Perception of dimethyl sulfide (DMS) by loggerhead sea turtles: a possible mechanism for locating high-productivity oceanic regions for foraging

During their long-distance migrations, sea turtles of several species feed on jellyfish and other invertebrates that are particularly abundant in ocean regions characterized by high productivity. An ability to distinguish productive oceanic regions from other areas, and to concentrate foraging activities in locations where prey density is highest, might therefore be adaptive. The volatile compound dimethyl sulfide (DMS) accumulates in the air above productive ocean areas such as upwelling and frontal zones. In principle, DMS might therefore serve as an indicator of high prey density for turtles. To determine whether turtles perceive DMS, juvenile loggerhead sea turtles

The sensory ecology of ocean navigation

How animals guide themselves across vast expanses of open ocean, sometimes to specific geographic areas, has remained an enduring mystery of behavioral biology. In this review we briefly contrast underwater oceanic navigation with terrestrial navigation and summarize the advantages and constraints of different approaches used to analyze animal navigation in the sea. In addition, we highlight studies and techniques that have begun to unravel the sensory cues that underlie navigation in sea turtles, salmon and other ocean migrants. Environmental signals of importance include geomagnetic, chemical and hydrodynamic cues, perhaps supplemented in some cases by celestial cues or other sources of information that remain to be discovered. An interesting similarity between sea turtles and salmon is that both have been hypothesized to complete long-distance reproductive migrations using navigational systems composed of two different suites of mechanisms that function sequentially over different spatial scales. The basic organization of navigation in these two groups of animals may be functionally similar, and perhaps also representative of other long-distance ocean navigators

Multi-Modal Homing in Sea Turtles: Modeling Dual Use of Geomagnetic and Chemical Cues in Island-Finding

Sea turtles are capable of navigating across large expanses of ocean to arrive at remote islands for nesting, but how they do so has remained enigmatic. An interesting example involves green turtles (Chelonia mydas) that nest on Ascension Island, a tiny land mass located approximately 2000 km from the turtles’ foraging grounds along the coast of Brazil. Sensory cues that turtles are known to detect, and which might hypothetically be used to help locate Ascension Island, include the geomagnetic field, airborne odorants, and waterborne odorants. One possibility is that turtles use magnetic cues to arrive in the vicinity of the island, then use chemical cues to pinpoint its location. As a first step toward investigating this hypothesis, we used oceanic, atmospheric, and geomagnetic models to assess whether magnetic and chemical cues might plausibly be used by turtles to locate Ascension Island. Results suggest that waterborne and airborne odorants alone are insufficient to guide turtles from Brazil to Ascension, but might permit localization of the island once turtles arrive in its vicinity. By contrast, magnetic cues might lead turtles into the vicinity of the island, but would not typically permit its localization because the field shifts gradually over time. Simulations reveal, however, that the sequential use of magnetic and chemical cues can potentially provide a robust navigational strategy for locating Ascension Island. Specifically, one strategy that appears viable is following a magnetic isoline into the vicinity of Ascension Island until an odor plume emanating from the island is encountered, after which turtles might either: (1) initiate a search strategy; or (2) follow the plume to its island source. These findings are consistent with the hypothesis that sea turtles, and perhaps other marine animals, use a multi-modal navigational strategy for locating remote islands

n-3 PUFAs in cancer, surgery, and critical care: a systematic review on clinical effects, incorporation, and washout of oral or enteral compared with parenteral supplementation

Background: n-3 (omega-3) Fatty acids (FAs) may have beneficial effects in patients with cancer or in patients who undergo surgery or critical care. Objective: Our aim was to systematically review the effects of oral or enteral and parenteral n-3 FA supplementation on clinical outcomes and to describe the incorporation of n-3 FAs into phospholipids of plasma, blood cells, and mucosal tissue and the subsequent washout in these patients. Design: We investigated the supplementation of n-3 FAs in these patients by using a systematic literature review. Results: In cancer, the oral or enteral supplementation of n-3 FAs contributed to the maintenance of body weight and quality of life but not to survival. We did not find any studies on parenteral supplementation of n-3 FAs in cancer. In surgical oncology, we did not find any studies on enteral supplementation of n-3 FAs. However, postoperative parenteral supplementation in surgical oncology may reduce the length of a hospital stay. For general surgery, we did not find any studies on enteral supplementation of n-3 FAs, and evidence on parenteral supplementation was insufficient. In critical care, enteral supplementation of n-3 FAs had beneficial effects on clinical outcomes; evidence on parenteral supplementation in critical care was inconsistent. The incorporation of n-3 FAs in plasma and blood cells was slower with enteral supplementation (4-7 d) than with parenteral supplementation (1-3 d). The washout was 5-7 d. Conclusions: This review shows the beneficial effects of n-3 FA supplementation in cancer, surgical oncology, and critical care patients. Supplementation in these specific patient populations could be considered with the route of administration taken into account. © 2011 American Society for Nutrition