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This paper reports on the first record of the bristlemouth Margrethia valentinae Parin, 1982 (Stomiiformes: Gonostomatidae) in the western South Atlantic, based on a single specimen (NPM 6856, standard length 52 mm) bottom trawled off Santa Catarina, Brazil, at 26°23′25′′ S, 46°01′50′′ W, 400 m depth, on December 13, 2000. Morphometric and meristic data for M. valentinae and its congener, M. obtusirostra, are given and compared to those reported in the literature. Remarks on the taxonomy of the genus Margrethia and an overview on its distribution are also provided. [ABSTRACT FROM AUTHOR]

For the first time the qualitative and quantitative lipid profile (total lipids and polar and nonpolar lipids) of the muscle tissue of six mesopelagic fish species, which are representatives of two deep-sea families widespread in the World Ocean: Stomiidae and Myctophidae were studied. It was found the species specificity of lipid accumulation for the studied fishes, which indicates differences in the mechanisms of compensatory responses. Triacylglycerols are the main form of lipid storage in the studied species. However, an accumulation of cholesterol esters and waxes (lipid characteristic of vertical migrants) has also been recorded in Borostomias antarcticus. The revealed distinctive features of Myctophidae and Stomiatidae, related to the accumulation of cholesterol and variations in the content of different phospholipid fractions, indicate that the fishes of these families use different mechanisms for regulating and maintaining the physicochemical state (permeability and fluidity) of biological membranes under conditions of change in a set of environmental factors (temperature, salinity, hydrostatic pressure, and specific photoperiod) with increase in the habitat depth. [ABSTRACT FROM AUTHOR]

Here we propose a unified terminology for the pigmentation of the lanternfish larvae (Myctophidae). The distinguished two main groups of pigmentation (external and internal) are subdivided into subunits according to their location on the fish body, in total including 77 structural units corresponding to a particular pigment cluster. The use of this nomenclature enables uniform description of pigmentation by different authors. Examples of characteristics of larval pigmentation are given using the proposed nomenclature in the forms of a formal description and summarized diagnostic tables. [ABSTRACT FROM AUTHOR]

We present the results of application of geometric morphometrics for studies of variability in populations of the members of two families of South Atlantic mesopelagic fishes, Sternoptyx diaphana (Sternoptychidae) and Ceratoscopelus warmingii (Myctophidae), in which an almost complete genetic isolation was previously discovered within the borders of hydrographic regions. A system of landmark points is developed, describing both anatomical features and configuration of luminescent organs, photophores, which allows to consider not only the influence of external physical and ecological conditions but also the existence of population-specific signaling system as a potential cause of genetic isolation. Morphological similarities are demonstrated for S. diaphana throughout the whole studied portion of the distribution area, while certain differences affecting the head shape and position of individual photophores on the body are discovered between C. warmingii populations. [ABSTRACT FROM AUTHOR]