Sensory Ecology: Giant Eyes for Giant Predators?

SummaryMathematical models suggest the enormous eyes of giant and colossal squid evolved to see the bioluminescence induced by the approach of predatory whales

RRS Discovery Cruise 243, 11th October to 22nd November 1999. Sensory Biology in the Deep-Sea: Anatomy, Physiology, and Molecular Biology

RRS Discovery cruise 243 had two principal objectives: to collect deep-sea animals for a variety of biological studies ranging from physiology to molecular biology, and to deploy benthic landers. The landers are described in Section 9.1, and the midwater and benthic trawling in Section 9.2. A complete list of the stations worked, with times, latitudes and longitudes, is given in Section 10, and a track chart for the whole cruise is shown in Section 11. Trawling was conducted first and foremost in order to provide specimens required for work associated with NERC grant GR3/B1212 “Analysis of light-induced interactions in the deep-sea: bioluminescence and its relation to vision, reflectance and fluorescence” to Professor Peter Herring, Dr Julian Partridge, and Dr Peter Shelton. Of equal importance to the success of the cruise, however, was the provision of biological samples for a range of inter-related studies. Descriptions of these studies are given in Section 9.3. Throughout the cruise a narrative (Section 6) was compiled to document, in diary format, the main scientific activities on board ship. It also records information about factors which affected work, such as the weather, and problems with equipment. The narrative is more or less a list of notes rather than proper prose, and was written during the cruise, documenting events as they were planned, as they unfolded, or after they had happened. In consequence, the tenses of verbs tend to vary in a haphazard way, for which I apologise. During the cruise, the Discovery “Rough Log” of biological specimens was maintained by Professor Peter Herring. A précis of some of the information from the Rough Log is incorporated into the narrative as a record of some of the most common, and some of the most unusual, animals that were collected. This is necessarily a biased record. Nevertheless, it may be useful to others planning or conducting similar cruises to the areas worked during D243, particularly those targeting the pelagic macrofauna. As the narrative shows, D243 was plagued by problems with the main winch. At one stage, early in the cruise, the severity of these problems made it likely that the cruise would have to be terminated prematurely, without any trawling having been undertaken. That this situation was reversed is due to the determination and hard work of the RVS technicians who were on board the ship. To them, Phil Taylor (RVS Technical Liaison Officer/TLO), Kevin Smith (RVS Mobilisation Officer/MO), Paul Duncan, and Rhys Roberts, we are much indebted: without their labours the cruise would not have succeeded in the way it ultimately did. Inevitably, the “science time” of the cruise was affected by the winch problems (see Section 8) and was contributory to a decision not to work the slope of the African continent, which had been part of the original cruise directive. This was, however, to some extent compensated by the generally stable weather conditions in the work area. Although we encountered conditions more extreme than are indicated in the ‘Africa Pilot’ for the region during October/November (anticipated average wind force 3), at no time was work stopped by poor weather. This in itself partly justifies the relatively long passage time to the work area. The main reason for working in the region, however, was the high diversity and abundance of midwater and benthic macrofauna in this region of upwelling and high surface water productivity. This, in combination with the trawling methods used, which included the use of the relatively large RMT25 net and a closing cod end on the RMT8 net, ensured that the requirements of the scientific personnel for specimens were well met. The scientific complement of the cruise consisted of 23 people, ranging from graduate students to professors, from five countries and eleven institutions. In addition, the cruise also hosted a team from the BBC Natural History Unit, who were on board to film for the “The Blue Planet”, a television series about the seas which is due for release in 2001. That this diverse group (who are listed, with their contact details, in Section 2) worked so well together, and were steadfastly cheerful firstly in the face of the winch problems, and later in the face of the relentlessness of trawling and catch processing, is very much to their credit. As Principal Scientist on D243 I am extremely grateful for their hard work and support in the run-up to the cruise, during the time at sea, and in its aftermath. In particular I would like to single out for thanks Ben Boorman and Nigel Merrett who, as scientific day and night watch leaders, ensured that the fishing and the supply of specimens continued without a break. D243 was also notable for one other event: it was Peter Herring’ last cruise before his retirement from the Southampton Oceanography Centre. Without a doubt, none of the participants on D243 would have been there but for Peter, such has been his impact on ocean going biology. Indeed, the format of D243 very much follows the successful formula developed by him on numerous previous cruises, including some to the Cape Verde region of the West African upwelling. If a cruise report can be dedicated, this is dedicated to him

The effects of surface structure mutations in <i>Arabidopsis thaliana</i> on the polarization of reflections from virus-infected leaves

<div><p>The way in which light is polarized when reflected from leaves can be affected by infection with plant viruses. This has the potential to influence viral transmission by insect vectors due to altered visual attractiveness of infected plants. The optical and topological properties of cuticular waxes and trichomes are important determinants of how light is polarized upon reflection. Changes in expression of genes involved in the formation of surface structures have also been reported following viral infection. This paper investigates the role of altered surface structures in virus-induced changes to polarization reflection from leaves. The percentage polarization of reflections from <i>Arabidopsis thaliana cer5</i>, <i>cer6</i> and <i>cer8</i> wax synthesis mutants, and the <i>gl1</i> leaf hair mutant, was compared to those from wild-type (WT) leaves. The <i>cer5</i> mutant leaves were less polarizing than WT on the adaxial and abaxial surfaces; <i>gl1</i> leaves were more polarizing than WT on the adaxial surfaces. The <i>cer6</i> and <i>cer8</i> mutations did not significantly affect polarization reflection. The impacts of <i>Turnip vein clearing virus</i> (TVCV) infection on the polarization of reflected light were significantly affected by <i>cer5</i> mutation, with the reflections from <i>cer5</i> mutants being higher than those from WT leaves, suggesting that changes in <i>CER5</i> expression following infection could influence the polarization of the reflections. There was, however, no significant effect of the <i>gl1</i> mutation on polarization following TVCV infection. The <i>cer5</i> and <i>gl1</i> mutations did not affect the changes in polarization following <i>Cucumber mosaic virus</i> (CMV) infection. The accumulation of TVCV and CMV did not differ significantly between mutant and WT leaves, suggesting that altered expression of surface structure genes does not significantly affect viral titres, raising the possibility that if such regulatory changes have any adaptive value it may possibly be through impacts on viral transmission.</p></div

A Novel Vertebrate Eye Using Both Refractive and Reflective Optics

SummarySunlight is attenuated rapidly in the ocean, resulting in little visually useful light reaching deeper than ∼1000 m in even the clearest water [1]. To maximize sensitivity to the relatively brighter downwelling sunlight, to view the silhouette of animals above them, and to increase the binocular overlap of their eyes, many mesopelagic animals have developed upward-pointing tubular eyes [2–4]. However, these sacrifice the ability to detect bioluminescent [5] and reflective objects in other directions. Thus, some mesopelagic fish with tubular eyes extend their visual fields laterally and/or ventrally by lensless ocular diverticula, which are thought to provide unfocused images, allowing only simple detection of objects, with little spatial resolution [2–4]. Here, we show that a medial mirror within the ventrally facing ocular diverticulum of the spookfish, Dolichopteryx longipes, consisting of a multilayer stack derived from a retinal tapetum, is used to reflect light onto a lateral retina. The reflective plates are not orientated parallel to the surface of the mirror. Instead, plate angles change progressively around the mirror, and computer modeling indicates that this provides a well-focused image. This is the first report of an ocular image being formed in a vertebrate eye by a mirror

Future Distribution of Suitable Habitat for Pelagic Sharks in Australia Under Climate Change Models.

Global oceans are absorbing over 90% of the heat trapped in our atmosphere due to accumulated anthropogenic greenhouse gases, resulting in increasing ocean temperatures. Such changes may influence marine ectotherms, such as sharks, as their body temperature concurrently increases toward their upper thermal limits. Sharks are high trophic level predators that play a key role in the regulation of ecosystem structure and health. Because many sharks are already threatened, it is especially important to understand the impact of climate change on these species. We used shark occurrence records collected by commercial fisheries within the Australian continental Exclusive Economic Zone (EEZ) to predict changes in future (2050-2099) relative to current (1956-2005) habitat suitability for pelagic sharks based on an ensemble of climate models and emission scenarios. Our predictive models indicate that future sea temperatures are likely to shift the location of suitable shark habitat within the Australian EEZ. On average, suitable habitat is predicted to decrease within the EEZ for requiem and increase for mackerel sharks, however, the direction and severity of change was highly influenced by the choice of climate model. Our results indicate the need to consider climate change scenarios as part of future shark management and suggest that more broad -scale studies are needed for these pelagic species

Shark conservation hindered by lack of habitat protection

Many of the world's shark populations are in decline, indicating the need for improved conservation and management. Well managed and appropriately located marine parks and marine protected areas (MPAs) have potential to enhance shark conservation by restricting fisheries and protecting suitable habitat for threatened shark populations. Here, we used shark occurrence records collected by commercial fisheries to determine suitable habitat for pelagic sharks within the Australian continental Exclusive Economic Zone (EEZ), and to quantify the amount of suitable habitat contained within existing MPAs. We developed generalised linear models using proportional occurrences of pelagic sharks for three families: Alopiidae (thresher), Carcharhinidae (requiem), and Lamnidae (mackerel) sharks. We also considered aggregated species from the Lamnidae and Carcharhinidae families ('combined sharks' in the models). Using a set of environmental predictors known to affect shark occurrence, including chlorophyll-a concentration, salinity, sea surface temperature, and turbidity, as well as geomorphological, geophysical, and sedimentary parameters, we found that models including sea surface temperature and turbidity were ranked highest in their ability to predict shark distributions. We used these results to predict geographic regions where habitat was most suitable for pelagic sharks within the Australian EEZ, and our results revealed that suitable habitat was limited in no-take zones within MPAs. For all shark groupings, suitable habitats were found mostly at locations exposed to fishing pressure, potentially increasing the vulnerability of the pelagic shark species considered. Our predictive models provide a foundation for future spatial planning and shark management, suggesting that strong fisheries management in addition to MPAs is necessary for pelagic shark conservation