Ocean deoxygenation and zooplankton: Very small oxygen differences matter.

Oxygen minimum zones (OMZs), large midwater regions of very low oxygen, are expected to expand as a result of climate change. While oxygen is known to be important in structuring midwater ecosystems, a precise and mechanistic understanding of the effects of oxygen on zooplankton is lacking. Zooplankton are important components of midwater food webs and biogeochemical cycles. Here, we show that, in the eastern tropical North Pacific OMZ, previously undescribed submesoscale oxygen variability has a direct effect on the distribution of many major zooplankton groups. Despite extraordinary hypoxia tolerance, many zooplankton live near their physiological limits and respond to slight (≤1%) changes in oxygen. Ocean oxygen loss (deoxygenation) may, thus, elicit major unanticipated changes to midwater ecosystem structure and function.

Ciliate species diversity and host-parasitoid codiversification in Pseudocollinia infecting krill, with description of Pseudocollinia similis sp. nov.

All parasitoid apostome ciliates infecting krill in the northeastern Pacific are currently assigned to the genus Pseudocollinia. Each krill specimen is apparently infected by only 1 Pseudocollinia species. We describe Pseudocollinia similis sp. nov., discovered infecting the krill Thysanoessa spinifera off Oregon, USA. Its protomite-tomite stage resembles that of P. beringensis, which infects T. inermis (type host species), T. longipes, and T. raschii females in the Bering Sea. These ciliates have similar numbers of somatic kineties (18-21 vs. 16-20) and typically have 3 oral kineties. Furthermore, these 2 apostomes are sister species on gene trees based on sequences of small subunit rRNA (0.06% difference) and cytochrome c oxidase subunit 1 (cox1; 30% difference). P. brintoni and P. oregonensis are closely related as a separate group from P. similis and P. beringensis. The similar tree topologies based on the cox1 sequences of 21 host krill individuals representing 6 krill species (Euphausia pacifica, Nyctiphanes simplex, T. inermis, T. longipes, T. raschii, and T. spinifera) and the apostomes isolated from these krill suggest host-parasitoid codiversification. However, this hypothesis was statistically rejected by an approximately unbiased test in which the host tree topology was used to model parasitoid evolution (p ≤ 0.05).

Polysplenia in a fetus with bradycardia from 26 to 36 weeks' gestation, complex cardiac malformations, and heart block.

Polysplenia is one of several splenic anomalies. Frequently, as in the case presented here, significant cardiac anomalies coexist. These cardiac malformations determine the clinical course. In this case, early death was expected and occurred. This patient is different from others described in the literature in that persistent fetal bradycardia was noted at 26 weeks' gestation.

Vaginal leiomyoma as a cause of pelvic pain and cystitis cystica.

Leiomyoma of the vagina occurs extremely rarely and may be confused with a variety of benign vaginal tumors. A preoperative diagnosis is seldom made. The author reports a case of leiomyoma found in the anterior vaginal wall beneath the urethra and associated with pelvic pain and urinary symptoms.

Marked elevation of serum transaminase activity associated with extrahepatic biliary tract disease.

Nine patients with choledocholithiasis or cholelithiasis developed transient elevations of serum glutamic oxalacetic transaminase (SGOT) levels of greater than 600 units. Awareness of such transient biliary disease will prevent an unnecessary evaluation of a primary hepatocellular disorder. In our study, we concluded that 1) The SGOT level rose and fell rapidly within a 24- to 72-hour period. 2) Higher SGOT levels were seen in patients with choledocholithiasis in whom the gallbladder had been removed. 3) In patients with choledocholithiasis a fall in SGOT level did not necessarily mean the stone had passed.