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.     

Variation of metallothioneins in gills of the clam Ruditapes decussatus from the Gulf of Gabès (Tunisia)

Cadmium (Cd) and metallothionein (MT) concentrations were determined in the subcellular fractions of the gills of the clam Ruditapes decussatus. Clams were collected monthly during the period of sexual development (from June to August 2001) from two different sites situated in the Gulf of Gabès (Tunisia). These sites differ by their degree of metal contamination. Differences in condition index (CI) were observed in June and August between clams from both sites. In clams from both sites, cadmium was approximately equally distributed between the soluble (S1) and insoluble (C1) fractions. MT levels varied according to month but not sex. Site and body mass of clams seem to be important factors to explain the variation of MT levels compared to cadmium.     

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.     

Does cadmium pollution affect reproduction in the clam Ruditapes decussatus? A one-year case study

The effect of cadmium (Cd) on the reproduction of Ruditapes decussatus was monitored over a period of 12 months, from June 2001 to June 2002. Two sites "Bordj d'Ungha" and "El Hofra" differing by their degree of cadmium contamination were chosen in the Gulf of Gabès area (Tunisia). Annual mean concentrations of Cd in the whole soft tissues of clams from the site El Hofra were more than 4 times higher than those from the site Bordj d'Ungha (reference site). The gametogenic cycle of the clam R. decussatus was also investigated by histological examination and monthly observations of gonadal sections in a population of clams from both sites. The results show that gametogenesis occurred from March to December in clams from both sites. Nevertheless, spawning and emission of gametes were synchronized in both sexes from only the clams of the reference site. Although this species is considered as gonochoristic, 6.6% of hermaphroditic cases were observed in clams from both sites in which gametes of both males and females were in ripe stage. Moreover, the period of ripening of sexual products led to an increase of condition index and to a decrease of Cd concentrations in the whole soft tissues of clams from both sites, hence reflecting the phenomenon of "biological dilution".     

Reproductive cycle of the European clam Ruditapes decussatus from Óbidos Lagoon,Leiria, Portugal

ABSTRACT

In Portugal, the European clam (Ruditapes decussatus) is an important commercial resource. Óbidos Lagoon is a strong candidate as a cultivation area to increase European clam exploitation. However, the reproductive biology of this population has not been described. In this work, the reproductive cycle of R. decussatus was characterized by determining gonadal development stages, gonad index, condition index, and biochemical composition. The relationship between reproduction and environmental parameters (sea surface temperature, chlorophyll a, and particulate organic matter) was assessed. Ruditapes decussatus had an annual reproductive cycle. The gametogenic cycle started in late winter, and the ripe stage in spring was followed by spawning that began at the end of spring/early summer and extended until early autumn. The subsequent period of sexual rest occurred during the winter. Condition index showed seasonal variations related to food availability (chlorophyll a). The European clams in Óbidos Lagoon recovered rapidly after their reproductive period, most likely owing to the availability of food. This study will help to improve sustainable management of this wild stock and is important for future aquaculture development of this species.     

Seasonal changes of reproductive behavior and fecal steroid concentrations in Père David's deer.

From July 1997 to September 1997 and from March 1998 to July 1998, we studied reproductive behaviors of Père David's deer in Dafeng, China. During the field behavioral observations, we collected fresh voided fecal samples from the Père David's stags and hinds periodically and kept those samples under -20 degrees C until laboratory analysis. We analyzed the fecal testosterone, estradiol, and progesterone concentrations in those samples using radioimmunoassay. During this study, we also recorded 17 types of male reproductive behaviors and nine types of female reproductive behaviors. Reproductive behaviors and the fecal steroid concentrations showed overt seasonal fluctuations. There were statistically significant correlations between some male reproductive behaviors, such as anogenital sniffing, urine sniffing, urine spraying, wallowing, bellowing, antler adorning, Antler swags mud, chasing, herding hinds, chin resting, mounting and copulating, with the fecal testosterone concentrations. These results suggested that seasonal reproductive behaviors in stags are strongly associated with circulating testosterone. We also found that some female reproductive behaviors fluctuate corresponding with changes in fecal estrogen concentrations. Although there was no direct evidence to confirm the correlations between female reproductive behaviors and fecal estrogen in our experiment, we could not rule out that reproductive activities of hinds were largely related to ovarian estrogen secretion, and estrogen is necessary for inducing female reproductive behaviors.     

Wintering waterbird assemblages in the central part of the Gulf of Gabès in southern Tunisia

Although the Gulf of Gabès is recognised as an Important Bird Area, several aspects of the ecology of waterbirds inhabiting this area still need to be investigated. We observed how waterbird foraging guilds varied among habitats. In total, 49 species belonging to 16 families were recorded. Winter visitors accounted for 73% of counts. The avifauna was dominated by shorebirds (52% of records), followed by large wading birds (25%), open-water birds (18%) and waterfowl (5%). However, the structure of local waterbird communities and their composition in terms of foraging guilds varied according to habitat type. The bird communities of sandy beaches were dominated by open-water birds, whereas large mudflats were dominated by shorebirds, and wadi estuaries showed a more even representation of foraging guilds. Locally rare species had narrow distributions, whereas locally abundant species were found widely within the gulf. For four species the 1% population level criterion of the Ramsar Convention was exceeded. Overall, our results show that the Gulf of Gabès hosts important numbers of waterbirds with different ecological requirements, which confirms the importance of this gulf as a wintering area for Palearctic waterbirds.     

Increased squalene concentrations in the clitoral gland during the estrous cycle in rats: an estrus-indicating scent mark?

Squalene in the rat clitoral gland is reported to be semi-volatile and may serve as a chemo-signal. The objective was to determine squalene concentrations in the clitoral gland throughout the reproductive cycle. Clitoral glands were extracted with dichloromethane; 23 compounds were identified with Gas Chromatography linked Mass Spectrometry (GC-MS). Since squalene concentrations were significantly higher during proestrus and estrus, and remarkably reduced during metestrus and diestrus, we inferred that it could be an ovulation-indicating chemosignal in the female rat, acting as a scent mark for the male. This hypothesis was tested by investigating its efficacy to attract males, including studying the role of the olfactory-vomeronasal system of the male in perceiving squalene. For detection of squalene, males used their conventional olfactory system when at a distance from the female, whereas the vomeronasal organ was used when they were in close proximity to the female. We concluded that squalene was a female-specific chemosignal that attracted males, and furthermore, that the olfactory-vomeronasal system had an important role in the perception of squalene.     

High interannual variation in the hatching sex ratio of Tengmalm’s owl broods during a vole cycle

The sex ratio at hatching in broods of Tengmalms owl (Aegolius funereus) in northern Sweden was investigated for 3 years characterized by different phases of the vole and owl cycle. Previous work showed the sex ratio in this species to be male-biased for 1 year with a favourable food supply, and that in feeding experiments male nestlings (but not females) suffered higher mortality when food was limited, but not otherwise. Here we present data from a complete 3-year owl cycle, showing that mean brood sex ratio varied significantly among years, being male-biased (65% males) in the first year of high owl breeding density, unbiased (49%) in the second year of high owl breeding density, and female-biased (33% males) in the owls low year. Brood sex ratio did not vary significantly within years with laying date or parental age. Vole availability, and therefore the owls food supply, declined during the 3 years studied. Tengmalms owl parents thus appear to adaptively adjust the sex ratio of their broods according to the expected annual mortality risk of sons.     

Intersex in the clam Scrobicularia plana: a sign of endocrine disruption in estuaries?

The phenomenon of endocrine disruption is currently a source of growing concern. Feminization of male fish in UK rivers has been shown to occur extensively and has been linked with exposure to endocrine-disrupting compounds present in the environment. Much less is known of the extent and scale of endocrine disruption in estuarine and marine ecosystems, particularly in invertebrates. We present evidence that intersex, in the form of ovotestis, is occurring in the common estuarine bivalve Scrobicularia plana, which is considered to be inherently gonochoristic. We report varying degrees in the severity of ovotestis in male S. plana, and have adopted and developed a grading method to assess the extent of this intersex condition. These findings indicate that S. plana offers potential for widespread screening and investigation of endocrine disruption, helping to focus remediatory strategy.     

Vitellin and vitellogenin concentrations during oögenesis in the first gonotrophic cycle of the house fly,Musca domestica

The house fly, Musca domestica, contains at least two native vitellin and two vitellogenin proteins. Both vitellins appear to have an identical vitellogenin partner. The major native vitellin has a mol. wt of 281 K Daltons, and the major native vitellogenin has a mol. wt of 283 K Daltons. These proteins are composed of three subunits with mol. wt of 48, 45 and 40 K Daltons. The relationship of the subunits to the native proteins is not known.Haemolymph vitellogenin levels are cyclical during oögenesis with no detectable amounts in previtellogenic flies and low levels in postvitellogenic flies. The highest level of vitellogenin, 10.5 μg/μl, occurred in flies with stage-7 ovaries. The vitellogenin levels during oögenesis fit a parabolic curve and the fat body vitellogenin content during oögenesis showed this same pattern.Uptake of vitellogenin into the ovary during each stage of oögenesis also fit a parabolic curve and produced a high linear correlation with haemolymph vitellogenin levels. The greatest uptake was 37 μg/stage and occurred during stage 6.     

Breeding patterns in the pre-desert oniscid isopod Porcellio buddelundi of Matmata (Gabès,Tunisia)

Porcellio buddelundi inhabits arid areas in Tunisia. The reproductive pattern of a population at Oued El Jir, Matmata (Tunisia) was studied from July 2005 to June 2006. Monthly samples were taken during the study period. The overall sex ratio was biased toward females. Males, females, and newborns all had greater body-mass in autumn than in spring and their lowest mean body-mass was in June and July. Ovigerous females greater than 41.1 mg in body-mass, were collected from March through May and from September through October, suggesting seasonal reproduction with two breeding seasons: the longer one in spring (3 months) and another in the fall (2 months). Fecundity, which was positively correlated with the body-mass of females, varied between breeding seasons with a large number in spring and a small number in autumn. Seasonal variation of fecundity could be explained by the growth rate of ovigerous females affecting the fecundity more in spring than in autumn. The onset of breeding, in P. buddelundi, takes place when the day-length exceeds 12 h and the soil moisture decreases.     

Studying the evolution of social behaviour in one of Darwin’s Dreamponds: a case for the Lamprologine shell-dwelling cichlids

The link between the evolution of advanced sociality and cognition has been an important concept across fields and taxonomic boundaries. However, in many study systems, ecological and phylogenetic confounds impair evolutionary inferences drawn when comparing social organization. Here, we highlight the value of the shell-dwelling Lamprologine cichlids of Lake Tanganyika in studies of cognitive and social evolution. These species show differences in social organization, both within and across species, but otherwise exhibit remarkable similarities in their ecology and life history. We focus on the ecological and social attributes of 15 Lamprologine cichlids that live in permanent association with empty gastropod shells, often in syntopy and with largely overlapping ecological niches. We then discuss difficulties with terminology and categorization of social organization, outlining current and emerging methodologies to address these limitations. Our goal is twofold: (i) to gather available empirical evidence on the behaviour, life history, and ecology of shell-dwelling Lamprologine cichlids, highlighting their potential in comparative studies of cognition and evolution, and (ii) to stimulate debate and critical appraisal of current terminology and categorizations of social structure, ideally leading to more precise and empirically standardized definitions of sociality in cichlids.

     

Validation of a culturally modified short form of the McCarthy Scales of Children’s Abilities in 6 to 8 year old Zimbabwean school children: a cross section study

Background

The burden of cognitive impairment among school children from developing communities is under reported due to lack of culturally appropriate screening tools. The objective of this study was to validate a culturally modified short form of the McCarthy Scales of Children Abilities (MSCA) in school children aged 6–8 years from varied backgrounds.

Methods

One hundred and one children aged 6–8 years attending mainstream classes were enrolled cross-sectionally from three schools: one rural and two urban. Two assessments were conducted on each child and the Short form MSCA was compared to an independent assessment by the educational psychologist.

Results

When comparing the results of the MSCA to local standard at -2SD, -1.5 SD and -1SD the sensitivity rates ranged from 17 to 50% with lower sensitivity at -2SD cut-off point. Specificity rates had less variation ranging from 95% to 100%. The number of children identified with cognitive impairment using -2SD, -1.5SD and -1SD below the mean for MSCA as a cut-off point were 3(3%), 7(7%) and 13(13%) respectively while the psychologist identified 18 (18%). The overall mean score on MSCA was 103 (SD 15). The rural children tended to score significantly lower marks compared to their peers from urban areas, mean (SD) 98(15) and 107(15) respectively, p=0.006. There was no difference in the mean (SD) scores between boys and girls, 103(17) and 103(15) respectively, p=0.995.

Conclusion

The culturally modified short form MSCA showed high specificity but low sensitivity. Prevalence of cognitive impairment among 6 to 8 year children was 3%. This figure is high when compared to developed communities.

     

School’s Out: Seasonal Variation in the Movement Patterns of School Children

School children are core groups in the transmission of many common infectious diseases, and are likely to play a key role in the spatial dispersal of disease across multiple scales. However, there is currently little detailed information about the spatial movements of this epidemiologically important age group. To address this knowledge gap, we collaborated with eight secondary schools to conduct a survey of movement patterns of school pupils in primary and secondary schools in the United Kingdom. We found evidence of a significant change in behaviour between term time and holidays, with term time weekdays characterised by predominately local movements, and holidays seeing much broader variation in travel patterns. Studies that use mathematical models to examine epidemic transmission and control often use adult commuting data as a proxy for population movements. We show that while these data share some features with the movement patterns reported by school children, there are some crucial differences between the movements of children and adult commuters during both term-time and holidays.     

A study of spatial and temporal variability in the adenine nucleotides of lake phytoplankton during a diel cycle (Lac Pavin — France)

A study of diel variations in the adenine nucleotide concentrations of natural phytoplanktonic populations led to the following conclusions:There are significant diel variations in cellular ATP concentrations. However, this temporal variability is not as great as the spatial variability between the various sampling depths, characterized by different phytoplankton populations. Within a globally stable pool of adenine nucleotides, diel variations inside the algal cell mainly take place at the expense of ATP and AMP, while ADP concentrations remain relatively stable.The statistical relationship between algal biomass obtained from cell counts and from adenine nucleotides also confirms maximum stability for ADP and (ATP + ADP + AMP). The diel variations in adenine nucleotide cell concentrations gradually become smaller with depth. This probably reflects the importance of light in causing such variability.     

Variation in body condition of breeding Savi’s Warblers Locustella luscinioides: the reproductive stress and flight adaptation hypothesis revisited

Current theory suggests that mass change in adult birds while breeding may be adaptive (to reduce wing-loading during nestling feeding) or result from physiological stress. To test which might be more important in determining mass loss in breeding Savi’s Warblers (Locustella luscinioides), we used a new approach in which the variation in four indices of body condition was described: weight, fat score, muscle score and lean weight (i.e. excluding fat and muscle). We expected weight variations to be adaptive if they involved changes in fat and lean weight, whereas physiological stress should influence the muscle score to a greater extent. As in other species, females showed a greater variation in weight, and carried more fat, than males during the breeding cycle. During incubation, females had greater weight and fat score than males. The weight remained constant and lean weight declined in both sexes, whereas females increased in muscle, which probably reflects the regression of the reproductive organs. During the nestling stage, both sexes declined significantly in all four indices of condition, showing evidence of physiological stress. However, the greater decline in weight in females than in males is consistent with the flight-adaptation hypothesis, as are the cyclic changes in lean weight associated with the various nesting attempts. The fact that both sexes declined significantly in weight, muscle and lean weight with an increasing number of nesting attempts, but not in fat, which was recovered after each nestling period, also indicates that both reproductive stress and adaptive changes occur during breeding. When the whole breeding season was considered, females showed a greater decline in muscle than males, which we interpret to be evidence for a greater reproductive stress in females. We suggest that the small breast muscle size and depleted protein reserves at the end of the breeding period might influence future survival through impaired flight ability and a compromised post-breeding moult.     

Ostreopsis cf. ovata in the Gulf of Gabès (south-eastern Mediterranean Sea): morphological,molecular and ecological characterization

In the last few decades, the frequency of the toxic benthic dinoflagellate Ostreopsis cf. ovata proliferation has increased in the Mediterranean Sea. These blooms are associated with harmful effects on human health and the environment. The present work provides the first long term study on the spatio-temporal distribution of O. cf. ovata in relation to physical parameters in the Gulf of Gabès coastal waters (south-eastern Mediterranean Sea), as well as its morphological, molecular and physiological features. The strains of O. cf. ovata were identified morphologically by light and epifluorescence microscopy. The morphology and the size range of cultured strains were similar to those described regarding O. cf. ovata isolated from the Mediterranean Sea. The ultrastructural analysis of O. cf. ovata cells using the transmission electron microscopy showed the presence of numerous vesicles (VE) containing spirally coiled fibers (SCFs) connected to the mucus canal (CH). The phylogenetic tree based on the internal transcribed spacer region containing the 5.8S rDNA (ITS-5.8S rDNA) revealed that O. cf. ovata strains were placed into the Mediterranean/Atlantic clade. In addition, O. cf. ovata toxicity was evaluated by the mouse bioassay and a dose level ≥ 4 × 10⁴ cells was found to be lethal to mice. The examination of the O. cf. ovata occurrence in the Gulf of Gabès at a large temporal scale (1997–2012) revealed a clear seasonal pattern with dominance from midsummer (July) to late autumn (November). Furthermore, a positive correlation was found between the abundance of O. cf. ovata and salinity, whereas no correlation was found as regards temperature. The occurrence of O. cf. ovata was only detected at salinity above 35 and the highest concentrations were observed at 45. Laboratory experiments confirmed such a result and showed that isolated O. cf. ovata strains had optimal growth at salinity ranging between 35 and 45, with its peak at 40.