The thermal stress response to diel vertical migration in the hyperiid amphipod Phronima sedentaria

The hyperiid amphipod Phronima sedentaria experiences a temperature change of 15 °C during diel migration in the Eastern Tropical North Pacific (ETNP) from 8–10 °C at depth to 25–27 °C at night in the surface waters. The aim of this study was to determine if the natural temperature gradient experienced by P. sedentaria results in a thermal stress response. Individuals were initially exposed to their night time temperatures (23 °C) and subsequently subjected to temperatures within and above the range they typically experience. In the Eastern Tropical North Pacific P. sedentaria tolerates its normal night-time temperature (~ 23 °C), but only for the duration of its stay there (~ 9 h). Longer exposures (24 h) result in elevated heat shock protein (hsp) expression. 29 °C results in hsp expression, increased lactate production and 50% mortality at all exposure durations. This represents an upper critical temperature. Understanding the adaptations of pelagic amphipods to their current environment will help predict the physiological impacts of global warming for amphipods and their predators

A doubled down invasion of the northeast Pacific by the Asian mud shrimp, Upogebia major and its coevolved bopyrid isopod parasite, Orthione griffenis

Dramatic declines of the native northeast Pacific mud shrimp, Upogebia pugettensis over the last three decades have occurred in response to intense infestations by the Asian bopyrid isopod parasite, Orthione griffenis, that was introduced in the 1980s. We report herein the arrival of the Asian mud shrimp, Upogebia major, in San Francisco Bay no later than 2006. Complications of identifying juvenile U. major and inefficiencies of collecting mature and readily identified specimens recovered by conventional sampling devices are likely to have delayed its identification and discovery. U. major is less vulnerable to O. griffenis and is displacing or replacing U. pugettensis in its present 200 km range to the north and south of San Francisco Bay. Upogebia major, as a coevolved alternative host, assures persistence of O. griffenis in this region even where native species extinctions occur and can potentially expand to all habitats that are presently invaded by O. griffenis (Alaska to Baja California Norte). The individual and combined O. griffenis and U. major invasions thus threaten U. pugettensis in particular and all other native Upogebia species occurring north of Mexico. Our review of Upogebia taxonomy for a key to species revealed a previously reported 1912 invasion of San Francisco Bay by Upogebia affinis that was in error; hence, the introduction of U. major is the first confirmed gebiid invasion in the world. Greater resolution of U. major natural history and timing of its invasion is needed to test whether it evaded present vector management efforts. Intervention is warranted to limit the doubled down U. major and O. griffenis invasion and to conserve U. pugettensis and other native Upogebia species from ecological or absolute extinction in the coming decades.</p

A doubled down invasion of the northeast Pacific by the Asian mud shrimp, Upogebia major and its coevolved bopyrid isopod parasite, Orthione griffenis

Dramatic declines of the native northeast Pacific mud shrimp, Upogebia pugettensis over the last three decades have occurred in response to intense infestations by the Asian bopyrid isopod parasite, Orthione griffenis, that was introduced in the 1980s. We report herein the arrival of the Asian mud shrimp, Upogebia major, in San Francisco Bay no later than 2006. Complications of identifying juvenile U. major and inefficiencies of collecting mature and readily identified specimens recovered by conventional sampling devices are likely to have delayed its identification and discovery. U. major is less vulnerable to O. griffenis and is displacing or replacing U. pugettensis in its present 200 km range to the north and south of San Francisco Bay. Upogebia major, as a coevolved alternative host, assures persistence of O. griffenis in this region even where native species extinctions occur and can potentially expand to all habitats that are presently invaded by O. griffenis (Alaska to Baja California Norte). The individual and combined O. griffenis and U. major invasions thus threaten U. pugettensis in particular and all other native Upogebia species occurring north of Mexico. Our review of Upogebia taxonomy for a key to species revealed a previously reported 1912 invasion of San Francisco Bay by Upogebia affinis that was in error; hence, the introduction of U. major is the first confirmed gebiid invasion in the world. Greater resolution of U. major natural history and timing of its invasion is needed to test whether it evaded present vector management efforts. Intervention is warranted to limit the doubled down U. major and O. griffenis invasion and to conserve U. pugettensis and other native Upogebia species from ecological or absolute extinction in the coming decades.Key words: California, vectors, Decapoda, estuary, taxonomy, conservation, extinctio

The Thermal Stress Response to Diel Vertical Migration in the Hyperiid Amphipod \u3cem\u3e Phronima sedentaria \u3c/em\u3e

The hyperiid amphipod Phronima sedentaria experiences a temperature change of 15 °C during diel migration in the Eastern Tropical North Pacific (ETNP) from 8–10 °C at depth to 25–27 °C at night in the surface waters. The aim of this study was to determine if the natural temperature gradient experienced by P. sedentaria results in a thermal stress response. Individuals were initially exposed to their night time temperatures (23 °C) and subsequently subjected to temperatures within and above the range they typically experience. In the Eastern Tropical North Pacific P. sedentaria tolerates its normal night-time temperature (~ 23 °C), but only for the duration of its stay there (~ 9 h). Longer exposures (24 h) result in elevated heat shock protein (hsp) expression. 29 °C results in hsp expression, increased lactate production and 50% mortality at all exposure durations. This represents an upper critical temperature. Understanding the adaptations of pelagic amphipods to their current environment will help predict the physiological impacts of global warming for amphipods and their predators

Ecophysiological Implications of Vertical Migration into Oxygen Minimum Zones for the Hyperiid Amphipod \u3cem\u3e Phronima sedentaria \u3c/em\u3e

Phronima sedentaria is a hyperiid amphipod that diel migrates into a pronounced oxygen minimum zone (OMZ) in the Eastern Tropical North Pacific. In this study, oxygen consumption and lactate production were measured in P. sedentaria to estimate the aerobic and anaerobic contributions to total metabolism under conditions that mimic its day- (1% oxygen, 10°C) and night-time (20% oxygen, 20°C) habitat. When exposed to hypoxia and low temperature, the total metabolism of P. sedentaria was depressed by 78% compared with normoxic conditions. The metabolic enzymes citrate synthase (CS) and lactate dehydrogenase (LDH) were also measured as indicators of aerobic and anaerobic metabolism, and compared with specimens collected from the California Current and the North Atlantic to assess potential adaptations to low oxygen. LDH activity was not significantly different between regions. Significant differences in CS activity may be due to variation in food availability. Climate change is predicted to increase surface temperatures and cause the expansion of OMZs. This will result in vertical compression of the night-time range for P. sedentaria and is likely to have the same impact on other diel migrators. Habitat compression will reduce zooplankton contribution to carbon cycling and alter oceanic ecology, including predator–prey interactions

Metabolic Response of Antarctic Pteropods (Mollusca: Gastropoda) to Food Deprivation and Regional Productivity

Pteropods are an abundant group of pelagic gastropods that, although temporally and spatially patchy in the Southern Ocean, can play an important role in food webs and biochemical cycles. We found that the metabolic rate in Limacina helicina antarctica is depressed (~23%) at lower mean chlorophyll a (chl a) concentrations in the Ross Sea. To assess the specific impact of food deprivation on these animals, we quantified aerobic respiration and ammonia (NH3) production for 2 dominant Antarctic pteropods, L. helicina antarctica and Clione limacina antarctica. Pteropods collected from sites west of Ross Island, Antarctica were held in captivity for a period of 1 to 13 d to determine their metabolic response to laboratory-induced food deprivation. L. helicina antarctica reduced oxygen consumption by ~20% after 4 d in captivity. Ammonia excretion was not significantly affected, suggesting a greater reliance on protein as a substrate for cellular respiration during starvation. The oxygen consumption rate of the gymnosome, C. limacina antarctica, was reduced by ~35% and NH3 excretion by ~55% after 4 d without prey. Our results indicate that there is a link between the large scale chl a concentrations of the Ross Sea and the baseline metabolic rate of pteropods which impacts these animals across multiple seasons

Fig 2 -

Map of the Rocky Mountain region of the United States, with collection points across the native range of Oreohelix strigosa and their corresponding institution of origin indicated: SBMNH (Santa Barbara Museum of Natural History), UCM (University of Colorado Museum of Natural History), or FMNH (Florida Museum of Natural History).</p

Fig 8 -

(A) Average microbial richness in varying levels of human impact. High human impact populations had significantly higher microbial richness lower levels. Letters indicate significant differences. Error bars indicate standard error. (B) Non-metric multidimensional scaling analysis by site habitat type (PERMANOVA: p-value 2 = 0.09).</p

Fig 4 -

Gut microbiome differences within Colorado by locality: (A) Map of all O. strigosa sampling locations in Colorado (B) Non-metric multidimensional scaling analysis based on collecting locality (PERMANOVA: p-value 2 = 0.31).</p