Christian D. Ortega-Ortiz

Physiological responses to oxidative stress associated with pH variations in host tissue and zooxanthellae of hermatypic coral Pocillopora capitata

To study the adaptive mechanisms of host and symbiont in a decrease in pH, coral branches of Pocillopora capitata from La Boquita reef in the Bay of Santiago, México were assigned to experimental units (n = 38 per treatment) and three pH treatments were evaluated: (a) pH 8.00–8.40 (control; Treatment C1), (b) pH 7.85–7.95 (Treatment C2) and (c) pH 7.60–7.70 (Treatment C3). Corals were collected at the beginning of the experiment (T0) and at different times: T1 (5 h), T2 (12 h), T3 (48 h) and T4 (168 h). We examined malondialdehyde (MDA), antioxidant enzyme activities (SOD and CAT), antioxidant capacity and chlorophyll a (Chl a) content. The results showed a different response to the treatment between zooxanthellae and Cnidaria tissues. Initially in zooxanthellae, we observed a SOD response for the C3 treatment; however this response did not prevent lipid degradation. In Cnidaria, the C3 resulted in a greater SOD activity from the middle to the end of the experiment. The results improve our understanding of the effects of ocean acidification, the ability of coral to respond to environmental changes and the use of biochemical indicators related to the physiological condition for the recognition of coral communities affected by a decreases in pH.

Floating Marine Debris in waters of the Mexican Central Pacific

The presence of marine debris has been reported recently in several oceans basins; there is very little information available for Mexican Pacific coasts, however. This research examined the composition, possible sources, distribution, and density of Floating Marine Debris (FMD) during nine research surveys conducted during 2010-2012 in the Mexican Central Pacific (MCP). Of 1820 floating objects recorded, 80% were plastic items. Sources of FMD were determined using key objects, which indicated that the most were related to the presence of the industrial harbor and of a growing fishing industry in the study area. Densities were relatively high, ranging from 40 to 2440objects/km2; the highest densities were recorded in autumn. FMD were distributed near coastal regions, mainly in Jalisco, influenced by river outflow and surface currents. Our results seem to follow worldwide trends and highlight the need for further studies on potential ecological impacts within coastal waters of the MCP.

Melanin granules melanophages and a fully-melanized epidermis are common traits of odontocete and mysticete cetaceans

BACKGROUND The cellular mechanisms used to counteract or limit damage caused by exposure of marine vertebrates to solar ultraviolet (UV) radiation are poorly understood. Cetaceans are vulnerable because they lack protective skin appendages and are obliged to surface continuously to breathe, thus being exposed repeatedly to UV light. Although molecular mechanisms of photoprotection of cetaceans have been studied, there is limited knowledge about their epidermal structure and photoprotective effectors. OBJECTIVE To describe and compare the epidermis of mysticete and odontocete cetaceans and identify potentially photoprotective traits. ANIMALS Twenty eight free-living individuals belonging to six cetacean species were sampled in the Mexican Central Pacific and Gulf of California. Species sampled were the bottlenose dolphin, pantropical spotted dolphin, spinner dolphin, Brydes whale, fin whale and humpback whale. METHODS Histological and cytological evaluation of skin biopsy tissue collected in the field between 2014 and 2016. RESULTS All cetaceans had only three epidermal layers, lacking both the stratum granulosum and stratum lucidum. A relatively thick stratum corneum with a parakeratosis-like morphology was noted. Melanin was observed within keratinocytes in all epidermal layers, including the stratum corneum and apical melanin granules obscured the keratinocyte nucleus. Keratinocytes had a perinuclear halo. Keratinocyte diameter differed between cetacean suborders and amongst species. Melanophage clusters were common in most cetacean species. CONCLUSIONS The widespread presence of melanin and the unexpectedly high number of melanophages may constitute a unique photoprotective trait of cetaceans and could reflect primitive adaptations to their environment and to their obligate marine-bound life.

Isotopic effects of different preservation methods on scales of olive ridley sea turtles (Lepidochelys olivacea) from the Mexican Central Pacific

RATIONALE Stable isotope analysis can be used to obtain information on olive ridley sea turtles in the Mexican Central Pacific (MCP). Tissue samples such as scale, muscle, and blood are usually not analyzed immediately and are preserved in different substances such as ethanol, formalin, sodium chloride, the ideal being liquid nitrogen. Due to logistical reasons, the latter preservation method cannot always be used. The objective of the present study was to evaluate the efficiency of dimethyl sulfoxide (DMSO) as a preservation agent for later stable isotope analysis. METHODS Forty-eight paired scale samples of olive ridley were collected in MCP waters and preserved in DMSO and liquid nitrogen. We determined their δ13 C and δ15 N values using a Carlo Erba 1108 elemental analyzer coupled to a ThermoFinnigan Delta Plus XP isotope ratio mass spectrometer (precision ±0.2‰ for each stable isotope). The mean isotopic ratios of each preservation method were compared. RESULTS Significant differences were observed between the isotopic ratios of samples in the two preservatives. Samples preserved in DMSO resulted in more negative isotopic values than those in liquid nitrogen, and a correction factor was calculated. The correction factors were 2.1‰ for δ13 C values and 0.8‰ for δ15 N values. CONCLUSIONS DMSO is not equivalent to liquid nitrogen for the preservation of olive ridley scales to be used for isotopic analysis. If DMSO has to be used for logistical reasons a replicate sample should also be collected to be able to estimate a correction factor. Copyright

Insights into the Feeding Habits of False Killer Whales (Pseudorca crassidens) in the Mexican Central Pacific

The false killer whale (Pseudorca crassidens) is a widely distributed odontocete, and some aspects of its basic biology, such as feeding patterns at different time scales, are not well known. Stable isotope values (δN and δC) from the skin of ten false killer whales belonging to two distinct groups (A and B) sampled in October 2012 in the Mexican Central Pacific (MCP) were analyzed. Isotopic analyses were also run on muscle tissue from ten potential fish and squid prey species, some of which were extracted from billfish stomachs. Isotopic results for false killer whales showed mean values of 16.3‰ (Group A) and 17.0‰ (Group B) for δN, and -14.8‰ for δC (both Groups A and B). Fish and squid isotopic values showed a trophic discrimination factor in relation to those of false killer whales of +3.3 to 4.0‰ for δN and +2.9‰ for δC. This suggests that these whales probably fed within the study area on these prey species or on other species with similar isotopic values. Through photographic data, we identified individuals of Group B in the same area 2 mo later (December 2012) when they were observed feeding on fishes. One false killer whale from Group A had a fragment of billfish beak embedded in its body, indicating an interaction between these two species. Results suggest that false killer whales may share the same type of food resource with billfish species such as the sailfish, an abundant species in the MCP area.

Spatial and temporal distribution of sea turtles related to sea surface temperature and chlorophyll-a in Mexican Central Pacific waters

espanolEn este estudio se describe la distribucion espacio-temporal de tortugas marinas y su relacion con parametros oceanograficos en el Pacifico Central Mexicano (PCM) durante el 2010 (invierno, primavera y otono). Los resultados muestran variaciones en la distribucion de tortugas marinas. En invierno, la distribucion de tortugas fue homogenea en areas costeras y oceanicas; asociadas a la presencia de frentes termicos debido a la interaccion de una corriente de agua calida del sur y la intrusion de agua fria proveniente del noroeste, asi como con los limites de un giro ciclonico. En primavera, la distribucion de tortugas se concentro hacia la zona costera y parte central de la zona oceanica, donde prevalecieron los efectos de una surgencia y los limites de un giro ciclonico. El mismo patron de distribucion ocurrio al inicio de otono, mientras que las condiciones oceanograficas cambiaron para la segunda semana de muestreo, cuando ocurrio la formacion de una surgencia costera. Los eventos de apareamiento solo se registraron durante otono para la tortuga golfina (Lepidochelys olivacea), la especie dominante de la region. Se concluye que en otono el patron de distribucion de tortugas marinas fue hacia la zona costera del PCM, y se relaciono con actividades de reproduccion; mientras que en invierno y primavera este patron tendio a la region central/oceanica vinculado potencialmente con actividades de forrajeo. EnglishIn this study we describe the spatial and temporal distribution of sea turtles and their association with oceanographic parameters in waters of the Mexican Central Pacific (MCP) during 2010 (winter, spring and autumn). Our results showed variations in sea turtle distribution through the sampling year. Sea turtle distribution was homogeneous in coastal and oceanic areas during winter; there was an association with thermal fronts generated by a current of cold water flowing from the northwest and a warm current coming from the south, as well as with the boundaries of a cyclonic gyre. Sea turtles were distributed in the coastal zone and the central part of the oceanic zone in spring, where the effects of a cyclonic gyre and coastal upwelling prevailed. The same distribution trend was recorded at the beginning of autumn, whereas oceanographic characteristics changed during the second sampling week, when upwelling occurred. Mating events were only recorded in autumn for olive ridley sea turtles (Lepidochelys olivacea), the dominant species in the region. It was concluded that sea turtles were distributed in the coastal zone of MCP waters in autumn due to reproductive activities, whereas in winter and spring sea turtles were distributed towards the central/oceanic region, potentially related to foraging activities.