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The function and regulation of female nuptial colour signals are poorly understood. In fish, colour is often mediated by chromatophores, allowing for rapid and versatile signalling. Here, we examine a distinct but temporary black line around the eyes and snout ('dark eyes') displayed by female sand gobies before spawning and never observed in males. We investigate the regulatory mechanism of the display by analysing the number of melanophores in both sexes in vitro and their response to hormonal exposure. We also test the hypothesis that dark eyes serve an anti-glare function and focus the line of sight, by analysing the frequency, intensity and duration of the display in bright and dim light, with and without males present. We show that the sexes do not differ in terms of the number of melanophores, but that males and females respond in different ways to exposure to melanocyte-stimulating hormone, which has a stronger dilatory effect in females and results in a darker line. However, the darkness of the iris is not affected. Neither light levels nor the presence of potential mates affect the frequency of the dark eye display, but the display is longer lasting and more intense in the presence of smaller nest-holding males. [ABSTRACT FROM AUTHOR]

The demographic histories, genetic relationships and population structure of sedentary fish Pomatoschistus marmoratus (Risso, 1810), which was sampled from the north-eastern basin of the Mediterranean Sea (including the Turkish coasts of the Black Sea, Aegean Sea, Levantine Sea and Sea of Marmara), were investigated by mitochondrial cytochrome c oxidase subunit I (652 bp) and cytochrome b (526 bp) regions. It was found that the population groups had high haplotype diversity while the nucleotide diversity was quite low for both gene regions. Phylogeographic analyses of the haplotypes indicated that the Levantine population (LEV) were genetically different from other populations. Also, the gene flow between LEV and the other populations was very limited. The results of the analyses of neutrality and mismatch distributions that were applied to the population groups were evaluated as a whole. It was determined that the haplogroup that represents the Black Sea and Sea of Marmara populations (BLAMAR) was stable, but the Levantine population (LEV) was under the sudden demographic expansion model following the population bottleneck. The genetic variance indices indicated sudden demographic expansion following population contraction. This was supported by star-shaped haplotype networks. The reason for this limited gene flow and differentiation between the Levantine population (LEV) and the others was linked with wind-driven offshore transport of the larvae and surface currents in these sub-basins. The timing of the differentiation, demographic histories of populations associated with geological and palaeo-climatic events and current ecological conditions were discussed. [ABSTRACT FROM AUTHOR]

In many brood-rearing species, suitable nesting resources are needed for nest construction. Here, we used males of a small marine fish, the sand goby, Pomatoschistus minutus , to study the associations between the nest owner's phenotype (i.e. body size), the characteristics of the nesting resource used for nest construction (i.e. resource size and shape) and nest-building behaviour (i.e. eagerness to build a nest and extent of nest elaboration). We found that male body size was associated with nesting resource size and resource architecture in the field, with the smallest males occupying small flat resources and the biggest males occupying large arched resources. In the laboratory, the type of resource occupied in the field had a limited effect on the level of nest elaboration, but not on other nesting behaviours. Large body size, in turn, was associated with preference for larger resources and, in some circumstances, also the level of nest elaboration. Body size did not affect the eagerness to initiate nest building. Furthermore, males chose arched nesting resources more often than those that were flat, and this preference was also reflected under a 'no-choice' scenario, based on the time taken for males to initiate nest building. Overall, the results indicate that the importance of male size in nest building is context dependent, while nesting behaviours can also be affected by resource size, resource architecture and, under some circumstances, the nest builder's experience with resource use. • Choice of nesting resources can have important fitness consequences. • In a marine fish, male size, resource characteristics and nesting behaviour were linked. • Effect of body size on choice decisions and nesting behaviours was context dependent. • Nest architecture also matters: arched resources were more popular than flat ones. [ABSTRACT FROM AUTHOR]

Minor morphological differences between the Atlantic and Mediterranean populations of Pomatoschistus pictus (Malm, 1865) resulted in the description of two subspecies of this species by Miller (1973): Pomatoschistus pictus pictus and P. p. adriaticus. However, the similarity of morphometric and meristic characteristics led to an ambiguity about their status. Despite high morphological similarities between the Atlantic and Mediterranean populations, we found that the population in the Sea of Marmara (Erdek) differs from the Atlantic population in terms of the frequency of papillae in the occipital rows g and h, the position of the suborbital row b and the colouration of the second dorsal fin. Examination of the DNA sequence of the COI gene showed that the K2P genetic distance between the population in the Atlantic and the Sea of Marmara (Erdek) was 7.9%, while the minimum interspecific distance between any other Pomatoschistus species was determined as 4.3%. We concluded based on the combined genetic and morphological results that the population in the Sea of Marmara represents a species that is distinct from the Atlantic species P. pictus. It is likely that it belongs to Pomatoschistus pictus adriaticus described in the Adriatic Sea and should be given a species rank. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the senses that facilitate prey detection in the marble goby (Oxyeleotris marmorata) larvae. The ingestion ratios of live (generate chemical and mechanical stimuli) or frozen Artemia nauplii (generate chemical but no mechanical stimuli) by the intact or free neuromast (mechanoreceptor)-ablated O. marmorata larvae (11 mg/L streptomycin treatment before feeding) under the light or dark (fish vision was obstructed) condition were examined. Vision, mechano-, and chemoreceptions were all found to be essential in prey detection of the O. marmorata larvae. Prey movement has a significant influence as a visual stimuli on the O. marmorata larval feeding as the Artemia nauplii ingestion ratio was approximately 40% higher with significant (p = 0.001, d = 3.0), when the intact larvae were fed with the live (78.1 ± 1.5%), rather than the frozen (40.9 ± 2.8%) Artemia nauplii, under the light condition. This result was assured when no significant difference (p = 0.572, d = 0.2) was found between the ingestion ratios of frozen Artemia nauplii by the intact O. marmorata larvae under light and dark conditions. These findings demonstrate that prey detection in the O. marmorata larvae was facilitated by multi-modal senses, allowing O. marmorata larvae to survive in their natural habitats. • Vision is essential in prey detection of O. marmorata larvae. • Mechano- and chemoreceptions are also involved in prey detection of O. marmorata larvae. • O. marmorata larvae are attracted to prey movement. [ABSTRACT FROM AUTHOR]

Pomatoschistus anatoliaesp. n. is described from estuary of Göksu River on the Mediterranean coast of the Anatolia. It is distinguished from its congeners by the suborbital papilla pattern, meristic, and ecological features. DNA barcoding based on COI sequences revealed that there is a high nucleotide sequence divergence to the nearest neighbour. Kimura’s two parameter distances betweenP. anatoliaesp. n. and other species ofPomatoschistusandKnipowitchiahave found to be at least 5.1%. http://www.zoobank.org/urn:lsid:zoobank.org:pub:4592CF50-07B5-4C25-892F-5D009057675B [ABSTRACT FROM AUTHOR]

The new sand goby species Pomatoschistus nanus (Teleostei: Gobiidae) is described from the northern coast of the Levantine Sea (eastern Mediterranean Sea) based on both morphological and DNA barcoding data. The new species is the smallest fish in the Mediterranean Sea and may be distinguished from congeners by the following features: predorsal area, first dorsal-fin base and breast naked; δ-pore missing; anterior point of the suborbital row b not reaching level of posterior point of suborbital row d; slightly emarginated caudal fin and nape coloration pattern. DNA barcode data clearly discriminate Pomatoschistus spp. in the neighbour-joining tree with an average of 17·7% interspecific K2P distance. The most closely related taxon to P. nanus sp. nov. is Pomatoschistus bathi and the most distantly related is Pomatoschistus tortonesei with 11·9 and 21·9% K2P distances respectively. Morphometric and genetic data are also provided for Pomatoschistus bathi. [ABSTRACT FROM AUTHOR]

Background: Parental allocation and reproductive success are often strongly influenced by environmental factors. In this respect, salinity is a key factor influencing species distributions and community structure in aquatic animals. Nevertheless, the effects of salinity on reproductive behaviours are not well known. Here, we used the sand goby (Pomatoschistus minutus), a small fish inhabiting a range of different salinities, to experimentally assess the effects of changes in salinity on nesting behaviour, a key component of reproduction in sand gobies and many other taxa. Results: We found that salinity levels influenced some aspects of male nesting behaviour (i.e. nest entrance size) but not others (i.e. latency to build a nest, choice of nest site, sand on top of nest) and that small and large individuals were differently affected. In particular, the importance of body size in adjustment of nest entrance depended on the salinity level. Conclusion: The results support the prediction that geographically widespread aquatic species, such as sand gobies, are able to perform well under a range of salinity levels. The phenotype by environment interaction found between male size and behavioural responses to salinity can, in turn, help to explain the notable variation observed in nest-building (and other) behaviours closely linked to reproduction. [ABSTRACT FROM AUTHOR]

Pituitary gonadotrophs were studied in the adult female sand goby (Oxyeleotris marmoratus) during its annual reproductive cycle, aiming at investigating the alteration of gonadotropic cell types and their functions. The glands were divided into 3 groups according to maturity stages of the ovary: immature, mature and gravid stages. All of the ovarian stages were found throughout the year except in November, when only the gravid stage was identified. By using anti-chum salmon GTH Iβ and anti-chum salmon GTH IIβ antibodies for immunohistochemistry, strong anti-GTH IIβ reaction were observed in the proximal pars distalis (PPD) of the pituitary gland in all stages and the number of cells was significantly increased in the gravid stage (60.1±3.5 cell/mm2) compared to that of the immature (35.5±4.4 cell/mm2) and mature (48.3±7.2 cell/ mm2) stages (P

The annual reproductive cycle of the total 84 mature male sand gobies Oxyeleotris marmoratus, was investigated during March 2002 to March 2003. The specimens were obtained from the natural freshwater marsh in Pattani Province, southern Thailand. The seasonal changes in the testes were determined based on the histological characteristics during testicular development. The cranial, medial and caudal regions of testis are synchronously arranged with various stages of germ cells such as spermatogonia, spermatocytes, spermatids and spermatozoa. The germ cells are found from the periphery to the center of each seminiferous tubule. The testicular cycle of adult male O. marmoratus can be divided into five stages: resting, developing, mature, spawning, and spent stages. In the present study, O. marmoratus shows a seasonal cycle of spermatogenesis with a defined spermiation period. The highest spawning peak occurred in November 2002, and the second highest peak in May with respectively 100% and 66% of male spawning. Spawning did not take place during January to March. However, sperm production occurred throughout the year and presented three peaks ofmature stage in April, June, and September. The present work describes the ultrastructure of spermatogenesis with an emphasis on the spermiogenesis. The mature sperm consists of a head without an acrosome, a short midpiece and a long flagellar tail with lateral fins. The flagellum contains an axoneme of classical form with 9 peripheral double microtubules. The nucleus is symmetrical with a deep basal invagination and the centriolar complex is located outside the nuclear fossa. Sperm morphology and spermatogenesis between sand goby and those of the related families are compared.

Natural spawning of sand goby was carried out in earthen ponds and eggs were then collected. Fertilized eggs were incubated in a glass aquaria for hatching. The feed and feeding scheme experiments were done in the 500 liters (water volume 300 liters) rearing tanks containing 1,000-1,500 of two-day old larvae (stage at first feeding). It was found that the larvae 3-18 days old (average total length 0.31-0.41 cm) preferably fed only on rotifer while the 21-27 day-old larvae (average total length 0.44-0.65 cm) fed on rotifer and Artemia, and the 30-45 day- old larvae (average total length 0.69-2.15 cm) fed only on Moina.

Time of digestion experiments were carried out in a 15-liter rearing glass aquaria (water volume 10 liters) containing 1,500 larvae. The larvae were fed with sufficient rotifer, Artemia or Moina and then transferred to another rearing glass aquarium without food. Samples of 20 larvae were checked at 10-minute intervals until no food remained in the larval digestive tract. It was found that the time required to empty the larval digestive tract with rotifer, Artemia or Moina was as follows. Larvae 3-18 days old fed with rotifertook 130-180 minutes to empty the digestive tract while larvae 21-27 days old fed with rotifer and Artemia took 110-120 minutes and larvae 30-45 days old fed with Moina took 80-100 minutes at water temperature of 25-29ºC. Time consumed to empty the gut content tended to decrease as larval age increased. Experiments to determined the time and amount of prey required to get satiation were carried out in a 15-liter rearing glass aquaria (water volume 10 liters) containing 1,500 larvae. The larvae were fed with rotifer, Artemia or Moina after starvation of 24 hr. Samples of 20 larvae were checked at 10- inutes intervals after the start of feeding until 3 hr. It was found the time required to fill the larval digestive tract with rotifer, Artemia or Moina for 3-18 days old larvae was 80-110 minutes and amount of rotifer to get satiation was 4.8- 26 ind/larvae. For 21-27 day-old larvae the corresponding time was 60-80 minutes and was 28.5-31.6 ind/ larvae. For 30-45 day-old larvae the time was 40-60 minutes and amount of Moina to get satiation was 34.6- 52.4 ind/larvae at water temperature of 25-29ºC. The time required to fill the larval gut, tends to decrease with larval age but the amount of prey required to fill the larval gut, tends to increase with larval age. Experiments to determined the amount of food uptake in a day were done in a 15-liter rearing glass aquaria (water volume 10 liters) containing 500 larvae, and 10 ind/ml of rotifer, Artemia or Moina. The amount of food taken was calculated based on changes of rotifer, Artemia or Moina density in the rearing glass aquarium with and without fish larvae, the 5 samples of each replication were examined at 2 hourly intervals. The average amounts of rotifer uptake in a day for 3, 6, 9, 12, 15 and 18 day-old larvae were 58.8, 95.4, 64.0, 88.8, 134.0 and 147.4 ind/larvae, respectively. The mean numbers of rotifer added Artemia uptake in a day by 21, 24 and 27-day old larvae were 181.6, 185.6 and 241 ind/larvae, respectively. And average amounts of Moina uptake in a day for 30, 33, 36, 39, 42 and 45 day-old larvae were 177.4, 179.4, 214.8, 249.6, 362.8 and 366.2 ind/larvae, respectively.

Abstract: This study aims to characterize the estrogen receptor (er) in sand goby (Pomatoschistus minutus) and determine the temporal effects of 17α-ethinyl estradiol (EE2) on erα and vitellogenin (vtg) gene expression in males. Two partial cDNA sequences (erα and erβ1) are presented showing conserved structural features with ers of other species. Transcript levels for both ers were low in control fish but EE2 exposure (11 ng/L, for 29 days) increased both to a pattern similar to vitellogenic females. The relative expression of three vtg genes (vtga, vtgb and vtgc) along with erα was determined in control and male fish exposed to EE2 (11 ng/L) at multiple time-points over 29 days. All four transcripts were significantly induced due to exposure and expression rose during the time course with distinct temporal patterns and vtga reached a substantially higher level at the end of the time course coinciding with rapid elevation in erα expression. [Copyright &y& Elsevier]

Abstract: The sand goby (Pomatoschistus minutus), is a marine and estuarine teleost that is used in environmental, reproductive and behavioural studies of oestrogenic endocrine disruption. The xeno-oestrogen, 17α-ethinyloestradiol (EE2), induces expression of egg proteins vitellogenin (VTG) and zona radiata protein (ZRP) in male fish and impairs reproduction. Multiple forms of VTG and ZRP genes are found in other teleost species, yet the characteristics of VTG and ZRP in the sand goby are unknown. In this investigation, Suppressive Subtractive Hybridization was used to isolate cDNA fragments from liver, identified as belonging to 11 distinct sand goby genes, suggesting that these genes are transcriptionally upregulated by EE2. Assembly of these fragments revealed three VTG genes which shared homology with VTG classes A, B and C in other fish and two ZRP genes sharing homology with ZRP classes Ba and Bb. RTqPCR of RNA from the sand goby liver was used to show that these VTGs and ZRPs were present in low levels in control males and high levels in mature females. Exposure of males to a concentration of 11ngL−1 EE2 caused a significant increase in all VTG and ZRP transcript levels. The identification of these egg protein transcripts and the development of validated assays for their quantification will facilitate future work with this useful model species. [Copyright &y& Elsevier]

To be useful as mate choice cues, behavioural traits have to be performed consistently within individuals. This may also be true for nest construction, which, in addition to influencing offspring survival, can also function as an extended phenotype of the builder. We tested whether choice of a nesting resource and subsequent nest-building performance are repeatable traits in the sand goby, Pomatoschistus minutus, a small marine fish with paternal egg care and female mating preferences that are influenced by male nest-building behaviour. When given a choice between three different-sized nesting resources (flowerpots), males, on average, preferred medium-sized nesting resources, with larger males preferring larger nests than smaller individuals. At the individual level, the choice of nesting resources was so variable between consecutive trials that choice behaviour was not repeatable. Furthermore, nest building, measured as the amount of sand piled on top of the nesting resource, was highly repeatable when males were free to choose their nest, but had only a low repeatability when males had just a single option. In neither case was the size of the nest entrance repeatable between consecutive rounds of nest building. These results highlight the context-dependent signal value of extended phenotypes. In particular, reliability of nest-building behaviour as a signal seems to be influenced by the male''s opportunity to choose the object it uses for nesting. [Copyright &y& Elsevier]

Male courtship behaviour is known to correlate with body condition and other aspects of male phenotypic or genetic quality. Females often prefer males that express the most intense or elaborate displays, although recent findings indicate that this should not always be the case; males may be strategic in their courtship displays, signal dishonestly or deplete their energy reserves with intense courting. To study reliability of courtship effort as a mate choice signal, I assessed multiple aspects of male courtship using wild-caught sand gobies, Pomatoschistus minutus, in a controlled laboratory setting. I found consistent and repeatable between-male differences in courtship. However, females did not show a significant preference for males that courted intensively. Furthermore, other assessed male traits with a previously demonstrated role in sexual selection were not correlated with courtship effort. This indicates that courtship displays did not reliably signal male quality. The results also suggest that even when courtship has potential to convey useful information, females may have to trade between courtship and other cues they use in mate choice. Hence, to gain a more complete understanding of the selection regime acting on male courtship behaviour, and female preference for it, one should simultaneously investigate multiple factors that can affect female mating behaviour. [ABSTRACT FROM AUTHOR]

Abstract: Endocrine disrupting chemicals (EDCs) are a diverse group of compounds that can mimic, block or modulate the synthesis of natural hormones. They are known to cause impairment of reproduction of aquatic organisms at very low concentrations. The aim of this study was to examine how exposure from 10 to 31 days to 17α-ethinyl estradiol (EE2, 41ngL−1) affects the courtship and parental care behaviour of male sand gobies (Pomatoschistus minutus). The sand goby exhibits a polygynous mating system, where males compete for females and provide paternal care. First, male courtship performance towards a stimulus female was recorded with video camera. Secondly, after the male had received eggs his parental care behaviour was video recorded. In addition to behavioural endpoints, we measured the expression of hepatic vitellogenin (Vtg) and zona radiata protein (Zrp) mRNA, as well as common somatic indices. Our study shows that exposure to EE2 affected male fanning behaviour during both courtship and parental care. Interestingly, small exposed males increased their courtship fanning to similar levels as larger control males. However, during parental care egg fanning was not related to male size, and all exposed males fanned more than control males. The EE2-exposure induced Vtg and Zrp mRNA expression in males and decreased hepatosomatic index (HSI), and increased gonadosomatic index (GSI). Females prefer males that fan more, which will favour the small EDC exposed males. This may lead to mating that favours males that are not strong enough to tend the eggs until they hatch, thus decreasing the reproductive success of individuals. [Copyright &y& Elsevier]

Abstract: Endocrine disrupting chemicals (EDCs), natural or manmade, are known to interfere with the endocrinology of organisms and also cause behavioural changes. The aim of this study was to test how 1–4weeks exposure to 17α-ethinyl estradiol (EE2, 11ngL−1) affects nest building, courtship and aggressive behaviour of male fish. Our study species, the sand goby (Pomatoschistus minutus) exhibits a polygynous mating system, in which males compete for females and defend their nest against intruders. Nest takeovers are common in their nest-constrained habitat. In our experiment, control and EE2-exposed males were first allowed to build a nest and mate with non-exposed females. When the males had received eggs in their nest, three rival males were introduced into the test aquarium, and the males were left to compete for the nest site overnight. Courtship and aggressive defence behaviour were recorded using a video camera. In addition to behavioural endpoints we measured the expression of hepatic vitellogenin (Vtg) and zona radiata protein (Zrp) mRNA, and several common somatic indices. Our study showed that exposure to EE2 delays nest building and decreases male courtship and leading behaviour. Additionally, EE2-exposed males were significantly less aggressive than control males. Nest takeover rate was not affected by EE2 exposure: an equal percent of males in both treatments lost their nest to competitors. EE2 exposure also induced Vtg and Zrp mRNA expression in males and decreased the hepatosomatic index. The observed changes in nest building, courtship and aggressive behaviour of EE2-exposed males are likely to have negative implications for male reproductive success. [Copyright &y& Elsevier]

Abstract: Endocrine disrupting chemicals (EDCs) are a widely studied group of chemicals that interfere with the endocrinology of organisms. So far, few studies have demonstrated the effect of EDCs on the reproductive behavior of aquatic wildlife. Here we show that sand goby males'' (Pomatoschistus minutus) success in mating competition greatly decreases after an exposure for 7 to 24 days to 17α-ethinyl estradiol (EE2, measured concentration 4 ng L−1). The sand goby exhibits a polygynous mating system with male parental care, in which males compete for nest sites and females. The aim of this study was to test how EE2 exposure affects the ability of males to compete for breeding resources, i.e. nest sites and mates. First, EE2 exposed males competed over a nest site against a non-exposed, control male of the same size. Secondly, we examined male courtship behavior and female mate preferences for EE2 exposed males and similar-sized non-exposed, control males. In addition to the behavioral experiments we determined the zona radiata protein (Zrp) mRNA gene expression and measured morphometric indicators of sexual maturation. Our study revealed that EE2 treated males were not able to acquire or defend a nest site. Additionally, EE2 treated males spent significantly less time in active courtship and nest leading behavior than control males. As a result, females clearly preferred to mate with control males. However, we found no significant differences in Zrp mRNA expression or the morphometric indicators between treatments. Our study illustrates that exposure to this EDC can greatly reduce the chances of an individual reproducing successfully. Moreover, it demonstrates that severe behavioral effects can be seen before any effects are detectable at the molecular or morphometric level. [Copyright &y& Elsevier]

Costs and benefits of parental care are expected to affect filial cannibalism. One factor that increases the costs and decreases the benefits of care is the presence of egg predators. In general, the effect of egg predators on filial cannibalism is unknown. Here, we examine the effect of an egg predator on filial cannibalism in the sand goby. Males caring for eggs were exposed to three treatments: no egg predator, visual cues from an egg predator, and chemical and visual cues from an egg predator. We hypothesized that the perceived benefits of providing care in the presence of an egg predator would be relatively low, and we expected filial cannibalism to increase in the presence of the egg predator, especially when both chemical and visual predator cues were present, as this might represent a greater threat. When both visual and chemical predator cues were present, whole-clutch cannibalism increased. In addition, larger males and males in poorer condition showed less whole-clutch cannibalism than smaller males or males in better condition. There was no effect of egg predator on partial-clutch cannibalism. However, males that engaged in partial-clutch cannibalism ate more of their eggs when the eggs were spawned by a female in relatively good condition, but a smaller proportion and number of eggs when only a single female spawned. In general, our findings suggest that male sand gobies are sensitive to the costs and benefits of care and are more likely to terminate care when the expected benefits are relatively low. [Copyright &y& Elsevier]

Aim The Pleistocene glaciations were the most significant historical event during the evolutionary life span of most extant species. However, little is known about the consequences of these climate changes for the distribution and demography of marine animals of the north-eastern Atlantic. The present study focuses on the phylogeographic and demographic patterns of the sand goby, Pomatoschistus minutus (Teleostei: Gobiidae), a small marine demersal fish. Location North-eastern Atlantic, Mediterranean, Irish, North and Baltic seas. Methods Analysis was carried out by sequencing the mtDNA cytochrome b gene of sand gobies from 12 localities throughout the species’ range, and using this information in combination with published data of allozyme markers and mtDNA control region sequences. Several phylogenetic methods and a network analysis were used to explore the phylogeographic pattern. The historical demography of P. minutus was studied through a mismatch analysis and a Bayesian skyline plot. Results Reciprocal monophyly was found between a Mediterranean Sea (MS) clade and an Atlantic Ocean (AO) clade, both with a Middle Pleistocene origin. The AO Clade contains two evolutionary significant units (ESUs): the Iberian Peninsula (IB) Group and the North Atlantic (NA) Group. These two groups diverged during Middle Pleistocene glacial cycles. For the NA Group there is evidence for geographic sorting of the ancestral haplotypes with recent radiations in the Baltic Sea, Irish Sea, North Sea and Bay of Biscay. The demographic histories of the Mediterranean Clade and the two Atlantic ESUs were influenced mainly by expansions dated as occurring during the Middle Pleistocene glaciations and post-Eem, respectively. Main conclusions The pre-LGM (Last Glacial Maximum) subdivision signals were not erased for P. minutus during the LGM. Middle Pleistocene glaciations yielded isolated and differently evolving sets of populations. In contrast to the case for most other taxa, only the northern Atlantic group contributed to the post-glacial recolonization. The historical demography of Mediterranean sand gobies was influenced mainly by Middle Pleistocene glaciations, in contrast to that of the Atlantic populations, which was shaped by Late Pleistocene expansions. [ABSTRACT FROM AUTHOR]

Abstract: In aquatic environments, endocrine disrupting chemicals (EDCs) that interfere with the reproductive physiology of males form a threat to the reproduction of populations. This is often manifested as decreased sexual performance or sterility among males. We show that exposure to EDCs can directly affect the mating system of a marine fish, the sand goby (Pomatoschistus minutus). We exposed males for 1 to 4 weeks to two different concentrations (5 ng L−1 and 24 ng L−1) of 17α-ethinyl estradiol (EE2); a synthetic compound mimicking estrogen and a water control. The sand goby exhibits a polygynous mating system, in which male mating success is typically skewed towards the largest males, resulting in strong sexual selection for increased male size. Our experiment shows that when males have been exposed to EE2, male size has a smaller effect on mating success, resulting in weaker sexual selection on male size as compared to the control. There was an interaction between treatment and exposure time on the expression of vitellogenin and zona radiata protein mRNAs. Males exposed to high EE2 reached much higher expression levels than males exposed to low EE2. Of the somatic markers, the hepatosomatic index was lower in males exposed to high EE2 than in the low EE2 and control males. Our results suggest that exposure to EDCs can have effects on the mating system before physiological changes are observable. These effects can be of profound nature as they interfere with sexual selection, and may in the long run lead to the loss of traits maintained through sexual selection. [Copyright &y& Elsevier]

Courting males often use multiple signals to advertise their quality to females. Assuming that courtship traits are energetically costly, one would expect a limit to the overall courtship effort of an individual and that a high courtship effort takes its toll on individual condition. We tested this experimentally using a small marine fish, the sand goby, Pomatoschistus minutus, whose males attract females through courtship displays and well-built nests (mussel shells covered with sand). At the end of a 5-day period of supplemental food, or repeatedly induced courtship or construction of nests (or none of these, as a control), we tested whether male display intensity, nest quality (nest cover and nest opening size) and body condition were affected. Males provided with food in excess were in significantly better condition and had significantly higher nest quality than control males. Display rate, however, was not significantly affected by feeding regime. Fish that had been manipulated to perform increased courtship or nest building did not suffer in terms of reduced condition, display rate or nest quality. However, individual fish that displayed intensely after treatment also built better-covered nests. Both of these traits are important in female choice. Moreover, fish that displayed intensely before the treatment continued to do so after treatment, a result that is compatible with signalling of genetic or phenotypic quality. Our results suggest that (1) nest cover is an honest signal of male condition, although we found no cost of nest building per se and (2) courtship display does not signal male condition. [Copyright &y& Elsevier]

This study examines the effects of habitat-dependent nest structure on male parental behaviour in a small marine fish, the sand goby (Pomatoschistus minutus). In the northern Baltic, the sand goby breeds in two different habitats: on soft sand bottoms and on rocky beaches. We compared in laboratory conditions the behaviour of nest-guarding males occupying either a typical sand or rock habitat nest. We found that males with a rock habitat nest fanned their eggs considerably less and with shorter bouts than males in the sand habitat treatment. Hence, our study shows that nest structure can be an important factor determining parental care behaviour. The differences in nest structure may result in divergent selection pressures on male sand gobies occupying the two habitats. [ABSTRACT FROM AUTHOR]

Variation among individuals in mate choice has important implications for the evolution of sexually selected traits. For example, it offers an explanation for the continued existence of heritable genetic variation in sexually selected male traits. In this study, we first tested the suitability of association tests for assessing female mate preferences in the sand goby, Pomatoschistus minutus. Sand goby females showed sexually motivated association preferences that were repeatable and corresponded to actual mating decisions. We then compared the correlation between the preferences of two different females presented to the same male pair with the correlation between preferences of single females tested twice. We found a weak correlation between preferences in the two-female treatment, while the correspondence between preferences was much higher for the single-female treatment. These results are in accordance with the possibility that sand goby females show genetically based, individual differences in mate preferences. [Copyright &y& Elsevier]

Recent theory and empirical work suggests that there may be variation among females in mate preferences that is adaptive. One of the possible mechanisms maintaining variability in preferences and preferred traits is that the benefits of mate choice may depend on compatibility with potential mating partners. We examined fitness consequences of mate choice in a species of fish, the sand goby, Pomatoschistus minutus with a special focus on mate compatibility. Females were given the opportunity to establish their mate preferences in a dichotomous mate choice experiment. This information was then applied by mating the focal or control female with either the preferred or the non-preferred male. The parental performance of the males of these four mating combinations was then measured. In a separate experiment, we assessed the female differential allocation by determining the residual gonad weight of spawned females as a measure of the proportion of eggs spawned. We also estimated the amount of filial cannibalism separately for both sexes. Our results show that preferred males provided benefits in the form of an increased number of hatching eggs. This benefit was the same when the male was mated with a focal or a control female. Hence, we found no support for benefits that depend on mate compatibility. Neither did we find support for the hypothesis that females would lay a different number of eggs depending on the male status. The results also indicate that male filial cannibalism has a strong role in determining hatching success in this species. [ABSTRACT FROM AUTHOR]

Abstract: The effects of 17β-oestradiol (E2) on mortality, growth rates, sexual maturation, hepatic vitellogenin (VTG) mRNA expression and reproductive success were investigated during an 8-month, water-borne exposure of a marine fish, the sand goby (Pomatoschistus minutus). Indicators of oestrogenic exposure were investigated as predictors of population-level reproductive success. E2 exposure concentrations were <5 (below limit of detection), 16±3, 97±20 and 669±151ngl−1 (bootstrap means and standard errors). The carrier solvent (<20μll−1 propan-2-ol) significantly reduced the rate of egg production compared to untreated fish, but did not significantly affect male VTG mRNA expression, brood size, or the other studied parameters. Fish exposed to 16ngl−1 E2 showed few adverse effects compared with solvent only-exposed fish. Exposure to 97ngl−1 E2 significantly inhibited male sexual maturation, induced male VTG mRNA expression and delayed spawning. The 97ngl−1 E2 exposed population also produced fertile eggs at a significantly slower rate than solvent controls; however, brood size, fertility and overall reproductive success were not significantly affected. Exposure to 669ngl−1 E2 significantly increased mortality, adversely affected haematological parameters and caused an almost total lack of reproductive activity, with both sexes failing to mature. Reproductive failure following exposure to 669ngl−1 E2 was evident in both sexes when crossed with untreated animals. This work indicates that marine fish are similarly as sensitive to oestrogenic exposure as freshwater fish, that exposure biomarkers such as VTG are more sensitive to exposure than are reproductive effects, and that the use of carrier solvents in long-term reproductive studies should be avoided. [Copyright &y& Elsevier]

Pomatoschistus minutus show paternal care in a resource defence mating system. We investigated the effect of nest-site availability on parasitic spawning. Each experimental pool contained four potentially nest-building males, four females and nests-sites in shortage (2) or excess (6). Both treatments were conducted in two populations; one with natural nest-sites in excess, one with a nest-site shortage. Microsatellite-DNA revealed that all nest-holders had fertilized most of the eggs they tended. Yet, 35% of the nests contained eggs fertilized by another male and 14.4% of the males had performed parasitic spawning. There was no site or treatment effect. Several females spawned in two nests, which coincided with parasitic spawnings, suggesting a cost to the nest-holder in terms of lost mating success. Nest-holders with and without eggs and non-nesting males all spawned parasitically, generating a significantly lower opportunity for sexual selection compared to if there had been no parasitic spawning. [ABSTRACT FROM AUTHOR]

Marine fish seem to experience evolutionary processes that are expected to produce genetically homogeneous populations. We have assessed genetic diversity and differentiation in 15 samples of the sand goby Pomatoschistus minutus (Pallas, 1770) (Gobiidae, Teleostei) from four major habitats within the Southern Bight of the North Sea, using seven microsatellite and 13 allozyme loci. Despite its high dispersal potential, microsatellite loci revealed a moderate level of differentiation (overall FST= 0.026; overall RST= 0.058). Both hierarchical analysis of molecular variance and multivariate analysis revealed significant differentiation (P< 0.01) between estuarine, coastal and marine samples with micro-satellites, but not with allozymes. Comparison among the different estimators of differentiation (FST and RST) pointed to possible historical events and contemporary habitat fragmentation. Samples were assigned to two breeding units in the estuary and coastal region. Despite this classification, there were indications of a complex and dynamic spatiotemporal structure, which is, most likely, determined by historical events and local oceanic currents. [ABSTRACT FROM AUTHOR]

The sand goby Pomatoschistus minutus is a major component of marine shelf and estuarine food webs and an important study organism in behavioural research. Yet, despite the sand goby’s significance, its past and present patterns of migration and gene flow are poorly understood. Here we use the mtDNA control region and parts of the flanking tRNA genes of 63 fish from six localities in the Adriatic (Eastern Mediterranean), Western Mediterranean, Atlantic, and North Sea to investigate the phylogeography of this gobiid. Phylogenetic analyses and population genetics statistics reveal the existence of an Evolutionarily Significant Unit, sensu Moritz (1994), in the Adriatic and another in the Western Mediterranean, Atlantic, and North Sea. A possible biogeographical scenario for the separation of the ancestral population is that sand gobies in the Adriatic and Western Mediterranean split between 10,000 and 5000 years ago when due to the rise in sea temperature they migrated northwards and were bisected by the Italian peninsula. A testable prediction of this scenario is that sand gobies from the Western Mediterranean, Adriatic, and Aegean form three reciprocally monophyletic groups which are the descendants of a three-way diversification event. [Copyright &y& Elsevier]

The sand goby (Pomatoschistus spp.) is a small estuarine fish. Its abundance, life history, and sedentary nature lead to its adoption as a key species in the U.K. Endocrine Disruption in the Marine Environment (EDMAR) Program. This study investigated the presence of classic markers of estrogenic exposure by determining vitellogenin (VTG) and zona radiata protein (ZRP) mRNA levels and ovotestis in estuarine-caught male gobies and investigated morphological changes in the urogenital papilla (UGP). Laboratory exposures to estrogens were also conducted to ascertain the responses of these markers. Wild-caught male fish showed no evidence of ovotestis, VTG, or ZRP mRNA induction. Laboratory exposures suggested that sensitivity of the goby to VTG/ ZRP mRNA induction was similar to flounder. The UGP inspection of wild-caught specimens revealed evidence of feminization of male papillae, a condition denoted as morphologically intermediate papilla syndrome (MIPS). Morphologically intermediate papilla syndrome was more prevalent at estrogenically contaminated sites. Juvenile goby experimentally exposed to 17β-estradiol for 11 to 32 weeks exhibited signs of the MIPS condition, showing that it was inducible by estrogenic exposure and could therefore be a form of estrogenic endocrine disruption. The estuaries where the MIPS condition was most prevalent (>50% at certain sites) were the Tees, Mersey, and Clyde. The potential of the MIPS condition to significantly interfere with reproductive performance is discussed as well as its use as a monitoring tool for endocrine disruption in the estuarine environment. [ABSTRACT FROM AUTHOR]

I tested the effect of food addition on reproductive success in male sand gobies, Pomatoschistus minutus, by comparing food-supplemented males with unfed, control males. The sand goby is a small marine fish with paternal egg care. The males were breeding in artificial nest sites in otherwise natural conditions in the field. I quantified energy reserves by extracting nonpolar lipids. The food supplement improved the fat reserves of the fed males as compared to unfed males. Fed males spent more time at the nest, whereas unfed males spent a much smaller proportion of their time at the nest. As a consequence, fed males mated sooner than unfed males and tended to get more eggs. In the unfed group, mating speed was correlated to body length so that bigger males mated sooner. The results suggest that the reproductive success of breeding sand goby males is constrained by the availability of energy but that this constraint is most severe for small males and less severe for bigger males. Energy availability through its effect on condition will affect the investment in reproductive effort. [ABSTRACT FROM AUTHOR]

The interspawning interval of female sand gobies, Pomatoschistus minutus, a batch-spawning fish with paternal care, was significantly shorter when the fish were fed daily than when they were fed every fourth day. The incubation time of males was not affected by feeding, nor was the interbrood interval Males have an equal or higher potential reproductive rate than females. As females reproduce more slowly when food is scarce than when it is abundant, and males do not, the difference between the sexes in potential reproductive rate increases when there is food shortage. Because of this difference, both male bias in operational sex ratio and intensity in male-male competition for mates are predicted to increase as food availability decreases. Furthermore, a tradeoff between current and future reproduction is demonstrated to operate only when resources are limited, because the correlation between egg number of the first and second clutch was positive among high-food females but negative among low-food females. The number of eggs per female clutch did, however, not differ between treatments in first or second dutch. I conclude that operational sex ratio and sexual selection are expected to vary within and between sand goby populations in accordance with prey availability [ABSTRACT FROM AUTHOR]

An operational sex ratio is defined as the ratio of males to females ready to mate. Temperature has been shown to affect patterns of mating competition over the breeding season, as ambient water temperature differentially influences the potential reproductive rates of male and female sand gobies, Pomatoschistus minutus (Pallas), creating an unbiased operational sex ratio in colder water, and a male biased operational sex ratio in warmer water. Here, the direct effect of water temperature on frequencies of inter- and intrasexual interactions was studied in a short (24 hr) time perspective in aquaria with an unbiased adult sex ratio. Males were found to interact significantly more with other males, and also tended to interact more with females, in a warm (16 °C) water treatment, as compared with a cold (8 °C) treatment, even though there was no general increase in total number of interactions in the warm water treatment. Female-initiated interactions were not significantly affected by temperature. An altered operational sex ratio is unlikely to account for the observed difference in male-male interactions between treatments, for two reasons: (1) the operational sex ratio, which was estimated after the last behavioural recording in each replicate, was slightly, but equally, male biased in both treatments; (2) the operational sex ratio of each replicate was not correlated with the number of male-male interactions recorded from that replicate. Instead, these results suggest that temperature may influence the intensity of male mating competition directly, and I propose that individual fish use water temperature as a proximate cue for estimating and forecasting operational sex ratios. [ABSTRACT FROM PUBLISHER]

The article presents a study on the effects of variations in female mate preferences on male sexual traits. The study aimed to test a theory that directional female choice for male sexual traits can lead to genetic variations. Significant fluctuations in mate preferences in the sand goby or Pomatoschistus minutus which is said to be important in understanding persistence of genetic variation in underlying male traits were shown. The fluctuating preferences reportedly have the potential to alter the intensity or direction of sexual selection.