Investment in testes,sperm‐duct glands and lipid reserves differs between male morphs but not between early and late breeding season in Pomatoschistus minutus

This study of the sand goby Pomatoschistus minutus, a nest‐holding fish with paternal care, focused on gonadal investment among males of different sizes collected early and late in the breeding season. All males caught at the nest had breeding colour, whereas trawl‐caught fish consisted of males both with and without colour. The absence or presence of breeding colour was a good predictor of testes investment. Compared to males with breeding colour, males without colour were smaller in body size but had extraordinarily large testes. In absolute terms, testes mass of males without breeding colour was on average 3·4 times greater than those of males with breeding colour. Since small colourless males are known to reproduce as sneaker males, this heavy investment in testes probably reflects that they are forced to spawn under sperm competition. Contrary to testes size, sperm‐duct glands were largest among males with breeding colour. These glands produce mucins used for making sperm‐containing mucous trails that males place in the nest before and during spawning. Since both sneakers and nest‐holders potentially could benefit from having large glands, this result is intriguing. Yet, high mucus production may be more important for nest‐holders, because it also protects developing embryos from infections. There was no significant effect of season on body size, testes or sperm‐duct glands size, but colourless males tended to be less common late in the season. Possibly this may indicate that individual small colourless males develop into their more colourful counterparts within the breeding season.     

A new marine goby of genus Callogobius (Teleostei: Gobiidae) from Taiwan

A new marine goby Callogobius sheni collected from coral reefs off southern Taiwan is described. The new species can be distinguished from congeneric species by the following combination of features: dorsal fin rays VI-I, 9; anal fin rays I, 7; pectoral fin rays 18; longitudinal scale rows 27–28; predorsal scale rows 9–10; no posterior oculoscapular and preopercular canals; body pale white with five blackish brown cross bands; caudal and pectoral fins each with a large blackish brown blotch.     

A new species of Rhinogobius (Teleostei: Gobiidae) from the Hanjiang Basin in Guangdong Province, China

A new freshwater goby, Rhinogobius wangi, was collected from a small tributary of the Hanjiang Basin, Guangdong Province, southeastern China. The species can be distinguished from all congeneric species by the following unique combination of features: second dorsal fin rays I, 8; anal fin rays I, 7; pectoral fin rays 16; rather large scales as longitudinal scale series 26–27; predorsal scales 8–9; vertebral count 10 + 17 = 27; seven parallel, deep brown oblique stripes crossing on cheek in male; branchiostegal membrane with brownish-red spots in male; seven longitudinal deep brown lines on lateral side of body; pectoral fin base with a blackish-brown bar. A key to all nominal species with high vertebral counts from China (Hanjiang to Chiangtangjiang basins), Taiwan, and Japan is also provided.     

Patterns of agonistic behaviour, shelter occupation and habitat preference in juvenile Lipophrys pholis, Coryphoblennius galerita and Gobius cobitis

The patterns of agonistic behaviour and substratum preferences were investigated in captive groups of juveniles of Lipophrys pholis (Blenniidae), Coryphoblennius galerita (Blenniidae) and Gobius cobitis (Gobiidae). In monospecific groups, size was an excellent predictor of the rank attained by each individual. In heterospecific groups, both C. galerita and L. pholis were dominant over G. cobitis of similar size, and C. galerita dominated L. pholis . Although G. cobitis showed higher rates of activity and of attacks per minute, and a higher ratio of attacks over threats, all these measures were depressed in the presence of either blenniid. In both blennies, in monospecific groups, the dominance rank of each fish was a good predictor of the time spent inside shelters. G. cobitis occupied preferentially the sandy substratum both in mono- and heterospecific groups. Both blennies, when in monospecific groups, occupied preferentially the rocky substratum, with C. galerita showing the highest level of selectivity. In nature, C. galerita also showed a marked preference for rocky substrata, while G. cobitis was especially abundant in mixed bottoms. L. pholis occupied an intermediate position. In the blenniids studied, competition for access to shelter may be one major functional consequence of agonistic behaviour in non-reproductive contexts.     

Temperature selection and avoidance in the sand goby,Pomatoschistus minutus (Pallas), collected at different seasons

Synopsis The sand goby from the Oslofjord, Norway, is extremely eurythermal. In spring and autumn it avoids temperatures lower than about 4° C, in summer 6° C. Acclimation did not influence the lower avoidance temperature, but the critical thermal maximum, the upper avoidance temperature and the temperature where the whole fish darkened (the darkening temperature) varied with acclimation and season. The darkening temperature is suggested to be the upper temperature limit with the greatest ecological significance. The fish, collected at different seasons darkened at between 19.5 and 22° C. In the field the fish is not found at 20° C and higher.The preference temperature varied with season and with acclimation temperature, generally with low precision. In May, the preference temperature was 13.5° C, that is higher than the ambient temperature of 10° C. In summer, the temperature in sampling locality and preference temperature was the same, 17 and 16.5° C respectively. In October, temperature preference was 7.5° C as compared to 9° C in the field. The variation is explained as a behavioural thermoregulation to direct the fish towards optimal conditions at any time.The seasonal variation in preference temperature can not be ascribed only to seasonal variation in temperature, that is an acclimation phenomenon, but other factors are operative as well, factors which will modify the temperature tolerance in the fish.     

Interactions Between Habitat Use and Patterns of Abundance in Coral-dwelling Fishes of the Genus <Emphasis Type="Italic">Gobiodon</Emphasis>

Coral-dwelling fishes from the genus Gobiodon are some of the most habitat specialised fishes on coral reefs. Consequently, we might expect that their population dynamics will be closely associated with the abundance of host corals. I used a combination of log-linear modelling and resource selection ratios to examine patterns of habitat use among eight species of Gobiodon in Kimbe Bay, Papua New Guinea. I then used multiple regression analysis to investigate relationships between the abundance of each species of Gobiodon and the abundance of the corals they inhabited. Each species of Gobiodon used one or more species of coral more frequently than expected by chance. The pattern of habitat use exhibited by each species of Gobiodon did not vary among reef zones or among reefs with different exposures to prevailing winds, despite changes in the relative abundances of corals among reef zones. This consistency in habitat use might be expected if the coral species inhabited confer considerable fitness advantages and, therefore, are strongly preferred. For most species of Gobiodon, abundances among reef zones and exposure regimes were correlated with the abundance of the coral species usually inhabited. Therefore, it appears that habitat availability helps determine abundances of most species of Gobiodon in Kimbe Bay. In addition to correlations with habitat availability, the abundances of G. histrio, G. quinquestrigatus, G. rivulatus (dark form) and the group others were also associated with particular reef zones and exposure regimes. Therefore, in these species, reef type appears to influence patterns of abundance independently of coral availability. In contrast to other species of Gobiodon, the abundance of the most specialised species, Gobiodon sp.A, was not closely associated with the abundance of the only coral species it inhabited. This study demonstrates that even for habitat specialised species, the relationship between habitat availability and abundance varies widely and is multiscale.     

A new species of the genusamblyeleotris (pisces: Gobiidae) from Japan

A new shrimp-associated goby,Amblyeleotris melanocephala, is described on the basis of specimens from Okinoshima Island. Kochi Prefecture, and Okinawa Island, Okinawa Prefecture, Japan. The species is distinguished from other members of the genus by the following combination of characters: head dark brown, a few yellow spots on pectoral fin base and opercular margin, 13 second dorsal and 13 anal fin soft rays, 20 pectoral fin rays, longitudinal scales 92–101, proportional length of interpelvic connecting membrane relative to longest pelvic fin ray (CM-value) 0.46–0.55, presence of a ventral frenum, midline of nape naked, sides scaled above midpoint between preopercle and opercle.     

Genetic structure of Sufflogobius bibarbatus in the Benguela upwelling ecosystem using microsatellite markers

The bearded goby Sufflogobius bibarbatus is an abundant endemic small fish species on the continental shelf of the northern Benguela. The goby habitat is characterised by generally low bottom oxygen concentrations that vary spatially and seasonally. In the present study of population structure, 13 samples of S. bibarbatus from inner and outer shelf areas between 19°S and 32°S were screened using ten microsatellite loci. The genetic data were analysed in relation to isolation by distance and depth. Furthermore, for the first time, this study examined genetic data in relation to bottom oxygen concentration at the sampling locations. The data show low but significant genetic heterogeneity (G-test; F_ST = 0.007, p < .05). There was weak but significant genetic differentiation along a latitudinal gradient across all sampling sites from 19.50°S to 32.37°S (Mantel test; r = .464, p = .001), but this disappeared when the southernmost sample was removed. On the other hand, a positive correlation of bottom oxygen concentration with pairwise F_ST (r = .336; p = .017) was observed among the sampling sites from the Northern Benguela shelf area. Overall, the data are complex but suggest that isolation by distance and bottom oxygen concentration may play a role in the genetic structuring of S. bibarbatus. The findings are discussed in relation to the species’ life history features and oceanographic characteristics of the Benguela upwelling ecosystem.     

The chromosomal complement of Aphia minuta, a paedomorphic goby

The diploid complement of the paedomorphic goby Aphia minuta ranged from 44 to 41 due to Robertsonian fusions (fundamental number=44). Data on spermatogenesis suggest that structural heterozygotes are fertile and that these chromosomal changes are not involved in a speciation process.