Involvement of contractile elements in control of bioluminescence in Northern krill, Meganyctiphanes norvegica (M. Sars)

Effects of partial replacement of unwashed Antarctic krill surimi by Litopenaeus vannamei surimi on the heat-induced gelling and three-dimensional-printing properties

There is an emerging consumption of the Antarctic krill (AK) muscle-based food due to its excellent nutritional value and enormous biomass storage capacity. However, the coarse texture of the muscle and the weak gelling properties of AK protein impede its expansion in surimi-based products. This investigation successfully prepared heat-induced gels of AK surimi with desirable textural properties by including Litopenaeus vannamei in varying proportions. Higher concentrations of L. vannamei resulted in improved three-dimensional printability, greater water-holding capacity (WHC), larger viscoelastic modulus, and a well-formed microstructural matrix of AK surimi, due to an increased level of myofibrillar protein. Compared with AK, L. vannamei muscle had double the salt-soluble protein content, which was corroborated by increased intensity of bands of actin, paramyosin, tropomyosin, and myosin light chains on reducing SDS-PAGE. DSC results indicated that a high ratio of L. vannamei elevated the denaturation temperature and enthalpy of myosin, sarcoplasmic protein, and actin, suggesting a high degree of cross-linking. It was also found that when hydroxypropyl cassava starch was added at 0.5% (w/w), WHC and gel strength were further improved with a more compact gel matrix. The successful preparation of unwashed mixed surimi with AK meat fully exploited in this study provides an option for AK surimi-based product industrialization.

Physiological control of bioluminescence in a deep-sea planktonic worm, Tomopteris helgolandica Greeff, 1879

Tomopteris helgolandica Greeff 1879 (Tomopteridae) is a transparent holoplanktonic polychaete that can emit a bright light. In this work, we investigated the emission pattern and control of this deep-sea worm's luminescence. Potassium chloride depolarisation applied on anesthetised specimens triggered a maximal yellow light emission from specific parapodial sites, suggesting that a nervous control pathway was involved. A pharmacological screening revealed a sensitivity to carbachol, which was confirmed by a dose-light response associated with a change in the light emission pattern, where physiological carbachol concentrations induced flashes and higher concentrations induced glows. The light response induced by its hydrolysable agonist, acetylcholine, was significantly weaker but was facilitated by eserine pretreatment. In addition, a specific inhibitory effect of tubocurarine was observed on carbachol-induced emission. Lastly, KCl- and carbachol-induced light responses were significantly reduced when preparations were pre-incubated in Ca2+-free artificial sea water or in different calcium channel blockers (verapamil, diltiazem) and calmodulin inhibitor (trifluoperazine) solutions. All of these results strongly suggest that T. helgolandica produces its light flashes via activating nicotinic cholinergic receptors and a calcium-dependent intracellular mechanism involving L-type calcium channels.

Bioluminescence in the sea

Bioluminescence spans all oceanic dimensions and has evolved many times--from bacteria to fish--to powerfully influence behavioral and ecosystem dynamics. New methods and technology have brought great advances in understanding of the molecular basis of bioluminescence, its physiological control, and its significance in marine communities. Novel tools derived from understanding the chemistry of natural light-producing molecules have led to countless valuable applications, culminating recently in a related Nobel Prize. Marine organisms utilize bioluminescence for vital functions ranging from defense to reproduction. To understand these interactions and the distributions of luminous organisms, new instruments and platforms allow observations on individual to oceanographic scales. This review explores recent advances, including the chemical and molecular, phylogenetic and functional, community and oceanographic aspects of bioluminescence.

An introduction to the biology of Northern krill (Meganyctiphanes norvegica Sars)

This chapter provides a background to research on Northern krill biology, starting with a description of its morphology and identifying features, and the historical path to its eventual position as a single-species genus. There is a lack of any euphausiid fossil material, so phylogenetic analysis has relied on comparative morphology and ontogeny and, more recently, genetic methods. Although details differ, the consensus of these approaches is that Meganyctiphanes is most closely related to the genus Thysanoessa. The light organs (or photophores) are well developed in Northern krill and the control of luminescence in these organs is described. A consideration of the distribution of the species shows that it principally occupies shelf and slope waters of both the western and eastern coasts of the North Atlantic, with a southern limit at the boundary with sub-tropical waters (plus parts of the Mediterranean) and a northern limit at the boundary with Arctic water masses. Recent evidence of a northward expansion of these distributional limits is considered further. There have been a variety of techniques used to sample and survey Northern krill populations for a variety of purposes, which this chapter collates and assesses in terms of their effectiveness. Northern krill play an important ecological role, both as a contributor to the carbon pump through the transport of faecal material to the deeper layers, and as a key prey item for groundfish, squid, baleen whales, and seabirds. The commercial exploitation of Northern krill has been slow to emerge since its potential was considered by Mauchline [Mauchline, J (1980). The biology of mysids and euphausiids. Adv. Mar. Biol. 18, 1-681]. However, new uses for products derived from krill are currently being found, which may lead to a new wave of exploitation.