Depuration Kinetics and Growth Dilution of Caribbean Ciguatoxin in the Omnivore Lagodon rhomboides: Implications for Trophic Transfer and Ciguatera Risk

Modeling ciguatoxin (CTX) trophic transfer in marine food webs has significant implications for the management of ciguatera poisoning, a circumtropical disease caused by human consumption of CTX-contaminated seafood. Current models associated with CP risk rely on modeling abundance/presence of CTX-producing epi-benthic dinoflagellates, e.g., Gambierdiscus spp., and are based on studies showing that toxin production is site specific and occurs in pulses driven by environmental factors. However, food web models are not yet developed and require parameterizing the CTX exposure cascade in fish which has been traditionally approached through top-down assessment of CTX loads in wild-caught fish. The primary goal of this study was to provide critical knowledge on the kinetics of C-CTX-1 bioaccumulation and depuration in the marine omnivore Lagodon rhomboides. We performed a two-phase, 17 week CTX feeding trial in L. rhomboides where fish were given either a formulated C-CTX-1 (n = 40) or control feed (n = 37) for 20 days, and then switched to a non-toxic diet for up to 14 weeks. Fish were randomly sampled through time with whole muscle, liver, and other pooled viscera dissected for toxin analysis by a sodium channel-dependent MTT-based mouse neuroblastoma (N2a) assay. The CTX levels measured in all tissues increased with time during the exposure period (days 1 to 20), but a decrease in CTX-specific toxicity with depuration time only occurred in viscera extracts. By the end of the depuration, muscle, liver, and viscera samples had mean toxin concentrations of 189%, 128%, and 42%, respectively, compared to fish sampled at the start of the depuration phase. However, a one-compartment model analysis of combined tissues showed total concentration declined to 56%, resulting in an approximate half-life of 97 d (R2 = 0.43). Further, applying growth dilution correction models to the overall concentration found that growth was a major factor reducing C-CTX concentrations, and that the body burden was largely unchanged, causing pseudo-elimination and a half-life of 143–148 days (R2 = 0.36). These data have important implications for food web CTX models and management of ciguatera poisoning in endemic regions where the frequency of environmental algal toxin pulses may be greater than the growth-corrected half-life of C-CTX in intermediate-trophic-level fish with high site fidelity.

Morphological aspects and its influence in the ecological role of two simpatric species (Lagodon rhomboides and Archosargus rhomboidalis) in Terminos lagoon, Mexico

In Terminos Lagoon the Sparidae family is represented mainly by Lagodon rhomboides (Lr) and Archosargus rhomboidalis (Ar), both reported with herbivorous habits, however, the record of carnivorous or omnivorous habits in other regions raises questions about the correct classification of the ecological role they play and the influences that morphological aspects may have (e.g. oral difference and intestine length). The objective was to analyze the trophic role (amplitude, overlap and trophic level) through the stomach content and its possible relationship with the morphological aspects of L. rhomboides. and A. rhomboidalis during three climatic seasons (30 individuals per species per season). As results, 180 individuals were analyzed with an average total length of 14.0 ± 2.5 (cm) for both species. According to the Index Importance Geometric (IGI), Thalassia testudinum was the main item of L. rhomboides (IGI= 86.3) and A. rhomboidalis (IGI= 63.3), however, the secondary items for A. rhombiodalis (Brachidontes (Hormomya) exustus= 5.70) and L. rhomboides (Parvilucina (Parvilucina) multilineata= 16.80) were different. The trophic breadth (“Bi”) indicated that L. rhomboides. and A. rhomboidalis are specialists (BiLr= 0.02 and BiAr= 0.01). At the intraspecific level, there is high similarity (ANOSIM) in the diet of both Sparids between seasons (RLr= 0.03 and RAr= 0.05), however, at the interspecific level, low similarity was observed (Rg= 0.15), which was reflected in the NT of both Sparids (NTLr= 2.22 and NTAr= 3.71). The average buccal area was smaller in L. rhomboides (12.90 mm) compared to A. rhomboidalis (13.07 mm). Based on the intestinal index, L. rhomboides is classified. (Ii= 2.20) as herbivore, and A. rhomboidalis (Ii= 0.71) as carnivore. In conclusion, both species presented differences in trophic roles, probably related to specific morphological aspects. This information is relevant to know the vulnerability of a species from simulation studies to different phenomena such as climate change. Keywords: Herbivore, Gulf of Mexico. Protected Natural Area, ANOSIM and Coastal Lagoons.

Genetic relationships and hybridization among three western Atlantic sparid species: sheepshead (Archosargus probatocephalus), sea bream (A. rhomboidalis) and pinfish (Lagodon rhomboides)

Three species of sparids in the western Atlantic, sheepshead (Archosargus probatocephalus), sea bream (A. rhomboidalis), and pinfish (Lagodon rhomboides), share overlapping habitats, spawning seasons, and spawning grounds, providing opportunities for interaction among these species. Three regions of mitochondrial DNA and three nuclear DNA intron sequences were used to construct the genetic relationships among these species. The results showed that these species are closely related, suggesting the presence of soft polytomy with sheepshead and western Atlantic sea bream as sister species. However, western Atlantic sea bream and pinfish are equally divergent from sheepshead. We used a suite of 18 microsatellite markers to verify the occurrence of hybridization, identify the parental types, and evaluate the filial-generation status of 36 individuals morphologically identified as hybrids from the Indian River Lagoon system, in Florida. The 36 putative hybrids were analyzed with a reference group of 172 western Atlantic sea bream, 232 pinfish, and 157 sheepsheads and were all genetically determined to be F1 of sheepshead and western Atlantic sea bream with very little indication or no introgressive hybridization among the 172 reference specimens of western Atlantic sea bream. Hybridization was asymmetric, with western Atlantic sea bream males crossing with sheepshead females. Hybrids were first observed in the Indian River Lagoon in 2005, after the western Atlantic sea bream had become common there, in the 1990s. Their occurrence could be associated with unique features of the Indian River Lagoon that bring the two species together or with recent anthropogenic changes in this system. Further study is needed to determine the causes and long-term effects of the recurrent production of F1 hybrids and the degree of their sterility in the Indian River Lagoon.

A comparison of blood gases, biochemistry, and hematology to ecomorphology in a health assessment of pinfish (Lagodon rhomboides)

Despite the promise of hematological parameters and blood chemistry in monitoring the health of marine fishes, baseline data is often lacking for small fishes that comprise central roles in marine food webs. This study establishes blood chemistry and hematological baseline parameters for the pinfishLagodon rhomboides, a small marine teleost that is among the most dominant members of near-shore estuarine communities of the Atlantic Ocean and Gulf of Mexico. Given their prominence, pinfishes are an ideal candidate species to use as a model for monitoring changes across a wide range of near-shore marine communities. However, pinfishes exhibit substantial morphological differences associated with a preference for feeding in primarily sea-grass or sand dominated habitats, suggesting that differences in the foraging ecology of individuals could confound health assessments. Here we collect baseline data on the blood physiology of pinfish while assessing the relationship between blood parameters and measured aspects of feeding morphology using data collected from 37 individual fish. Our findings provide new baseline health data for this important near shore fish species and find no evidence for a strong linkage between blood physiology and either sex or measured aspects of feeding morphology. Comparing our hematological and biochemical data to published results from other marine teleost species suggests that analyses of trends in blood value variation correlated with major evolutionary transitions in ecology will shed new light on the physiological changes that underlie the successful diversification of fishes.