Pelagic Eggs Research Articles

Multiple vitellogenin‐derived yolk proteins in gray mullet (Mugil cephalus): Disparate proteolytic patterns associated with ovarian follicle maturation

Disparate proteolytic patterns of yolk proteins, derived from three types of vitellogenin (VgA, VgB, and VgC), were observed in gray mullet. Immuno-biochemical analyses of extracts obtained from vitellogenic ovaries (VO) and ovulated eggs (OE) confirmed that a large proportion of VgA-derived lipovitellin (LvA) was degraded into free amino acids (FAAs) during ovarian follicle maturation. The maturation-associated alteration of VgB-derived Lv (LvB) involved only limited proteolysis; the heavy and light LvB chains were dissociated into at least three and one polypeptide fragments, respectively. The native mass of VgC-derived Lv (LvC) exhibited little difference between VO and OE, although it was apparent that the LvC was 'nicked' during maturation, resulting in the appearance of several bands in OE. Similar analyses confirmed that VgA-derived beta'-component (beta'-cA) and VgB-derived beta'-c (beta'-cB) decreased during maturation in both quantity and native mass, while phosvitin derived from either VgA (PvA) or VgB (PvB) appeared to be degraded into FAAs. The pattern of maturation-associated proteolysis of mullet yolk proteins is similar to that reported for other marine teleosts spawning pelagic eggs. However, the depository ratio of the three distinct types of Lv in the mullet VO appeared to be different from that estimated for another marine pelagophil, the barfin flounder. These results support a recent paradigm regarding the significance of Vg multiplicity upon successive physiological events in this group of fishes including the hydration of maturing oocytes, the acquisition of proper egg buoyancy, and the generation of requisite nutrient stocks for each stage of embryogenesis and larval development.

Pelagic eggs and larvae of Coryphaenoides marginatus (Gadiformes: Macrouridae) collected from Suruga Bay, Japan

The pelagic eggs, yolk-sac and pelagic larvae of the macrourid fish, Coryphaenoides marginatus, from Suruga Bay in southern Japan, are described. The identification of the pelagic eggs based on 16S rRNA gene nucleotide sequences agreed with that obtained from morphological analyses. The spherical eggs, 1.14–1.30 mm in diameter, contained a single oil globule 0.30–0.38 mm in diameter, and had hexagonally patterned ornamentation on the chorion, 0.025–0.033 mm in width. Many melanophores were present on the anterodorsal region of the embryo after the caudal end had detached from the yolk. Within a day after hatching, each of the yolk-sac larvae had a body axis that was bent slightly at the anterior trunk region, many dorsal and lateral melanophores on the trunk plus several on the gut, and small irregular wrinkles on the dorsal and anal fin membranes. The pelagic larvae had a short caudal region in comparison to other known congeners (length 2.0–3.2+ times head length vs. 4–7, respectively), a short stalked pectoral fin base, and no elongate first dorsal and pelvic fin rays. They were further characterized by the presence of numerous very dense melanophores from just behind the eye to the anterior part of the caudal region at 5.1 mm head length (25.8+ mm total length). The significant difference in vertical distribution between the pelagic eggs and larvae (dominant depths ca. 200–350 m vs. ca. 10–100 m, respectively), with no subsequent collection of pelagic larvae with greater than 6 mm head length, indicate two stages (rising and falling) of ontogenic vertical migration.

Temporal variation in fish egg and larval production by pelagic and bottom spawners in a large Newfoundland coastal embayment

In highly seasonal environments such as coastal Newfoundland, local production, advection, and life history may influence ichthyoplankton community structure. The spring bloom occurs in cold water that slows development of eggs from pelagic spawners and may transport propagules from optimal nearshore areas before hatch. For bottom spawners that affix eggs to the bottom, the problem is reduced because only actively swimming larval stages are pelagic. We hypothesize that larvae of pelagic spawners are limited to warmer, summer waters, whereas larvae of bottom spawners are less constrained temporally and less subject to flushing from the nearshore environment. Ichthyoplankton taxa sampled in Placentia Bay, Newfoundland, during spring–summer in 1997–1999 showed consistent seasonal peaks in egg and larval abundance. Although pelagic egg production spanned spring and summer, larval abundance peaked late in summer or early fall in the most productive areas of the bay. Larval abundance of bottom spawners peaked in spring for most taxa. Thus, pelagic eggs hatch quickly in summer, and larvae can utilize the late peak in nearshore copepod abundance. Bottom spawners can utilize spring zooplankton because temperature-dependent development does not influence egg advection. Coastal advection and temperature influence how different life history groups exploit spatial and temporal peaks in production.

Evidence for population structuring of blue whiting (Micromesistius poutassou) in the Northeast Atlantic

AbstractWas, A., Gosling, E., McCrann, K., and Mork, J. 2008. Evidence for population structuring of blue whiting (Micromesistius poutassou) in the Northeast Atlantic. – ICES Journal of Marine Science, 65: 216–225. Many marine fish species are characterized by large population sizes, strong migratory behaviour, high fecundity, and pelagic eggs and larvae that are subject to passive transport by ocean currents, all factors that tend to reduce the rate of development of genetic partitioning among localized populations. The blue whiting (Micromesistius poutassou) is a commercially important gadoid that exhibits all these characteristics, although to date there has been little evidence of genetic heterogeneity except at the latitudinal extremes of its range in the NE Atlantic. Genetic variation was analysed at five microsatellite loci in 16 samples, 14 comprising spawning adults, collected along the continental shelf from 44°N to 60°N, a distance of ∼1900 km. Although pairwise FST values were low (0.0–0.040; mean 0.0097), more than 40% of the estimates were significant, with Celtic Sea and Bay of Biscay samples significantly differentiated from samples from the Porcupine Bank, Hebridean Shelf, Sulisker Bank, and Papa Bank. There was also significant differentiation between samples taken in different years on Rockall Bank. Mantel tests revealed no significant isolation by distance. We used a landscape genetics approach, which combines spatial and genetic information, to detect barriers to gene flow. Four zones of lowered gene flow were identified, generally in concordance with hydrographic patterns, fish spawning behaviour, and the simulated transport of larvae in the NE Atlantic Ocean.

Spawning pattern and type of fecundity in relation to ovarian allometry in the round herring Etrumeus teres

Spawning pattern (assessed by seasonal changes in ovarian developmental stages) and type of fecundity (assessed by analysis of oocyte-size frequency distributions) of the round herring Etrumeus teres were studied in relation to ovarian growth and seasonal changes in the gonadosomatic (GSI), hepatosomatic (HSI) and liposomatic (LSI) index as well as the somatic condition of spawners (CS) in a spawning ground of southern Japan. Except for summer, mature and recently spawned ovaries occurred all year round. Oogonia and primary oocytes were present in all ovaries, and cortical alveoli stage (CA) oocytes occurred in all mature, hydrated and partially spent (PS) females (PS: females containing post-ovulatory follicles). Before hydration, a clutch of larger yolked oocytes, undergoing synchronous growth (range 0.7–1.1 mm), was present in mature ovaries which was completely separated from a more heterogeneous clutch of oogonia, primary and secondary oocytes (<0.150 mm) and oocytes in the CA stage (range 0.15–0.60 mm). As vitellogenesis progressed, the yolked clutch increased in size but the CA oocytes remained arrested. The latter entered into the secondary growth phase when hydration started in the advanced batch. Ovarian growth was isometric in all developmental stages, validating the use of GSI, which showed a consistent monthly evolution among years. Spawning stopped in summer (July and August) and peaked in winter and spring. HSI correlated positively with GSI on both a monthly mean basis (r = 0.76) and individual fish basis (liver weight explained 67–83% of the variability in ovary weight when females were grouped into 1-unit GSI intervals) suggesting a significant role of liver in vitellogenesis. LSI and CS also showed marked seasonal changes peaking from summer to middle autumn. Overall results suggest that E. teres is a multiple spawner with a group-synchronous ovarian development and indeterminate annual fecundity, with the three processes linked to an isometric growth of the ovary. We propose that such a reproductive pattern is an adaptation to produce batches of large pelagic eggs through a protracted spawning season.

Goldsinny wrasse (Ctenolabrusrupestris) is an extreme vtgAa‐type pelagophil teleost

During oocyte maturation in the goldsinny wrasse (Ctenolabrus rupestris) extensive proteolysis of yolk proteins generates a large pool of free amino acids that drive hydration of the pelagic egg. By cloning hepatic vitellogenins (vtg) and using mass spectrometry, N-terminal microsequencing, and Western-immunoblotting to identify the yolk proteins (Yp), we show that multiple forms of vitellogenin mRNAs (vtgAa, vtgAb, and vtgC) are expressed in the liver, but only a single major class of the Yps derived from vtgAa predominates in the oocytes. Some Yps derived from vtgAb and vtgC appear also to be incorporated in the oocytes and eggs, but only at background levels. During oocyte hydration the vtgAa-derived lipovitellin heavy chain (LvH-Aa) and its cleavage variants are completely degraded leaving only a processed lipovitellin light chain (LvL-Aa) fragment as the major yolk protein for embryonic development. The maturational cleavage site of the LvL-Aa is identified as two amino acids downstream from the conserved Tyr(1168) of VtgAa in Atlantic halibut. In addition, although a beta'-component (approximately 18 kDa) is present in the oocytes, it is not fully degraded during the hydration process.

Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 349:255-267 (2007) - DOI: https://doi.org/10.3354/meps07107 Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes Jeffrey M. Leis1,3,*, Amanda C. Hay1, Matthew M. Lockett1, Jeng-Ping Chen2, Lee-Shing Fang2,4 1Ichthyology, Australian Museum, 6 College Street, Sydney, New South Wales 2010, Australia 2National Museum of Marine Biology and Aquarium, 2 Houwan Road, Checheng, Pingtung 944, Taiwan 3School of Biological Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia 4Present address: Department of Sport, Health and Leisure, Cheng Shiu University, 840 Chengcing Road, Niaosong hsiang, Kaohsiung County 83347, Taiwan *Email: jeff.leis@austmus.gov.au ABSTRACT: During the pelagic larval phase of teleost fishes, the larvae are subject to dispersal by currents. Dispersal trajectories can be substantially modified if the larvae have sufficient swimming abilities, so it is important to document how swimming ability develops during the pelagic larval phase. We used reared larvae (4 to 29 mm standard length) from commercial aquaculture farms in Taiwan to measure the development of swimming ability (critical speed, Ucrit) in larvae of 9 species (from 7 families) of Indo-Pacific coral reef and coastal fishes that hatch from pelagic eggs: Trachinotus blochii (Carangidae – jacks), Chanos chanos (Chanidae – milkfish), Platax teira (Ephippidae –batfishes), Leiognathus equulus (Leiognathidae – ponyfishes), Lutjanus malabaricus (Lutjanidae – snappers), Eleutheronema tetradactylum (Polynemidae – threadfins), and Epinephelus coioides, E. fuscoguttatus and E. malabaricus (Serranidae – groupers). Mean critical swimming speeds increased from <5 cm s–1 in the smallest larvae to a maximum of 47 cm s–1 in settlement stage larvae, with the increase in speed by the time of settlement ranging from 6- to 100-fold. Increase in swimming speed was more strongly correlated with size of larvae (R2 = 0.38 to 0.93, p < 0.005) than with age (correlation with age was absent in 3 species and explained 10 to 43% less variation than did size in the others). The relationship between speed and size was linear. In 6 species (T. blochii, C. chanos, L. malabaricus and the 3 Epinephelus species) speed increased at a rate of 2.1 to 2.6 cm s–1 for each 1 mm increase in size. Three species (P. teira, L. equulus and E. tetradactylum) had a significantly slower rate of increase of 1.3 to 1.7 cm s–1 for each 1 mm increase in size. On average, the best performers in each 1 mm size increment were 1.5 to 7.3 cm s–1 faster than mean performers, depending on species. Throughout development the vast majority of mean length-specific speeds were 10 to 20 body lengths (BL) s–1, and length-specific speed increased significantly with size in 6 species. Maximum length-specific speeds for each species reached 18 to 31 BL s–1. Although the ontogeny of swimming speed varies among species of tropical marine fishes, over similar size ranges, larvae that hatch from pelagic eggs have swimming abilities similar to those reported for larvae that hatch from demersal eggs. KEY WORDS: Marine fishes · Pelagic eggs · Pelagic larvae · Swimming speed · Ontogeny · Dispersal · Serranidae · Lutjanidae · Carangidae · Chanidae Full text in pdf format PreviousNextCite this article as: Leis JM, Hay AC, Lockett MM, Chen J, Fang L (2007) Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes. Mar Ecol Prog Ser 349:255-267. https://doi.org/10.3354/meps07107Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 349. Online publication date: November 08, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Life history strategy of sandy sprat Hyperlophus vittatus (Clupeidae): a comparison with clupeoids of the Indo-Pacific and southern Australia

Summary The life history strategy of sandy sprat (whitebait) Hyperlophus vittatus was compared to those of other clupeoids found in the Indo-Pacific and southern Australia. Hyperlophus vittatus is a small (100 mm, fork-length, FL) pelagic species that spawns in inshore waters of southern Australia. The average growth rate for larvae (20.1–27.6 mm, total length, TL) inside the Coorong Lagoon was 0.12 mm day−1. Von Bertalanffy growth parameters were k = 1.83 year−1 and L∞ = 78.10 mm and the oldest fish was ∼4 years of age. Males and females attained 50% sexual maturity at 59 and 58 mm FL, respectively, and all individuals were sexually mature at lengths ≥75 mm, at ∼1.5 years of age. Macroscopic gonad staging showed the spawning season extended from October to February (spring and summer) and peaked during November. Mean egg densities were highest between September and November. Females produced batches of pelagic eggs at a mean frequency of 5 days and batch fecundities ranged between 743 and 5600 hydrated oocytes. The life history of H. vittatus is similar to those of larger, iteroparous clupeoids that occur in southern temperate Australian waters, e.g. sardine Sardinops sagax and Australian anchovy Engraulis australis, and dissimilar to those of small tropical clupeoids and the sympatric blue sprat Spratelloides robustus, which is semelparous.

Inferring gene flow in coral reef fishes from different molecular markers: which loci to trust?

Contrasting results are usually reported in the literature regarding the factors influencing observed structuring of genetic variability. The goals of this study were, for five coral reef fishes in French Polynesia, (1) to infer the theoretical variance of single locus F(ST) estimates expected under neutrality in order to exclude outlier loci before inferring gene flow and (2) to test thereafter whether species laying pelagic eggs effectively disperse more than species laying benthic eggs in this system. For this purpose, a total of 952 individuals from five species belonging to two families (Chaetodontidae and Pomacentridae) were screened among populations sampled within a 60-600 km spatial range for intron length polymorphism at 11 loci in order to illuminate contrasting results previously published on allozymes and mitochondrial DNA (mtDNA) control region polymorphisms. Statistically speaking, among the five species, four loci (three allozymes and one intron) were identified as outliers and discarded before interpretation of genetic differentiation in terms of effective dispersal. Biologically speaking, our results suggest that the observed genetic structure is not significantly related to the reproductive strategy of coral reef fish in the island system we analysed and that observed random genetic differentiation accommodates Wright's island model in all five species surveyed. Overall, our study emphasizes how cautious one has to be when trying to interpret present-day genetic structure in terms of gene flow while using a limited number of loci and/or different sets of loci.

Egg distribution, bottom topography and small-scale cod population structure in a coastal marine system

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 333:249-255 (2007) - doi:10.3354/meps333249 Egg distribution, bottom topography and small-scale cod population structure in a coastal marine system Halvor Knutsen1,2,*, Esben Moland Olsen1,2, Lorenzo Ciannelli2,4, Sigurd Heiberg Espeland2, Jan Atle Knutsen1, Jan Henrik Simonsen1, Stig Skreslet3, Nils Chr. Stenseth1,2 1Institute of Marine Research, Flødevigen, 4817 His, Norway2Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, PO Box 1066, Blindern, 0316 Oslo, Norway 3Bodø University College, Department of Fisheries and Natural Sciences, 8049 Bodø, Norway 4Present address: College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA *Email: halvor.knutsen@imr.no ABSTRACT: Coastal marine species with pelagic egg and larval stages, such as the Atlantic cod Gadus morhua, can be structured into genetically distinct local populations on a surprisingly small geographic scale considering their dispersal potential. Mechanisms responsible for such small-scale genetic structure may involve homing of adults to their natal spawning grounds, but also local retention of pelagic eggs and larvae. For example, spawning within sheltered fjord habitats is expected to favour local retention of early life stages. Here, we studied the distribution of cod eggs along inshore– offshore transects in 20 Norwegian fjords. The general pattern exhibited across all fjords was a higher concentration of cod eggs inside the fjords than further offshore. In particular, fjords with shallow sills (model threshold 37 m) show an abrupt reduction in egg density over the sill. This study provides empirical support for an offspring retention hypothesis, which may help to explain the maintenance of local population structure in pelagic marine systems. KEY WORDS: Atlantic cod · Gadus morhua · Egg distribution · Population structure Full text in pdf format Supplementary appendices PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 333. Online publication date: March 12, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

The Maturational Disassembly and Differential Proteolysis of Paralogous Vitellogenins in a Marine Pelagophil Teleost: A Conserved Mechanism of Oocyte Hydration1

A structural analysis of the differential proteolysis of vitellogenin (Vtg)-derived yolk proteins in the maturing oocytes of a marine teleost that spawns very large pelagic eggs is presented. Two full-length hepatic cDNAs (hhvtgAa and hhvtgAb) encoding paralogous vitellogenins (HhvtgAa and HhvtgAb) were cloned from nonestrogenized Atlantic halibut, and the N-termini of their subdomain structures were mapped to the oocyte and egg yolk proteins (Yps). The maturational oocyte Yp degradation products were further mapped to the free amino acid (FAA) pool in the ovulated egg. The deduced amino acid sequences conformed to the linear NH(2)-(LvH-Pv-LvL-beta'-CT)-COO(-) structure of complete teleost Vtgs. However, the Yps did not match the expected cleavage products of complete Vtgs. Specifically, the phosvitin subdomain of the HhvtgAa paralogue remains covalently attached to the lipovitellin light chain, while the phosvitin subdomain of the HhvtgAb paralogue remains covalently attached to a C-terminal fragment of the lipovitellin heavy chain (LvH). During oocyte hydration, the LvH of the HhvtgAa paralogue is disassembled and extensively degraded to FAA. In the HhvtgAb paralogue, the LvH is nicked in the C-sheet in a manner similar to that seen in lamprey and other teleosts. A small part of the C-terminal end of the LvH-Ab undergoes proteolysis to FAA, together with the phosvitin, beta' component, and much ( approximately 65%) of the lipovitellin light chain (LvL-Ab). The independently measured FAA pool in the ovulated egg corroborates that calculated from differential proteolysis of the Yps. Based on the 3:1 (HhvtgAb:HhvtgAa) Yp expression ratio, each paralogue contributes approximately equal amounts of FAA to the organic osmolyte pool of the hydrating oocyte during maturation.

Year-to-year variation in larval fish assemblages of the Southern North Sea

In order to test the temporal stability within and the reproducibility of larval fish assemblages between years, the larval fish assemblage at Helgoland Roads, North Sea (NE Atlantic) was quantitatively sampled almost daily from January 2003 to December 2005. The survey resulted in a total of 462 samples containing 50,632 larval fish of at least 42 taxa. In winter the larval fish assemblage was mainly dominated by larvae emerging from demersal eggs. This changed gradually to larvae hatching from pelagic eggs. Larvae from pelagic eggs dominated the ichthyoplankton assemblage in summer. A remarkably stable seasonality in terms of dominance patterns with recurring, season-specific fish assemblages was observed over the 3 years, despite substantial variation in environmental conditions such as a temperature difference of almost 20°C between summer and winter. The lesser sandeel (Ammodytes marinus), was the only species which showed significant fluctuations in abundance between the years. After removal of this species from the analysis, the dominance patterns of the remaining fish species were almost identical between years.

Energetics and metabolism of yellowtail kingfish ( Seriola lalandi Valenciennes 1833) during embryogenesis

A study was undertaken to measure changes in oxygen consumption and metabolite concentration (ammonia, free amino acids, glucose, glycogen, ninhydrin positive substances and protein) in embryos of yellowtail kingfish ( Seriola lalandi) incubated at different temperatures (17, 19, 21 and 23 °C). The oxygen uptake at hatch and total oxygen consumed during embryogenesis was negatively correlated with temperature, and resulted in Q 10 values less than 1. This was attributed to the fact that embryos and first hatch larvae have been reported to be smaller at warmer incubation temperatures and therefore consumed less oxygen. Free amino acids were present in high concentrations immediately after spawning (188 ± 15.3 nmol ind − 1 ) and were dominated by the neutral amino acids alanine, glycine, isoleucine, leucine, serine, and valine. The free amino acid pool was rapidly depleted until hatch (20–40 nmol ind − 1 ), after which the pool was dominated by glycine, serine, valine and arginine/taurine (unresolved). The loss of positive buoyancy around the time of hatch was likely to be correlated with the decrease in free amino acid content during embryogenesis. The sequence of metabolic fuel use during embryogenesis is likely to be similar to that observed in other marine fish species with pelagic eggs, namely that carbohydrates, lipid and protein are of relatively minor importance compared to the catabolism of free amino acids for energy. Eggs incubated at 17, 19 and 21 °C had similar profiles of metabolite concentration during embryogenesis, however, eggs incubated at 23 °C were found to have a considerably different pattern of substrate utilisation, possibly indicative of abnormal physiological development at a temperature above that which is routinely encountered in the wild.

Genetic structure of whiting Merlangius merlangus in the northeast Atlantic and adjacent waters

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 330:201-211 (2007) - doi:10.3354/meps330201 Genetic structure of whiting Merlangius merlangus in the northeast Atlantic and adjacent waters Grégory Charrier1,2,*, Steve H. Coombs3, Ian H. McQuinn4, Jean Laroche1 1Laboratoire LEMAR (UMR CNRS 6539), Institut Universitaire Européen de la Mer, Place Nicolas Copernic, Technopôle Brest-Iroise, 29280 Plouzane, France 2NOAA Southwest Fisheries Science Center, Santa Cruz Laboratory, 110 Shaffer Road, Santa Cruz, California 95060, USA 3The Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK 4Hydroacoustic Laboratory, Marine Fish and Marine Mammals Division, Department of Fisheries and Oceans, Maurice Lamontagne Institute, CP 1000, 850 route de la Mer, Mont-Joli, Quebec, Canada *Email: gregory.charrier@noaa.gov ABSTRACT: Accurate identification of stock boundaries is essential for efficient fisheries management; hence, the present study focused on the genetic structure of whiting. To this aim, 488 individuals collected from the southern Bay of Biscay to the southern Norwegian coast were genotyped using 7 microsatellites. A low level of genetic structuring was detected in Atlantic waters; only the Bay of Biscay differentiated from more northern samples. The lack of genetic structure along the western margin of the British Isles is consistent with a high level of passive transport of pelagic eggs and larvae due to the combined influence of the North Atlantic Current and the Shelf Edge Current. High levels of dispersal could also occur between the western British Isles and the North Sea through both the branching of the North Atlantic Current into the northern North Sea and the residual current flowing from the English Channel to the Southern Bight. In contrast, a significant genetic structure was identified within the North Sea, and this may be associated with the complex oceanography of this basin and retention systems reducing larval dispersal. In addition, considering also genetic, phenotypic and tag–recapture data collected on whiting, a learned homing behaviour of adults toward spawning areas may be hypothesised. KEY WORDS: Whiting · Merlangius merlangus · Microsatellites · Genetic structure · Larval dispersal Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 330. Online publication date: January 25, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Vertebrate Vitellogenin Gene Duplication in Relation to the “3R Hypothesis”: Correlation to the Pelagic Egg and the Oceanic Radiation of Teleosts

The spiny ray-finned teleost fishes (Acanthomorpha) are the most successful group of vertebrates in terms of species diversity. Their meteoric radiation and speciation in the oceans during the late Cretaceous and Eocene epoch is unprecedented in vertebrate history, occurring in one third of the time for similar diversity to appear in the birds and mammals. The success of marine teleosts is even more remarkable considering their long freshwater ancestry, since it implies solving major physiological challenges when freely broadcasting their eggs in the hyper-osmotic conditions of seawater. Most extant marine teleosts spawn highly hydrated pelagic eggs, due to differential proteolysis of vitellogenin (Vtg)-derived yolk proteins. The maturational degradation of Vtg involves depolymerization of mainly the lipovitellin heavy chain (LvH) of one form of Vtg to generate a large pool of free amino acids (FAA 150–200 mM). This organic osmolyte pool drives hydration of the ooctye while still protected within the maternal ovary. In the present contribution, we have used Bayesian analysis to examine the evolution of vertebrate Vtg genes in relation to the “3R hypothesis” of whole genome duplication (WGD) and the functional end points of LvH degradation during oocyte maturation. We find that teleost Vtgs have experienced a post-R3 lineage-specific gene duplication to form paralogous clusters that correlate to the pelagic and benthic character of the eggs. Neo-functionalization allowed one paralogue to be proteolyzed to FAA driving hydration of the maturing oocytes, which pre-adapts them to the marine environment and causes them to float. The timing of these events matches the appearance of the Acanthomorpha in the fossil record. We discuss the significance of these adaptations in relation to ancestral physiological features, and propose that the neo-functionalization of duplicated Vtg genes was a key event in the evolution and success of the teleosts in the oceanic environment.

Patchiness of eggs, larvae and juveniles of European hake Merluccius merluccius from the NW Mediterranean

AbstractWe estimated patchiness for different life stages (egg, larvae and juveniles) of European hake (Merluccius merluccius) from two ichthyoplankton surveys (September and November 1999) and four bottom‐trawl surveys (November 1998, February, June and September 1999). Lloyd's patchiness P = 1 + 1/k, where k is the dispersion parameter of the negative binomial distribution, was calculated. Juveniles showed lower indices of patchiness than early ontogenetic stages. In juveniles, patchiness was highest for smaller size classes (3.5–5 cm TL) settling to their near‐bottom habitat and was very low for those larger than 5 cm up to the 30–35 cm size class (approximately 3 yr of age, 50% mature individuals). Patchiness of settling juveniles was especially high in the June and September surveys, coinciding with peak recruitment to the bottom. Both eggs and yolk sac larvae showed patchiness values &lt;10, increasing in flexion stage larvae from 12 to 20. This pattern is different to that observed in other studies for pelagic species, where patchiness of early‐stage eggs is very high, but coincides with results obtained for other demersal species with pelagic eggs. Factors that may explain these patterns are discussed in light of oceanographic conditions, adult distribution and larval ontogenesis.

Sperm motility in three coral reef fish species

A method of computer assisted sperm analysis (CASA) is used to determine the parameters of sperm motility in three fish species from the coral reefs of the Nha Trang Bay, South China Sea, Vietnam: Zebrasoma scopas (Acanthuridae), Abudefduf sexfasciatus, and Dascyllus trimaculatus (Pomacentridae). The representatives of the families are characterized by different reproductive tactics and possess pelagic and demersal eggs, respectively. The main morphological parameters of spermatozoa have been measured. The average curvilinear velocity of spermatozoa movement along the real trajectory (VCL) after 1 min of sperm activation ranges from 15.3 to 74.5 μm/s in Z. scopas, it is comparatively low (12.7–21.6 μm/s) in A. sexfasciatus, and high (58.4–92.2 μm/s) in D. trimaculatus. The duration of progressive movements in more than 50% of spermatozoa at 25°C is 3–20, 5–11, and 6–9 min after sperm activation, respectively. Following storage of the sperm of three species at 4.5°C for 7, 20, and 28 h, respectively, spermatozoa retain the ability of progressive movements. The results are discussed based on the available information on the activity of sperm in fish.

Carbohydrate Metabolism of Vitellogenic Follicles and Eggs of Serranus cabrilla (Serranidae) and Mullus barbatus (Mullidae) and of Embryos of Sparus aurata (Sparidae)

The present study compared the carbohydrate metabolism of pelagic eggs of three marine species, Serranus cabrilla (Serranidae), Mullus barbatus (Mullidae) and Sparus aurata (Sparidae). In particular, in Serranus cabrilla and Mullus barbatus the changes in carbohydrate metabolism from the vitellogenic follicle stage to the ovulated egg stage (final maturation of the egg) were investigated, and in Sparus aurata the changes from the unfertilized egg stage to the late-embryo stage just before hatching were observed. In mature, unfertilized eggs of these three species the qualitative and quantitative composition of carbohydrates, enzymes and metabolites were similar, indicating no differences in carbohydrate metabolism. Glycolysis, gluconeogenesis and the pentose phosphate pathway occurred in the follicles and eggs. From the vitellogenic follicle stage to the mature egg stage glycolytic activity was constant in S. cabrilla and M. barbatus, while the activity of the pentose phosphate pathway and of gluconeogenesis decreased. Quantitative carbohydrate composition changed as the levels of hexose, ketose, 6-deoxyhexose, uronic acid and fructose-6-phosphate increased from the vitellogenic follicle stage to the mature egg stage, while the levels of D-glycerate-2-phosphate and phosphoenolpyruvate decreased. In S. aurata, the investigated parameters of carbohydrate metabolism were similar between unfertilized eggs and eggs in the first cleavage stage. From the first cleavage stage to the late embryo stage the levels of hexose, 2-deoxyhexose, ketose, ribose, uronic acid and phosphoenolpyruvate increased, while the levels of D-glycerate-2-phosphate decreased.

An examination of the feasibility of passive transport from coastal spawning grounds to estuarine nursery areas for English sole

English sole recruitment has been linked to environmental conditions occurring during their 6–10 week pelagic egg and larval stages, prior to their appearance in nursery estuaries during their first summer. The purpose of this study was to predict the spawning locations of juvenile English sole observed in estuaries to assess the feasibility of passive transport of egg and larval stages. Current meter data were used to back-calculate the transport trajectories of 19 cohorts of English sole observed as juveniles during estuarine trawl surveys. Only six of these cohorts were predicted to be spawned outside the Oregon–Washington shelf system, assuming passive transport of eggs and larvae. Predicted egg and larval trajectories indicate that most of the English sole found in Oregon and Washington estuaries were spawned off the coast of Washington, with some spawning off northern California and central Oregon. Although these results are not consistent with the presumed spawning locations for the Oregon and Washington shelf, they indicate that passive transport assumptions may be adequate to preserve the larvae in the coastal system until settlement.

Molecular characterization of three forms of vitellogenin and their yolk protein products during oocyte growth and maturation in red seabream (Pagrus major), a marine teleost spawning pelagic eggs

Full-length cDNAs encoding three forms of vitellogenin (Vg) were obtained from a liver cDNA library of estrogen-treated red seabream, Pagrus major. Two of the three Vg sequences had high homology with type-A and -B Vgs (VgA and VgB) of other teleosts. The third red seabream Vg was classified as a type-C or phosvitinless (Pvl) Vg due to its lack of a phosvitin (Pv) domain. Two Vg preparations (610 and 340 kDa) from blood serum of estradiol-treated fish were biochemically characterized. Analyses of precursor-product relationships by examination of N-terminal amino acid sequences verified cleavage of the 610 kDa Vg into a 540 kDa lipovitellin (Lv) and a 32 kDa beta'-component. Each of these yolk preparations comprising both VgA- and VgB-derived polypeptides. The 340 kDa Vg, which was immunologically verified to be a PvlVg, was accumulated by vitellogenic oocytes with no alterations to its native molecular mass. During oocyte maturation, the VgA- and VgB-derived yolk proteins were differentially processed, presumably to generate a pool of free amino acids for oocyte hydration or for allocation of specific types of nutrients, amino acids, and proteins, to the developing embryo. Conversely, the 340 kDa Vg-derived yolk protein is unlikely to contribute to oocyte hydration or diffusible nutrients since the molecule underwent only minor proteolytic nicking during oogenesis. The present study elucidates for the first time specific functions of three different forms of Vg and their product yolk proteins in a higher taxonomic group of marine teleosts that spawn pelagic eggs.