Maternal transfer and sublethal immune system effects of brevetoxin exposure in nesting loggerhead sea turtles (Caretta caretta) from western Florida

Abstract

Blooms of Karenia brevis (also called red tides) occur almost annually in the Gulf of Mexico. The health effects of the neurotoxins (i.e., brevetoxins) produced by this toxic dinoflagellate on marine turtles are poorly understood. Florida's Gulf Coast represents an important foraging and nesting area for a number of marine turtle species. Most studies investigating brevetoxin exposure in marine turtles thus far focus on dead and/or stranded individuals and rarely examine the effects in apparently "healthy" free-ranging individuals. From May-July 2014, one year after the last red tide bloom, we collected blood from nesting loggerhead sea turtles (Caretta caretta) on Casey Key, Florida USA. These organisms show both strong nesting and foraging site fidelity. The plasma was analyzed for brevetoxin concentrations in addition to a number of health and immune-related parameters in an effort to establish sublethal effects of this toxin. Lastly, from July-September 2014, we collected unhatched eggs and liver and yolk sacs from dead-in-nest hatchlings from nests laid by the sampled females and tested these samples for brevetoxin concentrations to determine maternal transfer and effects on reproductive success. Using a competitive enzyme-linked immunosorbent assay (ELISA), all plasma samples from nesting females tested positive for brevetoxin (reported as ng brevetoxin-3[PbTx-3] equivalents [eq]/mL) exposure (2.1-26.7ng PbTx-3eq/mL). Additionally, 100% of livers (1.4-13.3ng PbTx-3eq/mL) and yolk sacs (1.7-6.6ng PbTx-3eq/mL) from dead-in-nest hatchlings and 70% of eggs (<1.0-24.4ng PbTx-3eq/mL) tested positive for brevetoxin exposure with the ELISA. We found that plasma brevetoxin concentrations determined by an ELISA in nesting females positively correlated with gamma-globulins, indicating a potential for immunomodulation as a result of brevetoxin exposure. While the sample sizes were small, we also found that plasma brevetoxin concentrations determined by an ELISA in nesting females significantly correlated with liver brevetoxin concentrations of dead-in-nest hatchlings and that brevetoxins could be related to a decreased reproductive success in this species. This study suggests that brevetoxins can still elicit negative effects on marine life long after a bloom has dissipated. These results improve our understanding of maternal transfer and sublethal effects of brevetoxin exposure in marine turtles.

Field rates of Sivanto™ (flupyradifurone) and Transform® (sulfoxaflor) increase oxidative stress and induce apoptosis in honey bees (Apis mellifera L.)

“…Oxidative stress was measured by assaying total reactive oxygen species (ROS) and total reactive nitrogen species (RNS) activities using OxiSelect™ In vitro ROS/RNS Assay Kit-Green Fluorescence (Cell Biolabs. Inc., San Diego, USA) [48,49] using the manufacturer's microplate assay protocols. Briefly, the assay principle is based on oxidizing a fluorogenic probe (2',7'-dichlorodihydrofluorescin DiOxyQ) to a fluorescent product (2',7'-dichlorodihydrofluorescein) in the presence of ROS and RNS.…”

Hematological and Biochemical Reference Intervals for Euphrates Softshell Turtle (Rafetus euphraticus)

“…The lysozyme activity in the serum of Euphrates turtles (R. euphraticus) was 9.3 ± 4.0 U min -1 (5.0-13.0 U min -1 ) (Table 3). Perrault et al (2016) found that the lysozyme activity in the serum of C. caretta was 5.2 ± 2.0 lg mL -1 .…”

“…The mean concentration of phosphorus in the serum of Euphrates turtles (R. euphraticus) was 5.36 ± 0.59 mg dL -1 (4.13-6.13 mg dL -1 ) (Table 3). According to Banaee et al (2020) and Perrault et al (2016), the phosphorus concentration in the serum of E. orbicularis was 4.32 ± 0.38 mg dL -1 , and 7.5 ± 1.4 mg dL -1 , respectively.…”

Use of intravenous lipid emulsion therapy as a novel treatment for brevetoxicosis in sea turtles

“…Across studies, plasma brevetoxin concentrations in stranded sea turtles overlapped in range (Table 2 ), with highest mean concentrations in (1) loggerheads sampled during the bloom of Aug–Oct 2006 13 , (2) Kemp’s ridleys sampled during the blooms of 2005–2006 5 , and (3) green turtles from the present study. Any additional differences in exposure, despite large-scale blooms occurring across all studies, are likely related to localized K. brevis concentrations, location of stranding, avoidance behaviors, body mass and condition, habitat preference, and/or other physiological mechanisms 5 , 8 , 16 , 17 .…”