Environ Biol Fish (2012) 95:185–189 DOI 10.1007/s10641-012-9981-9 BOOK CRITIQUE Fish on glass The science and art of histology Fish histology: female reproductive systems, 2007 McMillan, D.B Springer, 598 pp., $269.00 Kathleen S Cole Received: 27 October 2011 / Accepted: 16 January 2012 / Published online: 14 February 2012 # Springer Science+Business Media B.V 2012 Histology, the study of minute structure of tissues and organs of plants and animals in relation to their function, is fundamental to our modern understanding of organismal biology The expansion of histology as a scientific discipline dates from the formulation of cellular theory by Matthias Jakob Schleiden (1838) and Theodor Schwann (1839) who independently developed the concept of the cell as the basic unit of life This idea was subsequently expanded by Rudolph Virchow (1858) to the concept that all cells arise from pre-existing cells Concurrently, an improved optical compound microscope developed by Carl Zeiss became commercially available and both the ongoing classification of tissues and the fledgling science of histopathology took a step forward (Fournier et al 2008) By the late 1800s, histology was a well-established discipline that served as the main driver for the development of new biological concepts As a reflection of the impact of this field on Biology, two histologists, Camillo Golgi and Santiago Ramon y Cajal, were awarded the 1904 Nobel Prize in Physiology or Medicine for their study of the neural structure of the brain K S Cole (*) Department of Zoology, University of Hawaii at Mānoa, 2538 McCarthy Mall, Edmondson 152, Honolulu, HI 96822, USA e-mail: colek@hawaii.edu It is against this historical background that, with great dismay, I must acknowledge a sad fact: the study and practice of comparative histology is a dying discipline The technique is taught with less and less frequency in undergraduate Biology curricula in universities With luck, an intrepid student may trek over to the campus medical school and learn how the human body is constructed from a micro-anatomical perspective Unfortunately, she or he is unlikely to learn much about comparative organismal histology or of the composition and architecture of non-human tissues and organs Nor will the student be able to develop the insights that a broader treatment of the topic provides in order to recognize evolutionary patterns and innovations at the micro-anatomical level The fact that traditional histology is becoming an orphan discipline, reduced to a limited presence in medically-oriented fields and pathology laboratories, represents a critical loss to our knowledge base in the biological sciences Within this context, the publication of Fish Histology, Female Reproductive Systems by Donald B McMillan is a much needed and welcome addition to the library of histology resources There are few other books currently available that focus on fish histology, much less histology of the female reproductive system The seminal atlas by Takashima and Takashi (1995) and a book by Rocha (2009), both of which cover the histology of fish systems in a broad sense, are out of print A volume by Genten et al (2009), Atlas of Fish Histology that is currently available provides limited coverage of all anatomical systems 186 in a volume less than half the length of the MacMillan book Sharks, Skates and Rays by Hamlett (1999) includes a chapter on the female reproductive system which is well-illustrated and detailed, but offers relatively little histological information Consequently, the book reviewed here provides a new and critically important addition to fish research I was also delighted at the publication of this book for a more personal reason When I was a wide-eyed undergraduate, I was privileged to take a year-long course in Histology with Don McMillan Histology was certainly not my primary interest (at that time I was far more interested in animal behavior) And, I certainly had no inkling of how important histology would be for my future research I remember spending hours looking through a microscope, completely mesmerized by a world of vibrantly colored cells tinted by various tissue stains and arranged in astonishing patterns, a universe onto themselves I also remember the first time I saw (and recognized!) a simple duct nestled within a crowded field of tissues, with its neatly arranged cuboidal cells organized like a ring of tightly packed Chiclets Pattern existed! As I became more experienced in reading slides, I learned to recognize arrangement patterns of cells as functionally distinct units that collectively built tissues and organ systems And by their morphologies, I could infer cellular and tissue function Identifying cell and tissue functions by their arrangements and respective morphologies, I was able to use histology as a diagnostic tool to identify reproductive state within hermaphroditic (and gonochore) fishes Over time, my sense of wonder for the microanatomical world has not diminished In class and laboratory, Don was an ideal mentor: patient, insightful and deeply knowledgeable He would explain what we were looking at on our slides with such highly informed enthusiasm that you wanted to dive right back into that micro-sized world that appeared to float on a glass slide I didn’t fully appreciate his extraordinary breadth of knowledge until many years later when I found myself in the unexpected position of teaching comparative vertebrate histology I still had my detailed notes from his class, and my old copy of Ham’s Histology (1969), which proved invaluable It was while developing lectures and laboratories for the course that I realized how really lucky I had been to have received my own instruction from Don and, through his mentorship, to fall in love with the discipline Environ Biol Fish (2012) 95:185–189 The volume that Don McMillan has crafted reflects both his vast knowledge and his attention to detail The topic is female reproductive systems of fishes This represents a tremendous undertaking, given the wide diversity of fish taxa (62 orders, 515 families and an estimated 32,500 species [Nelson 2006]) and the extraordinary variation of their reproductive modes Any attempt at a comprehensive review of fish reproductive modes faces almost overwhelming challenges In this, Don McMillan’s book succeeds The book is subdivided into six chapters that comprise 560 pages (the book totals 598 pages, including references and the index) and include 509 figures, the majority half or full page size The images are the dominant component and central strength of this volume They include histological sections of tissues which provide cellular and tissue-level detail, SEMs which detail cell surface features and TEMs that bring cell components into the visual realm In addition, a good number of figures are schematic representations that provide clear and simplified constructs to help the reader better understand the photographed images In each chapter, the text portion leads, followed by the chapter figures The text serves as a research review of the chapter topic, but is broken down into easily digestible, well-written subsections My only disappointment is that much of the review information presented in the text is somewhat dated Only twenty-five percent of the references cited are from the last two decades and of these, less than 2% are from 2000 on, comprising two papers published in 2001 Some of this can be ascribed to the time lag between completion of a manuscript and final publication (late 2007) and the even later date of this review However, the paucity of coverage of post2000 work limits the usefulness of this volume as a current-state-of-knowledge resource The real value of this book is in its atlas-style, fully captioned, imagery Do you want to visualize how an oocyte develops, and how this development may vary from species to species? On pages 93–130 you will be transported through a wide range of fish taxa, each carefully detailing in figure(s) and legend the process of oogenesis across a broad reach of systematic diversity Do you want to understand how ovarian follicles form? That is covered in exquisite illustrative detail between pages 131 and 208 Equally stunning visual treatments are provided for ovulation and for fertilization events In the last chapter, on viviparity, illustrations Environ Biol Fish (2012) 95:185–189 show how embryos are frequently associated with specialized portions of the maternal reproductive system I found this chapter among the most engaging, probably because it relates most closely to the organismal level The first chapter, ‘Female genital systems of fish’, provides a basic overview of female reproductive systems and the early development of the system components It includes a brief outline of the early formation of the gonadal primordium and the subsequent arrangement of primordial germ cells (PGCs), somatic cells and the germinal epithelium This is followed by a comparison of reproductive morphology, mostly of the ovary, drawing on studies spanning a wide variety of fish species Most frequently discussed include the Japanese ricefish or Medaka (Oryzias latipes), Atlantic hagfish (Myxine glutinosa), Sea lamprey (Petromyzon marinus), Gulf pipefish (Syngnathus scovelli), Zebrafish (Danio rerio, referred to in the text by its older name Brachydanio rerio]), Green swordtail (Xiphophorus hellerii), Mummichog (Fundulus heteroclitus) and Goldfish (Carassius auratus) Parts of the text could be clearer For example, information on different fish species is often drawn from various cited studies but the species themselves are not identified Presumably the reader is expected to tease these out by checking the references or, when included, figure legends However, the absence of such information within the text itself makes it difficult to fully appreciate where information reflects common patterns across taxa versus where it corroborates existing information on a single species Much of the material in this chapter will provide a good review for the non-specialist Some statements are outdated or incorrect, and this will likely be noticeable to readers who are well-informed in those areas For example, there is some doubt expressed by the author as to whether the germinal epithelium is the intra-gonadal source of PGCs and oogonia in all fishes (pg.2) This argument has been settled: oogonia restricted to the germinal epithelium is the general condition of teleosts (see Grier and Taylor 1998; Grier 2000), with the notable exception of syngnathids (seahorses and pipefishes) in which PGCs and their next developmental stage, oogonia, are confined to a germinal ridge within the ovary (Grier 2000) On page 3, PGCs are stated to “arise early in development within embryonic endoderm or mesoderm” and that their origins are “extragonadal and, in some fishes, may be extraembryonic” In fact, PGCs have been shown to arise as a germ cell line, the precursors of which are 187 identifiable as early as the 32-cell stage in Zebrafish, Danio rerio (Yoon et al 1997; Braat et al 1999; Knaut et al 2000) and even earlier, at the 16-cell stage in two species of goby (Saito et al 2004; Miyake et al 2006), well before the formation of endoderm or mesoderm The germ cell line, which is initiated at the onset of symmetric segregation of germ plasm-bearing cells, also occurs early in development, anywhere from the early blastula to late gastrula stage depending on the species, and, therefore, before completion of germ layer formation (see Knaut et al 2000; Shinomiya et al 2000; Otani et al 2002; Fujimoto et al 2006) Regarding where germ cells originate, in all fish taxa so far studied the germ cell line originates outside the embryo proper (Richards and Thompson 1921; Hamaguchi 1982; 1983; Weidinger et al 1999; Shinomiya et al 2000; Kurokawa et al 2006) Only after the formation of the coelomic cavity and dorsal and ventral mesenteries the PGCs migrate into the embryo, either along the splanchnic or somatic mesoderm, to the site of the future gonadal primordium (Moore 1937; Gamo 1961; Weidinger et al 2002; Saito et al 2002; 2004; Reichman-Fried et al 2004; Kurokawa et al 2006), so in all known cases the origin of PGCs is extraembryonic The section of the text on oviduct origins (pg.5), which is described as being formed by the caudal extension of a peritoneal sheath surrounding the ovary, presents a highly simplified scenario Across teleosts, the oviduct can have different, and frequently more complex, origins Depending on the species, oviduct formation may result from either somatic cell proliferation from the posterior gonad, proliferation of mesenchymal cells surrounding the urethra, cavitation of a solid cord of posteriorly located peritoneal cells, posterior tubular extensions of gonadal serosa, peritoneal folds, dorsal mesentery folds, or by some combination of the above (Essenberg 1923; Anteunis 1959; Takahashi and Iwasaki 1973; Shimizu and Takahashi 1980; Suzuki and Shibata 2004) However, as stated at the outset, this chapter offers a good review of female fish genital systems for the non-specialist reader The second chapter is entitled ‘Ovarian follicles.’ For the uninitiated, the follicle is a compound structure made up of a single oocyte and surrounding layers of somatic cells which become organized through a series of induction events, following the formation of the gonadal primordium This section of the book provides detailed descriptions of the events that take place during the development of the maturing oogonium 188 through various oocyte stages, and of ovarian follicle development The information in this chapter is both detailed and comprehensive, with the figures providing a perfect complement to the text This and the following chapters also illuminate and seek to rectify a persistent and problematic issue in histology, that of confusing terminology Descriptions of reproductive histology are permeated with a bewildering array of terms that are often poorly, or incompletely, defined To address this issue, a series of workshops have been chaired by Nancy J Brown-Peterson of the Gulf Coast Research Laboratory in an effort to streamline and standardize terminology associated with reproductive morphology and processes The establishment of these workshops attests to the need for a new and more critical approach to reproductive terminology associated with fishes and so far has resulted in a timely publication on this topic (Brown-Peterson et al 2011) In this light, this and the succeeding chapters are valuable not only for the detailed information they provide, but also for the inclusion of alternate terminology, which serves as an invaluable guide to the present terminological maze The next two chapters (3 and 4) cover ovulation and fertilization-associated events and are rich in descriptive detail and imagery Early in Chapter (entitled ‘Ovulation’) the processes involved in the exit of the ovum from the ovary are discussed over a broad range of fish taxa Most of the text is devoted to the fate of the ovarian follicle post-ovulation (or pre-ovulation in the case of atretic follicles) and to changes associated with the chorion or zona pellucida just prior to, and following, ovulation For this, the author draws on primary literature representing a wide range of fish taxa to construct a step by step scenario of ovulation-associated events This information nicely sets up Chapter (‘Events associated with fertilization’) for describing the series of events that are triggered by the penetration of the ovum wall by a spermatozoon Each step from first contact through to the formation of the fertilization membrane is discussed using information available from a variety of fish taxa Together, these two chapters should be required reading for every upperclass student majoring in Biology or Zoology The information provided is succinct, clearly written, and provides good introductory overviews of their respective topics The fifth chapter (‘Oviducts and oviparity’) is relatively short Little is known regarding the ontogeny of teleost oviducts (see Wake 1985, 1986 for an early treatment and Cole 2010 for a review) and this section Environ Biol Fish (2012) 95:185–189 of the chapter is understandably short Much of the chapter is devoted to the chondrichthyan reproductive system, for which much more information is available, and to differences associated with reproductive mode (oviparity versus viviparity) The sixth and final chapter, ‘Viviparity’, deals with fish that have internal fertilization followed by partial or complete embryonic development within the maternal body Associated with the retention of embryo(s) within the maternal body are a variety of modifications to the reproductive system, some of which are extensive, including features that facilitate the storage of sperm for delayed insemination, the accommodation of one or more embryos in different stages of development (superfetation), and the provision of a supportive environment for the developing young The development and final morphology of these features can differ substantially across viviparous fish taxa The chapter is divided into three sections One section is devoted to viviparity among elasmobranchs consisting of the sharks, skates and rays (note that viviparity is unknown among the other branch of chondrichthyans, the holocephalans, or rabbitfishes) Another section reviews viviparity in teleosts and provides excellent coverage, both in text and images, of the considerable diversity of morphological adaptations found within this equally large and diverse group A brief third section is devoted to Latimeria chalumnae, one of the two species of living the coelacanth Not surprisingly, this section is quite short, reflecting the paucity of information on coelacanth reproductive morphology As a whole, this chapter will be of interest not only to those with a histological background, but also to a broader audience within ichthyological, morphological and vertebrate biology disciplines Here the interested reader will find a solid micro-anatomical overview of the extraordinary diversity of viviparous specializations and adaptations found among fishes In summary, this book fills a critical need for the coverage of female fish reproduction from a histological perspective This is a topic that has broad applications but for which information has been relatively limited, and somewhat scattered throughout the primary literature As mentioned earlier, one notable drawback of this volume is that it provides little information on recent research developments in the field Despite that, Fish Histology, Female Reproductive Systems provides an excellent overview of the topic, uses a broad comparative approach, and offers superb imagery that will make it a classic and influential atlas-style reference Environ Biol Fish (2012) 95:185–189 Acknowledgements I am grateful to L.R Parenti for insightful comments on an earlier version of this review References Anteunis A (1959) Recherches sur la structure et la développement de l’ovaire et l’oviducte chez Lebistes reticulatus (Téléostéen) Arch Biol (Liege) 70:783–809 Braat AK, Speksnijder JE, Zivkovic D (1999) Germ line development in fishes Int J Dev Biol 43:745–760 Brown-Peterson NJ, Wyanski DM, Saborido-Rey F, Macewicz BJ, Lowerre-Barbieri SK (2011) A standardized terminology for describing reproductive development in fishes Mar Coastal Fish Dyn Mgmt Ecosys Sci 3:52–70 Cole KS (2010) Gonad development in hermaphroditic gobies In: Cole KS (ed) Reproduction and sexuality in marine fishes University of California Press, Berkeley, pp 165–202 Essenberg JM (1923) Sex- differentiation in the viviparous teleost Xiphophorus helleri Heckel Biol Bull 45:46–97 Fournier I, Wisztorski M, Salzet M (2008) Tissue imaging using MALDI-MS: a new frontier of histopathology proteomics Expert Rev Proteonomics 5:413–424 Fujimoto T, Kataoka T, Sakao S, Saito T, Yamaha E, Arai K (2006) Developmental stages and germ cell lineage of the loach (Misgurnus anguillicaudatus) Zool Sci 23:977–989 Gamo H (1961) On the origin of germ cells and the formation of gonad primordia in the medaka, Oryzias latipes Jpn J Zool 13:101–115 Genten F, Terwinghe E, Danguy A (2009) Atlas of fish histology Science Publishers, Enfield Grier H (2000) Ovarian germinal epithelium and folliculogenesis in the common snook, Centropomus undecimalis (Teleostei: Centropomidae) J Morph 243:265–281 Grier HJ, Taylor RG (1998) Testicular maturation and regression in the common snook J Fish Biol 53:521–542 Ham AW (1969) Histology J.B Lippincott Co, Philadelphia Hamaguchi S (1982) A light- and electron-microscopic study on the migration of primordial germ cells in the teleost, Oryzias latipes Cell Tissue Res 227:139–151 Hamaguchi S (1983) Asymmetrical development of the gonads in the embryos and fry of the fish, Oryzias celebensis Dev Growth Differ 25:553–561 Hamlett WC (1999) Sharks, skates and rays, the biology of elasmobranch fishes The Johns Hopkins University Press Knaut H, Pelegri F, Bohmann K, Schwarz H, Nusslein-Volhard C (2000) Zebrafish vasa RNA but not its protein is a component of the germ plasm and segregates asymmetrically before germline specification J Cell Biol 149:875–888 Kurokawa H, Aoki Y, Nakamura S, Ebe Y, Kobayashi D, Tanaka M (2006) Time-lapse analysis reveals different modes of primordial germ cell migration in the medaka Oryzias latipes Dev Growth Differ 48:209–221 Miyake A, Saito T, Kashiwagi T, Ando D, Yamamoto A, Suzuki T, Nakatsuji N, Nakatsuji T (2006) Cloning and pattern of expression of the shiro-au vasa gene during embryogenesis and its roles in PGC development Int J Dev Biol 50:619–625 Moore GA (1937) The germ cells of the trout (Salmo irideus Gibbons) Trans Ame Microsc Soc 56:105–112 189 Reichman-Fried M, Minina S, Raz E (2004) Autonomous modes of behavior in primordial germ cell migration Dev Cell 6:589–596 Richards A, Thompson JT (1921) The migration of the primary sex-cells of Fundulus heteroclitus Biol Bull 40:325–348 Nelson JS (2006) Fishes of the world Wiley, Hoboken, New Jersey Otani S, Maegawa S, Inoue K, Arai K, Yamaha E (2002) The germ cell lineage identified by vas- mRNA during the embryogenesis in goldfish Zool Sci 19:519–526 Rocha MJ (2009) Fish histology Science Publishers Inc Saito T, Otani S, Fujimoto T, Suzuki T, Nakatsuji T, Arai K, Yamaha E (2004) The germ line lineage in ukigori, Gymnogobius species (Teleostei: Gobiidae) during embryonic development Int J Dev Biol 48:1079 Saito T, Otani S, Nagai T, Nakatsuji T, Arai K, Yamaha E (2002) Germ cell lineage from a single blastomere at 8-cell stage in shiro-uo (ice goby) Zool Sci 19:1027–1032 Schleiden MJ (1838) Beiträge zur Phytogenesis Archiv für Anatomie, Physiologie und Wissenschaftliche Medici 13:137–176 Schwann T (1839) Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstum der Thiere und Pflanzen Sander’schen Buchhandlung, Berlin Shimizu M, Takahashi H (1980) Process of sex differentiation of the gonad and gonoduct of the three- spined stickleback, Gasterosteus aculeatus L Bull Fac Fish Hokkaido Univ 31:137–148 Shinomiya A, Tanaka M, Kobayashi T, Nagahama Y, Hamaguchi S (2000) The vasa- like gene, olvas, identifies the migration path of primordial germ cells during embryonic body formation stage in the medaka, Oryzias latipes Dev Growth Differ 42:317–326 Suzuki A, Shibata N (2004) Developmental process of genital ducts in the medaka, Oryzias latipes Zool Sci 221:397–406 Takahashi H, Iwasaki Y (1973) The occurrence of histochemical activity of 3- betahydroxysteroid dehydrogenase in the developing testes of Poecilia reticulata Dev Growth Differ 15:241–253 Takashima F, Takashi H (1995) An atlas of fish histology, normal and pathological features Gustav Fischer Verlag, New York Virchow R (1858) Die Cellularpathologie in ihrer Begründung auf physiologische und pathologische Gewebelehre August Hirschwald, Berlin Weidinger G, Wolke U, Köprunner M, Raz E (1999) Identification of tissues and patterning events required for distinct steps in early migration of zebrafish primordial germ cells Dev 126:5295–5307 Wake MH (1985) Oviduct structure and function in nonmammalian vertebrates Fortschr Zool 30:427–435 Wake MH (1986) Urogenital morphology of dipnoans, with comparisons to other fishes and to amphibians J M Suppl 1:199–216 Weidinger G, Wolke U, Köprunne M, Thisse C, Thisse C, Raz E (2002) Regulation of zebrafish primordial germ cell migration by attraction towards an intermediate target Dev 129:25–36 Yoon C, Kawakami K, Hopkins N (1997) Zebrafish vasa homologue RNA is localized to the cleavage planes of 2- and 4- cell- stage embryos and is expressed in the primordial germ cells Dev 12:3157–3166 Environ Biol Fish (2012) 95:191–194 DOI 10.1007/s10641-012-9979-3 Using energy dispersive x-ray fluorescence microchemistry to infer migratory life history of Atlantic sturgeon Matthew T Balazik & Stephen P McIninch & Greg C Garman & Michael L Fine & Clint B Smith Received: May 2011 / Accepted: January 2012 / Published online: 26 January 2012 # Springer Science+Business Media B.V 2012 Abstract Atlantic sturgeon migrate between ocean and freshwater habitats to spawn, and juveniles spend several years in fresh/brackish water before returning to the ocean Because strontium/calcium (Sr/Ca) ratios are diagnostic for freshwater and marine environments, we examined the utility of energy-dispersive x-ray fluorescence (EDXRF) to quantify Sr/Ca ratios of Atlantic sturgeon pectoral fin spines Atlantic sturgeon spines from wild adults and experimental juveniles were analyzed along a linear transect from the primordium to the outermost point To verify the technique hatchery juvenile Atlantic sturgeon were held in experimental tanks at [...]... observed in the gut of 65–75 mm SL fishes, beginning with the anterior part of the stomach The occurrence of a black submucosa in the walls of the alimentary tract of several species of the genus Saurida, not observed in Synodus species and Trachinocephalus, is remarkable A dark appearance of the alimentary tract in fishes has mostly been described from the dark serosa, a part of the melanised dark peritoneum... recognized that environmental stress induces the production of alpha—MSH (melanin stimulating hormone) (Thody 1999) Is melanin deposition in the submucosa of fishes, as described for some of the nocturnal or deep-water species, a response to stress, for example to the low levels of illumination or darkness during their activity? Or is melanin a form of ironstorage that enables the recycling of this element,... elemental fingerprint of YOY fish and the natal region of age ≥1 fish or the age-1 region of age-2 fish All statistical analysis was done in R (R Development Core Team 2009) Detecting significant differences in scores indicates that the multivariate centre of gravity of the sample of fish from one or more locations or times differs significantly in spatial position from the centers of gravity of scores from... described above about the movement of fish after their first winter Results Fig 3 Hypothetical results for the locations of the mean discriminant scores of the elemental fingerprints of YOY (solid lines) and the natal region of age-1 fish (dashed lines) from two sites, and lines represent the 95% confidence interval of the multivariate centre of gravity from a sample of fish from one location or time... to the Gulf of Mexico (Bestgen and Platania 1991), but was listed as endangered by the U.S Fish and Wildlife Service in 1994 (USFWS 1994) Officially, H amarus only occurs in the Middle Rio Grande of New Mexico, a Environ Biol Fish (2012) 95:201–212 280 km (174 mi) stretch of river that runs from Cochiti Dam to the headwaters of Elephant Butte Reservoir or approximately seven percent (7%) of its former... representation of the data for physical and chemical characteristics of habitats occupied by fish across temporal and spatial scales The CCA is a multivariate analysis technique that directly relates community composition to known variation in the environment (ter Braak 1986) Two data sets are used, one on the occurrence or abundance of a number of species at a series of sites, and data on a number of environmental. .. the ichthyofauna community of the MRG and the flood pulse of 2005 provided the first opportunity to investigate habitat use Fig 8 Declining trend for peak discharge in MRG for the years 1942–2010 Environ Biol Fish (2012) 95:201–212 by Rio Grande fishes over many river kilometers The findings of the present study have revealed the importance of floodplains in the MRG and provide adequate proof that flood... age-1 or older regions of the otolith, the core and any annuli were visually identified before the transect began, and the time was recorded Environ Biol Fish (2012) 95:213–226 when the laser passed over these areas so that the composition of the different age bands of the otolith could be distinguished To ensure that the site of collection of YOY fish corresponded to the region of the otolith we examined,... of lizardfishes (Synodontidae, Teleostei) of the genera Saurida, Synodus and Trachinocephalus, from various sites of their distribution, revealed melanization of the tract wall This phenomenon was observed in several species of the genus Saurida, but not in the other two genera This melanization is caused by layers of melanosomes rich in melanin granules and deposited within the connective tissue of. .. real group of YOY fish was less than the standard deviation of the randomly selected groups of age-1 fish, divided that number by the number of iterations (1000) and then multiplied by two Comparisons of otolith regions The otoliths we compare come from fish from different locations, years of capture and ages When the fish were greater than one year old, we compared more than one age band of the otolith