1,720,977 research outputs found
Sexual dimorphism and male mating success in the tentacled blenny, Parablennius tentacularis (Teleostei : Blenniidae)
No full textAlthough external sexually dimorphic traits are
commonly found in males of combtooth blenny species,
little is known about the benefit they can convey to male
mating success. Indeed, while female preferences for
large males have been demonstrated in some species, the
possible role played by dimorphic ornaments has been
neglected. We now report on the tentacled blenny, Parablennius
tentacularis, a species where males are characterized
by bulb glands on the anal fin and both sexes
exhibit a dark spot on the dorsal fin and orbital tentacles.
Males are territorial, make nests in empty bivalve
shells, and provide solitary parental care for the eggs.
Using morphometric analysis and field collected data on
male and female external features, nest characteristics
and number of eggs in the nests, we have assessed the
development of dimorphic traits in both sexes and male
mating success. The results reveal that orbital tentacles
of males are more developed and more variable in size
than those of females. Larger males exhibit longer
orbital tentacles and larger anal glands but do not necessarily
occupy larger nests. Male mating success is significantly
correlated with the inner nest surface area and
with orbital tentacle size but not with body size. These
results provide support for a primary role of male
ornaments in enhancing blenny male mating success and
are discussed in the context of mate choice for direct and
indirect benefits
Sperm morphology and size of 15 elasmobranch species: comparing data in the light of phylogenetic relationships
No full text
A male sexually dimorphic trait provides antimicrobials to eggs in blenny fish
No full textPredation and microbial infections are the major
causes of natural mortality for early life stages of
oviparous species. The parental traits reducing
the effects of predation are rather well described,
whereas antimicrobial mechanisms enhancing
offspring survival are largely unexplored. In this
paper, we report that a male sexually dimorphic
trait, the anal glands, of the redlip blenny
(Ophioblennius atlanticus atlanticus) and the
peacock blenny (Salaria pavo), two fish species
with paternal egg care, produce a mucus enriched
with antimicrobial substances. Histological and
histochemical analyses showed that the anal
glands of these species are characterized by the
massive presence of mucus-secreting cells. Anal
gland extracts, from both the hydrophilic and
the hydrophobic protein fraction, exhibited a
lysozyme-like activity. Field observations demonstrated
that redlip blenny males, while performing
egg care, rub the anal region over the nest
internal surface, probably facilitating the transfer
of mucus to eggs. These results strongly indicate
that this sexually dimorphic trait is involved in
egg defence againstmicrobial infections
When fathers make the difference: efficacy of male sexually selected antimicrobial glands in enhancing fish hatching success
No full text1. Egg and offspring resistance to pathogens is a major determinant of survival and has been
mainly ascribed to maternal factors. However, paternal production of antimicrobials was
recently suggested to increase offspring survival in species where males perform egg care.
2. In the peacock blenny, Salaria pavo, a demersal spawning species where males exhibit a pair of
anal glands producing lysozyme-like compounds, we tested the antimicrobial activity and the
egg protection efficacy of these glands. The anal gland secretion (AGS) has an inhibitory effect
on the growth of both Gram-negative and Gram-positive bacteria, including those causing the
most severe fish diseases in marine culture. The egg clutches cared for by males deprived of anal
glands have a significantly lower survival rate than those cared for by sham-operated males and
non-viable eggs showed clear signs of bacterial infection.
3. Anal gland secretion production and its protein content are proportional to gland size. In species
where male parental care plays a crucial role in offspring survival, females are expected to
assess mates selecting those traits that are reliably associated with parental ability. Hence, we
experimentally challenged females with dummy males differing in anal gland size. Females definitely
preferred dummy males with larger anal glands, suggesting that their choice is driven by
the pursuit of direct fecundity benefits.
4. These findings indicate that antimicrobial production is a crucial component of male parental
care. The contribution of antimicrobials to male performance as fathers suggests that the development
of traits devoted to this function may influence male attractiveness and be sexually
selected
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sperm duct gland secretion of the grass goby, Zosterisessor ophiocephalus, exhibits antimicrobial activity.
No full textThe grass goby Zosterisessor ophiocephalus sperm-duct gland extract displayed antimicrobial
activity against gram-positive and gram-negative bacteria. This suggests that spermduct
gland mucins might be functional in protecting eggs and possibly parents from
pathogens, an activity of great adaptive value for Z. ophiocephalus, which lays eggs in mud
nests
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
