Differential digestion and evacuation rates of prey in a warm-temperate grouper, gag Mycteroperca microlepis (Goode & Bean)

Prey-specific gastric evacuation rates and digestion state indices were modelled for gag Mycteroperca microlepis , a large warm-temperate grouper, consuming meals of either baitfish (scaled sardine Harengula jaguana ) or crab (purple swimmer crab Portunus gibbesii ). Power exponential models best fit the wet and dry mass gastric evacuation data and the average digestion indices over post-prandial time (PPT), regardless of prey type or gag size (Adjusted R² ≥ 0·79). Gag mass ( M ) or total length ( L _T) incorporated into an expanded power exponential model, along with exponential scalars, resulted in highly predictive ( R² ≥ 0·87) gastric evacuation and average digestion state models. The expanded power exponential models fit to the baitfish and crab wet mass gastric evacuation data differed significantly (Kimura's likelihood ratio test (LRT), both P < 0·001). Gag consuming crab showed a digestive lag period of at least 4 h (wet mass) and took a longer time to complete digestion relative to gag consuming baitfish. Gag, as well as many other warm-temperate and tropical groupers, consume a mixture of fish and crab prey and they will therefore require the development of a consumption model that incorporates mixed-prey gastric evacuation models.     

Stock Identification of Gag, Mycteroperca microlepis, Along the Southeast Coast of the United States

The gag grouper Mycteroperca microlepis is an important component of commercial and recreational fisheries along the South Atlantic coast of the United States and in the Gulf of Mexico. Over the past two decades, this species has experienced significant declines in abundance and an increasing skew in sex ratios. Analysis of microsatellite DNA variation in this species shows mosaic patterns of population subdivision and significant departures from Hardy-Weinberg equilibrium in all sampling locations. Given the length of the pelagic stage (egg and larvae), the prevailing current patterns, and the migratory capabilities of the adults, it is unlikely that these observations are the result of restricted gene flow among genetically differentiated populations. The apparent structure of gag populations most likely reflects inbreeding in size-limited populations. Population declines, skewed sex ratios, and perhaps variance in female fecundity appear to have acted in concert to limited the number of individuals that contribute to a given year class. These data are reinforced by studies of other fish stocks that have experienced precipitous declines over the past two decades. Received April 13, 1998; accepted September 30, 1998.     

Patterns of serum cortisol levels in ovariectomized females with and without androgen administration.

Serum cortisol levels in humans and primates display a circadian rhythm. A study in monkeys showed that orchiectomy abolishes this circadian rhythm. The present study compared the patterns of serum cortisol levels between 9 a. m. and 3 p. m. in two groups of ovariectomized females, one treated with testosterone (T) and one without sex steroid administration. Over the first 80 minutes of the sampling period cortisol levels declined similarly in both groups, probably due to waning of stress of the experiment. Thereafter, levels fell further in the T-administered group, but not in the group without sex steroid administration. From this pilot study it is tentatively concluded that ovariectomy, in analogy with orchiectomy in monkeys, produces a loss of a circadian pattern of cortisol levels, which is reversed by administration of T. Furthermore, upon comparison of mean serum cortisol levels in the two groups, T appeared to have a suppressive effect on values of serum cortisol levels.     

Defense of females, but not social status, predicts plasma androgen levels in male spotted hyenas

A positive correlation between male social status and testosterone levels is expected and often found in social species with high rates of agonistic interactions or when social relationships among males are unstable. In contrast, in species with low rates of agonistic interactions or when social relationships are stable, testosterone levels should not correlate with social status. The "challenge hypothesis" predicts that androgen levels should rise during periods of courtship or mate guarding. We addressed these questions in free-ranging spotted hyenas, a species with low rates and low intensities of aggression among males but where males spend extensive effort to court females. In males, we measured testosterone, its precursor androstenedione, and its metabolite 5alpha-dihydrotestosterone. As predicted, testosterone levels were significantly higher and androstenedione levels tended to be higher in males that, at the time of sampling, defended a female, compared with males that did not defend a female. Also, as predicted, there was no correlation between social status and androgen levels in male spotted hyenas.     

Developmental androgen fluctuations and the five dimensions of mammalian sex (with emphasis upon the behavioral dimension and the human species)

Evidence reported largely in the past twenty years is reviewed regarding how mammals are sexually differentiated through variations in circulating levels of a set of biochemicals called androgens. Five fairly distinct dimensions of the sexual differentiation process are identified as follows: the genetic dimension, the genital dimension, the neuro-organization dimension, the nongenital morphological dimension, and the behavioral dimension. The problem of designating a mammal's “overall sex” is briefly discussed. Then, the basic process whereby a “dynamic equilibrium” in androgen levels tends to be maintained within an animal is described, along with an account of the kinds of experiential encounters a mammal can have that can dramatically “upset” the equilibrium. Finally, a “threshold range” concept of androgenic effects upon behavior is discussed, along with an outline of four basic interactive processes whereby behavior apparently can be affected by variations in androgens.     

Seasonal fluctuations of pancreatic activities and cyclic nucleotide levels in the frog Rana esculenta

1. Seasonal influence on pancreatic activity has been determined in the frog Rana esculenta. 2. Protein content, amylase activity and cyclic nucleotide levels, show significant changes throughout the year, being higher in the active period (spring, summer), with respect to a constant pancreas weight. 3. A significant correlation between protein content and cyclic AMP levels has been observed. 4. Results suggest that feeding habits exert a control on the pancreatic activity even if stimuli other than food intake cannot be ruled out.     

Seasonal variations of diatoms and dinoflagellates in a shallow,temperate estuary,with emphasis on neritic assemblages

Seasonal changes in the diatom and dinoflagellate assemblages were examined in the neritic zone of the Urdaibai estuary (north Spain) with regard to some major physical and chemical variables during an annual cycle. A total of 81 diatoms and 38 dinoflagellates were identified and quantified during the study period. Both groups displayed a distinctive pattern of seasonal succession. The seasonal distribution of the Shannon index showed a trend of increasing values from the upper estuary to the lower neritic segment. The diatom diversity maxima were observed in February, April and September, and dinoflagellate maxima in April–May, July and October. Diatoms dominated the assemblages, reaching 1×10⁶ cells l^–1 from April to September. A shift from large diatoms and dinoflagellates to small bloom-forming taxa was observed during winter–early spring. A spring diatom bloom composed of Rhizosolenia spp. was observed in April, while small chain-forming taxa (chiefly Chaetoceros spp.) dominated from June to September. Cell maxima for both groups in late summer were produced by the diatoms Chaetoceros salsugineum and Skeletonema costatum, and by the dinoflagellates Heterocapsa pygmaea and Peridinium quinquecorne. Silicate availability by river supply and strong tidal-mixing of the water column seem to determine the year-round dominance of diatoms over dinoflagellates.     

Tsg101, an inactive homologue of ubiquitin ligase e2, interacts specifically with human immunodeficiency virus type 2 gag polyprotein and results in increased levels of ubiquitinated gag

The final stages of budding and release of a retroviral particle from the cell require the late (L) domain of Gag. Recently, ubiquitin and ubiquitin ligases have been implicated in the late stages of retroviral budding. In a yeast two-hybrid screen of a T-cell cDNA library to identify cellular proteins that interact with human immunodeficiency virus type 2 (HIV-2) Gag polyprotein, we identified Tsg101, an inactive homologue of ubiquitin ligase E2. Tsg101 and HIV-2 Gag interact specifically in vitro and in vivo. The interaction requires the L domain PTAPP motif in the p6 domain of HIV-2 Gag and the N-terminal Ubc-conjugation homology domain of Tsg101. Tsg101 is incorporated into HIV-2 virions. Expression of the N-terminal Ubc-conjugation homology domain of Tsg101 inhibits the release of HIV-2 virus particles. Overexpression of Tsg101 results in an increase in the level of ubiquitination of HIV-2 Gag. Our results provide evidence for recruitment of the ubiquitination machinery of the cell during late stages of the viral life cycle, mediated by the viral Gag protein.     

Seasonal fluctuations of the testicular androgenic function in rats

Testicular steroid-delta 5-3 beta-ol-dehydrogenase activity and plasma testosterone level in pubertal Wistar rats in spring and summer are 2-4 times higher than in autumn and winter. On the contrary the weight of the ventral prostate and seminal vesicles is lower in summer as compared with that in other seasons. This divergence is probably caused by fluctuations of the glandular secret content.     

Seasonal changes in the daily rhythms of animals

Seasonal changes in the timing of circadian activity rhythms have been recorded in mammals, birds, reptiles and arthropods. There are probably far more wide spread than is generally realised and are especially important in desert regions with large daily temperature fluctuations. Synchronisation of the onset of circadian activity with changes in the times of dusk and dawn is achieved mainly by responses to changes in photoperiod.

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Zusammenfassung An Beispielen wird gezeigt,dass jahreszeitliche Veränderungen in der Steuerung der circadianen Aktivitäts-Rhythmen bei Säugern, Vögeln,Reptilien und Arthropoden bestehen. Sie sind wahrscheinlich viel häufiger, als im allgemeinen erkannt wird und sind besonders wichtig in Wüstenregionen mit grossen täglichen Temperaturschwankungen. Die Synchronisation des Beginns der circadianen Aktivität mit Veränderungen der Zeiten der Abend- und Morgendämmerung wird hauptsächlich durch Reaktionen auf Veränderungen der Tageslänge erreicht.

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Resume On démontre au moyen d'exemples qu'il existe des modifications saisonnières dans la dispersion des rythmes circadiens de l'activité des mammifères, des oiseaux, des reptiles et des arthropodes.Ces modifications sont probablement beaucoup plus fréquentes qu'on ne l'admet généralement et sont importantes surtout dans les régions désertiques où l'on rencontre de très grandes variations de température. La synchronisation du début de l'activité circadienne avec les changements de l'heure de l'aube et du crépuscule est due, en général,à des réactions aux modifications du photopériodisme.

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Parts of this paper were presented during the Fourth International Biometeorological Congress, New Brunswick, N.J., 26 August–2 September 1966.     

Seasonal changes in the cardiomyocytes of heterothermal animals

In 20 Citellus erythrogenys the volumetric and surface densities of myofibrils, mitochondria, sarcoplasmic reticulum, T-system and lipid drops were estimated in cardiomyocytes by means of stereological methods before, during and after hibernation. The volumetric and surface-volumetric ratios for the main intracellular compartments were calculated. Certain morphological criteria were found for the seasonal peculiarities in the structural organization of cardiomyocytes in the hibernating rodents. During hibernation, myocardial atrophy (seasonal regression of the heart weight and decreasing diameter of cardiomyocytes) takes place. It is accompanied with an adaptive rearrangement of the cardiomyocyte ultrastructure. The latter facilitates to myocardial contractility at low body temperatures at the expense of activation of the cellular transport-energic interaction system.     

Exploring the structure of genetic variation and the influences of demography on effective population size in the gag grouper Mycteroperca microlepi (Goode & Bean)

Using 11 microsatellite markers, genetic analyses of three successive year-classes of gag Mycteroperca microlepis juveniles across the north-eastern Gulf of Mexico revealed a lack of spatial structure and very little temporal variation between year-classes. These results are consistent with long-term effective population sizes on the order of 30 000 adults. The importance of reproductive-style and sex-ratio variation is discussed as an important influence on long-term effective sizes.     

Glutathione levels during the mosquito life span with emphasis on senescence

Glutathione levels were determined in mosquitoes of all ages of the life span. Specific analyses for reduced (GSH) and oxidized (GSSG) glutathione were used and validated to ensure minimal autoxidation of GSH and conversion of these forms. Indeed GSH accounted for greater than 97% of the total glutathione (GSH + GSSG) content in all samples. Marked changes occurred during the life span, and the highest levels of GSH and total glutathione were found during larval growth and metamorphosis (P less than 0.001). Thereafter the levels decreased in the early adult, plateaued in the mature, and decreased 46% in the old and very old mosquito (P less than 0.001). This aging-specific decrease was a general phenomenon, for it occurred in all body regions of both sexes. Starvation up to 3 days did not affect the GSH levels. The importance of these changes in glutathione is its relationship to the reducing and biosynthetic capacities of different life span stages. Of special interest is the senescence decrease which can lead to lower biosynthetic activity and also impaired detoxification capacity.     

Seasonal fluctuations of body condition in northern sika deer on Hokkaido Island, Japan

We analyzed seasonal and sexual fluctuations in kidney mass (KM) and kidney fat mass (KFM) as indices of condition in Hokkaido sika deerCervus nippon yesoensis Heude, 1884. For 76 male and 132 female sika deer, seasonal fluctuations in KM and KFM were given by fitted sine wave growth curves. Although the kidney fat index (KFI) is used frequently to evaluate animal condition, we reject it because it is based on the assumption that kidney mass is proportional to body mass in all seasons. Our data did not support this assumption. KFM is a better indicator of Hokkaido sika deer condition than KFI. Although sex-based differences in cervid KFM are said to reflect differences in reproductive cycles, the seasonal similarities in sika deer KFM levels may represent adaptations to the long severe Hokkaido winter. Because in our study deer populations were at low densities and had high pregnancy rates, our sine wave growth models can be regarded as reference for fat level fluctuations in Hokkaido sika deer.     

Patterns of stable carbon isotope turnover in gag, <Emphasis Type="Italic">Mycteroperca microlepis</Emphasis>, an economically important marine piscivore determined with a non-lethal surgical biopsy procedure

To determine the feasibility of using stable isotopes to track diet shifts in wild gag, Mycteroperca microlepis, populations over seasonal timescales, we conducted a repeated measures diet-shift experiment on four adult gag held in the laboratory. Fish were initially fed a diet of Atlantic mackerel, Scomber scombrus, (mean δ¹³C = −21.3‰ ± 0.2, n = 20) for a period of 56 days and then shifted to a diet of pinfish, Lagodon rhomboids, (mean δ¹³C = −16.6‰ ± 0.6, n = 20) for the 256 day experiment. We developed a non-lethal surgical procedure to obtain biopsies of the muscle, liver, and gonad tissue monthly from the same four fish. We then determined the δ¹³C value of each tissue by isotope ratio mass spectrometry. For the gonad tissue we used the relationship between C/N and lipid content to correct for the influence of lipids on δ¹³C value. We observed a significant shift in the δ¹³C values of all of the tissues sampled in the study. Carbon turnover rates varied among the three tissues, but the shift in diet from mackerel to pinfish was clearly traceable through analysis of δ¹³C values. The turnover rates for muscle tissue were 0.005‰ day⁻¹, and for gonad tissue was 0.009‰ day⁻¹. Although it is generally thought that tissue turnover rates in ectotherms are driven primarily by growth, we found that metabolic rate can be a major factor driving tissue turnover in adult gag.     

Patterns of mating-system evolution in hermaphroditic animals: correlations among selfing rate, inbreeding depression, and the timing of reproduction

In hermaphrodites, traits that influence the selfing rate can coevolve with inbreeding depression, leading to the emergence of evolutionary syndromes. Theory predicts a negative correlation between inbreeding depression and selfing rate across species. This prediction has only been examined and validated in vascular plants. Furthermore, selfing rates are often influenced by environmental conditions (e.g., lack of mates or pollinators), and species are predicted to evolve mechanisms to buffer this variation. We extend previous studies of mating-system syndromes in two ways. First, we assembled a new dataset on Basommatophoran snails (17 species, including new data on 12 species). Second, we measured how species responded to variation in mate availability. Specifically, we quantified the waiting time before selfing (i.e., how long the onset of reproduction is delayed in the absence of mates). Selfing rates were negatively correlated with both inbreeding depression and the waiting time. Species with stronger inbreeding depression exhibited longer waiting times. These patterns obtained on Basommatophorans still hold when including eight other hermaphroditic animals. Our results support the hypothesis that selection drives the evolution of mating-system syndromes in animals. The reaction norm of selfing rates to mate availability is a key target of natural selection in this context.     

Stimulatory activity of cysteamine on juvenile hormone release in adult females of the cockroach, Blattella germanica

1. A study of the activity of cysteamine in relation to juvenile hormone (JH) production in adult females of Blattella germanica was carried out. 2. In vivo assays showed that cysteamine stimulates protein synthesis in the left colleterial gland and, in some instances, enhances oocyte growth. 3. In vitro assays demonstrated that cysteamine enhances JH release by incubated corpora allata (CA), and that this effect is more pronounced when using CA from 10-day-old females (period of ootheca transport), either connected to the corpora cardiaca (CC) or to the CC and to the brain. 4. Possible antiallatostatic effects of cysteamine are discussed.