The Interactive Effects of the Anti-Sea Lice Pesticide Azamethiphos and Temperature on Oxidative Damage and Antioxidant Responses in the Oyster Ostrea chilensis.

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L-1, 15 µg L-1 and 100 µg L-1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.

Understanding the Symbiotic Relationship between the Sea Urchin Loxechinus albus (Molina, 1782) and the Pea Crab Pinnaxodes chilensis (H. Milne Edwards, 1837): a Potential Parasitism.

The echinoderm Loxechinus albus has a symbiotic relationship with the pinnotherid crustacean Pinnaxodes chilensis. Females of the crustacean develop in the terminal section of the sea urchin's digestive system, remaining there for life. This relationship has been suggested as commensalism. However, a potential negative impact on gonadal development and on the morphology of the sea urchin's digestive system suggest that it is instead parasitic. To study if there is a negative impact of the crustacean symbiont on the host, specimens of L. albus of all sizes were collected from a rocky shore in southern Chile. The gonadal and somatic tissues of sea urchins that were and were not harboring the pinnotherid were weighed and compared. Our results show that the presence of the pinnotherid was related to sea urchin gonads of lower biomass, decreased gonadosomatic index levels, and alterations in the morphology of the terminal portion of the host digestive system. The lower gonadal biomass suggests a negative impact on gamete production as well as a diversion of energy due to changes of the digestive system tissues and the potential consumption of algal food by the resident crustacean. These results suggest that the prolonged relationship between these two species is one of parasitism rather than one of commensalism.

Specific plasticity of the anemone Anthopleura hermaphroditica to intertidal and subtidal environmental conditions of the Quempillén estuary.

The cellular capacity of marine organisms to address rapid fluctuations in environmental conditions is decisive, especially when their bathymetric distribution encompasses intertidal and subtidal zones of estuarine systems. To understand how the bathymetric distribution determines the oxidative damage and antioxidant response of the estuarine anemone Anthopleura hermaphroditica, individuals were collected from upper intertidal and shallow subtidal zones of Quempillén River estuary (Chile), and their response analysed in a fully orthogonal, multifactorial laboratory experiment. The organisms were exposed to the effects of temperature (10°C and 30°C), salinity (10 ppt and 30 ppt) and radiation (PAR, > 400-700 nm; PAR+UV-A, > 320-700 nm; PAR+UV-A+UV-B, > 280-700 nm), and their levels of lipid peroxidation, protein carbonyl and total antioxidant capacity were determined. The results indicated that the intertidal individuals of A. hermaphroditica presented higher levels of tolerance to the stressful ranges of temperature, salinity, and radiation than individuals from the subtidal zone, which was evident from their lower levels of oxidative damage to lipids and proteins. These results were consistent with increased levels of total antioxidant capacity observed in subtidal organisms. Thus intertidal individuals could have greater plasticity to environmental variations than subtidal individuals. Future studies are needed to understand the mechanisms underlying stress adaptation in individuals from this estuarine anemone subjected to different environmental stressors during their life cycles.

The interactive effect of anti-sea lice pesticide azamethiphos and temperature on the physiological performance of the filter-feeding bivalve Ostrea chilensis: A non-target species.

The pesticide azamethiphos used by the salmon industry to treat sea lice, is applied as a bath and subsequently discharged into the sea. The effects of azamethiphos concentration (0, 15 and 100 µg L-1) on the physiology of the Chilean oyster (Ostrea chilensis) at two temperatures (12 and 15 °C) was examined. In all azamethiphos treatments, oysters kept at 15 °C had clearance rates (CR) higher than oysters kept at 12 °C. The oxygen consumption rate (OCR) increased at higher temperatures, except with 100 µg L-1 of azamethiphos, where no changes were observed. Sixty days after the exposure, survival rates of 91 and 79% (15 and 100 µg L-1, respectively), were observed compared to the controls, a situation independent of the experimental temperature. The interaction between temperature and pesticide has detrimental effects on the physiological performance and survival of O. chilensis, and these effects should also be assessed for other non-target species.

Effects of Ultraviolet Radiation on Sediment Burial Parameters and Photo-Oxidative Response of the Intertidal Anemone Anthopleura hermaphroditica.

Anthopleura hermaphroditica is an intertidal anemone that lives semi-buried in soft sediments of estuaries and releases its brooded embryos directly to the benthos, being exposed to potentially detrimental ultraviolet radiation (UVR) levels. In this study, we investigated how experimental radiation (PAR: photosynthetically active radiation; UVA: ultraviolet A radiation; and UVB: ultraviolet B radiation) influences burrowing (time, depth and speed) in adults and juveniles when they were exposed to PAR (P, 400-700 nm), PAR + UVA (PA, 315-700 nm) and PAR + UVA + UVB (PAB, 280-700 nm) experimental treatments. The role of sediment as a physical shield was also assessed by exposing anemones to these radiation treatments with and without sediment, after which lipid peroxidation, protein carbonyls and total antioxidant capacity were quantified. Our results indicate that PAB can induce a faster burial response compared to those anemones exposed only to P. PAB increased oxidative damage, especially in juveniles where oxidative damage levels were several times higher than in adults. Sediment offers protection to adults against P, PA and PAB, as significant differences in their total antioxidant capacity were observed compared to those anemones without sediment. Conversely, the presence or absence of sediment did not influence total antioxidant capacity in juveniles, which may reflect that those anemones have sufficient antioxidant defenses to minimize photooxidative damage due to their reduced tolerance to experimental radiation. Burrowing behavior is a key survival skill for juveniles after they have been released after brooding.

Early development and metabolic rate of the sea louse Caligus rogercresseyi under different scenarios of temperature and pCO2.

Anthropogenic CO2 emissions have led to ocean acidification and a rise in the temperature. The present study evaluates the effects of temperature (10, 15 and 20 °C) and pCO2 (400 and 1200 µatm) on the early development and oxygen consumption rate (OCR) of the sea louse Caligus rogercresseyi. Only temperature has an effect on the hatching and development times of nauplius I. But both factors affected the development time of nauplius II (

Reproductive biology of the encapsulating, brooding gastropod Crepipatella dilatata Lamarck (Gastropoda, Calyptraeidae).

Among calyptraeid gastropods, males become females as they get older, and egg capsules containing developing embryos are maintained beneath the mother's shell until the encapsulated embryos hatch. Crepipatella dilatata is an interesting biological model considering that is an estuarine species and thus periodically exposed to elevated environment-physiological pressures. Presently, there is not much information about the reproductive biology and brooding parameters of this gastropod. This paper describes field and laboratory observations monitoring sex changes, brooding frequencies, sizes of brooding females, egg mass characteristics, and embryonic hatching conditions. Our findings indicate that C. dilatata is a direct-developing protandric hermaphrodite, changing from male to female when individuals were between 18 and 20 mm in shell length. At our study site in Quempillén estuary, females were found to be brooding almost continuously throughout the year, having an average maximum of 85% of simultaneous brooding, with a short rest from April through June. No relationship was found between the number of capsules per egg mass and the size of the brooding female. However, capsule size and the number of embryos and nurse eggs were strongly related to female size. The offspring hatched with an average shell length > 1 mm. About 25% of the hatched capsules were found to contain both metamorphosed (juveniles) and non-metamorphosed (veliger) individuals. The sizes of the latter were < 1000 µm. The length of hatching juveniles was inversely related to the number of individuals per capsule, which seems related to differences in the availability of nurse eggs per embryo. Although fecundity per reproductive event of this species is relatively low (maximum approx. 800 offspring per egg mass) compared with those of calyptraeid species showing mixed development, the overall reproductive potential of C. dilatata seems to be high considering that females can reproduce up to 5 times per year, protecting their encapsulated embryos from physical stresses until well-developed juveniles are released into the population, avoiding a dangerous pelagic period prior to metamorphosis.

Growing Safe: Acute Size Escape from Desiccation in Juvenile Crepipatella peruviana (Mollusca: Gastropoda).

Desiccation is an important limiting factor in the intertidal zone. Generally decreasing seaward, desiccation stress can also be alleviated in wet microhabitats. Juvenile snails are generally more susceptible to desiccation than adults, and, for some species, juveniles must therefore hide in microhabitats to survive emersion. The transition from hiding in safe microhabitats to being able to survive fully exposed for the duration of low tide is not well documented. In this study, we investigated the influence of size on desiccation tolerance in juveniles of the calyptraeid gastropod Crepipatella peruviana to determine the size at which they can first survive exposure to air. Juveniles 2-13 mm long were exposed to 75% or 100% relative humidity for 0.5-6.5 hours. Juveniles smaller than 5 mm in shell length did not survive emersion at 75% relative humidity for even 0.5 hours; surprisingly, most also perished after short exposures to air at 100% relative humidity, suggesting that something other than desiccation stress may also be at play. In marked contrast, 82% of juveniles larger than 6 mm in shell length survived exposure to 75% relative humidity for the full 6.5 hours. In a field survey, no juveniles smaller than 9 mm were found on exposed rock but rather were found only in wet microhabitats. We suggest that the clearly defined size escape from desiccation may reflect a change in gill functioning or a newfound ability to retain water more effectively within the mantle cavity at low tide.

Role of the Substrate in Feeding and Growth of the Marine Suspension-Feeding Gastropods Crepidula fornicata and Crepipatella peruviana.

Unlike lamellibranch bivalves, suspension-feeding calyptraeid gastropods lack siphons and paired shell valves to regulate water inflow. This study was designed to determine if calyptraeid gastropods use the solid surface to which they attach to facilitate food particle capture. Juveniles of both Crepidula fornicata and Crepipatella peruviana were maintained with phytoplankton for 3 to 6 wk in the laboratory, either attached to solid substrate or without solid substrate. Individuals of C. fornicata and C. peruviana that were reared on solid substrate grew about five to ten times more, or two times more, respectively, than those deprived of solid substrate. Final tissue weights were also significantly greater for individuals of both species that had been reared on solid substrate. For the two species, phytoplankton clearance rates were about two to three times higher for individuals attached to solid substrate than for those without solid substrate; rates of food cord production from the gills were also significantly higher. About 50% of C. peruviana that were deprived of solid substrate died during the first 3 wk of observation, and about 60% were dead by 6 wk. In contrast, most individuals of C. peruviana that were attached to solid substrate survived for the entire 6-wk study period, and all of the C. fornicata survived whether or not they were attached to solid substrate. The solid substrate to which calyptraeid gastropods attach clearly plays an important role in their feeding biology, although the precise role remains to be explored.

Brooding strategy in fluctuating salinity environments: oxygen availability in the pallial cavity and metabolic stress in females and offspring in the Chilean oyster Ostrea chilensis.

Organisms that encounter stressful situations in nature often cope using behavioral (e.g., avoidance) or physiological tactics. In sessile mollusks, the only available behavioral option in dealing with salinity stress is to "clam up", isolating their tissues from the environment. Though effective in the short term, prolonged isolation can have detrimental physiological consequences, particularly for females brooding embryos in a mantle cavity that is isolated from the external environment. In the Quempillén estuary, the Chilean oyster, Ostrea chilensis, spent nearly one-third of its brooding season at salinities low enough to cause female isolation. When females thus isolated themselves, the dissolved oxygen in their mantle cavity fluid dropped to hypoxic levels within 10 min. In females that were brooding embryos, this depletion of oxygen was not uniform: oxygen was depleted more quickly in the palp region (where embryos accumulate) than in the inhalant region. Additionally, oxygen was reduced even more quickly in the palp region when females were brooding late-stage embryos, which consumed oxygen significantly more quickly than embryos in earlier developmental stages. Finally, O. chilensis used anaerobic metabolism to cope with the hypoxia induced by isolation, as lactate accumulated in the tissues of both females (brooding > non-brooding) and embryos (late stage > early stage). Our findings demonstrate the trade-off between an adaptive avoidance behavior (clamming up) and the potentially detrimental consequences brought on by such a behavior (hypoxia). Cycling of embryos throughout the mantle cavity by deliberate female pumping keeps them from accumulating in the area between the palps, forestalling the creation of hypoxic conditions there. In addition, the capacity for anaerobic metabolism by both females and their embryos should help them tolerate the low oxygen levels that do eventually arise when the pallial cavity is isolated from the surrounding environment during long periods of reduced ambient salinity.

Cellular changes associated with the acclimation of the intertidal sea anemone Actinia tenebrosa to ultraviolet radiation.

To assess the relative importance of long- and short-term cellular defense mechanisms in seasonally UV-R-acclimated Actinia tenebrosa (Anthozoa, Actiniidae), individuals were exposed to summer doses of PAR, UV-A, UV-B and enhanced UV-B (20%) for a period of 4 days. Mycosporine-like amino acids (MAAs) and cyclobutane pyrimidine dimer (CPD) concentrations were quantified, while oxidative damage to lipids and proteins, and the activities or levels of the antioxidant enzymes SOD, CAT, GR, GPOX and total glutathione were determined. Our results show that summer UV-R-acclimated individuals had a higher UV-R tolerance, with no significant increases in CPDs levels, than winter-acclimated sea anemones possibly due to higher MAA concentrations. Summer-acclimated individuals showed increased lipid and protein oxidation and GPOX activity only when they were exposed to UV-B at 20% above ambient UV-R levels. In contrast, winter-acclimated sea anemones showed elevated levels of oxidative damage, GPOX and SOD activities after exposure to UV-A or UV-B at ambient and elevated levels. Thus, this study indicates that long-term UV-R acclimation mechanisms such as the accumulation of MAAs could be more important than short-term increases in antioxidant defenses with respect to reducing indirect UV-R damage in intertidal sea anemones.