Parasite Component Community of Smalltooth Sawfish Off Florida: Diversity, Conservation Concerns, and Research Applications

Compared with that of other charismatic elasmobranchs, the component community of metazoan parasites infecting endangered smalltooth sawfish Pristis pectinata is exceedingly poorly characterized: adults of Dermophthirioides pristidis and Neoheterocotyle inpristi (ectoparasitic flatworms of skin and gill, respectively) were the only confirmed parasites prior to the description, based on specimens reported herein, of Mycteronastes caalusi. Our opportune and directed parasitological examinations of 290 smalltooth sawfish (277 live inspections; 13 necropsies; 671 to 2640 mm stretch total length) in south Florida coastal waters revealed at least 8 species of Platyhelminthes, 9 of Arthropoda, 4 of Annelida, and 1 of Nematoda. This collection includes representatives of an undescribed species of Aporocotylidae (Digenea) and myriad new host records, considerably updating and advancing our understanding of smalltooth sawfish symbionts. We also confirm that D. pristidis and N. inpristi are extant and propose D. pristidis as a reliable biological tag. Some of these parasites are evidently highly host-specific and so vulnerable to extinction

Bypass of DNA interstrand crosslinks by a Rev1-DNA polymerase zeta complex

DNA polymerase zeta (Pol zeta) and Rev1 are essential for the repair of DNA interstrand crosslink (ICL) damage. We have used yeast DNA polymerases eta, zeta and Rev1 to study translesion synthesis (TLS) past a nitrogen mustard-based interstrand crosslink (ICL) with an 8-atom linker between the crosslinked bases. The Rev1-Pol zeta complex was most efficient in complete bypass synthesis, by 2-3 fold, compared to Pol zeta alone or Pol eta. Rev1 protein, but not its catalytic activity, was required for efficient TLS. A dCMP residue was faithfully inserted across the ICL-G by Pol eta, Pol zeta, and Rev1-Pol zeta. Rev1-Pol zeta, and particularly Pol zeta alone showed a tendency to stall before the ICL, whereas Pol eta stalled just after insertion across the ICL. The stalling of Pol eta directly past the ICL is attributed to its autoinhibitory activity, caused by elongation of the short ICL-unhooked oligonucleotide (a six-mer in our study) by Pol zeta providing a barrier to further elongation of the correct primer. No stalling by Rev1-Pol zeta directly past the ICL was observed, suggesting that the proposed function of Pol zeta as an extender DNA polymerase is also required for ICL repair

An Environmental DNA Tool For Monitoring the Status of the Critically Endangered Smalltooth Sawfish, \u3ci\u3ePristis pectinata\u3c/i\u3e, In the Western Atlantic

The Critically Endangered Smalltooth Sawfish, Pristis pectinata, was once widespread in the tropical and subtropical waters of the Atlantic Ocean, but following substantial declines over the past century, the remaining population(s) are currently confined to Florida in the U.S., and the Bahamas. Recent research and verified public encounter reports suggest that the core population in south and southwest Florida may be stabilizing and potentially expanding into formerly occupied areas of their historic range in the western Atlantic; however, the status of this species outside of core waters is not well understood. Environmental DNA (eDNA) methods provide a relatively cost effective and rapid assessment tool for monitoring species occurrence in aquatic habitats. Here, we have developed an eDNA tool: a species-specific Droplet Digital™ PCR assay targeting a 100-base pair portion of the mitochondrial NADH dehydrogenase subunit 2 gene in P. pectinata, with the ability to reliably detect as little as 0.25 pg of target DNA. The assay was validated by analyzing a water sample from an occupied nursery in southwest Florida, which was found to contain an average of 11.54 copies of target DNA/µL (SE = 0.72) in the reaction. The assay was then further tested by placing a juvenile sawfish in an ex situ tank and analyzing water samples collected at time intervals. The implementation of this eDNA tool into field surveys will provide additional, reliable data to assess species recovery and aid in prioritizing localities in which to focus new research, conservation, and education initiatives

Von Bertalanffy growth functions for smalltooth sawfish.

<p>A) Size at fractional age for smalltooth sawfish samples collected in south Florida and aged via analysis of vertebrae centra thin sections. Plotted line is a von Bertalanffy growth function (VBGF) fit to the data with the method of least squares. Parameter estimates for the function are 4.48 m for L_∞, 0.219 y⁻¹ for k, and −0.81 years for t₀. B) Comparison of VBGF function estimated in this study with those estimated by Simpfendorfer et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone.0047850-Simpfendorfer2" target="_blank">[11]</a> with length frequency data (ELEFAN seasonal; PROJMAT non-seasonal).</p

Association between Sr:Ca and estuarine nursery bottom salinity.

<p>Correspondence between Sr:Ca versus estimated date and bottom salinity versus date A) a 1.96 m female smalltooth sawfish (fish 10 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>) whose carcass was collected in the Caloosahatchee River. B) Continuous bottom salinity data in the Caloosahatchee River during the time period depicted in A. C) a 2.22 m female (fish 7) whose carcass was collected near the mouth of the Turner River in Chokoloskee Bay. D) Continuous bottom salinity data in the Turner River during the time period depicted in C. Sr:Ca data are presented from the natal mark to the edge of the vertebra section. Gray circles in each panel indicate individual measurements, red circles indicate opaque bands, and black lines indicate loess regression fits to the data.</p

Thin sections of vertebrae from three sawfish.

<p>Digital images of thin sections of smalltooth sawfish vertebrae centra from carcasses opportunistically sampled in south Florida from 2003 through 2012. Vertebrae were from A) a 1.50 m TL male (fish 8 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>), B) a 2.22 m TL female (fish 7), and C) a 4.35 m TL female (fish 13). Black circles indicate opaque zones, with the first opaque zone in each section being the natal mark following birth.</p

Trends in calcium versus phosphorus count data.

<p>Trends in Ca and P count data (cps  =  counts per second) from laser ablation-inductively coupled plasma-mass spectrometry transects across vertebral sections of three smalltooth sawfish. Data were smoothed by computing 5-spot moving averages prior to plotting lines. Red circles indicate location of opaque bands. Panel labels correspond to fish sample numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>.</p

Collection and biological information for 15 sawfish carcasses opportunistically sampled in south Florida from 2003 to 2012.

<p>Maturity: M =  mature, I =  immature. Exact locations of collection are provided on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-g001" target="_blank">Figure 1</a>.</p

Trends in Sr:Ca across vertebrae sections.

<p>Trends in Sr:Ca across smalltooth sawfish vertebrae sections analyzed with laser ablation-inductively coupled plasma-mass spectrometry. Gray circles in each panel indicate individual measurements, while black lines indicate loess regression fits to the data. Red circles indicate location of subsequent opaque bands. Panel labels correspond to fish sample numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>.</p