Reproductive biology of the electric lanternfish Electrona risso (Myctophidae) and the bigscale fishes Melamphaes polylepis and Scopelogadus mizolepis (Melamphaidae)

This study was the first to investigate the key reproductive traits of the electric lantern fish Electrona risso (Myctophidae, n = 918) and the bigscale fishes (Melamphaidae) Melamphaes polylepis (n = 260) and Scopelogadus mizolepis (n = 649). Specimens of these mesopelagic species were collected in March and April 2015 in the eastern Central Atlantic (0–24° N, 20–26° W). Sex ratio was not significantly different from 1:1 in E. risso and M. polylepis but significantly skewed toward female dominance in S. mizolepis. Reproductive phases were determined macroscopically and by histological analyses on selected individuals. Female length at 50% maturity (L50) was 55.1 mm standard length (LS) in E. risso, with an observed female maximum length (Lmax) of 81.2 mm LS. M. polylepis females had an L50 of 40.2 mm LS and an Lmax of 86.7 mm LS. S. mizolepis had an L50 of 46 mm LS and an Lmax of 97.9 mm LS. The three species show histological features of iteroparity, but the E. risso population appears to occur in two year-classes and experience only one spawning season per lifetime in the study region. All three species are batch-spawners. A batch fecundity of 2668 eggs was estimated from one E. risso individual, with a relative batch fecundity of 369 eggs g−1 gonad-free body mass. M. polylepis had a batch fecundity of 1027 eggs and a relative batch fecundity of 149 eggs g−1 (n = 3). S. polylepis had a batch fecundity of 1545 eggs and a relative batch fecundity of 215 eggs g−1 (n = 21). The median gonado-somatic index during the actively spawning phase of E. risso was 4.5, significantly lower than that of M. polylepis (7.5) and S. mizolepis (7.1). No regressing or regenerating phases were observed in this study. Batch-spawning in all three species is suggested to be advantageous to cope with intra-annual variability in food supply and other risks for offspring survival. With what appears to be in effect a (facultative) semelparous strategy in combination with a short life span in E. risso, interannual differences would have a great effect on population dynamics of this species. Knowledge is still lacking on temporal aspects of reproduction such as the duration of the spawning season and the frequency of spawning, as well as age and growth

Reproductive data of Electrona risso, Melamphaes polylepis and Scopelogadus mizolepis from the Eastern Central Atlantic in March and April 2015

Knowledge on life history traits of mesopelagic fishes is still sparse. This dataset contains reproductive data of the myctophid Electrona risso (Cocco, 1829) and the melamphaids Melamphaes polylepis Ebeling, 1962 and Scopelogadus mizolepis (Günther, 1878). The specimens were collected in March and April 2015 during cruise 383 of the fishery research vessel "FFS Walther Herwig III" in the Eastern Central Atlantic. A pelagic midwater trawl ("Aalnet", Engel Netze, Bremerhaven Germany) with multiple opening-closing device with three net bags of 20 mm mesh size and 1.8 mm mesh size in the cod-end container was used for catching fish at three depth strata per station between 50 and 700 m depth. Fish was stored in phosphate buffered 4% formalin solution and later on land in laboratories, specimens were measured, weighed, and dissected to examine gonads and oocytes under a stereo microscope. Reproductive phases were assigned based on macroscopic inspection following the standardised terminology for reproductive development in fish by Brown-Peterson et al. (2011, doi:10.1080/19425120.2011.555724). Histological cross sections of selected individuals were used for validation. The Gonadosomatic Index was calculated as GSI = 100 x gonad mass / (total mass – gonad mass). Batch fecundities were determined with the gravimetric method, counting the most advanced eggs in weighed subsamples

Highly efficient maternal-fetal Zika virus transmission in pregnant rhesus macaques

<div><p>Infection with Zika virus (ZIKV) is associated with human congenital fetal anomalies. To model fetal outcomes in nonhuman primates, we administered Asian-lineage ZIKV subcutaneously to four pregnant rhesus macaques. While non-pregnant animals in a previous study contemporary with the current report clear viremia within 10–12 days, maternal viremia was prolonged in 3 of 4 pregnancies. Fetal head growth velocity in the last month of gestation determined by ultrasound assessment of head circumference was decreased in comparison with biparietal diameter and femur length within each fetus, both within normal range. ZIKV RNA was detected in tissues from all four fetuses at term cesarean section. In all pregnancies, neutrophilic infiltration was present at the maternal-fetal interface (decidua, placenta, fetal membranes), in various fetal tissues, and in fetal retina, choroid, and optic nerve (first trimester infection only). Consistent vertical transmission in this primate model may provide a platform to assess risk factors and test therapeutic interventions for interruption of fetal infection. The results may also suggest that maternal-fetal ZIKV transmission in human pregnancy may be more frequent than currently appreciated.</p></div

Complete blood counts (CBCs) and serum chemistries for pregnant macaques infected with ZIKV.

<p>Animals were infected with 10⁴ PFU of ZIKV. Animals infected in the first or third trimesters are represented by color coding (<b>A</b>) as presented in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006378#ppat.1006378.g001" target="_blank">Fig 1</a>. All animals had CBC analysis performed on EDTA blood and chemistry analysis performed on serum at -7, -3, 0, 1–10 and additional indicated dpi. <b>B.</b> AST blood chemistries, <b>C.</b> ALT serum chemistries, <b>D.</b> CK serum chemistries, <b>E.</b> WBC counts, <b>F.</b> % lymphocytes, <b>G.</b> red blood cell (RBC) counts.</p

Fetal growth following ZIKV infection.

<p>Growth curves of femur length (FL), biparietal diameter (BPD), and head circumference (HC) obtained from fetal ultrasound images throughout gestation are presented as individual lines or symbols with specific colors as in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006378#ppat.1006378.g001" target="_blank">Fig 1</a>. (<b>A</b>) FL, (<b>B</b>) BPD (<b>C</b>) and HC were determined for the fetuses in this study and plotted against data from Tarantal [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006378#ppat.1006378.ref035" target="_blank">35</a>], which is presented as the mean (solid black line) and 1, 2, and 3 standard deviations from the mean as grey lines above and below the mean. The data from the last month of pregnancy are also presented as a magnified view of the scatter of individual data points on the right. Representative ultrasound images of FL, BPD, and HC are also shown at the right.</p

Fetal growth as assessed by predicted gestational ages.

<p>The predicted gestational age (pGA) as described by Tarantal [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006378#ppat.1006378.ref035" target="_blank">35</a>] from each of the pregnancies is plotted against the actual day of gestation estimated from breeding activity and animal menstrual records. The pGA was derived from the average of BPD+FL (dashed lines), or the HC (solid lines). <b>A</b> (animal 827577) and <b>B</b> (animal 660875), first trimester infection. <b>C</b> (animal 357676) and <b>D</b> (animal 598248), late second/early third trimester infection.</p

Study layout and viral RNA burden in pregnant rhesus fluids.

<p>(<b>A</b>) Schematic representation of the timeline of infection, sampling for maternal viral burden, and experimental cesarean section, for all animals in the study. Animals received a ZIKV challenge in the first or late second/early third trimesters of pregnancy, and blood and other fluid samples were collected according to the schedule indicated in detail in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006378#ppat.1006378.s001" target="_blank">S1 Fig</a>. (<b>B</b>) ZIKV viral load in pregnant macaque fluids. Viral RNA loads (vRNA copies/ml) measured in plasma, urine, saliva, and amniotic fluid presented individually for the four pregnant animals. The day post-inoculation is indicated below each graph, and gestational age (days) for each animal is indicated above (term = 165±10 days). Limit of assay quantification is 100 copies/mL. Limit of detection is 33 copies/mL. Colors for individual animals are continued through the rest of the Figures, including the Supplementary Figures.</p