Assemblages of pelagic thaliaceans in oceanographic features at the tropical-temperate transition zone of a western boundary current.

Mesoscale oceanographic features influence the composition of zooplankton. Cyclonic eddies can promote upwelling and production of gelatinous zooplankton, which play critical roles in ocean biogeochemical cycling. We examined variation in assemblages of thaliaceans (salps, doliolids and pyrosomes) among mesoscale oceanographic features at the tropical-temperate boundary of the East Australian Current (EAC) in Spring 2019 and Autumn 2021. The influence of cyclonic eddies was examined in a large offshore cyclonic eddy in 2019 and a newly formed frontal eddy in 2021. Pyrosomes were most abundant in the offshore EAC jet, and salps and doliolids were most abundant in coastal features, including within eddies that were transported offshore. In 2019, Salpa fusiformis increased 4-fold over 8 days in the large cyclonic eddy, and in 2021, doliolids increased > 50-fold over 2 weeks in a chlorophyll-rich coastal eddy while abundances of other thaliaceans remained unchanged or decreased. Correlations between abundances of thaliaceans and chlorophyll-a concentrations across the 102 samples collected during both voyages revealed that doliolids occupy a wider range of chlorophyll-a concentrations than salps. Our observations indicate that doliolids thrive in productive shelf environments, salps occur in less productive shelf waters and pyrosomes are most abundant in oligotrophic waters of the south Coral Sea.

Symbiotic microalgae do not increase susceptibility of zooxanthellate medusae (Cassiopea xamachana) to herbicides.

Herbicides are among the most detected pesticides in coastal environments. Herbicides may impact non-target organisms, but invertebrates that have a symbiotic relationship with microalgae (zooxanthellae) may be particularly susceptible. How zooxanthellae influence the response of organisms to herbicides, however, remains untested. We exposed zooxanthellate and azooxanthellate Cassiopea xamachana medusae to environmentally relevant concentrations of the herbicide atrazine (0 µg L - 1, 7 µg L - 1 and 27 µg L - 1) for 20 days. We hypothesised that atrazine would have adverse effects on the size, rate of bell contractions and, respiration of medusae, but that effects would be more severe in zooxanthellate than azooxanthellate medusae. We also predicted that photosynthetic efficiency, chlorophyll a (Chla) content and zooxanthellae density would decrease in zooxanthellate medusae exposed to atrazine. Both zooxanthellate and azooxanthellate medusae shrank, yet the size-specific respiration rates were not constant during the experiment. Photosynthetic efficiency of zooxanthellate medusae significantly decreased at 7 and 27 µgL-1 atrazine, but atrazine did not affect the Chla content or zooxanthellae density. Our results showed that even though atrazine inhibited photosynthesis, zooxanthellae were not expelled from the host. We conclude that the presence of zooxanthellae did not increase the susceptibility of C. xamachana medusae to atrazine.

Chronic pesticide exposure elicits a subtle carry-over effect on the metabolome of Aurelia coerulea ephyrae.

Chemical pollutants, such as pesticides, often leach into aquatic environments and impact non-target organisms. Marine invertebrates have complex life cycles with multiple life-history stages. Exposure to pesticides during one life-history stage potentially influences subsequent stages; a process known as a carry-over effect. Here, we investigated carry-over effects on the jellyfish Aurelia coerulea. We exposed polyps to individual and combined concentrations of atrazine (2.5 µg/L) and chlorpyrifos (0.04 µg/L) for four weeks, after which they were induced to strobilate. The resultant ephyrae were then redistributed and exposed to either the same conditions as their parent-polyps or to filtered seawater to track potential carry-over effects. The percentage of deformities, ephyrae size, pulsation and respiration rates, as well as the metabolic profile of the ephyrae, were measured. We detected a subtle carry-over effect in two metabolites, acetoacetate and glycerophosphocholine, which are precursors of the neurotransmitter acetylcholine, important for energy metabolism and osmoregulation of the ephyrae. Although these carry-over effects were not reflected in the other response variables in the short-term, a persistent reduction of these two metabolites could have negative physiological consequences on A. coerulea jellyfish in the long-term. Our results highlight the importance of considering more than one life-history stage in ecotoxicology, and measuring a range of variables with different sensitivities to detect sub-lethal effects caused by anthropogenic stressors. Furthermore, since we identified few effects when using pesticides concentrations corresponding to Australian water quality guidelines, we suggest that future studies consider concentrations detected in the environment, which are higher than the water quality guidelines, to obtain a more realistic scenario by possible risk from pesticide exposure.

Polyps of the Jellyfish Aurelia aurita Are Unaffected by Chronic Exposure to a Combination of Pesticides.

Pesticides are a major contaminant in coastal waters and can cause adverse effects in marine invertebrates such as jellyfish. Most studies have investigated short-term responses of organisms to unrealistically high concentrations of pesticides; however, chronic exposure to persistent low concentrations, which are more likely to occur in the environment, are rarely analyzed. We tested the response of polyps of the moon jellyfish Aurelia aurita to environmental concentrations of the herbicide atrazine and the insecticide chlorpyrifos, individually and in combination, over 9 wk. We hypothesized that exposure to individual pesticides would reduce rates of asexual reproduction and alter polyps' metabolite profiles, and that the results would be more severe when polyps were exposed to the combined pesticides. Polyps survived and reproduced (through budding) in all treatments, and no differences among treatments were observed. Proton nuclear magnetic resonance spectroscopy revealed no difference in profiles of polar metabolites of polyps exposed to the individual or combined pesticides. Our results suggest that A. aurita polyps are unaffected by chronic exposure to atrazine and chlorpyrifos at concentrations recommended as being protective by current Australian water quality guidelines. Environ Toxicol Chem 2020;39:1685-1692. © 2020 SETAC.

Revisión de la familia Phyllophoridae (Holothuroidea: Dendrochirotida) de las aguas mexicanas / Review of the Phyllophoridae family (Holothuroidea: Dendrochirotida) in Mexican waters

Resumen La fauna de equinodermos de México está representada por 643 especies. Dentro de éstas, 113 pertenecen a la Clase Holothuroidea (pepinos de mar). Los filofóridos (Holothuroidea: Phyllophoridae) se distinguen por presentar más de 10 tentáculos y un anillo calcáreo con prolongaciones posteriores, formado por piezas pequeñas a manera de mosaico. Sus hábitos crípticos han hecho difícil su registro a través de muchos años en la historia de la taxonomía del grupo en México. El presente trabajo tiene como objetivo, informar el estado del conocimiento sobre la diversidad de pepinos de mar, de la familia Phyllophoridae, en las aguas territoriales mexicanas. Se presentan 16 especies, pertenecientes a seis géneros, habitantes tanto de las zonas someras (0 - 200 m) como de las profundas (> 200 m) del Pacífico mexicano, Golfo de California, Caribe mexicano y Golfo de México. Dentro de éstas, se incluyen tres nuevos registros para México. Se elaboró un catálogo taxonómico de identificación para cada especie, brindando información sobre la morfología externa e interna, el material examinado, el material y localidad tipo, los reportes previos para México, así como la distribución geográfica y batimétrica; además se incluyen las fotografías tomadas con Microscopía Electrónica de Barrido (MEB) de la forma y combinación de las espículas. El trabajo se complementa con una clave dicotómica para su identificación.

Abstract The fauna of the echinoderms of Mexico is represented by 643 species. Within these, 113 belong to the class Holothuroidea (sea cucumbers). The phyllophorids (Holothuroidea: Phyllophoridae) are characterized by the presence of more than 10 tentacles and a calcareous ring prolonged posteriorly with small pieces forming a mosaic-like appearance. Their cryptic habits have made them difficult to record during the many years of taxonomic studies regarding this group in Mexico. This paper aims to raise awareness of the state of knowledge on the diversity of the Phyllophoridae family in Mexican territorial waters. We present 16 species belonging to six genera, living in shallow (0 - 200 m) to deep (> 200 m) waters in the Mexican Pacific, Gulf of California, Mexican Caribbean and Gulf of Mexico. Within these, three new records are included. A taxonomic identification catalog was obtained for each species, providing information about external and internal morphology; the material was examined and recorded with information from type material and locality, all previous reports for Mexico, the geographic and bathymetric distribution as well as photographs taken with Scanning Electron Microscopy (SEM) of the shape and combination of the spicules. The work is complemented with a dichotomous key for identification. Rev. Biol. Trop. 63 (Suppl. 2): 77-85. Epub 2015 June 01.