Structure and function of Halice hesmonectes (Amphipoda: Pardaliscidae) swarms from hydrothermal vents in the eastern Pacific

Swarms of the pardaliscid amphipod Halice hesmonectes were sampled at low-temperature hydrothermal vents in the Venture Hydrothermal Fields of the East Pacific Rise. In excess of 3000 individuals were collected from a range of sites/habitats, and at two points in time (December 1991 and March 1994). The structure of swarms was described in terms of growth stages, the development of primary and secondary sex characteristics and the accumulation of nutritional reserves. The results demonstrated that swarms contained a wide range of growth stages, but that small juveniles and mature males and females were absent. Swarm structure was interpreted as an equilibrium dependent on the relative proportion of time spent by each growth stage in the swarm habitat. This equilibrium swarm structure was very similar at different sites and times. Swarms dominated by small juveniles occurred at the northern sites in December 1991 following a period of eruption and new venting in April 1991. Equilibrium swarm structure had become re-established at these sites by March 1994. The function of swarming was considered. The results indicated that swarming was not associated with reproductive activity. The available evidence, though not conclusive, suggested that swarms were associated with feeding. Received: 28 May 1999 / Accepted: 16 February 2000     

Current controversies in prenatal diagnosis 2: The 59 genes ACMG recommends reporting as secondary findings when sequencing postnatally should be reported when detected on fetal (and parental) sequencing

Genome sequencing is increasingly being used to aid genetic diagnosis in fetuses with structural abnormalities detected on ultrasound examination. However, with clinical exome and genome sequencing, there is potential for the recognition and reporting of incidental or secondary findings unrelated to the indication for ordering the sequencing, but of potential medical value for patient care. In the postnatal setting, the American College of Medical Genetics and Genomics (ACMG) has clear guidelines that state that when offering sequencing, secondary findings should be reported in 59 genes for which ACMG consider there is a clinical evidence that pathogenic variants may result in disease that might be prevented or treated, with the option to opt out of receiving this information. However, these guidelines specifically exclude prenatal sequencing. Here, we report the debate on whether or not pathogenic findings in these 59 genes should or should not be reported in the prenatal setting. Although more were in favour of reporting before the debate, there was no significant consensus from the audience. After the debate there was a swing toward not reporting, but a slim majority (55%) remained in favour, indicating that this is an area requiring further research and the development of evidence-based guidelines applicable to prenatal proband and trio sequencing.     

Maternal liver transplant: Another cause of discordant fetal sex determination using cell-free DNA

Noninvasive prenatal testing (NIPT) can very accurately determine fetal sex during pregnancy. We present an exceptional case where NIPT contradicts the ultrasound-based sex determination. The pregnant woman was recipient of a liver transplant from a male donor. Graft-derived cell-free DNA released into the maternal circulation clouded the NIPT-based sex determination. Hence, NIPT is not advisable when the pregnant mother underwent an organ transplant.