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According to sex allocation theory, hermaphrodites allocate a fixed amount of resources to their male and female functions, and the proportion of resources invested in each sex depends on the mating group size. Measures of trade-offs between male and female functions are usually made directly by estimating the number of gametes or the size of the gonads. In this study, we focused on the effect of social conditions (i.e. mating opportunities) on the expression of some morphological traits and on their plasticity in the protandrous simultaneously hermaphroditeOphryotrocha diadema. We investigated whether inO. diademathe morphological traits, which are dimorphic inOphryotrochadioecious species – upper-jaw size, prostomium size, body size and number of rosette glands − are plastic when they respond to variations in social conditions and whether variations in these traits are associated with variations in male and/or female reproductive success. Plasticity of the traits was analysed during both the juvenile and the adult phases in order to check whether phenotypic plasticity is limited to the developmental phase or can be manifested throughout the whole lifespan of the animals. Our results showed that the number of rosette glands, the upper-jaw size and the prostomium size are traits that are plastic inO. diadema. Indeed, the number and size of these traits changed according to the variation of social conditions. However, we found no association between the plastic morphological traits and male or female reproductive success. [ABSTRACT FROM AUTHOR]

Labile sex expression is considered to play a key role in the evolution of breeding systems and in the transition from hermaphroditism to dioecy, according to the evolutionary models proposed for plants. While in hermaphrodites sex allocation within the individual can be plastically adjusted in response to social environment, in dioecious species it is predicted to be fixed. However, labile sex expression in the form of gender plasticity can still be present in dioecious species of animals with environmental sex determination. It is still unclear how gender plasticity is involved in the evolution of breeding systems and what its role is in the transition from hermaphroditism to dioecy. We assessed the degree of plasticity in gender expression in three dioecious species of polychaete worms of the genus Ophryotrocha. We found sexual polymorphism and plasticity in sex expression during the juvenile phase to be a response to social environment. The majority of juveniles reared with an adult female or male expressed the gender opposite of that of the partner, so as to form heterosexual pairs. On the basis of these findings we outline a possible evolutionary pathway of the transition from hermaphroditism to dioecy in the genus Ophryotrocha. [ABSTRACT FROM AUTHOR]

Sex allocation theory assumes that male and female reproductive functions share a common limited resource pool and are negatively correlated in hermaphrodites. Here we report on the first artificial selection experiment designed to test the existence of genetically-based correlations between sex functions in hermaphroditic animals. The polychaete wormOphryotrocha diademahas a long juvenile male phase, and then shifts to the simultaneously hermaphroditic phase. We selected two sets of lines of worms for a short male phase and, after four generations, worms had a significantly shorter male phase than their generation-0 ancestors. As negatively correlated responses, generation-4 worms spent more time maturing eggs and produced a higher number of eggs at 1st laying than worms of generation 0. Both traits contributed to the female function and were not the target of the selection experiment. In contrast, selection was ineffective in the lines descending from phenotypically-hermaphroditic worms that reproduced only via their male function. Our results provide the first empirical support of a genetic basis for a trade-off between traits related to the male and female function in hermaphroditic animals and highlight that these trade-offs are complex. Our results also suggest that the trade-off between male and female functions breaks up as hermaphrodites evolve some sexual specialization where resources are channeled towards a single sexual function. [ABSTRACT FROM PUBLISHER]

A longitudinal study was done on the infant feeding practices in a rural area. One hundred and ten infants were followed up from birth to 1 year of age by alternate day home visits, to inquire about the type of food, and frequency of consuming it. It was found that 100% mothers breast-fed their infants from birth to 1 year, almost every day. But, bottles containing various kinds of milk and starchy food were added to 60% of infants diets by 3 months, and 80% by 5 months of age. This additional food was given mostly in diluted form, which was more so in case of tinned milk. Family food such as rice and vegetables were given in 30% and 40% child days respectively from 6 months to 1 year. Rural people withhold protein food and fruits during infancy. It is concluded, that infant feeding practices in our population is improper and mothers should, therefore, be trained and motivated on weaning practices for timely and adequate supplementation to ameliorate the presently observed dietary deficiency and early malnutrition in rural Bangladesh. [ABSTRACT FROM AUTHOR]

Ophryotrocha diademais an outcrossing, simultaneous hermaphroditic polychaete with external fertilization. In isolated pairs, mature worms take turn contributing eggs upon the condition that their partners reciprocate egg donation. In dense populations, these worms do not reciprocate. Instead, they strongly compete for mating in their preferred male role and produce few eggs. This plastic sex allocation may result in an overall different reproductive performance: mean individual reproductive output will be larger in sparse than in dense populations. We tested this hypothesis by measuring the individual reproductive output (paternal and maternal offspring) of worms in sparse and dense replicated populations. In dense populations, mean individual reproductive output was fourfold lower than that in sparse populations. We hypothesise that such dramatic demographic costs are potentially widespread in outcrossing simultaneous hermaphrodites with external fertilization and plastic sex allocation. The reproductive output of hermaphroditic organisms is a function of population density (i.e. the number of conspecifics) and studies on population growth and reproductive performance should take this effect into account. [ABSTRACT FROM PUBLISHER]

Local Mate Competition theory (LMC) predicts female-biased offspring sex ratios when mate competition occurs locally between siblings. The mating system of the marine polychaete wormDinophilus gyrociliatusapparently fits LMC theory well. Females lay egg capsules with 3–6 large eggs (which produce females), and 1–2 small eggs (which produce males), resulting in female-biased sex ratios. However, mating occurs between larvae, inside egg capsules, and brothers fertilize sisters, possibly preventing any competition between unrelated males and obviating the need for sex ratio adjustments to local population size. Therefore, we tested whether mothers adjusted their offspring sex ratio to local population size, controlling for density. As predicted by LMC theory, sex ratios of single females were less male-biased than those of populations of multiple females, suggesting that males also compete with unrelated males. Sex ratio adjustments occurred irrespective of density, revealing sophisticated perception of the social environment in these worms. [ABSTRACT FROM AUTHOR]

Karyotypes of four chironomid species were studied: Cryptochironomus obreptans Walker, Cryptochironomus sp., Chironomus plumosus Linnaeus, and Stictochironomus rosenscholdi Zetterstedt. All these species belong to the subfamily Chironominae. Each species is characterized by a specific karyotype structure. The first species in the list has 2 n = 4, while the three other species have 2 n = 8. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is the environment-induced change in the phenotype of an organism. Natural selection operates for the ability of individuals to adjust their phenotype to the current environmental conditions when environmental conditions fluctuate. Simultaneous hermaphrodites may exhibit plasticity in sex allocation according to the availability of mates at any particular time. The plasticity in sex allocation has probably evolved under fluctuating mating opportunities, which are usually low but increase when hermaphrodites incur sudden demographic expansion. Here we compare the plasticity in sex allocation in two different populations of the hermaphroditic polychaete wormOphryotrocha diadema– a laboratory population and a wild one. Worms from the laboratory population were kept under constant crowded conditions for about 200 generations (i.e. they were exposed to high mating opportunities). Worms from the wild population were kept under crowded conditions for 20 generations only. Worms from the laboratory population showed significantly less plasticity in sex allocation than worms from the wild population. Although we cannot rule out the hypotheses that genetic drift or local adaptation played a role in the differences between the two populations, the most likely explanation for our results is that worms of the laboratory population underwent a loss of plasticity in sex allocation because they were kept under constant mating opportunities. In fact, the sensory and regulatory machinery that worms use for exhibiting plastic sex allocation responses is likely to be the same as the machinery that is required for mate searching and sex role synchronization between mating partners. The need to maintain this machinery can explain why worms from the laboratory population diminished their plasticity in sex allocation but did not lose it completely. Therefore our results give some clues as to how plasticity in sex allocation evolves or is constrained. [ABSTRACT FROM PUBLISHER]

The long-term impact of pollution in freshwater aquatic environments can be assessed realistically only if the mutagenic effects of pollutants on organisms inhabiting aquatic biotopes are evaluated. To do this, the larvae of Chironomids (Diptera) can serve as suitable indicators of potential environmental genotoxicity. These larvae exhibit aberrations in their polytene chromosomes, which, when analyzed, indicate an early response to toxicity more efficiently than morphological analysis, up to now the usual technique. Chironomids have excellent salivary gland chromosomes with well-defined bands and permanent somatic pairing, where there are two important regions of active transcription—Balbiani rings (BRs) and Nucleolar organizers (NOR). We have described the responses of different Chironomid species in two situations: in the field and in the laboratory, where we performed Cr, Al, Pb and Cu trace-metal-exposure experiments with Chironomus riparius. In both situations, the genome response consisted in a statistically significant increase in somatic chromosome aberrations and decrease in BR and NOR activity to levels lower than those of larvae under standard conditions. The main chromosome aberrations consisted in inversions, amplifications, deletions and deficiencies. Deletions in the chromosome G in C. riparius transformed it into a pompon-like structure. Chromosome aberrations were not randomly distributed: they occurred mainly in sites with repetitive DNA elements that have a highly interspersed location in the C. riparius genome. Hence C. riparius is the species most likely to produce aberrations and can be used as a model for cost-effective monitoring of the early genomic response to trace metals and other stress agents. [ABSTRACT FROM AUTHOR]

The isonymic method has been generally accepted in population genetic studies and surnames have been successfully used to investigate human populations as if they were genetic markers associated to the Y chromosome. In this study we analysed the microevolution dynamics of Postua, a mountain village of North Western Italy, by means of demographic methods. The uniqueness of this community is due to its past geographical and cultural isolation and to the high frequency of marriage between relatives. During the study period considered (1640–1989) the population underwent several fluctuations in size and other demographic parameters such as the endogamy, isonimy and consanguinity rates. Until the first half of the XIX century Postua appears to be a village characterised by a closed and isolated community, with high endogamy (80–90%) and isonimy (up to 34.4%). Only at the beginning of the XX century, when the population started to be subjected to significant immigration fluxes, data show a progressive reduction of the isolation. The population showed two demographic peaks, the first around the second half of the XVIII century (1639 inhabitants) and the second at the end of the XIX century (1464 inhabitants). The S/N ratio was low (0.2–0.3) and relatively constant until the beginning of the last century, and only in the last three decades of the XX century, when the population was subjected to immigration, Postua showed a significant increase in the S/N ratio values (to about 0.9). The surname frequency was constant until the 1850 when almost all surnames were the same as those already present in the XVII century. From the first half of the XIX century, the founder surnames decreased, whereas new surnames started to increase and became persistent in the population. [ABSTRACT FROM AUTHOR]

The role of sexual selection in shaping the mating system of hermaphrodites is currently widely accepted. However, a quantification of the intensity of sexual selection in hermaphroditic animals has never been accomplished. We evaluated the opportunity for sexual selection for both the female and the male functions in the simultaneous outcrossing hermaphrodite Ophryotrocha diadema by measuring focal hermaphrodites’ paternal and maternal offspring in experimental replicated monogamous and promiscuous populations, using genetic markers to estimate paternity. Opportunity for sexual selection for each of the two sexual functions was quantified by means of the Crow’s index, i.e. the ratio of variance in progeny number to the squared mean number of progeny. In addition, the extent to which the reproductive success was shared among competing individuals was estimated by means of the Nonacs’s B index. We documented that the strength of selection on the male and female function in hermaphrodites with external fertilization depends on the reproductive context. Under a promiscuous regime, hermaphrodites have higher opportunities for selection for both the male and the female function than under the monogamous regime. Moreover, the reproductive skew for the female function becomes greater than that for the male function, moving from monogamy to promiscuity. In our model system, allocation to one sexual function is opposed by any degree of allocation to the other, indicating that sex-specific patterns of selection operate in this model species. [ABSTRACT FROM AUTHOR]

Because of their double sex functions, hermaphrodites are selected to optimize their investment in the two sex functions. Sex allocation (SA) theory predicts that, in promiscuous mating conditions, simultaneous hermaphrodites should adjust their reproductive investment so as to invest an amount of resources into the male relatively larger than that invested into the female function. In contrast, in monogamy, individuals should invest relatively larger amount of resources into the female function at the expenses of the male function. In the study of SA patterns of simultaneous hermaphrodites little attention has been paid to allocate adjustments costs, which may play an important role in determining variations in SA pattern among species. Indeed, the costs paid for such adjustments may constrain sex investment resulting in suboptimal allocation. We evaluated the costs of SA adjustments on individual fitness in each sexual function in the simultaneous, outcrossing hermaphrodite Ophryotrocha diadema. Following a crossover design, we compared the reproductive success in paternal and maternal offspring of focal hermaphrodites, which were put in replicated monogamous and promiscuous regimes. We document that those hermaphrodites that switched mating regimes and altered their sex investment accordingly did not entail large short-term fitness costs in any sexual function compared to those that were in stable mating regimes. Indeed, individuals changed their sex investment quickly and appropriately to current mating conditions. Hermaphrodites, which had to adjust their SA, did not decrease their maternal or paternal reproductive output with respect to those which did not change their SA. Time needed to shift resources from one to the other sex function is 5 days (the time interval between successive egg layings is of 3 days) indicating that selective pressures for SA adjustments may favour great plasticity and quick adjustments of sex investments in simultaneous hermaphrodites. [ABSTRACT FROM AUTHOR]

We present a new surface velocity field for Baja California using GPS data to test the rigidity of this microplate, calculate its motion in a global reference frame, determine its relative motion with respect to the North American and the Pacific plates, and compare those results to our estimate for Pacific–North America motion. Determination of Pacific Plate motion is improved by the inclusion of four sites from the South Pacific Sea Level and Climate Monitoring Project. These analyses reveal that Baja California moves as a quasi-rigid block but at a slower rate in the same direction, as the Pacific Plate relative to North America. This is consistent with seismic activity along the western edge of Baja California (the Baja California shear zone), and may reflect resistance to motion of the eastern edge of the Pacific Plate caused by the ‘big bend’ of the San Andreas fault and the Transverse Ranges in southern California. [ABSTRACT FROM AUTHOR]

Sex allocation theory predicts that simultaneous hermaphrodites shift sex allocation facultatively in response to variation in local group size. This study was performed to evaluate the relative investment in each sex function by the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema and to test whether allocation to each sex depends on the number of reproductive competitors. Four experimental groups were set up (in a 2 × 2 factorial design) with small or large group size and with small or large enclosures to control for potential confounding effects of density. We measured the proportion of female and male investment in focal individuals. Results revealed that individuals regulated their reproductive output so that when reproductive competitors were present, the number of female gametes was strongly reduced and the male function increased. In contrast, under monogamy, individuals in small groups produced lower numbers of sperm but had a higher egg output than worms in large groups. Density did not affect sex allocation in our experiment. Our findings provide qualitative support for Local Mate Competition theory, but also show that the pattern of sex allocation specific to this species is more complex than expected by current theory. [ABSTRACT FROM AUTHOR]

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SEMG investigation protocols are described within the neurological framework. A neuro- anatomic pathway is utilized including muscular disease, neuromuscular junction conditions, peripheral neuropathy, radiculopahy, myleopathy, brainstem disorders, cerebellar disorders, subcortical and cortical disease. SEMG findings within the clinical presentation of those pathologies are aimed at improving the diagnostic process and serve to focus the SEMG neuromuscular reeducation (biofeedback) component of the overall treatment plan. [ABSTRACT FROM AUTHOR]

Ophryotrocha diadema is a simultaneous hermaphroditic worm whose peculiar mating system involves forming pairs within which partners exchange eggs repeatedly in a kind of serial monogamy. To test whether direct recognition of the former partner exists in this species we checked whether two familiar partners, after a short separation, spawned again without engaging in a new courtship. In contrast, non-familiar partners were expected to invest a longer time in courtship before spawning again. Results indicate that no direct individual recognition of a former mate exists and that only indirect cues are used to identify former partners. [ABSTRACT FROM PUBLISHER]

Among polychaetes sequential hermaphrodites are generally protandrous and their sex allocation strategy appears to fit well with the Ghiselin size advantage hypothesis. In Ophryotrocha puerilis male reproductive success drops with increasing size because females prefer to mate with small males to avoid a costly conflict over sex. Moreover both partners of a pair can simultaneously change sex several times after some spawnings. Females being soon drained of resources, due to the higher reproductive and social costs of their role, switch to the less costly male role and males thus become more apt to function as females. Also in the simultaneously hermaphroditic species so far studied, O. diadema and O. gracilis, the male profit-effort function for reproductive success shows a decreasing slope. Some 80% of the physiological reproductive effort is allocated to the female functions. Simultaneous hermaphroditism is stabilized by slow sperm production and regular egg trading between partners of a pair. Local mate competition (LMC) has probably been important in the evolution of facultative change of gender in many polychaetes. In the population of the labile gonochoric Capitella sp. I males which are unable to gain access to females may develop into hermaphrodites and function as females, thereby offsetting the loss of mating success as males. The LMC model could explain also the female biased sex ratios found in several polychaete populations. Due to the slow mobility of adults, many populations are subdivided into very small breeding groups or show sib mating (e.g., in Dinophilus gyrociliatus daughters are inseminated by their brothers and mothers can control the sex of their offspring). Finally, conditions that lead to the evolution of biparental, uniparental or paternal care of embryos in polychaetes that do not spawn freely into the sea are discussed. [ABSTRACT FROM PUBLISHER]

Genome size (or C-value) in benthic polychaetes was studied from both experimental data and literature. Nuclear DNA content variation was analysed as related to both phylogenetic relationships of various families, general life habit of the species (interstitial vs macrobenthic), diploid chromosome number (2n), and mean body size (length). Experimental data on genome size were obtained for 43 lower taxa (genera and species) by means of microdensitometric analysis of the amount of Fuelgen-stained haploid DNA in interphase nuclei. These data, added to those available in the literature (36 taxa studied by Conner et al., 1972) gave a total of 79 taxa (genera and species), representing 30 families and 14 orders. Twenty-one of the species studied belonged exclusively to interstitial (=meiofaunal) families or genera. [ABSTRACT FROM PUBLISHER]

Patella caerulea L., P. aspera Lam. (= P. ulyssiponensis Gmelin). P. rustica L. (= P. lusitanica Gmelin) are coexisting Mediterranean species of the genus Patella. P. caerulea and P. rustica have a haploid complement of n=9 with seven metacentric and two telocentric chromosomes, while P. aspera has a haploid complement of n=8 without telocentric chromosomes. To better define the phylogenetic relationships among these three species, an electrophoretic analysis of 12 enzyme coding loci was performed on samples of the three species collected from Laigueglia (Liguria, Italy) in 1989. On the whole, genotypic frequencies were in agreement with Hardy-Weinberg expectations and no significant differences were observed among the populations of the three species as far as their genetic structure is concerned. Nearly 50% of the sampled loci were diagnostic. Nei's genetic distance was 0.82 between P. caerulea and P. aspera, 0.97 between P. aspera and P. rustica and 0.94 between P. caerulea and P. rustica. By greatly separating P. rustica from the other two species, results of the electrophoretic analysis are consistent with the traditional view, which regards P. aspera and P. caerulea as more closely related than P. rustica on the basis of radular teeth morphology. Using genetic distances and the assumptions of the molecular clock, lineages leading to P. aspera and to P. caerulea may have diverged from the stem common to P. rustica ca. 18 million years ago. [ABSTRACT FROM AUTHOR]

In the Polychaete worm Ophryotrocha diadema, the yellow coloration of egg yolk is due to the selective uptake of lutein from food. The genetic control of this mechanism depends on a single locus with 2 alleles, the dominant Y (yellow) allele, and the recessive y (absence of coloration) allele. [ABSTRACT FROM AUTHOR]