Occurrence of vertebral deformities in Gobiidae (Pisces) from the Tagus estuary

In four species of gobiid fish caught in Tagus estuary during 1996, the incidence of skeletal deformities ranged from 2 to 5%. Differences between sampling stations or between the two most abundant species Pomatoschistus minutus and Gobius niger were statistically not significant (p > 0.05). The type of deformity depended upon species. P. minutus and P. microps showed bone nodules at the inferior side of the abdominal vertebrae, whilst G. niger and G. paganellus had shortened caudal vertebrae (achondroplasia) and deformed ural plates. The possible role of pollution or other conditions in the Tagus estuary is discussed.     

An electrophoretic study of the systematic relationships of some closely related goby species (Pisces, Gobiidae)

An electrophoretic study of genetic variation at 31 loci in each of nine closely related gobiid species was carried out in order to assess their systematic relationships. The species used were: Pomatoschistus canestrinii, P. lozanoi, P. marmoratus, P. microps, P. minutus, P. norvegkus, P. pictus, Knipowitschia caucasica, Neogobius melanostomus. Genetic distances ( D ) and identities ( I ) were calculated by Nei's method for all 36 pairwise comparisons and dendrograms were constructed.
The results show that the very similar and cross-fertile species pair, P. lozanoi and P. minutus , have the highest I value; P. norvegkus has high I values with both species. Pomatoschistus marmoratus and P. microps also display high genetic similarity with each other. The remaining Pomatoschistus species and Knipowitschia caucasica are broadly and moderately equidistant from each other and from the five species refferred to above, while Neogobius melanostomus is considerably more distant from all other species.
These findings essentially agree with the pattern of relationships established using classical taxonomic approaches. However, the observation that Knipowitschia caucasica is as similar to Pomatoschistus spp. as the latter are to each other suggests that the generic distinction of Knipowitschia could usefully be reconsidered.     

Age-structure and life-span in the Common goby, Pomatoschistus microps

Age-structure and longevity in the euryhaline Common goby, Pomatoschistus microps (Krøyer), has been studied by monthly sampling of estuarine and shore populations in the Isle of Man and in collections from other parts of the British Isles. Age of individuals was determined by examination of caudal peduncle scales, where time of annulus formation was confirmed from monthly changes in mean terminal sclerite width and in frequency of scale-types. After the first winter of life, an annulus of narrow sclerites is produced on resumption of growth in spring and a separate summer annulus, corresponding with a growth retardation during the peak breeding season, is laid down usually in June. Maximum age did not exceed 21–26 months, with most adult fishes dying in the second autumn of life a few months after their first breeding season (within possible age-limits of 12–20 months). Seasonal migration is discussed with reference to the downstream movement of estuarine P. microps when sexually mature after the first winter of life, the winter distribution relative to temperature, and the preference of newly demersal young for less saline parts of the estuary. Cases of mortality from predation and environmental extremes are listed. The question of senescence in relation to life-history pattern and survival in P. microps and some other teleosts is discussed with special reference to gonad maturation and spawning, and the attainment of limiting size.     

Identification of a host-associated species complex using molecular and morphometric analyses,with the description of Gyrodactylus rugiensoides n. sp. (Gyrodactylidae,Monogenea)

Gyrodactylus rugiensis was originally described as a parasite occurring on the marine gobies Pomatoschistus minutus and Pomatoschistus microps. In our preliminary survey this species was also frequently found on Pomatoschistus pictus and Pomatoschistus lozanoi. Subsequent molecular analysis of the internal transcribed spacers rDNA region revealed that this parasite actually represents a complex of two apparently cryptic species, one restricted to P. microps and the other shared by P. minutus, P. lozanoi and P. pictus. Morphometric analyses were conducted on 17 features of the opisthaptoral hard parts of specimens collected from all four host species. Standard discriminant analysis showed a clear separation of both genotypes by significant differences in marginal hook and ventral bar features. Statistical classifiers (linear discriminant analysis and nearest neighbours) resulted in an estimated misclassification rate of 4.7 and 3.1%, respectively. Based on molecular, morphological and statistical analyses a new species, Gyrodactylus rugiensoides is described. This species seems to display a lower host-specificity than generally observed for Gyrodactylus species as it infects three sympatric host species.However, seasonal and host-dependent morphometric variation is shown for G. rugiensoides collected on P. pictus. Host-switching and gene flow might be important factors preventing speciation on closely related and sympatric host species. The presence of host associated species complexes in this Gyrodactylus-Pomatoschistus system is also confirmed by the presence of two host-dependent genotypes within G. micropsi found on P. minutus and P. lozanoi, and P. microps, respectively. By comparing host and parasite phylogeny, phylogenetic and ecological factors influencing host-specificity are discussed.     

First record of Kudoa (Myxosporea) in Pomatoschistus microps in the Rhône Delta, France

Myxosporidiosis due to Kudoa sp. has been recorded in gobies Pomatoschistus microps , collected from the Etang du Vaccarès (Rhône Delta, France).     

A New Myxosporean Parasite, Kudoa Camarguensis N. Sp., Recorded On Two Goby Species (Teleostei: Pisces) In the Rhône Delta (Mediterranean Sea, France)

ABSTRACT. A new species of myxosporean of the genus Kudoa was found in the muscle tissues of Pamatoschistus minutus (Pallas, 1770), a migratory fish species from the Mediterranean Sea. Previously this Kudoa species had been observed in Pomatoschistus microps (Krøyer, 1838), a sedentary species of the Vaccarés lagoon system. the parasite caused rapid myoliquefaction of the affected muscles within one hour after host death. Using both light and electron microscopy, whitish, longitudinal, spindle-shaped bodies, 2-5 mm long and 1-2 mm wide, were found in the caudal peduncle or in muscle tissues of the abdominal wall. Spore length, width, and thickness (n = 30) ranged between 4.4-6.0 üm, 6.4-8.0 üm, and 4.4-6.0 üm, respectively, while the polar capsules averaged 2.5 times 1.5 üm (n = 30). Anatomic comparison with other myxosporean parasites enabled us to determine this to be a new species that we name Kudoa camarguensis n. sp.     

Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)

The sand goby, Pomatoschistus minutus , was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male-male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non-random mating success in male P. minutus.     

Studies on scale regeneration in the Common goby, Pomatoschistus microps (Pisces)

The longevity of original scales and the process and consequences of scale regeneration in the euryhaline Common goby, Pomatoschistus microps (Kroyer), has been studied by monthly sampling of two populations. Scale regeneration comprises four stages: formation of a new growth centre, a regenerated area in the form of a wide central irregular area lacking concentric circuli: formation of short and widely spaced circuli at the outermost region of the regenerated area: a check in regenerated scale growth on reaching the size of the original scales: and the commencement of normal growth similar to that of the surrounding original scales. Growth of regenerated scales within 30 days was not sufficient to attain the same size of the original ones. The average percentage of regenerated scales in successive months during the life span of P. microps is about 20% in immature fish and sharply increases up to about 60% of the total scales during the breeding season. The correlation between sharp increases in regenerated scales and the breeding season is also confirmed on examining scales from two other gobioid species, Gobius paganellus and Gobius cobitis. It is suggested that the loss of a large number of scales may result in the check in body growth during the breeding season.     

The food of Pomatoschistus minutus (Pisces, Gobiidae) in Belgian coastal waters, and a comparison with the food of its potential competitor P. lozanoi

Data are presented on the food and gonadosomatic index of Pomatoschistus minutus obtained from the bycatch of a commercial shrimp trawler. P. minutus has a diverse diet including zooplankton and hyperbenthos but mainly epibenthic and benthic animals. During the spawning season males consumed high numbers of Pomatoschistus eggs, presumably after aggressive take–overs of territories. The food of P. minutus is compared to the food of P. lozanoi of the same size classes obtained from the same hauls. In the absence of data on predator and prey abundance the discussion on possible interference competition between the two species remains largely speculative.     

The identification of Pomatoschistus minutus (Pallas) and Pomatoschistus lozanoi (de Buen) (Pisces, Gobiidae)

Sand gobies areextremely abundant in coastal waters and estuaries. Pomuroschistus lozunoi tends to be overlooked due to identification problems. This paper summarizes the characteristics to distinguish P. lozanoi from P. minutus and presents a new distinctive feature that allows identification of juveniles from 15-20 mm standard length onward. The known geographic distribution of P. lozanoi is extended northward to 53°30' N and southward to 40°N on the coast of Europe. In northern Europe P. loxmoi seems better adapted to the estuarine habitat than previously thought.     

A new species of Pomatoschistus (Teleostei,Gobiidae): the Mediterranean's smallest marine fish

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.     

A new West Balkanian sand-goby (Teleostei: Gobiidae)

A new species of West Balkanian freshwater sand-goby Pomatoschistus montenegrensis sp. nov. (Teleostei: Gobiidae) is described from the Morača River, southern Montenegro, and shown to be related to the euryhaline Adriatic Pomatoschistus canestrinii . The generic status of these two species is discussed with reference to the limits of Pomatoschistus (type Gobius minutus ) and the status of a subgenus [ Ninnigobius (type-species Gobius canestrini )]. The habitat and the local distribution of the new species are described.     

Alkaline phosphatase activity in the skin of the Common goby, Pomatoschistus microps (Krøyer), in relation to cycles in scale and body growth

A histochemical study of the distribution of alkaline phosphatase in the skin of the Common goby, Pomatoschistus microps , showed that the enzyme is present in the dermis, not in the epithelium, and is more pronounced around the growing edge of the scale and below the fibrillary plate. The intensity of the enzyme reaction is higher in regenerated scales. In conjunction with the phenology of P. microps , a method was adopted to measure the enzyme activity in the skin, including scales, for successive months over a period of two years. Enzyme activity displayed seasonal fluctuations which were closely related to both body and scale growth. Enzyme activity also reflected other phenological cycles during the life-span of P. microps .     

Tolerance, behaviour and oxygen consumption in the sand goby, Pomatoschistus minutus (Pallas), exposed to hypoxia

Behavioural and metabolic reactions of Pomatoschistus minutus (Pallas) exposed to various degrees of hypoxia were studied. At 15°C and 20‰ mortality was 50% at 15.2% oxygen saturation. Avoidance and oxygen saturation showed a linear inverse relationship. At levels lower than 60% saturation increased activity occurred; avoidance was significant at 30% saturation. Active, routine and standard MO₂ correlated linearly with weight at 6 and 15°C (salinity = 19‰). During hypoxia at 15°C routine MO₂ rose significantly at 60–50% and 40–30% saturation expressed either as MO₂ during longer periods at night or MO₂ at shorter intervals during the day. Standard MO₂ was unaffected by hypoxia at 15°C. Haemoglobin concentration was significantly increased when P. minutus was acclimatized to 35% saturation.     

Dynamics of Kudoa camarguensis (myxosporean) infection in two gobiid species,Pomatoschistus microps and P. minutus (Teleostei: Pisces), in the Rhĵne River delta,France

The occurrence of the myxosporean parasite Kudoa camarguensis was surveyed monthly during 1997 in a brackish-water lagoon of the Rh?ne River delta (France). K. camarguensis was found on its typical host, Pomatoschistus microps, and on an additional host, P. minutus. Prevalence and mean abundance were higher in the typical host than in the additional host due to differences in the temporal occupancy of the lagoon by the 2 species. The temporal occurrence of this myxosporean parasite is discussed in relation to the migratory habits of P. minutus and the sedentary habits of P. microps.     

Sexually selected nest-building--Pomatoschistus minutus males build smaller nest-openings in the presence of sneaker males

Both natural selection and sexual selection may act on nest-building. We tested experimentally how different regimes of egg-predation and male-male competition influence nest-building before mating, using the marine fish sand goby, Pomatoschistus minutus. Males with sneaker males present built the smallest nest-openings, smaller than males held alone or with Pomatoschistus microps males (which may predate eggs and compete over nest-sites but not compete over fertilizations). Males with visual access to other nest-building males tended also to build smaller openings than males held alone or with P. microps. Males with egg-predators present built nests with openings not differing significantly from any other treatment. Our results indicate that the small nest-openings found in the sneaker male treatment are sexually selected through protection against sneaking or by female choice. Across treatments, time span before a male started to build his nest also explained variation in nest-opening width; males starting late built larger nest-openings.     

Phosphoglucose isomerase polymorphism in the common goby, Pomatoschistus microps (Krøyer) (TeleosteirGobiidae), around the British Isles

Phosphoglucose isomerase (PGI) polymorphism has been investigated by horizontal starch-gel electrophoresis in the common goby, Pomatoschistus microps (Krøyer), from 21 localities around the British Isles and at Roscoff, France. Sixteen PGI phenotypes were observed, consistent with occurrence of four alleles at each of the two loci (A,B). In the Teign estuary at Shaldon, Devon, seasonal fluctuation in PGI-A allele frequencies was accompanied in some months by departure from Hardy-Weinberg equilibrium. At this locality, a significant change in PGI-A allele frequencies was found with increasing modal age of sample (within a year class) but not between year-classes over eight years. Similar stability is noted for other areas. Major alleles (PGI-A2, A3; PGI-B2, B3) were found at all localities, but with marked differences in proportions. Atlantic coast populations tended to have higher A2 and B2 frequencies than those of the North Sea and English Channel, with Irish Sea populations having high A2 but low B2. Historical and selective causes for this geographical variation are discussed. A significant correlation exists between the frequencies of the major PGI-A alleles and maximum monthly mean sea temperature for the same area.     

Parasites as indicator of fish behaviour

In the present study two species of gobies, Pomatoschistus microps and P. minutus from southwest Wales were studied and appearance of some unusual parasite of gobies, were used as an indicator for fish behaviour. The occurrence of pleurocercoids of Ligula intestinalis in the body cavity of these fish and Proteocephalus sp., excysted metacercariae and adult of Timoniella spp., excysted metacercariae of Bucephalus baeri , the excysted metacercariae of Podocotyle atomon and progenetic adult of Bucephaloides gracilescens in their gut indicate host anadromous, cannibalistic and scavenging behaviour.     

Current and historic gene flow of the sand goby Pomatoschistus minutus on the European Continental Shelf and in the Mediterranean Sea

Phylogeographical patterns of the sand goby Pomatoschistus minutus (Gobiidae, Teleostei) were studied by means of sequence and single-stranded conformational polymorphism analysis of a 283-bp fragment of the cytochrome b locus of the mtDNA. A total of 228 individuals sampled at 13 sites throughout the species's distributional range revealed a moderate level of diversity and a low but significant level of overall genetic differentiation at all but one site. The goby sample from the Adriatic Sea differed in sequence by approximately 10% from the Atlantic P. minutus and is thought to belong to a cryptic species of the genus Pomatoschistus . Limited genetic differentiation with a weak pattern of isolation-by-distance was recorded throughout the distributional range of the typical P. minutus . Phylogeographical analysis suggested a contiguous range expansion in the Atlantic and Baltic basins during the Eemian and evidence for a glacial refugium in the southern North Sea during the Weichselian. In P. minutus from the western Mediterranean Sea a high number of endemic haplotypes as well as the most common Atlantic haplotype were recorded in appreciable frequencies. This might be explained by secondary contact between different mitochondrial lineages, which evolved in allopatry.   © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 561–576.