Sterol composition of gonad,muscle and digestive gland of Pecten maximus from Málaga (South Spain)

Sterol composition and content and their seasonal variations over 18 months were investigated in adductor muscle, digestive gland and gonads of Pecten maximus. Sterols were isolated by Silicagel 60 thin layer chromatography and identified by gas chromatography/mass spectrometry. Eleven sterols were identified, with cholesterol, brassicasterol, 24-methylenecholesterol and 22-trans-dehydrocholesterol being the principal components. The same sterols were found in all three tissues independent of season. The relative amounts of each sterol present in each tissue differed. Total sterol levels in gonad and muscle were higher than in digestive gland. Statistically significant differences (P<0.05) were found between the concentrations of each of the sterols isolated from the gonad or muscle and digestive gland. The seasonal variations in the sterol content of the gonad seem be related to the reproductive cycle, while the sterol content of the digestive gland appears to be linked to diet, mainly diatoms or dinoflagellates. The muscle sterol content showed minor changes throughout the year.     

Seasonal variations in biochemical composition during the reproductive cycle of the veined rapa whelk Rapana venosa (Valenciennes, 1846) from the northern coast of China

Seasonal variations in the biochemical composition of Rapana venosa in relation to reproductive cycle and environment on the northern coast of China were investigated from March 2012 to February 2013. The results indicated that R. venosa has an annual reproductive cycle with synchronized gonad development in both females and males. Gametogenesis was initiated in September and gametes developed slowly during the winter, followed by rapid gonad development during spring and summer. Most individuals from this study were sexually mature between May and June, and gamete release occurred mainly between May and August. The peak of spawning was found in July and the recovery of the gonad was observed between August and November. The key biochemical components including glycogen, protein and lipid were analysed in four tissues, specifically the gonad, digestive gland, mantle and foot. The declining glycogen content in the gonad, digestive gland and mantle during maturation suggested that glycogen was consumed during the development of the gonad. Lipids and protein can be stored in the digestive gland and used during the winter in a period of food shortage. The protein and lipid contents in the ovaries increased during gonad development, which suggested that the protein and lipid had been accumulated as vitellin in oocytes.     

Environmental Influences on Mass Dynamics of the Cotton Rat (Sigmodon hispidus) Thymus Gland

The influence of season on thymus gland mass was examined relative to captivity, gender, and age in 921 cotton rats (Sigmodon hispidus) from free-ranging and laboratory populations. Age-related involution of the thymus gland was evident in free-ranging males and females and captive females. A distinct seasonal cycle in thymus mass dynamics was apparent among adult cotton rats. Mass of the thymus gland was greatest from late fall to early winter before declining 2-4 fold during spring. Thymus gland mass remained low through spring and summer in adult cotton rats when reproductive activity was maximum. No seasonal cycle in thymus mass was apparent among juveniles. Possible involvement of sex hormones in regulating thymus size is discussed.     

Purification and biochemical characterization of a cadmium metallothionein from the digestive gland of the Antarctic scallop Adamussium colbecki (Smith, 1902)

A cadmium-binding protein was purified from the digestive gland of the Antarctic scallop, Adamussium colbecki, and biochemically characterized. Purification procedures included gel permeation and anion exchange chromatography, followed by preparative polyacrylamide gel electrophoresis. Our results demonstrate that the A. colbecki cadmium-binding protein has the general properties of metallothioneins: low molecular weight of about 10 kDa, spectroscopic features typical of cadmium thiolate clusters and high metal (cadmium) content. Analysis of amino acid composition reveals the absence of aromatic amino acids, histidine, methionine and arginine. Asparagine and glutamine are also absent. The A. colbecki metallothionein shows high levels of glycine (14%), aspartic acid (14%), glutamic acid (11%) and a low lysine content (4%); the A. colbecki metallothionein shows a lower cysteine content (12%) compared to other metallothioneins (17–30%) purified from both vertebrate and invertebrate organisms. The presence of a metallothionein in the digestive gland of A. colbecki suggests that in cold-ocean-adapted molluscs the heavy metal homeostasis mechanisms may have evolved similarly to those of organisms living in temperate marine environments, although the A. colbecki cadmium-binding protein shows a typical amino acidic composition that might reflect a peculiar physiological role. Accepted: 7 August 2000     

Growth and reproduction of the bay scallop, Argopecten irradians (Lamarck) at its southern distributional limit

Growth and reproduction in a Florida population of bay scallop, Argopecten irradians (Lamarck), existing at the southern limit of its distribution, was monitored over a 3-yr period. Somatic growth accompanied increasing water temperature between May and August, when maximum mantle, digestive gland, and adductor muscle weights and indexes were observed. From July through September, reproductive development was correlated with a decline in adductor muscle weight and index. Maximum gonad weight, gonad index, and oocyte diameter were found in late September and early October. Spawning commenced at this time in conjunction with decreasing water temperature.In comparison to more northern populations, the reproductive cycle of the Florida bay scallop occurs later in the year and is characterized by a higher gametogenic initiation temperature, a decreased maximum gonad index and decreased oocyte diameter, and a shift in reproductive energy resources from digestive gland (available food) to adductor muscle (pre-stored reserves). Increased metabolic rate associated with higher temperature and coupled with decreased food supply results in the Florida bay scallop having less energy available for reproduction, ultimately limiting its southern distribution.     

Biochemical characterization of the antioxidant system in the scallop Adamussium colbecki, a sentinel organism for monitoring the Antarctic environment

 The scallop Adamussium colbecki can be profitably used for monitoring Antarctic coastal environments but its utility would be increased if chemical analyses of pollutants were integrated with data on their biological effects. Since oxidative stress is a common pathway of toxicity induced by xenobiotics, a preliminary biochemical characterization was carried out on the antioxidant system of this species and baseline data collected for future assessment of the anthropogenic impact in this remote area. The digestive gland and gills were investigated for levels of glutathione and the activity of several glutathione-dependent and antioxidant enzymes: gluthathione reductase, EC 1.6.4.2; glyoxalase I, EC 4.4.1.5; glyoxalase II, EC 3.1.2.6; gluthathione S-transferases, EC 2.5.1.18; Se-dependent, EC 1.11.1.9 and Se-independent, EC 2.5.1.18 gluta-thione peroxidases; catalase, EC 1.11.1.6; and super-oxide dismutase, EC 1.15.1.1. The same enzymatic activities were measured for comparison in the Mediterranean molluscs Mytilus galloprovincialis and Pecten jacobaeus. Very high levels of glutathione S-transferases were found in the digestive gland of both species of scallop compared to mussels, suggesting the importance of different feeding behaviour among these molluscs. However, catalase activity, much higher in Adamussium colbecki than in the Mediterranean molluscs, may represent a biochemical adaptation to the Antarctic marine environment with high levels of dissolved oxygen. Enzymes from the Antarctic species appeared to be generally more active at low temperatures but, with a few exceptions, their activities increased at higher temperatures. Received: 20 March 1996/Accepted: 29 May 1996     

Variation of lipid classes among organs of the Northern krill Meganyctiphanes norvegica, with respect to reproduction.

Lipid content and class in the Northern krill Meganyctiphanes norvegica (digestive gland, stomach, gonad, fat body, abdomen) was investigated and correlated with sex and reproductive stage. Ready to spawn females, have high lipid content in ovaries, while in males and spent females, the major site of lipid deposits was the digestive gland, followed by the fat body. These differences among spawning and spent females are indicative of strong interactions between the ovary and digestive gland and the ovary and fat body during vitellogenesis. Triacylglycerols (TAG) were the major neutral lipid class with high levels in the digestive gland. The major phospholipid was phosphatidylcholine (PC) particularly in the muscular tissue of the abdomen. Phosphatidyl-ethanolamine (PE) and -serine-inositol (PS-PI), were present at intermediate levels. Reproductive males were depleted in TAG and diacylglycerols (DAG) in the digestive gland, gonad and fat body, and had 4 times lower cholesterol in the gonad than ready to spawn females. Furthermore, ready to spawn females had in the ovary higher amounts of TAG, DAG and phospholipids (PC, PE, PS-PI) than spent females. Linear relationships between lipid content and main lipid class (TAG, PC, PE, PS-PI) in different fractions of males and ready to spawn females showed that: (1). TAG was stored for both sexes in all cephalothorax fractions with highest values in the digestive gland and ovary fluid; (2). PC was accumulated for both sexes in the fat body and the gonad with a higher slope for females, with the highest values in the ovary fluid and in the abdomen of males and that (3). PS-PI was stored only in the ovary and abdomen of mature females. These results are discussed in terms of the strategy developed by Meganyctiphanes norvegica to allocate lipids to the next generation for optimised embryogenesis.     

Storage and reproductive strategy of the carpet-shell clam,Ruditapes decussatus in the Gulf of Gabès (Tunisia)

In this study, the variations of glycogen concentrations in Ruditapes decussatus from Sfax coasts (Tunisia) were described in relation to the reproductive cycle. Separate analyses were made of gonad, adductor muscle and ‘remainder’. The timing of gametogenic development and spawning was evaluated using qualitative histology associated with image analysis including (1) the estimation of the gonadal occupation index (GOI), (2) surface area occupied by reserve tissues and (3) variation in oocyte diameter. The reproductive cycle of R. decussatus exhibited partial asynchronization between sexes, the major difference being observed in the duration of the spawning period. Contrary to previous studies, we observed continuous partial spawning (e.g. 50% of ripe oocytes still subsisted at the partial spawning stage). During the gametogenic cycle, GOI varied significantly in males and in females. Most oocytes were ripe and ready to spawn when their diameter reached or exceeded 45?µm. The expansion of gonad was inversely proportional to the development of the foot tissue. Glycogen concentration showed significant temporal variations between tissues, indicating the clear differentiation in energy storage between the clam organs.     

The reproductive cycle,condition index and biochemical composition of the horse-bearded mussel <Emphasis Type="Italic">Modiolus barbatus</Emphasis>

The horse-bearded mussel Modiolus barbatus (Linneus, 1758) is an important edible bivalve in the Adriatic Sea; its population is especially large in the Mali Ston Bay area, where the species is present at depths up to 8 m. In order to assess the sustainable exploitation rate for this species, as well as to estimate its potential capacity for a sustainable aquaculture production, we determined the species’ reproductive cycle along with its nutrient storage strategy, employing histological and biochemical methods. The population shows significantly more females than males, and no hermaphrodites. The smallest adult individual, an active male, was 16.0 mm in length, suggesting that sexual maturation starts around this length. While the period between January and February is characterized by sexual repose, early and late stages of gametogenesis were found between March and May, and spawning peaked from June till August. The increase of oocyte diameter followed the same trend. A significant positive correlation was observed between gonad index and temperature, and a negative correlation between gonad index and salinity. Oscillations of stored nutrients were tightly coupled with the gametogenic cycle.     

Age,growth and reproduction of a population of spined loach,Cobitis taenia (L.)

751 specimens of spined loach, Cobitis taenia (L.), were collected and studied over the period October 1972–October 1974. The majority of the males were found to die at the end of the 2+ season and the majority of the females at the end of the 3+ season. Back calculations for length at age were carried out from otolith measurements and found to correspond closely to actual measurements. Males and females grew similarly up until the end of their 1+ year of life, with most rapid growth occurring in the first year. Females continued to grow rapidly up to 2+, the rate then being reduced; the males showed an increasingly reduced rate of growth after the 1+ year. Ford Walford plots gave L∞ results which corresponded closely in most cases with the largest observed specimens. Gonad development and maturation of males and females followed different patterns. Males matured during the 1 + year at a length of approximately 40 mm from which point their dry gonad weight remained at a steady 0.02–0.03% of the body weight. Females appeared to mature a year later and their ovary weight and oocyte diameter increased with fish age. A seasonal cycle in gonad development was evident in females. There was a greater proportion of females to males, especially in the older age group. Spawning time was estimated to be between June and July.     

Metal (Fe, Zn, Mn and Cu) levels in the Antarctic fish Notothenia coriiceps

During the 1994/1995 Antarctic summer 20 Antarctic cod (Notothenia coriiceps) of both sexes were collected at King George Island, South Shetland Islands, Antarctica, to determine the levels of Fe, Zn, Mn and Cu in muscle, liver, gonad and kidney. Metal levels were assessed using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) technique. The levels of Fe, Zn, Mn and Cu observed in both sexes of N. coriiceps were significantly lower in muscle tissue than in liver, kidney and gonad; the livers of males and gonads of females had the highest levels. The differences between the sexes were significant for Zn and Mn in gonads and for Cu in liver. Despite the modest size-range of the specimens, the Cu levels in liver, muscle and kidney were significantly inversely correlated with female mass (P < 0.05) as was gonad Cu level and male body length. Fe mainly presented the highest concentrations and Cu and Mn the lowest ones. Mean muscle metal levels are similar to those of hake, cod, herring and mackerel; however, the level of Fe was slightly higher. Accumulation may occur for Fe, Zn and Mn in liver, kidney and gonad, which have higher levels than those of most prey. Received: 21 October 1997 / Accepted: 1 February 1998     

Sex‐specific reproductive investment of summer spawners of Illex argentinus in the southwest Atlantic

Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length‐weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade‐offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length‐digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning.     

Spawning season and size at sexual maturity of <Emphasis Type="Italic">Kyphosus bigibbus</Emphasis> (Kyphosidae) from northwest Kyushu,Japan

The reproductive characteristics of Kyphosus bigibbus were examined using individuals collected between June 2004 and February 2009 off Nagasaki Peninsula in northwest Kyushu, Japan. The spawning season and size at sexual maturity of this species were characterized based on a gonad index and histological examination of the gonads. The spawning season extends from June to October. This species is assumed to be an indeterminate, multiple-batch spawner. Females reached sexual maturity at larger size than males (fork length at 50% sexual maturity: males 284 mm, females 360 mm).     

黑斑侧褶蛙消化道重量及长度的性别和季节差异

消化道是联系脊椎动物能量摄入和能量支出之间关系的纽带,其重量和长度对外界环境具有高度的敏感性和弹性(flexibility)。以黑斑侧褶蛙(Pelophylax nigromaculata)为研究对象,测定了山东聊城地区2012年夏季(16只,8♀/8♂)、秋季(19只,9♀/10♂)及翌年春季(17只,8♀/9♂)其体重、体长、胴体湿重和干重系数、总消化道及各段(食道、胃、小肠和大肠)的湿重、干重和长度系数的性别和季节差异(双因素方差分析),对有性别差异的指标,用单因素方差分析分别比较了雌、雄蛙的季节差异。结果显示,1)雌蛙的体重、体长均高于雄蛙,都在秋季最高,春季或夏季最低;雄蛙的胴体湿重系数高于雌蛙,夏季高于秋季;胴体干重系数既无性别差异,也无季节差异。2)除食道湿重系数无性别差异外,雌蛙总消化道及各段的湿重系数均高于雄蛙;除胃湿重系数无季节差异外,春季或秋季的总消化道及各段的湿重系数都高于夏季;雌蛙的总消化道干重和胃干重系数高于雄蛙,食道、小肠和大肠的干重系数无性别差异,所有的干重系数均无季节性差异。3)除雌蛙的大肠长系数高于雄蛙外,总消化道及各段的长度系数均无性别差异,春季和秋季的总消化道长、食道长及胃长系数均高于夏季,小肠长和大肠长系数均无季节性差异。结果表明,随着季节更替,黑斑侧褶蛙消化道各段的重量和长度表现出一定的弹性特征,这与各器官的功能及其生活环境的多样性是相适应的。     

Impact of a castrating trematode, Neophasis sp., on the common whelk, Buccinum undatum, in the northern Gulf of St. Lawrence

We observed heavy trematode infections of whelks, Buccinum undatum, from the Mingan Islands, eastern Canada, by larval stages of a species of Neophasis. Only sexually mature whelks were infected, 23% of mature females and 15% of mature males, and prevalence increased rapidly with whelk size. In most cases the parasite completely occupied the gonad, causing castration. The digestive gland was also infected, although to a lesser degree (0% to 50% occupation), and a marked reduction in the mass of the penis was associated with the infection. A decrease in the proportion of whelks with a highly infected digestive gland between May and August 1994 suggested mortality of infected individuals. Whelks held for 12 to 15 months in the laboratory retained the infection but did not show significant mortalities (possibly because food was abundant and predators absent). The larval stage of Neophasis sp. found in whelks was a cercaria; however, the tail easily detached. The putative infective stage (metacercaria) was not observed but may be present in whelks in late winter and early spring. Other trematode parasites observed were adult Steringophorus furciger in the stomach and larval Renicola sp. in the digestive gland.     

Seasonality in the uropygial gland size and feather mite abundance in house sparrows Passer domesticus: natural covariation and an experiment

The seasonal change, i.e. the marked differences between seasons of low and high productivity, in the abundance of ectosymbionts and the defence intensity of the host against pathogens is a well defined characteristic of temperate zone organisms. Here we investigate the seasonal variation in the uropygial gland size and the abundance of Proctophyllodes feather mites on the wing feathers of house sparrows Passer domesticus in two breeding populations. The size of the uropygial gland varied significantly in male and female house sparrows over the annual cycle. The gland was small during the non‐breeding and mating season, after that it started to grow sharply, reaching its maximum size during breeding. Females had larger gland volumes than males during breeding, and the increase in gland size during breeding was more pronounced in females than in males. The number of feather mites was the lowest during breeding, followed by an increase during moult, and reaching its maximum between the wintering and mating seasons. The absence of a significant relationship between the uropygial gland size and the abundance of feather mites, after controlling for potential confounding variables, supports the view that gland oils do not regulate the number of mites. To investigate further this hypothesis, through a full factorial experimental design we tested the effect of uropygial gland and photoperiod manipulation on the population size and population dynamics of feather mites. The manipulation of uropygial gland had no effect on mites, supporting our observational results. As a result of the experimentally increased day‐length, the abundance of feather mites on wing feathers decreased significantly and more sharply than in the control group, supporting the previous anecdotal evidence about the photosensitivity of these organisms. Using photoperiodic cues, feather mites may respond to seasonal changes that affect their life‐history and population dynamics.     

Space use of common genets<Emphasis Type="Italic">Genetta genetta</Emphasis> in a Mediterranean habitat of northeastern Spain: differences between sexes and seasons

The seasonal home range size and spatial relationships of 16 adult genetsGenetta genetta Linnaeus, 1758 (6 males and 10 females) were estimated in a Mediterranean habitat of northeastern Spain. Genets minimum density was estimated as 0.98/km². Mean annual home range was 113.1 ha in males and of 72.0 ha in females. Males had larger home ranges than females in all seasons, but differences were only significant in winter. Home range size changed seasonally and showed a similar pattern in both sexes, with lower values in summer (males — 41.2 ha, females — 29.0 ha) and maximum ones in spring (males — 78.8 ha, females — 56.1 ha). Animals displayed spatial fidelity throughout the year. Core areas (MCP50) represented 27% and 19% of total home range size for males and females, respectively. Resting home ranges (based on locations of inactive animals) were 9 times lower than overall home range size. Individuals of the same sex overlapped less than individuals of different sexes, especially with regard to core areas, which showed almost no overlap. The results obtained suggest that (1) different factors are likely to affect the space use of genets, such as body mass, food abundance and reproductive cycle; (2) genets use space in a heterogeneous way, with areas of greater activity than others within their home range; (3) there was intrasexual segregation with regard to space use.     

Histology of the reproductive tissue of the clam Ruditapes decussatus from the gulf of Gabès (Tunisia)

Summary

The gametogenic cycle of the clam Ruditapes decussatus was investigated during one year. Samples were collected each month in two different sites located at the gulf of Gabès area. Gametogenic activity was characterized on the basis of histological analysis of the gonads. A classification and a scoring system were then proposed. According to our study, Ruditapes decussatus gametogenesis can be divided in four major steps: (1) a sexual rest (December- February), (2) starting of gametogenesis (February-March), (3) development (March-May), (4) ripe (from April onwards). This study revealed that the gonad of the clam Ruditapes decussatus was surrounded by muscular tissue which could represent the principal storage tissue. Two kinds of hermaphroditism appeared since maturity of gonads: simultaneous one showing gonadal tubules of both males and females in regionally distinct and separate zones and a “superposed” one showing a gonad consisting essentially of mature male gametes and few residual oocytes.     

Seasonal changes in the flight apparatus of winged females and sexual males of the aphid <Emphasis Type="Italic">Tuberculatus quercicola</Emphasis> (Hemiptera: Aphididae)

Tuberculatus quercicola (Matsumura) feeds on Quercus dentata Thunberg, and has mutualistic interactions with ants. Tuberculatus quercicola has two winged morphs in its life cycle, winged females appear in summer and sexual males appear in autumn. Previous studies have shown that wing loading (ratio of body volume to wing area) is higher for the winged females, because of ant attendance, resulting in extremely low dispersal. It is known that the nutritional quality of host plants is high in spring and autumn, when leaves are growing or senescent, and low in summer when leaves are mature. This study examined the effects of seasonal plant deterioration on the development of flight apparatus (wing size and flight muscle) of winged females and males. Moreover, field intercept traps were used to examine the extent of dispersal of males. The results showed that seasonal plant deterioration affected development of the flight apparatus of winged females, particularly flight muscle. Flight muscle development was significantly higher in winged males in autumn than in winged females. However, winged males were not caught in any of the traps. The different resource allocation to the flight apparatus of winged females and males is discussed.     

Cytomorphology of female and male gonads in Antarctic toothfish <Emphasis Type="Italic">Dissosctichus mawsoni</Emphasis> (Nototheniidae) from the Ross Sea in the summer period

Results of histological analysis of gonads of female and male Antarctic toothfish Dissostichus mawsoni caught in the Ross Sea of the Pacific sector in the period of Antarctic summer (December–February) 2004–2005 are presented. Morphological indices and index of gonad maturity are described and ecological criteria of assessment of maturity stages of ovaries, cytological indices of oocytes, and the type of toothfish oogenesis are determined. It was established that in the period of fishing Antarctic toothfish, females and males with gonads at maturity stage III dominate. Ovaries contain two groups of oocytes of the period of trophoplasmatic growth and large oocytes of the nearest spawning season that comprise the smallest proportion of total sex cells. In the testes of two male toothfish, the primary fusion of renal and generative tissues was revealed. It is suggested that the termination of gonad maturity of toothfish takes place from March to April, and spawning takes place from June to August.