Carlotta Mazzoldi

Sperm Competition and Mode of Fertilization in the Grass Goby Zosterisessor ophiocephalus (Teleostei: Gobiidae)

2 AND ABSTRACT Accessory structures to the male reproductive system are known in several fami- lies of teleost, but their role in sperm production patterns and fertilization dynamics is still un- clear. The intraspecific variability in seminal vesicles, shown by the grass goby Zosterisessor ophiocephalus, presents an opportunity to examine both its possible correlation to alternative male mating tactics and the function of these accessory structures. In this species, males are known to release sperm in the form of sperm trails, bands of mucosubstances in which sperm are embedded. Surgical removal of seminal vesicles and histochemistry demonstrate that mucins, involved in the production of sperm trails, are secreted by the seminal vesicles. Gametes show a high longev- ity; sperm motility lasts on average 80 minutes. Eggs can be fertilized for several hours and do not need to be laid over trails because sperm are able to reach them via the surrounding water. Gonosomatic and seminal vesicle somatic indices, histology and histochemistry of gonads and seminal vesicles, sperm counts, and sperm trail longevity, suggest the presence of alternative male mating tactics in this species. Larger males have smaller testes and larger seminal vesicles compared to those of smaller males. The major role of seminal vesicles is mucin secretion in larger males, sperm storage in smaller ones. Trails of larger males last longer and release sperm more constantly over time than those of smaller males. Overall differences between males support the presence of differences in the intensity of sperm competition, with larger males performing nesting behaviour while smaller ones sneak spawnings. J. Exp. Zool. 283:81n 90, 1999.

On the mechanism of sperm release in three gobiid fishes (Teleostei: Gobiidae)

SynopsisIn fish, gamete release is commonly assumed to be synchronous in externally inseminating fishes. By collecting and counting the number of sperm and eggs released during separate matings in three demersal spawners, the mediterranean gobies, Zosterisessor ophiocephalus, Gobius niger, and Knipowitschia panizzae, we observed that gametes are released asynchronously. Males release sperm before females start laying their eggs. Sperm is released in the form of sperm trails laid on the nest surface; subsequently active spermatozoa leave the trails and move in the water for several minutes. Sperm trails consist of bands of viscous material in which sperm is embedded. In most cases eggs are not laid directly over the sperm trail, suggesting that sperm may contact the eggs after the latter are released in the water. Male sperm duct glands, seminal vesicles, known to secrete mucosubstances, are likely involved in the production of sperm trails. The possible influence of this mode of insemination on the mating style of marine gobies is discussed.

The application of visual census on Mediterranean rocky habitats

In this study we examined the effect of: observer presence; observer speed; and the impact that multiple surveys had on the number of counted fish in a visual census survey in a typical Mediterranean rocky habitat. SCUBA observer presence had no influence on the number of fish per survey. An improvement in the methodology to estimate the number of fish was demonstrated by using two different speeds: slow speed for benthic species and higher speed for epibenthic ones. No differences in the number of fish per survey were found among successive surveys along the same transects, even with the shortest time interval used: 5 min. We also examined the ability of observers to estimate fish length during visual census by using wooden fish models. Significant differences in size estimations were found using two different estimation methods (i.e. size-classes estimates and continuous measures). Estimating fish length to a size class was more accurate in estimating size, while transformed size to calculate biomass from length estimates was more accurate using continuous measures.

Long-term changes in community composition and life-history traits in a highly exploited basin (northern Adriatic Sea): the role of environment and anthropogenic pressures

The changes in a marine community in the northern Adriatic Sea were explored over a period of 65 years using landings data from a commercial fishing fleet, and the role of fishing pressure and environmental variations in driving these changes was investigated. A total of 40 taxonomic categories, including one or several species, were analysed, representing 93·7% of the total landings. From 1945 to 2010 a significant decrease in the evenness index was observed, indicating a trend towards landings dominated by fewer taxa. The composition of the landings showed a temporal shift during the 1980s; from 1945 to the 1980s a continuous, clear change in composition took place, probably driven by an increase in fishing pressure as well as riverine nutrient inputs. Since the 1980s, a different trend of changing composition emerged. Among the analysed predictors, fishing capacity, summer seawater temperature, inflow from the Po River (the major river of the northern Adriatic Sea) and nutrients were related to the changes in landings. In relation to life-history traits of the landed species, the community shifted from large, late-maturing species to more fecund, smaller and earlier-maturing species. A high fishing pressure is probably the major cause of these changes, possibly acting synergistically with environmental variations.

Pelagia benovici sp. nov. (Cnidaria, Scyphozoa): a new jellyfish in the Mediterranean Sea

A bloom of an unknown semaestome jellyfish species was recorded in the North Adriatic Sea from September 2013 to early 2014. Morphological analysis of several specimens showed distinct differences from other known semaestome species in the Mediterranean Sea and unquestionably identified them as belonging to a new pelagiid species within genus Pelagia. The new species is morphologically distinct from P. noctiluca, currently the only recognized valid species in the genus, and from other doubtful Pelagia species recorded from other areas of the world. Molecular analyses of mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 28S ribosomal DNA genes corroborate its specific distinction from P. noctiluca and other pelagiid taxa, supporting the monophyly of Pelagiidae. Thus, we describe Pelagia benovici sp. nov. Piraino, Aglieri, Scorrano & Boero.

Extended breeding season in the marbled goby, Pomatoschistus marmoratus (Teleostei: Gobiidae), in the Venetian Lagoon

Life cycle and reproductive biology of the marbled goby Pomatoschistus marmoratus was studied in the Venetian Lagoon. Lifespan was determined by reading otoliths. The maximum age recorded was 17 months juveniles occurred in samples from July to November. Nests were found in two different periods: from the middle of April to the middle of July and from the middle of August to the end of September. While individuals in a wide range of body size (35–62 mm total length) mated during the first spawning peak during the second one only small individuals (28–32 mm total length) developed during the first peak were in reproductive activity. Histological analyses showed that most of the juveniles developed during the first spawning peak delayed sexual maturation to the following year. Ripe females appeared to be multiple spawner showing an asynchronous ovary with oocytes at different stages of development. From nesting male body sizes gonadosomatic indices and histological analyses no indication of the presence of alternative male mating tactics emerged.

Littoral fish community of the Island Lampedusa (Italy): A visual census approach

Abstract Fish community structure of the Island Lampedusa, with a special focus on the fish assemblage inhabiting the infralittoral rocky substrate, was studied from July to October 1995. Visual census techniques (strip transects and random censuses) and the application of an anaesthetic (quinaldine), to sample cryptic and benthic species, were used. A total of 77 species and 29 fish families were censused. The most common families were Labridae and Spari‐dae. Factor analysis applied to the 84 visual assessments, using the 9 most common species, divided the samples according to their position along the coast, depth, substrate, algae cover and presence of the vascular plant, Posidonia oceanica. In addition, discriminant analyses indicated the ecological preferences of some species. Size frequency distributions indicated the distribution of different life stages. Despite the shallow depths sampled, the present study shows how the fish community of this island has high species richness

The Clodia database: a long time series of fishery data from the Adriatic Sea

Long-term time series of species abundances can depict population declines and changes in communities in response to anthropogenic activities, climate changes, alterations of trophic relationships. Here we present a database of historical marine fishery landing data, covering a remarkably long time series (1945–2013) and referring to one of the most exploited areas of the Mediterranean Sea, the Adriatic Sea. The database includes two time series of landing data, 1945–2013 and 1997–2013, from the official statistics of the fish market of Chioggia, where the major fishing fleet of the area operates. Comparisons between the landing data of the database and landing data from other fisheries or data from scientific surveys support the reliability of the time series in depicting changes in species abundances. The database is expected to be used by fishery biologists and ecologists interested in depicting and understanding temporal variations in species abundances and community composition, in relation to environmental and anthropogenic factors.

Male lagoon gobies, Knipowitschia panizzae, prefer more ornamented to larger females

Female ornamentation may be directly sexually selected, by male choice or female competition, or occurs as the result of a genetic correlation, arising from sexual selection on males. However, increasing evidence supports the former hypothesis, suggesting that males actively choose their partner preferring traits indicative of female quality. In the lagoon goby, Knipowitschia panizzae, a polygynous species whose males perform parental care to eggs, body length and the size of a sex-specific yellow patch on the belly are known to be reliable indicators of female fecundity. In this paper, we tested, using dummies, the male’s mating preferences for female body and yellow belly patch sizes. The two experimental trials in which a single female trait was variable showed that males prefer a larger belly patch and a larger body size, indicating that both these characters are selected by male mate choice. However, when faced with dummies exhibiting an inverse combination of body and belly patch sizes (experiment 3), males significantly preferred the smaller ones with larger yellow belly patches. A calculation of dummy theoretical fecundity reveals that in the first two experiments, males would have received an immediate benefit from their choice in terms of egg number, whereas in the third one, males chose partners that would have provided them with fewer eggs. The male lagoon goby preference for females with larger belly patches, regardless of their size, suggests that this trait, in addition to indicating fecundity, conveys information about other aspects of female and/or egg quality.

Multiple paternity and hybridization in two smooth-hound sharks.

Multiple paternity appears to be a common trait of elasmobranch mating systems, with its occurrence likely driven by convenience, due to females seeking to minimize the stress of male harassment. Here we use molecular markers to analyse the frequency of multiple paternity in two related viviparous sharks, Mustelus mustelus and Mustelus punctulatus. We first applied molecular methods to assign pregnant females, embryos and additional reference adults (N = 792) to one of the two species. Paternity analysis was performed using a total of 9 polymorphic microsatellites on 19 females and 204 embryos of M. mustelus, and on 13 females and 303 embryos of M. punctulatus. Multiple paternity occurs in both species, with 47% of M. mustelus and 54% of M. punctulatus litters sired by at least two fathers. Female fecundity is not influenced by multiple mating and in 56% of polyandrous litters paternity is skewed, with one male siring most of the pups. Genetic analyses also revealed hybridization between the two species, with a M. punctulatus female bearing pups sired by a M. mustelus male. The frequency of polyandrous litters in these species is consistent with aspects of their reproductive biology, such as synchronous ovulation and possible occurrence of breeding aggregations.