Feeding ecology of the deep-sea lanternshark Etmopterus pusillus (Elasmobranchii: Etmopteridae) in the northeast Atlantic

This study provides the first description of the feeding ecology of the smooth lanternshark Etmopterus pusillus based on stomach contents of specimens caught as bycatch in the Algarve (southern Portugal) with bottom trawling and bottom longline. The diet of E. pusillus consists mainly of fish (dry weight (% W)=87.1%; frequency of occurrence (%FO)=28.6%; number (%N)=30.3%), crustaceans (%W=7.7%; %FO=36.7%; %N=3.4%) and cephalopods (%W=4.7%; %FO=11.3%; %N=11.1%). The diet did not vary between sexes. Ontogenic changes were detected: crustaceans decreased in importance as the sharks increased in size and fish became dominant in the diet of adults. Combining two fishing methods provided broad information on the diet of E. pusillus, as bottom trawling caught smaller specimens and longlines caught larger individuals. E. pusillus feeds mainly on non-commercial species, and therefore does not compete directly with commercial fisheries. Finally, E. pusillus feeds in various parts of the water column and thus it can access a wide range of prey; however, this also means that it can be caught by both gears, making it more vulnerable in terms of conservation.

Development of an ecotoxicological protocol for the deep-sea fauna using the hydrothermal vent shrimp Rimicaris exoculata

In light of deep-sea mining industry development, particularly interested in massive-sulphide deposits enriched in metals with high commercial value, efforts are increasing to better understand potential environmental impacts to local fauna. The aim of this study was to assess the natural background levels of biomarkers in the hydrothermal vent shrimp Rimicaris exoculata and their responses to copper exposure at in situ pressure (30MPa) as well as the effects of depressurization and pressurization of the high-pressure aquarium IPOCAMP. R. exoculata were collected from the chimney walls of the hydrothermal vent site TAG (Mid Atlantic Ridge) at 3630m depth during the BICOSE cruise in 2014. Tissue metal accumulation was quantified in different tissues (gills, hepatopancreas and muscle) and a battery of biomarkers was measured: metal exposure (metallothioneins), oxidative stress (catalase, superoxide dismutase, glutathione-S-transferase and glutathione peroxidase) and oxidative damage (lipid peroxidation). Data show a higher concentration of Cu in the hepatopancreas and a slight increase in the gills after incubations (for both exposed groups). Significant induction of metallothioneins was observed in the gills of shrimps exposed to 4μM of Cu compared to the control group. Moreover, activities of enzymes were detected for the in situ group, showing a background protection against metal toxicity. Results suggest that the proposed method, including a physiologically critical step of pressurizing and depressurizing the test chamber to enable the seawater exchange during exposure to contaminants, is not affecting metal accumulation and biomarkers response and may prove a useful method to assess toxicity of contaminants in deep-sea species.

The deep-sea fish Kali macrodon: a new record for the tropical eastern Atlantic off Cape Verde

A new deep-sea fish is reported for the tropical eastern Atlantic. The rare chiasmodontid Kali macrodon was caught for the first time in Cape Verdean waters during an oceanographic survey in September 2009. This record provides the fifth occurrence for the species in the north-eastern Atlantic and represents the third specimen ever caught in tropical waters.

Co-localization of GnRH ligands and their receptors in the European sea bass, Dicentrarchus labrax

The migration of the hypophysiotropic GnRH (GnRH-I) neurons during early development is a crucial step in establishing a normally functioning reproductive system in all vertebrates. These neurons derive from progenitor cells in the olfactory placode and subsequently migrate to their final position in the ventral forebrain, where they mediate hypophysiotropic control over Lh. We use zebrafish as a model to investigate the path and the factors that mediate the migration of the GnRH-I neurons during early development. A transgenic line of zebrafish, in which GnRH- I neurons specifically express a reporter gene (GFP) has been developed in our lab. This was achieved by integrating a GnRH-I promoter/GFP reporter transgene into the zebrafish genome. The resulting transgenic line allows us to track the route of the GnRH-I neuronal migration in real time and in vivo. We have used this line to conduct time lapse imaging to ascertain the exact migrational path and the final position in the ventral forebrain of the GnRH-I neurons.

Estimating depth and explosive charge weight for an extremely shallow underwater explosion of the ROKS Cheonan sinking in the Yellow Sea

We estimated the detonation depth and net explosive weight for a very shallow underwater explosion using cutoff frequencies and spectral analysis. With detonation depth and a bubble pulse the net explosive weight for a shallow underwater explosion could simply be determined. The ray trace modeling confirms the detonation depth as a source of the hydroacoustic wave propagation in a shallow channel. We found cutoff frequencies of the reflection off the ocean bottom to be 8.5 Hz, 25 Hz, and 43 Hz while the cutoff frequency of the reflection off the free surface to be 45 Hz including 1.01 Hz for the bubble pulse, and also found the cutoff frequency of surface reflection to well fit the ray-trace modeling. We also attempted to corroborate our findings using a 3D bubble shape modeling and boundary element method. Our findings led us to the net explosive weight of the underwater explosion offshore of Baengnyeong-do for the ROKS Cheonan sinking to be approximately 136 kg TNT at a depth of about 8 m within an ocean depth of around 44 m. © 2015 Elsevier B.V.