Sexual maturity cycle and spawning of Greenland halibut Reinhardtius hippoglossoides in the Davis Strait

Female sexual maturation cycle and the main spawning time of Greenland halibut Reinhardtius hippoglossoides in the Davis Strait were studied through regularly collected samples during 1 year starting in spring 2003. Samples were collected from the southern slope of the Davis Strait Ridge between Canada and Greenland in the depth range 1000–1500 m. Female sexual maturation was described using different approaches: gonado‐somatic index, visual macroscopic maturity stage index, histological microscopic maturity index and oocyte diameter measurements. A significant increase in the gonado‐somatic index was seen from September onwards until February with a maximum estimated value of 18%. The proportion of mature fish increased from December until March. At the same time, the proportion of females with a low gonado‐somatic index also increased from February, indicating that spawning had occurred and females were recovering. Oocyte diameter distribution revealed a leading cohort development during autumn through to December to February. A coupling between sexual maturity and fish condition was seen for females in maturing condition indicating a steady build up of stored energy in the liver from June to November.     

Preliminary assessment of Greenland halibut diet in Cumberland Sound using stable isotopes

We provide preliminary carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope assessment of the Greenland halibut (Reinhardtius hippoglossoides) diet in Cumberland Sound, with focus on two possible prey sources: pelagic represented by capelin (Mallotus villosus) and epibenthic represented by shrimp (Lebbeus polaris). The δ¹³C for the Greenland halibut stock indicated a pelagic carbon source in Cumberland Sound while stable isotope mixing models, IsoSource and MixSIR, indicated a 99% dietary composition of capelin relative to the shrimp. The δ¹⁵N did not vary across Greenland halibut size ranges and placed them at a fourth trophic position relative to a primary herbivore. This study provides the starting point for more elaborate Cumberland Sound research on the local Greenland halibut feeding ecology by confirming pelagic feeding and establishing relative trophic position as well as identifying stable isotopes as a useful tool for the study of diet in cold water fish species.     

A first glimpse of larval ecology of halibut species in the Gulf of St. Lawrence,Canada

Knowledge of the larval ecology of winter-spawning fish from the Estuary and Gulf of St. Lawrence, Canada, remains scarce due to the seasonal ice cover that prevents ichthyoplankton sampling using conventional methods. Two winter-spawning species, Atlantic halibut (AH, Hippoglossus hippoglossus) and Greenland halibut (GH, Reinhardtius hippoglossoides), support the most important groundfish fisheries of this area. In March 2020, the authors captured 10 halibut larvae ranging in size from 5 to 14 mm during an opportunistic survey in the GSL onboard an icebreaking vessel. Of these, eight were AH and two GH. Judging by their very small size, the larvae were only a few days old, suggesting that the spawning grounds are close to the capture sites. This effort constitutes a first step in validating the putative spawning areas for these two important GSL stocks. This knowledge is important for the conservation and sustainable management of these fisheries.     

High‐density aggregations of rodlet cells in the gonads of Greenland halibut Reinhardtius hippoglossoides,a deep‐water marine flatfish

Large aggregations of rodlet cells in the gonads of male and female Greenland halibut Reinhardtius hippoglossoides are reported for the first time. These rodlet cells were not arranged epithelially but rather were found throughout the connective tissue between oocytes (females) or within lymphatic spaces between testicular lobules (males). The reason for large aggregations of rodlet cells in the gonads and not other tissues of this species is uncertain.     

Morphological development and allometric growth patterns in hatchery-reared California halibut larvae

Morphological development, allometric growth and behaviour of hatchery-reared California halibut Paralichthys californicus were studied from hatching to metamorphosis (42 days post hatch, dph) at 187° C. Mean standard length ( L _S) of larvae and juveniles increased from 2.1 mm at hatching to 10.5 mm at metamorphosis with the increase in length being approximately linear. Stages of morphological development were described using the alphabetic staging (A–I) used for other flatfish species. Organogenesis and differentiation were more rapid and complex in yolk-sac (hatching, stage A–3 dph, stage B), preflexion (3–19 dph, stages B–C), and flexion larvae (from 20 to 23 dph, stages D–E), as larvae developed most of their sensory, feeding, respiratory and swimming systems. After notochord flexion at 24–25 dph (stage F), most morphological changes were related to the progressive transformation from a bilateral symmetrical larva to an asymmetrical benthic juvenile (42 dph, stages G–I).     

Oogenesis and the spawning pattern in Greenland halibut from the North-west Atlantic

Gametogenesis in Greenland halibut Reinhardtius hippoglossoides from the North-west Atlantic is not synchronous between individuals of the same population suggesting that the spawning season is not well defined. Differences in oocyte size–frequency distributions in prespawning, spawning and spent conditions suggest that Greenland halibut are capable of de novo vitellogenesis prior to and during spawning, indicating that the spawning pattern is not determinate. Greenland halibut may be capable of fast-tracking oocytes to maturity, whereby during the spawning season oocyte batches may be brought quickly through vitellogenesis so as to increase the fish's yearly reproductive output. 1999 The Fisheries Society of the British Isles     

Diets of hooded seals (Cystophora cristata) in coastal waters and drift ice waters along the east coast of Greenland

To provide data on the diets of hooded seals (Cystophora cristata) in the Greenland Sea, seals were collected for scientific purposes on expeditions conducted in the pack ice belt east of Greenland in September/October 1999, 2002 and 2003 (autumn), July/August in 2000 (summer), and February/March in 2001 and 2002 (winter). The results from analyses of stomach and intestinal contents from captured seals revealed that their diet was comprised of relatively few prey taxa. The squid Gonatus fabricii and polar cod (Boreogadus saida) were particularly important, whereas capelin (Mallotus villosus) and sand eels (Ammodytes spp.) occasionally contributed more. These four prey items constituted 60-97% of the diet biomass. Gonatus fabricii was the most important food item in autumn and winter, whereas polar cod dominated the summer diet, with important contributions from G. fabricii and sand eels. The latter was only observed on the hooded seal menu during the summer period, whereas polar cod, which was an important component during the autumn survey, was almost absent from the winter samples. During the latter survey, capelin also contributed to the hooded seal diet. Samples obtained from hooded seals in more coastal waters indicated a more varied diet based on fish such as polar cod, redfish (Sebastes sp.) and Greenland halibut (Reinhardtius hippoglossoides).     

An autofluorescence-based survey of late follicular atresia in ovaries of a teleost fish (Thunnus thynnus)

In this study, the authors examined late atretic follicles in the ovaries of Atlantic bluefin tuna, Thunnus thynnus (Linnæus 1758), at different times of the year using transmitted light and epifluorescence microscopy. Atresia (degeneration and resorption of developing ovarian follicles) is a natural process involved in fecundity downregulation in teleosts and is substantially enhanced in stressful conditions. Early (α and β) atretic stages of yolked oocytes have a relatively short duration in seasonally reproducing species, whereas later (γ and δ) atretic follicles (LAF) persist for longer time in the ovary, serving as a sign of previous vitellogenic activity. LAF can thus be used as reliable markers of maturity during non-reproductive periods. Lipofuscin granules accumulate in the cytoplasm of LAF cells as a result of lysosomal digestion of oocyte components. Taking advantage of the well-known autofluorescent properties of lipofuscins, LAF may be identified in unstained histological sections under fluorescence microscopy using appropriate excitation and emission wavelengths. The authors explore in this study the applicability of fluorescence microscopy to provide a fast and effective method to assess late atresia in fishes. This method may be particularly useful to determine sexual maturity in individuals sampled long after the spawning season, where LAF are difficult to detect in standard histological sections. Furthermore, LAF autofluorescence provides a rapid way to quantify late atresia in fishes using image analysis.     

Reproductive biology of the tarpon snook Centropomus pectinatus (Perciformes,Centropomidae) in estuarine waters in the south‐western Atlantic

The reproductive biology of Centropomus pectinatus is described from an artisanal fish landings collaborative monitoring programme between May 2012 and April 2013 in estuarine waters in north‐eastern Brazil. The total length (L_T) at which 50% are mature was 24 cm, corresponding to 37·7% of the maximum recorded L_T. Gonado‐somatic indices were variable, but highest values were in June and August 2012. Length‐frequency distributions showed male dominance in smaller length classes (15–30 cm) and females in larger length classes (>30 cm).     

Reproductive biology of female bigeye tuna Thunnus obesus in the western Pacific Ocean

The reproductive biology of female bigeye tuna Thunnus obesus was assessed by examining 888 fish (ranging from 84·9 to 174·4 cm fork length, L_F) caught by Taiwanese offshore longliners in the western Pacific Ocean from November 1997 to November 1998 and November to December 1999 and 258 gonad samples from these fish. The overall sex ratio of the catch during the sampling differed significantly from 0·5, but males were predominant in sizes >140 cm L_F. Reproductive activity (assessed by histology), a gonado‐somatic index, and the size‐frequency distributions of whole oocytes indicated that spawning occurred throughout the year and the major spawning season appeared to be from February to September. The estimated sizes at 50% maturity (L_F50) of females was 102·85 cm (95% c.i .: 90·79–110·21 cm) and the smallest mature female was 99·7 cm L_F. They are multiple spawners and oocytes develop asynchronously. The proportion of mature (0·63) and reproductively active (0·70) females with ovaries containing postovulatory follicles indicated that they spawn almost daily. Batch fecundity for 15 females with the most advanced oocytes (>730 µm) ranged from 0·84 to 8·56 million eggs (mean ± s.d . = 3·06 ± 2·09). The relationships between batch fecundity (F_B, in millions of eggs) and L_F (cm) and round mass (M_R, kg) were (r² = 0·84) and (r² = 0·80), respectively. The parameters estimated in this study are key information for stock assessments of T. obesus in the western Pacific Ocean and will contribute to the conservation and sustainable yield of this species.     

Effects of low-salinity on the growth and development of spotted halibut Verasper variegatus in the larva-juvenile transformation period with reference to pituitary prolactin and gill chloride cells responses

Low-salinity adaptability was investigated in a flatfish spotted halibut Verasper variegatus during the period from late metamorphic larvae to early juveniles by a 20-day rearing experiment under different salinity regimes (1, 4, 8, 16 and 32 ppt). Effects of low-salinity on growth and development were examined and the changes in the prolactin (PRL) production level in the pituitary and the gill chloride cell morphology were examined as physiological backgrounds for low salinity adaptation. PRL cells and chloride cells were identified by immunocytochemistry with a specific antiserum for PRL₁₈₈ and Na⁺,K⁺-ATPase. Most of the fish exposed to over 4 ppt survived for 20 days, but all the fish exposed to 1 ppt died within 5 days. Fish kept in intermediate salinities (8, 16 ppt) grew significantly better than those in the control group (32 ppt). Fish exposed to 4 ppt attained almost the same body length as the control group at 20 days after transfer, although these fish showed an abnormally dark body color as well as delayed development. These results suggested that spotted halibut has a high-adaptability to low-salinity environments and prefers an intermediate salinity near iso-osmolality (about 12 ppt) from the late metamorphic larval stage, but does not completely adapt to a hypoosmotic of 4 ppt salinity or less than half of the osmolality. The percentage of PRL-cell volume to pituitary volume was significantly higher at 4 ppt than in the control group. The chloride cells in gill filaments were significantly larger at 4 ppt than in the control group. These results suggest that juveniles could adapt to a low-salinity environment due to the activation of PRL production and enlargement of chloride cells. These laboratory findings suggest that late metamorphic larvae and early juveniles of spotted halibut may utilize a low salinity environment such as estuarine tidal flats or very shallow coastal areas as their nursery grounds in the sea.     

小鼠胚胎卵巢卵泡体外无血清培养体系的建立(英文)

调节原始卵泡形成、起始生长的信号目前仍知之甚少。一个重要的原因就是缺乏一个良好的研究模型。我们以妊娠１３天昆明白小鼠胚胎卵巢为研究材料,经过５天的贴壁培养后,分别用牛血清（ＦＢＳ）、无血清（ＩＴＳ）和含有人卵泡刺激素（ＦＳＨ－ＩＴＳ）培养液继续体外培养到第１９天,发现ＩＴＳ组培养的胚胎卵巢卵泡发育要显著优于ＦＢＳ组（Ｐ＜０．０１）,如：培养至第７天时（Ｐ１,相当于出生日）,卵泡数分别为２９５±１８和 ２０６±１７;培养至第１３天时（Ｐ７）,卵泡数分别为 ５９４±３１和 ２６２±２８;培养至第１９天时（Ｐ１３）,卵泡数分别为 ３７１±２５和 ５０±１１（Ｆｉｇ．１,２＆４）。ＩＴＳ处理组的绝大部分卵巢在培养早期（如：Ｐ５前）都形成了皮质－髓质样的卵泡生长模式,而ＦＢＳ处理组超过半数卵巢不能形成皮质一髓质样的卵泡生长模式;ＦＳＨ－ＩＴＳ处理组和ＩＴＳ处理组的胚胎卵巢卵泡发育并无显著差异（Ｆｉｇ．２,４＆５）。 结果提示所建立的以ＩＴＳ为血清替代物的无血清培养模型更益于小鼠胚胎卵巢卵泡的体外发育;ｈＦＳＨ不是小鼠胚胎卵巢早期发生发育所必须的。     

Temperature effects on spawning and egg development in Eurasian perch

Spawning, egg strand development and embryo survival was studied during 1995–1996 in perch Perca fluviatilis exposed to heated effluent from two coastal nuclear power plants on the Baltic. Spawning was earlier and more prolonged in the heated areas. Although the fertilization rate was high, most egg strands sampled in the heated areas did not develop to hatching. The egg strands disintegrated within a few days of spawning, and egg mortality was very high. All samples collected from reference areas developed up to hatching. Exposure to high temperatures during the final maturation of the gonad influenced the follicular mechanism producing the jelly membrane which constitutes the matrix of the egg strand. Effects were observed in fish in open effluent areas as well as in an enclosed research basin. These results suggest that there is a conflict between optimal reproduction and temperature preference in temperate area fish. Fish are attracted to cooling water effluent, at the expense of reduced reproductive performance.     

Gene expression during two alternative pathways of ovary development in Pisum sativum: fruit development and ovary senescence

Pea ovaries are induced to enter a fruit development pathway involving physiological and morphological changes by pollination or application of plant growth regulators. In the absence of these stimuli, overies stop growing and enter an alternative pathway of senesecence that leads to their degeneration. We have used two dimensional polyacrylamide gel electrophoresis in search of molecular changes underlying fruit development and ovary senescence at the level of total accumulated proteins, newly synthesized proteins, and translatable, RNA populations. We have found changes in gene expression during the processes of ovary formation and ovary senescence. Stimuli that induce fruit set do not appreciably alter the overall patterns of synthesized proteins or translatable RNAs, indicating that fruit development is apparently a natural continuation of ovary formation. However, ovary senescence is an alternative pathway that involves the presence of new RNA messengers and proteins as well as the disappearance of others. These changes were detected earlier than any morphological or structural changes could be observed in the ovary.     

Parental influence on early development in the European sea bass

Fertilization, survival during incubation and hatching were highly correlated and strongly influenced by the female parent and the interaction between both parents of the sea bass Dicentrarchus labrax. A single significant male effect was detected on hatching and may reflect a genetic component determining survival from fertilization to hatching. Egg size and total length of 8-day-old larvae (age of first feeding) were also subjected to the influence of the female but the two parameters were not correlated. A significant interaction between both parents was also observed for length of larvae. The survival rates were significantly correlated in two consecutive years indicating that reproductive performances may be repeatable. Although the effect of the male parent on early sea bass development is shown for the first time, it seems that most of the parental effects on early performance in this species are due to females even when hormonal stimulations are performed at very close prematurational stages of oocyte development.     

Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): developmental ultrastructure and secretion in relation to function

BACKGROUND AND AIMS: Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc. METHODS: Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber. KEY RESULTS: Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative. CONCLUSIONS: The continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality.     

霍氏啮小蜂的卵巢发育和卵子发生

霍氏啮小蜂是一些鳞翅目和双翅目昆虫蛹的寄生蜂。本文描述该寄生蜂从亚洲玉米螟羽化后0,6 12,18,24,30,36,42,48,54,60,66和72 h的卵巢发育和卵子发生过程。霍氏啮小蜂雌性生殖系统为典型的膜翅目姬小蜂类型,包括2个卵巢,每个卵巢通常有8-9根卵巢管,另有1对输卵管附腺,1个受精囊和1个受精囊腺等。卵黄和卵子形成于羽化后12 h,刚羽化的雌蜂不含成熟卵(成熟卵指数OI=0),成熟卵出现在羽化后24 h,成熟卵数量随后不断增加至数量较为稳定。卵巢管内卵数与雌蜂的体长和头宽呈正相关,相关系数分别为0.859和0.907。研究结果表明霍氏啮小蜂属卵育型(synovigeny)寄生蜂,本文还讨论了卵育型霍氏啮小蜂的卵成熟策略。     

Sexual maturity and shape development in cranial appendages of extant ruminants

Morphological disparity arises through changes in the ontogeny of structures; however, a major challenge of studying the effect of development on shape is the difficulty of collecting time series of data for large numbers of taxa. A proxy for developmental series proposed here is the age at sexual maturity, a developmental milestone potentially tied to the development of structures with documented use in intrasexual competition, such as cranial appendages in Artiodactyla. This study tested the hypothesis that ruminant cranial appendage shape and size correlate with onset of sexual maturity, predicting that late sexual maturity would correlate with larger, more complicated cranial appendages. Published data for cranial appendage shape and size in extant taxa were tested for correlations with sexual maturity using linear mixed‐effect models and phylogenetic generalized least‐squares analyses. Ancestral state reconstructions were used to assess correlated variables for developmental shifts indicative of heterochrony. These tests showed that phylogeny and body mass were the most common predictors of cranial appendage shape and sexual maturity was only significant as an interaction with body mass. Nevertheless, using developmental milestones as proxies for ontogeny may still be valuable in targeting future research to better understand the role of development in the evolution of disparate morphology when correlations exist between the milestone and shape.