specimens collected in April 2015 were measured for weight-length relationships, ageing and back-calculation of length at age. At both sites sex ratio did not differ from 1:1. Weatherfish otoliths were small, elliptic (1.85 mm longer axes of the largest otolith) and the annuli were clearly visible. Female lifespan was six years but the oldest males were four and five years. In both sites populations were dominated by 2+ (the River Ner) and 3+ (the Nowy Rów canal) specimens. In general, weatherfish grows isometrically (b = 3) and the intercept of the weight-length relationship differ between study sites but not between sexes. Its total length (TL) was predicted by an interaction between sex and age, as well as capture site and age. Back-calculated estimates of TL fitted a von Bertalanffy growth function, though Taylor’s criterion showed that the asymptotic length were overestimated. Multiple comparisons of the von Bertalanffy growth function parameter revealed difference between sexes and sites.
It is speculated that the wasps that attack the seeds of gymnosperm trees (conifers) before they are fertilized can induce unfertilized seeds to accumulate storage material whereas those that attack after the seeds are fertilized selectively oviposit in fertilized seeds. Moreover, in the case of the wasps that oviposit after fertilization of seed, the presence of unfertilized seeds and seedless fruit may increase plant fitness via reduced parasitism of the viable seed. To determine the relationship between the two strategies, host manipulation or selective oviposition, and the time of fertilization of the seeds of angiosperm host plants, fertilized seed of Ilex integra Thunb. was dissected out of berries either immediately after the flight of the seed wasp Macrodasyceras hirsutum Kamijo in the field or the death of adults in the laboratory. The wasps oviposited mostly in fertilized seeds and rarely in unfertilized seeds. Unfertilized seeds, produced by flowers enclosed in pollen exclusion bags, and then exposed to wasps did not contain immature wasps or storage material, which indicates that the wasp did not oviposit in unfertilized seeds. These results support the above mentioned hypothesis and indicate that the substantial proportion of seedless berries do not function as an egg sink.