Some biological parameters of the Mediterranean sand smelt Atherina (Atherina) hepsetus, Linnaeus, 1758 (Pisces: Atherinidae) from the middle eastern Adriatic (Croatian coast)

Data on the length–weight relationship, age, growth, sex ratio and mortality were analysed for the Mediterranean sand smelt, Atherina (Atherina) hepsetus L. (total = 2805; males = 1258; females = 1547) collected in the eastern middle Adriatic island area during the reproductive period (February to April) in 2002. The total length of sampled specimens ranged from 3.8 to 14.5 cm and the weight from 0.28 to 22.39 g. The overall sex ratio was 1.23 : 1 in favour of females, significantly different from the expected 1 : 1 ratio (χ² = 29.76; P < 0.05). All individuals >13.4 cm were females. The oldest collected male and female specimens were 5 years old. The von Bertalanffy growth formula was estimated for females (L_∞ = 15.79 (1−e^{−0.43(t+0.049)}) and males (L_∞ = 15.25 (1−e^{−0.43(t+0.018)}). The power values (b) of the length–weight relationship were very similar for both sexes (b = 3.14) and indicated a slightly allometric growth. The instantaneous rates of mortality for all collected fish were Z = 1.44 year⁻¹; M = 0.94 year⁻¹ and F = 0.50 year⁻¹. The exploitation ratio was E = F/Z = 0.35. The value for M is highly uncertain, however, as well as those values for F and E.     

Age and growth of the sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor coastal lagoon (SE Iberian Peninsula)

The age and growth of sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor (SE Iberian Peninsula) were studied in samples taken from catches of local fishermen obtained between November 1997 and September 1998. The maximum lengths were 94 mm (FL, fork length) in females and 87 mm (FL) in males. Age determination based on scale readings and validated by length frequency analysis shows that the population has a 3‐year life cycle. Females were significantly longer than males in each of the age classes. Both sexes of the sand smelt grow allometrically (b = 3.113 males; b = 3.043 females) and attain approximately 56.2% of their maximum fork length in their immature first year, after which the annual growth rate drops quickly. The highest growth rate was observed from winter to spring (G_L = 16.01 males 1+; G_L = 11.25 males 2+; G_L = 17.18 females 1+; G_L = 9.62 females 2+). The condition cycles were similar for both sexes, with a minimum in June–July and two maximums in April and November.     

Age,growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in Mellah Lagoon (Eastern Algeria)

This aim of this paper was the study of the reproductive biology and growth of the sand smelt, Atherina boyeri, in Mellah Lagoon (Algeria). These data are important for the sustainable exploitation of the stocks of this species. Examined was a total of 1402 Atherina boyeri specimens captured monthly from March 2010 to March 2011, in a population with a 3‐year life cycle. Length–weight relationship was estimated as W = 0.0047 L^3.077 (r² = 0.935) for males and W = 0.0047 L^3.176 (r² = 0.935) for females. Using scales, the von Bertalanffy growth function fitted to back‐calculated size‐at‐age data was Lt = 9.49 [1 ? e^{?0.316 (t + 0.928)}] for males, and Lt = 11.67 [1 ? e^{?0.179 (t + 1.514)}] for females; using otoliths this was Lt = 9.68 [1 ? e^{?0.3 (t + 1.02)}] for males, and Lt = 11.93 [1 ? e^{?0.171 (t + 1.55)}] for females. The growth performance index (Φ) indicated that males (Φ_scales = 3.34, Φ_otoliths = 3.33) grew at the same rate as females (Φ_scales = 3.19, Φ_otoliths = 3.24), with a sex ratio of 1 : 1.6 in favor of females. The reproductive season extended from February to June. Individual length at first sexual maturity was 4.20 cm for 1‐year‐old males and 4.35 cm for 1‐year‐old females.     

Biology of the Sand Smelt, Atherina presbyter (Teleostei: Atherinidae), Off the Canary Islands (central-east Atlantic)

Atherina presbyter is a common fish off the Canary Islands. Age, growth, reproduction, and mortality of the species are studied based on sampling carried out from July 1995 to June 1996. The parameters of the total length–total weight relationship are: a=0.004521, and b=3.0771. Otoliths age readings indicate that the sampled population consists of four age groups (0–III years). The von Bertalanffy growth parameters for all individuals are: L=122mm total length, k=0.79year^–1, and t₀=–0.21 years. Individuals grow quickly in their immature first year, attaining approximately 60% of their maximum length. After the first year, the annual growth rate drops rapidly, because the energy is probably diverted to reproduction. It is a gonochoristic species with no evidence of sexual dimorphism. The gonad is present as a single diffuse testis in males and as a single discrete ovary in females. The overall ratio of males to females is not significantly different from 1:1. The reproductive period of the species is protacted (February to June). The peak of the reproductive effort occurs in April–May. The size at first maturity is 68mm. The population is being heavily exploited.     

Phylogenetic relationships of Atherina hepsetus and Atherina boyeri (Pisces: Atherinidae) populations from Greece, based on mtDNA sequences

The genetic divergence and the phylogenetic relationships of six Atherina boyeri (freshwater and marine origin) and five Atherina hepsetus populations from Greece were investigated using partial sequence analysis of 12s rRNA, 16s rRNA and control region mtDNA segments. Three different well divergent groups were revealed; the first one includes A. boyeri populations living in the sea, the second includes A. boyeri populations living in the lakes and lagoons whereas the third one includes all A. hepsetus populations. Fifty-seven different haplotypes were detected among the populations studied. In all three mtDNA segments examined, sequence analysis revealed the existence of fixed haplotypic differences discriminating A. boyeri populations inhabiting the lagoon and the lakes from both the coastal A. boyeri and the A. hepsetus populations. The genetic divergence values estimated between coastal (marine) A. boyeri populations and those living in the lagoon and the lakes are of the same order of magnitude as those observed among coastal A. boyeri and A. hepsetus populations. The results obtained by different phylogenetic methods were identical. The deep sequence divergence with the fixed different haplotypes observed suggests the occurrence of a cryptic or sibling species within A. boyeri complex.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 151–161.     

Reproduction of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), parasitic on the sand smelt Atherina boyeri (Osteichthyes: Atherinidae) in Greek lagoons

The reproduction and growth pattern of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), a protandrous hermaphroditic gill parasite of Atherina boyeri (Osteichthyes: Atherinidae), were investigated in the Mesolongi and Etolikon lagoons. The parasite shows an extensive reproductive period. Gravid females were found between April and November, and juveniles between May and December. M. epimerica grew allometrically (slopes of the total weight-total length regressions were >3). Females were significantly heavier than males. The relationship between number of eggs or mancas larvae (F) and total length (TL) was investigated in gravid female parasites in which the marsupium was still closed; the relationship was clearly curvilinear: F = 0.128TL3.18. The number of eggs or mancas larvae held in the marsupia of females increased proportionally with female length, varying from 39 in an isopod of 6.3 mm length to 158 in one of 8.5 mm length. The average number of eggs or mancas larvae was 76.70 +/- 27.8.     

Multilocus phylogenetic analysis of the genus Atherina (Pisces: Atherinidae)

Sand-smelts are small fishes inhabiting inshore, brackish and freshwater environments and with a distribution in the eastern Atlantic and Mediterranean Sea, extending south into the Indian Ocean. Here, we present a broad phylogenetic analysis of the genus Atherina using three mitochondrial (control region, 12S and 16S) and two nuclear markers (rhodopsin and 2nd intron of S7). Phylogenetic analyses fully support the monophyly of the genus. Two anti-tropical clades were identified, separating the South African Atherina breviceps from the north-eastern Atlantic and Mediterranean Atherina' species. In European waters, two groups were found. The first clade formed by a well supported species-pair: Atherina presbyter (eastern Atlantic) and Atherina hepsetus (Mediterranean), both living in marine waters; a second clade included Atherina boyeri (brackish and freshwater environments) and two independent lineages of marine punctated and non-punctated fishes, recently proposed as separate species. Sequence divergence values strongly suggest multiple species within the A. boyeri complex.     

Mitochondrial DNA in Atherina (Teleostei,Atheriniformes): differential distribution of an intergenic spacer in lagoon and marine forms of Atherina boyeri

The big‐scale sand smelt Atherina boyeri lives in fresh water, brackish water and sea water of the western Atlantic Ocean and Mediterranean Sea. Previous studies concerning distribution, biometric characters and genetic molecular markers have suggested the possible existence of two or even three different groups or species of sand smelt, one ‘lagoon’ type and one (or two – punctuated and non‐punctuated on the flanks) ‘marine’ type. In this study, the presence and the localization of an insertion was described, c. 200 bp in length, in the mtDNA of the lagoon and marine punctuated specimens of A. boyeri and its absence in the marine non‐punctuated specimens, as well as in other two congeneric species, Atherina hepsetus and Atherina presbyter, and in the atheriniform Menidia menidia. The intergenic spacer is located between the tRNA^Glu and cytochrome b (cyt b) genes and shares a c. 50% sequence similarity with cyt b. The distribution and the features of the intergenic spacer suggest that it might have originated from an event of gene duplication, which involved the cyt b gene (or, more likely, a part of it) and which took place in the common ancestor of the lagoon and the marine punctuated specimens. The data obtained therefore support the hypothesis of the existence of three cryptic and, or sibling species within the A. boyeri taxon and provide a genetic molecular marker to distinguish them.     

Feeding strategies of Atherina boyeri (Risso 1810) in a freshwater ecosystem

This study investigates the adaptation of certain feeding strategies by a population of Atherina boyeri inhabiting a freshwater ecosystem (Lake Trichonis, Greece) and links feeding habits with ecosystem interactions, using stomach content analysis and food availability. The use of Ivlev's electivity index (E) revealed the selection of different prey categories in respect to size, species and even gender. A. boyeri showed positive selection for larger zooplankters such as adult copepods and the egg‐bearing females of Eudiaptomus drieschi (0.53 < E < 0.92 and 0.24 < E < 0.99, respectively) or the cladocerans Diaphanosoma orghidani and Daphnia cucullata (0.25 < E < 0.53 and 0.23 < E < 0.37, respectively) in spring and/or summer. In contrast, the fish totally avoided rotifers and copepod nauplii, while showing negative selection for smaller prey items like copepodites (?1.00 < E < ?0.14). A shift to larger prey was recorded as age increased. Larger specimens showed cannibalistic behaviour by consuming larvae of A. boyeri and the endemic, threatened, fish Economidichthys trichonis. The results provide certain indications that, through selective predation, A. boyeri is able to affect zooplankton abundance and community composition, the vertical distribution and migration of crustaceans and the abundance of other fish species, However, more research on the dynamics and feeding ecology of A. boyeri and other fish species is necessary.     

Biology of the sand-smelt (Atherina presbyter Valenciennes) around Fawley power station

Past studies of fish impingement at Fawley power station have shown that sand-smelts, Atherina presbyter Valenciennes, are susceptible to impingement and may be a useful species for examining effects of impingement mortalities on population size and structure. A 21 month study of populations in the vicinity of Fawley power station was carried out to obtain data on the biology of the species for future population dynamics modelling studies. Aspects included in the study were growth, sex ratio, reproduction, survival and mortality rates and diet. Differences in apparent and true rates of growth indicated some size-selective mortality towards younger age groups, possibly caused by the power station. A seasonallyoscillating von Bertalanffy growth equation is given to predict mean length-at-age. Most female sand-smelts (73%) matured at the end of their first year of life, fecundities ranging on average from 1394 eggs per female for 1+ group fish to 6872 for III+ fish. The sex ratio was even (1 : 1). An annual survival rate of 10–8% was estimated for mature fish, and the consequent age structure of the population indicates that the bulk of egg production lies with the smaller (1+ group) fish. Since smaller fish are generally more vulnerable to impingement this factor may render populations sensitive to impingement mortalities. Gut content analysis indicated that sand-smelts probably actively select zooplankters from the general plankton when young and, once larger than 104 mm in length, increasingly feed upon natant macrofaunal species.     

Histopathology in Atherina boyeri (Pisces: Atherinidae) resulting from infection by Telosentis exiguus (Acanthocephala)

The histopathology developing in the sand smelt Atherina boyeri Risso 1810 from Northern Italy as the result of a natural infection by Telosentis exiguus Von Linstow 1901 (Acanthocephala) was studied and described. Microscope examination of sections of intestinal tissues showed that the parasites did not penetrate through all intestinal layers, and that damage was mostly limited to the epithelium.     

Acanthocephalan infections in Atherina boyeri (Pisces: Atherinidae) from Tirso.

Infections by the acanthocephalan Telosentis exiguus (Von Linstow, 1901) and another unknown acanthocephalan were studied in the sand smelt Atherina boyeri (Risso, 1810) from the Tirso River mouth in Sardinia. Only a few specimens of T. exiguus (1 male and 2 cystacanths) were found in the host digestive tract; some larvae of an unidentified acanthocephalan encysted in the liver of A. boyeri were also found and are described.     

Feeding habits of sand smelt (Atherina boyeri, Risso 1810) in Trichonis Lake (Western Greece)

The feeding habits of sand smelt (Atherina boyeri, Risso, 1810) from Trichonis Lake (Western Greece) were investigated. Stomach contents were analyzed from 240 specimens with total lengths ranging from 35 to 112 mm. Samples were taken at monthly intervals (January–December 1997). Of the total number of stomachs examined, 53 were empty (22.1%). However, values varied greatly with season (maximum in January: 50%; minimum in August: 7.6%). Prey analyses of stomach contents identified 15 important items (%Rn > 0.05) belonging to six major groups: crustacean (copepods, cladocera), mollusca (bivalve: larvae), insects (larvae), cestode worms and finfish (fry and eggs). Dominant prey were larvae of the bivalve Dreissena polymorpha (%Rn = 33.8), the copepods Eudiadomus drieschi (%Rn = 26.4) and the cladocera Diaphanosoma brachyurum (%Rn = 24.2). The importance of cladocera and copepods decreased with increasing size of the sand smelt, while the importance of bivalve larvae, fish eggs and finfish fry increased with increasing sand smelt size. Seasonal changes in diet composition and prey abundance in sand smelt stomachs were recorded as coinciding with the seasonal composition and abundance of the zooplankton community in the surface layers of Trichonis Lake. Bivalve larvae were the dominant prey of A. boyeri during January to May, while copepods and cladocera dominated from June to December.     

Sand smelt (Atherina boyeri) migration within the water system of the Camargue,southern France

In the coastal lagoons of Southern France, sand smelt Atherina boyeri, is known as a sedentary species. However part of the sand smelt population living in the brackish water Vaccarès lagoon in the Camargue annually migrates to fresh waters. The movements of sand smelts within the watersystem of the Camargue were studied from 1986 to 1990. Fish traps and fyke nets were set and catches were standardised to Catch Per Unit Effort (CPUE). A Stepwise Multiple Correlation analysis was carried out to link fish abundance with various environmental factors. Between September and November, sand smelts living in the Vaccarès start to colonize fresh waters (drainage canals and then temporary marshes), until March. Spawning occurs from April to June, both in the shallow branches of the canal and in the marshes. From June onwards adults and young-of-the year leave the fresh waters and return to the Vaccarès lagoon where they remain until the next migration. This autumnal migration to freshwater habitats involves mainly fish less than 3 years old, the oldest individuals remaining all year in the Vaccarès. Water level and photoperiod contribute to 20.7% of the variation of CPUE within the drainage canal, while date, water temperature, and rainfall combined, only account for 2.5% of CPUE variations. Date and photoperiod contribute significantly to explaining the patterns of fish migrations between the canal and the marshes. The density of mature sand smelt in the marshes before spawning, varies between 4 and 4346 fish ha^–1. Fry mortality (against number of eggs spawned) over the first two months of life was assessed to vary between 97.5% and 99.9%. Physiological factors such as osmoregulation linked to water temperature are possibly the ultimate factors explaining these unusual annual migrations of sand smelt in the Camargue.     

Mating tactics and courtship behavior inCleogonus rubetra (Fabricius) (Coleoptera: Curculionidae)

Females of the tropical weevilCleogonus rubetra oviposit into fruits of the leguminous treeAndira inermis, and larvae develop in the pulp and seed of these fruits. We hypothesized three alternative tactics by which males might secure matings. By using focal observations of males and by evaluating predictions specific to each hypothesis, we demonstrate that males search within aggregations of conspecifics for receptive females, and upon finding a suitable partner, males mount and perform courtship behavior consisting of stroking the eyes and sides of the female's abdomen. Males also stridulate and emit a sequence of short buzzing sounds. While mounted, males actively prevent rival males from mating with their partner. Males defend their mates for a mean duration of 3.7 h (including copulation). As predicted, paired males were larger than solitary individuals, although the difference was marginally nonsignificant. The overabundance of fruits relative to males, the prolonged period during which females are active, and the probability of last male sperm precedence are factors that may have contributed to the evolution of this female-defense tactic by males. Paired females were significantly larger than solitary females. We observed no competition among females for mates, and the correlation between elytron length of paired males and females was not significant.     

Phylogenetic inference in Odontesthes and Atherina (Teleostei: Atheriniformes) with insights into ecological adaptation

This contribution provides an insight into Atheriniformes systematics based on four mitochondrial regions: 12S rRNA, cytb, COI and control region (2794bp in total). In the Atherinopsoidei (New World silversides), comparisons among five species of Odontesthes, O. argentinensis, O. bonariensis, O. smitti, O. hatcheri and O. incisa revealed a putative marine-freshwater pairing pattern of Odontesthes species, possibly driven by sea level fluctuations of South American waters. This study represents the first data on molecular phylogeny of Odontesthes species that can be of usefulness to biodiversity conservation policies. In the Atherinoidei (Old World silversides), Atherina boyeri was corroborated as a species complex constituted by a marine form, a marine with dark spots form and a brackish form. Concretely, Odontesthes and Atherina may represent geographically replicated models to study genetic adaptation and speciation of marine species to brackish and freshwater habitats. In addition, phylogenetic analyses supported Odontesthes and Atherina as monophyletic taxa and their separation into two differentiated suborders Atherinopsoidei and Atherinoidei, respectively.     

Courtship Behavior of Zaprionus indianus (Gupta) (Diptera: Drosophilidae) from Populations Colonizing South America

We describe for the first time the sexual behavior and the courtship song of males of the African fly Zaprionus indianus (Gupta), a recent invader of South America. The male courtship song is formed by monocyclic pulses and the courtship behavior is simple when compared to that of species of Drosophila. Two interpulse interval (IPI) distributions were observed: pre-mounting and mounting. No significant difference was observed between the pre-mounting IPIs of males that descended from three geographical populations from South America. We also observed the songs produced by females and the homosexual behavior exhibited by males. A sequence of bursts is produced by females as a refusal signal against males, while males emit a characteristic song that identifies sex genus, which differs from the courtship song. The short courtship and mating latencies recorded reveal vigorous males and receptive females, respectively.     

Atherina punctata and Atherina lagunae (Pisces,Atherinidae), new species found in the Mediterranean sea. 2. Molecular investigations of three Atherinid species

On the basis of morphoanatomical parameters, the sand smelt species (Atherina boyeri Risso, 1810) is viewed as a highly polymorphic complex. In this study, intraspecific sequence variation in a portion of the cytochrome b gene was examined in 88 individuals from Tunisia and France. The correlation between the results of statistical analysis of the sequence data using a variety of tree-building algorithms and morphoanatomical analyses demonstrated the subdivision into three putative species: A. boyeri, which only includes non-punctuated fishes, A. punctata, which corresponds to punctuated fishes and A. lagunae, which corresponds to atherines living in lagoons.     

Formation and maintenance of mating aggregations in a stink bug,Megacopta punctissimum (Montandon) (Heteroptera: Plataspidae)

Adults of a stink bug,Megacopta punctissimum, formed mating aggregations on their host plants: a few pairs in copula and a few bachelor males (males not in copula) stayed in the aggregation and the bachelor males waited for arriving females to mate with. The processes of formation and maintenance of the aggregations were observed using the individual marking technique. Aggregations initiated by 2 males or by 1 male and 1 female were usually joined by 1 or more individuals and lasted for several days, but aggregations initiated by 2 females broke up within 1 h. Aggregations were not maintained by the same members. The residence time (time from joining an aggregation to leaving the aggregation without copulating) of males was longer than that of females. There was a negative correlation between the residence time of males and the number of bachelor males in an aggregation when bugs joined it, while the residence time of females was positively correlated with the number of bachelor males in the aggregation. When bugs copulated after joining an aggregation, the postcopulatory residence time (time from completing copulation to leaving the aggregation) was longer in males than in females. Thus, males had a stronger tendency to initiate and maintain aggregations than females.