Diploid males of Scaptotrigona depilis are able to join reproductive aggregations (Apidae, Meliponini)

The sex determination system in the eusocial stingless bees (Apidae, Meliponini) is based on the combination of alleles at the complementary sex determination (CSD) locus. In this system, males are haploid and females are diploid. However, diploid males can develop from fertilized eggs when they are homozygous at single or multiple sex loci. The production of such males can negatively affect population viability, since they are usually infertile or inviable. Moreover, when they are viable but infertile, or siring sterile triploid offspring, this could cause another load on the population, leading the fertilized offspring of other females to be only haploid males or triploid sterile daughters. In this context, our aim was to verify whether diploid males of the stingless bee Scaptotrigonadepilis do in fact join reproductive aggregations. We showed that of 360 marked males from two different colonies, five were participating in a reproductive aggregation ca. 20 meters from their natal colonies. Using microsatellites markers, it was confirmed that three of these five males were diploid. They were captured in the mating aggregations when they were 15 to 20 days old. Further research is necessary to determine the mating success of stingless bee diploid males under natural conditions and to determine their impact on stingless bee population extinction risks.

Reproductive biology of the endemic skate Psammobatis lentiginosa in the San Matías Gulf (south-western Atlantic)

The reproductive biology of Psammobatis lentiginosa was studied in San Matías Gulf (Patagonia, south-west Atlantic). A total of 1033 skates was analysed, total length ranged from 17 to 52 cm for females and from 13 to 55 cm for males. Total length–total weights relationships differed between sexes, with TW = 0.005 × TL3.02 for females and TW = 0.005 × TL2.97 for males. The overall sex-ratio was 1:1. In females, the L50% was 41.06 cm, in males the L50% was 41.38 cm. The mean number of yolked oocytes per skate was 4.22 (±2.41). The mean number of yolked oocytes and the length of the female were linearly related. The diameter maximum of yolked oocytes was 24 mm. The species exhibited a continuous reproductive cycle throughout the year, with a peak of egg-case production during autumn that was synchronous with maximum values of the epididymis and uterus indices. This is the first record of a reproductive aggregation for P. lentiginosa in San Matías Gulf, North Patagonia. This finding together with its continuous presence around the year, suggest that this area is the main distribution area of P. lentiginosa in the south-west Atlantic.