Male mating success,sexual size dimorphism,and site fidelity in two species of Malacoctenus (Labrisomidae)

Synopsis In both Malacoctenus hubbsi and Malacoctenus macropus, males defended preferred oviposition sites from both other males and potential egg predators. In M. hubbsi, adult females were larger than adult males. Larger M. hubbsi males were not associated with territory parameters that were correlated with higher mating success, and male size was not correlated with mating success. Male size did affect mating success when territory parameters were statistically controlled for, but the failure of large males to associate with better territories eliminated any mating advantage for larger males. In M. macropus, males are larger than females. Larger males defended preferred oviposition sites, and had higher mating success than did smaller males. Male M. macropus also had much higher site fidelity than male M. hubbsi. These results suggest that the evolution of the differences in site fidelity and sexual size dimorphism between these two species may be due to sexual selection acting differentially in these two species.     

Observations on the life history of the belted sandfish,Serranus subligarius (Serranidae)

Synopsis The biology of Serranus subligarius, a typical inhabitant of low limestone reef outcroppings and artificial reefs from North Carolina to Florida and in the northern Gulf of Mexico, was studied on inshore jetties in the northeastern Gulf of Mexico from February 1974 to April 1975. The length-weight relationship was expressed by the equation W = 0.000006L^3.431. Growth was greatest in the first year (43.5 mm SL) and declined in the remaining three years of life (17.3, 10.5, and 7.1, respectively). In individuals larger than 40 mm SL, gammaridean and caprellid amphipods were the most numerous food items but crabs, shrimp, and fishes were the most important food items by weight. In individuals less than 40 mm SL, copepods were the most numerous food item, but gammaridean amphipods and shrimp were the most important items by weight. Two incidents of cannibalism were recorded. The ovotestis of the belted sandfish is composed of two lobes which are broadly united posteriorly, with the testicular tissue restricted to a broad band encircling the posterior region of the gonad. Age-group 1 fish are functional synchronous hermaphrodites. Testicular tissue matures in the fall or winter of a fish's first year (all specimens examined histologically, including those from the nonspawning season, contained flagellated spermatozoa) while ovarian tissue matures in the following spring. Spawning season in 1974 extended from late April or early May to September. Crossfertilization is the usual reproductive mode, although individuals are capable of selffertilization.     

Variation in reproductive success and gonadal allocation in the simultaneous hermaphrodite,Serranus fasciatus

Summary This paper examines the correlates of individual size, reproductive success, gonadal allocation, and growth in a hermaphroditic reef fish. Individuals in S. fasciatus mature as simultaneous hermaphrodites; large individuals subsequently lose female function and become functional males. Daily female reproductive success was highly correlated with both hermaphrodite size and amount of female gonadal tissue. Three separate comparisons gave a positive correlation between male reproductive success and male gonadal allocation: (1) Males had higher levels of male gonadal allocation and male reproductive success than hermaphrodites. (2) The percent of gonad allocated to male tissue in hermaphrodites was higher in the year they had higher male mating success. (3) Male gonadal tissue of hermaphrodites was positively correlated with male reproductive success in the year that male reproductive success by hermaphrodites was higher and more variable. There was no evidence for a trade-off between male function, female function, and growth among hermaphrodites. Many of these patterns have also been observed in plants, but the selective pressures leading to these patterns in S. fasciatus and plants are probably quite different.     

Expression pattern of vasa in gonads of sea cucumber Apostichopus japonicus during gametogenesis and reproductive cycle

The vasa gene is a reliable germline marker to study the origin and development of germ cells and gonads, although the gene product (mRNA or protein) varies between different species. However, there has been little study on vasa genes in holothuroids to date. Here we determined the expression characteristics of the Apostichopus japonicus vasa gene (Aj-vasa) during gametogenesis in the ovary and testis using in situ hybridization and immunohistochemistry. During oogenesis, the expression pattern of Aj-vasa coincided at the mRNA and protein levels. Intensive signals in oogonia decreased gradually with the development of oocytes. Interestingly, the pattern was different during spermatogenesis. The Aj-vasa mRNA level was the highest in spermatogonia, reduced in spermatocytes, low in spermatids and absent in spermatozoa, but the Aj-VASA protein was restricted to spermatogonia and early spermatocytes. These expression characteristics of Aj-vasa persisted in both male and female gonads throughout the reproductive cycle. Our findings show that Aj-vasa mRNA is a good marker for studying the origin and migration of germline cells; moreover, Aj-VASA is a useful tool to identify spermatogonia in A. japonicus. Our findings indicate that Aj-vasa is vital in the development and differentiation of germ cells.     

Sex allocation in simultaneous hermaphrodites: Trade-offs between sex-specific costs and lifespan

Fitness in self-incompatible simultaneous hermaphrodites incorporates gains and costs from both male and female reproductive function, and evolutionarily stable allocation of gonadal tissue to male or female function depends on these gains and costs. Paradoxically, despite the often equal expected gains but different costs associated with each sex, contributions to expected reproductive success through male and female function must be identical. Whenever allocation costs are unequal and limiting resources are energetically expensive or risky to acquire, these costs must ultimately be paid through reduced survival, resolving the paradox by equally diminishing expected reproductive success as male and as female. Maximizing fitness as lifetime reproductive success – not just reproductive rate alone, as in previous studies – maximizes the product of expected survival time and reproductive rate. The analysis shows how male-biased allocation can thereby arise and generate novel predictions on the relation between intensity of sperm competition and allocation to male function.     

A preliminary study on quantitative relations among growth,reproduction and mortality in fishes

As a quantitative approach to the life histories of fishes, the present paper attempted to predict a relation among reproduction, growth and mortality numerically with a technique of control theory, the discrete maximum principle. A method for predicting the relation was derived on the postulate that natural selection maximized the net reproductive rate subject to a few constraints. The derived method was applied to Atlantic cod and Atlantic herring populations in the Southern Gulf of St. Lawrence as numerical examples. The examples demonstrated that the theoretical reproductive effort and body weight were well consistent with the observed ones every age but the theoretical survival rates were slightly different from the observed ones. For the reasons mentioned below, however, it should be interpreted that the examples rather support the adopted postulate to a certain degree. First, in general, it is very difficult to obtain good estimates of the rates with traditional methods. Second, intense fishing pressure possibly changes the life history parameters to some extent in fish populations. Moreover, the examples also suggested that, to examine the postulate in further detail, similar analyses had to be made with the data of many fish populations on which intense fishing pressure had not been exerted.     

A catalogue of skulls and jaws of eastern tropical Pacific blennioid fishes (Blennioidei: Teleostei): A proposed evolutionary sequence of morphological change

Skulls and jaws are compared in 35 species of tropical eastern Pacific (mainly Gulf of California) blennioid fishes (5 species of Tripterygiidae, 13 Labrisomidae, 12 Chaenopsidae, 5 Blenniidae). Morphotypes are arranged in a series from relatively large-mouthed fishes (tripterygiids and a few labrisomids) with protrusible jaws and conical teeth to species with small, non-protrusible jaws and a single row of incisiform teeth. This polarity of arrangement probably reflects the direction of phylogenetic development, as suggested by outgroup comparison with other perciform fishes. Distribution patterns of morphotypes in a simple morphospace, obtained by combining dentition, shape of the jaw arch and jaw protrusibility, are discussed within an adaptive context.     

Feeding patterns in eastern tropical Pacific blennioid fishes (Teleostei: Tripterygiidae,Labrisomidae, Chaenopsidae,Blenniidae)

Summary In terms of species number (47) and numerical abundance, blennioids are the most important primary resident rocky reef fishes in the Gulf of California, Mexico. We present the feeding patterns of the 34 most abundant species of blennioid fishes, 8 of which are Gulf endemics. A total of 2,144 specimens were sampled at 51 anaesthetic stations in 9 areas throughout the Gulf. Four feeding guilds were distinguished: 1) The majority (29 of 34 species) are microcarnivores exhibiting a number of different feeding strategies (ambush and stalking predators, active foragers, pickers, etc.). The more important prey categories were mobile invertebrates, and to some extent also sedentary fauna. Algae were of no importance for most of the latter species. 2) Hypsoblennius brevipinnis and H. gentilis are two omnivorous species, browsing mainly on sessile items including 52% and 13% (Vol.) algae in their diets. 3) Entomacrodus chiostictus and Ophioblennius steindachneri are herbivores, grazing on fine algae. 4) Plagiotremus azaleus specializes in cropping mucus and scales from the body surface of other fishes.Crustaceans account for 58.6% of the total volume of prey items in the 34 species investigated. Benthic amphipods were most important and made up 26% of the total volume of all prey items.Cluster analysis of percentage volumetric data using Squared Euclidian Distance and Horn's Index of Overlap produced distinct subgroups which coarsely reflected taxonomic grouping.The species are separated either by their geographic ranges, habitat and microhabitat preferences, feeding, or a combination thereof. Only rarely do sympatric species significantly overlap in diet.Trophic diversity as measured by the Shannon-index provides a tool for distinguishing: 1) specialists (6 species) from 2) low diversity feeders (18 species) and 3) high diversity generalists (10 species). Two different types of specialists can be distinguished: those which feed on the same items as the generalists but utilize only a very restricted prey spectrum (Stathmonotus sinuscalifornici and the chaenopsids Chaenopsis alepidota and Emblemaria hypacanthus). A second group of specialists (Entomacrodus chiostictus and Ophioblennius steindachneri as well as Plagiotremus azaleus) feed on items not utilized by any of the generalists.There is some evidence that high diversity generalists are numerically more abundant than the other trophic groups.In the labrisomids and blenniids a phylogenetic trend from microcarnivory towards feeding on sessile items appears to be expressed.     

Gonadal development and spawning of female ocean whitefish, Caulolatilus princeps (Pisces: Branchiostegidae) in the Bay of La Paz, B.C.S., Mexico

The developmental stages of the gonads and the spawning season of the ocean whitefish, Caulolatilus princeps , were determined. Gonad maturation is annual, and the spawning season is prolonged, from late autumn to early spring. From November to March, around 80% of the females were in an advanced mode of gonadal development, and in April most gonads were spent. From May to October the gonads were at rest and preparing for the next spawning season.
The gonadosomatic index describes the reproductive activity of the species adequately.     

Horizontal dynamics of zooplankton in subtropical Lake Blanca (Uruguay) hosting multiple zooplankton predators and aquatic plant refuges

The Gulf of California, Mexico, consists of unique environmental conditions resulting in a rich array of biological diversity. Nematodes are present in most marine sediments and are probably the most abundant metazoans. This research analyses and compares nematode biodiversity in two shallow, littoral locations of the Gulf and compares the results with other Pacific and Atlantic faunae. Samples collected in Punta Estrella and Santa Clara were processed for nematode extraction by standard methods. A total of eighty genera were identified, sixty-seven occurring in coarser sediments at Punta Estrella and fifty-five in more silty sediments at Santa Clara. Nematode abundance was higher at the latter location, on average. The region was not especially high or low in diversity compared to other littoral sites, and was most similar to locations in Europe with a corresponding ecology but at temperate latitudes. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: K. Martens     

Evolutionary stability of egg trading and parceling in simultaneous hermaphrodites: the chalk bass revisited

Several species of simultaneously hermaphroditic seabasses living on coral reefs mate by alternating male and female roles with a partner. This is known as egg trading, one of the classic and most widely cited examples of social reciprocity among animals. Some of the egg-trading seabass species, including the chalk bass, Serranus tortugarum, switch mating roles repeatedly, having subdivided their clutch of eggs into parcels offered to the partner for fertilization. Here we attempt to understand these dynamics as a pair of evolutionary games, modifying some previous approaches to better reflect the biological system. We find that the trading of egg clutches is evolutionarily stable via byproduct mutualism and resistant to invasion by rare individuals that take the male role exclusively. We note why and how parceling may reflect sexual conflict between individuals in the mating pair. We estimate evolutionarily stable parcel numbers and show how they depend on parameter values. Typically, two or more sequential parcel numbers are evolutionarily stable, though the lowest of these yields the highest fitness. Assuming that parcel numbers are adjusted to local conditions, we predict that parcel numbers in nature are inversely related both to mating group density (except at low density) and predation risk.     

VOCALIZATIONS OF A CAPTIVE JUVENILE AND FREE-RANGING ADULT-CALF PAIRS OF BRYDE'S WHALES, BALAENOPTERA EDENI

Abstract: Vocalizations were recorded from a captive juvenile Bryde's whale, Balaenoptera edeni , that stranded off the gulf coast of Florida (Pinellas Co.) and was held at Sea World of Florida. The most common vocalization was a pulsed moan with durations of 0.5–51 set and acoustic energy from 200–900 Ht. Although these sounds are unlike any reported previously from this species, there are similarities to moans recorded opportunistically during a feeding study of free-ranging B. edeni in the Gulf of California (GOC). The pulsed moans recorded from Bryde's whale adults in the GOC were shorter in duration (0.7–1.4 set) than those recorded from the captive juvenile, but the frequencies were similar (165–875 Hz). In addition, a series of discrete, regularly spaced pulses (interpulse interval = 0.5–1.0 set, 700–950 Hz) were recorded only in the presence of Bryde's whale calves in the GOC.
Pulse rates produced by the captive juvenile (20–70 pulses/set) were intermediate between those recorded in the presence of GOC adults (60–130/sec) and calves (10–20/set). With these limited data it is not possible to determine to what extent the intermediate qualities of the juvenile call reflect maturational differences in the sound production apparatus, a phase of learning to vocalize like an adult, or the characteristics of a context-dependent call not recorded in the GOC.     

Linking fish consumption patterns and health risk assessment of mercury exposure in a coastal community of NW Mexico

We aimed at characterizing the methylmercury (MeHg) exposure through fish consumption in two populations (common general and fishing-related population (FRP)) using a probabilistic health risk assessment in children, women of childbearing age, and adults in Mazatlán. The hazard quotients (HQs) were obtained from fish consumption, defined through a survey, and the levels of mercury in fishery products, obtained from published information. The average fish ingestion rate (IR_food) was higher in the FRP (167.85 g d^?1) than in the general population (GP) (140.9 g d^?1). However, HQs were significantly (p < 0.05) higher in the GP (ranging from 0.18 to 10.91) compared to the FRP (0.20 to 2.48); significant differences were also found among groups of both populations. Remarkably, children in both populations exhibited the highest proportions of risk, reaching up to 97% in GP. For all populations, fish consumption was the most important variable influencing MeHg exposure. Overall, for MeHg exposure, there is no safe level of fish consumption without risk, and actions should be taken to mitigate possible risk; further research with current data is needed to assess potential health risks associated with MeHg exposure, particularly in children.     

Associations between stress reactivity and sexual and nonsexual risk taking in young adult human males

Release of the hormone cortisol represents a distress response to novel or stressful situations. Individual differences in such reactivity have been conceptualized as representing a relatively enduring, generalizable trait. In this study, cortisol responses to two experimentally manipulated "sexual" and "nonsexual" stressors were used to examine whether stress reactivity is related to sexual and nonsexual risk behavior in young adult males. Analyses were based on 150 males 18 to 25 years old; risk behavior was assessed in confidential, self-administered questionnaires. Analyses indicated that both stressors effectively elicited cortisol increases. Generalized reactivity, defined as a cortisol response to both stressors, was inversely associated with deviance (e.g., theft, substance use) and with two indicators of sexual risk taking (lifetime number of intercourse partners and frequency of condom use). Findings are discussed in terms of cross-situational consistency of stress responses, the utility of stress reactivity for understanding individual differences in risk taking, and the interpretive limitations imposed by study design.     

Endocrine control of sexual behavior in sneaker males of the peacock blenny Salaria pavo: effects of castration, aromatase inhibition, testosterone and estradiol

The effects of castration and sex steroid manipulations on the expression of sexual behavior were investigated in a small fish, the peacock blenny, Salaria pavo. In this species, large males defend nests and attract females while small "sneaker" males reproduce by imitating the female morphology and courtship behavior in order to approach nests during spawning events and parasitically fertilize eggs. Sneakers switch into nest holders in their second breeding season, thus displaying both male and female-like sexual behavior during their lifetime. We tested the effects of castration and of an aromatase inhibitor (Fadrozole, F), testosterone (T) or 17beta-estradiol (E(2)) implants on the expression of male and female-like behavior in sneakers. Sneakers were either sham-operated, castrated or castrated and implanted with vehicle, F, T+F or E(2)+F. Seven days after the treatment, sneakers were placed in a tank with a nesting male, two ripe females and an available nest. Castrated fish had lower levels of circulating T and increased the time spent displaying female typical nuptial coloration. T implants had the opposite effect, inhibiting the expression of female-like behavior and coloration. E(2) implants had no significant effect on the display of sexual behavior but the frequency of aggressive displays decreased. The results agree with previous findings in sneakers of S. pavo that demonstrated an inhibition of female-like behavior by 11-ketotestosterone (11-KT). The reported increase in T and 11-KT production when sneakers change into nest holders may thus contribute to behaviorally defeminize sneakers. Contrarily, both T and E(2) failed to promote male-like behavior, suggesting that behavioral masculization during tactic switching depends on other neuroendocrine mechanisms or that the time length of the experiment was insufficient to induce male-like behavioral changes in sneakers.     

A trade-off generated by sexual conflict: Mediterranean wrasse males refuse present mates to increase future success

A variety of mechanisms, including intrasexual competition,intersexual conflict, and physiological constraints, can explainpatterns of reproduction and the adaptive value of specificbehaviors. In a Mediterranean wrasse, Symphodus ocellatus (Labridae),large, nesting males occasionally refuse to spawn with willingfemales in the presence of small, sneaker males. We exploredthe possible adaptive significance of this behavior. Nestingmales refuse females despite the fact that it reduces theirimmediate mating success. This nesting-male behavior also decreasesfemale and sneaker mating success and occurs when sneaker malessurround the nest. Experiments that decreased the number ofsneakers around nests showed that nesting males respond immediatelyto mating opportunities when fewer sneakers are present, andthus they are not simply constrained by a lack of energy orlack of sperm. Experiments that increased the number of sneakersat the nest caused nesting males initially to refuse spawningopportunities, followed by a subsequent decrease in sneakerpresence and an increase in mating rate. We propose that thisbehavior is the result of a trade-off between immediate matingsuccess and future reproduction created by competition betweenmales and conflict between the sexes. Males reduce their immediatemating success by reducing spawning at the nest; sneaker malessubsequently leave, and this decreases mate competition forthe nesting male. Unresponsiveness of nesting males also causessexual conflict between females and nesting males over mating.We argue that this behavior and the existence of a trade-offcan only be understood by examining intersexual conflict andintrasexual competition simultaneously.     

ExpaRNA-P: simultaneous exact pattern matching and folding of RNAs

Background

Identifying sequence-structure motifs common to two RNAs can speed up the comparison of structural RNAs substantially. The core algorithm of the existent approach ExpaRNA solves this problem for a priori known input structures. However, such structures are rarely known; moreover, predicting them computationally is no rescue, since single sequence structure prediction is highly unreliable.

Results

The novel algorithm ExpaRNA-P computes exactly matching sequence-structure motifs in entire Boltzmann-distributed structure ensembles of two RNAs; thereby we match and fold RNAs simultaneously, analogous to the well-known “simultaneous alignment and folding” of RNAs. While this implies much higher flexibility compared to ExpaRNA, ExpaRNA-P has the same very low complexity (quadratic in time and space), which is enabled by its novel structure ensemble-based sparsification. Furthermore, we devise a generalized chaining algorithm to compute compatible subsets of ExpaRNA-P’s sequence-structure motifs. Resulting in the very fast RNA alignment approach ExpLoc-P, we utilize the best chain as anchor constraints for the sequence-structure alignment tool LocARNA. ExpLoc-P is benchmarked in several variants and versus state-of-the-art approaches. In particular, we formally introduce and evaluate strict and relaxed variants of the problem; the latter makes the approach sensitive to compensatory mutations. Across a benchmark set of typical non-coding RNAs, ExpLoc-P has similar accuracy to LocARNA but is four times faster (in both variants), while it achieves a speed-up over 30-fold for the longest benchmark sequences (≈400nt). Finally, different ExpLoc-P variants enable tailoring of the method to specific application scenarios. ExpaRNA-P and ExpLoc-P are distributed as part of the LocARNA package. The source code is freely available at http://www.bioinf.uni-freiburg.de/Software/ExpaRNA-P.

Conclusions

ExpaRNA-P’s novel ensemble-based sparsification reduces its complexity to quadratic time and space. Thereby, ExpaRNA-P significantly speeds up sequence-structure alignment while maintaining the alignment quality. Different ExpaRNA-P variants support a wide range of applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-014-0404-0) contains supplementary material, which is available to authorized users.     

Digit ratios, secondary sexual characters and condition in barn swallows Hirundo rustica

The second and fourth digit length ratio (2D:4D) is sexuallydimorphic in many vertebrates. This ratio has been suggestedto provide an estimate of steroid levels encountered duringprenatal development, which may have organizational consequencesfor physiology and behavior of adults. However, recent studiesshowed that the relation between digit ratio and steroids seemsinconsistent and may vary among species and populations. Wetested the hypothesis that digit ratios would be correlatedwith the expression of secondary sexual characters, using thebarn swallow (Hirundo rustica) as a model system. This was doneby testing whether variation in 2D:4D ratio was correlated withtail length and features of song, which are important secondarysexual characters positively correlated with circulating steroidconcentration in adult birds. Furthermore, we examined the predictionthat male and female digit ratios would correlate with bodymass in an antagonistic way. There was no significant sexualdimorphism in digit ratio, which may be due to low levels ofsexual selection in this population. Adult right 2D:4D ratiowas negatively linked to tail length but not to male song output.Moreover, right 2D:4D ratio was negatively correlated with bodymass in male and positively in females. These results are consistentwith high digit ratios reflecting low levels of testosteronein this bird species.