Geographical and Temporal FA Variation in Threespine Stickleback Populations from Galicia (NW Spain)

Subtle departures from bilateral symmetry (FA) in morphological traits has been used as a measure of developmental stability in populations subjected to genetic and environmental processes as inbreeding, pollution or parasitic infection. Geographic variation of FA was assessed in 19 threespine stickleback (Gasterosteus aculeatus) populations from Miño and Limia rivers, from Galicia (NW Spain). This variation was evaluated using four FA indices on five meristic and one morphometric traits. Temporal variation of FA was also assessed using several samples through time in only one population. Significant geographical variation was detected for pectoral fin rays, lateral forks, lateral plates and spine length. Lateral plates, upper gillrakers, pectoral fin rays and spine length showed significant variation through the time. The variation of FA through the time showed a common performance for all characters during the period considered: a slight increase in the intermediate months with a decrease at the end of the period. Symmetric and asymmetric sticklebacks exhibited similar infection, with one exception: symmetric sticklebacks for lower gillrakers of Antela populations exhibited increased parasite infection relative to asymmetric ones. Sticklebacks with extreme phenotypes exhibited much higher levels of asymmetry than modal ones in all samples for all traits.     

Geographical variations in freshwater populations of the three-spined stickleback,Gasterosteus aculeatus,in Japan

This paper describes an investigation of morphological variation among six freshwater populations (dominantly low-plated morph) of the three-spined stickleback,Gasterosteus aculeatus, in Japan. Such populations are mainly distributed in restricted water areas within a band from Ise to Wakasa Bays, the most constricted part of Honshu Island. According to some differences in morphological variation, i.e. plate morph, number of lateral plates, body size, body shape and body colour, they were classified into two types corresponding to occurrence in the Ibi River and Lake Biwa water systems. The former type was monomorphic dominated by lowplated morphs in spring-fed water, whereas the latter was a dimorphic population consisting of low- and partially-plated morphs. My results suggest that the plate morph type is not correlated with climate nor predation but is related to geological isolation patterns during the course of the landlocking process. Conversely, variations in meristic (number of dorsal and anal fin rays and gill rakers) and morphometric (body shape and body colour) characteristics may have been related to different environmental conditions. This study also provides supporting evidence that the freshwater three-spined stickleback is a distinct species from the anadromous stickleback,G. aculeatus.     

Meristic and morphometric variations in fluvial Japanese charr between river systems and among tributaries of a river system

Meristic and morphometric characters of local populations of fluvial Japanese charr, Salvelinus leucomaenis, which have been isolated above dams and a waterfall, were compared between river systems (Naka and Tone rivers, central Japan) and among the tributaries of the Naka River (Ashinagasawa, Akasawa, Ushirosawa and Moto-okashirasawa streams). Between the river systems, there was a significant difference in the mean number of dorsal fin rays, pyloric caeca, white spots under the lateral line and the proportion of the diameter of the white spots to the diameter of the pupil, respectively. On the other hand, among the tributaries within a river system, a significant difference was occurred in the mean number of anal fin rays, pored scales on the lateral line, gill rakers, vertebrae, pyloric caeca, white spots under the lateral line, white spots on the surface of the gill covers and the proportion of the diameter of the white spots to the diameter of the pupil, respectively. A dendrogram based on data of the meristic and morphometric characters showed that the population of the Tone River was included within the variation detected among the tributary populations of the Naka River. Meristic and morphometric characters of Japanese charr varied not only between river systems but also among tributaries within a river system.     

Morphological analysis of geographic variation of sea lamprey ammocoetes in Portuguese river basins

The main objective of this study was to compare the morphological variability of sea lamprey (Petromyzon marinus L.) larvae from the main Portuguese river basins. Samples were collected in rivers Minho, Lima, Cávado, Vouga, Mondego, Tejo and Guadiana. Specimens were analysed in terms of morphometric (linear body measures) and meristic (number of myomeres) characters to investigate the hypothesis of population fragmentation between river basins caused by some degree of homing behaviour. The discriminant analysis showed a morphological segregation of the studied populations based on the characters head, tail and branchial length. The discriminatory power of the meristic characters was comparatively weaker, with the number of trunk myomeres, and to some extent the head myomeres, being responsible for the reduced separation between groups. Both analyses were consistent in identifying the cephalic region as the most important morphological feature to discriminate populations of sea lamprey larvae in the Portuguese territory. The largest cephalic region of the ammocoetes sampled in the northern river basins may be responsible for a better feeding efficiency and, consequently, higher values of condition factor. Guest editors: S. Dufour, E. Prévost, E. Rochard & P. Williot Fish and diadromy in Europe (ecology, management, conservation)     

<Emphasis Type="Italic">Paraliparis adustus</Emphasis> and <Emphasis Type="Italic">Paraliparis bullacephalus</Emphasis>: two new snailfish species (Teleostei: Liparidae) from Alaska

Paraliparis adustus sp. nov., a snailfish species from the Bering Sea near the Aleutian Island Archipelago, Alaska, is described based on a single mesopelagic specimen. This new species is clearly distinguished by a combination of several morphological features and meristic counts, including long pointed gill rakers with 0–3 spinules at or near the tip, anus positioned forward near the pectoral symphysis, and color uniform brown. Paraliparis bullacephalus sp. nov. from Shelikof Strait, Gulf of Alaska, is also described. This new species is very similar in meristic characters and general body shape and size to P. holomelas Gilbert, but differs primarily in morphological features of the head, particularly in the shape of the dorsal contour of the head, snout, and opercular flap, mouth size, and eye position.     

基于形态学差异探讨秦岭细鳞鲑亚种有效性问题

秦岭细鳞鲑(Brachymystax lenok tsinlingensis Li)的亚种分类地位自命名以来一直饱受争议。研究运用单因素方差分析、主成分分析、判别分析、聚类分析及差异系数检验法, 对秦岭细鳞鲑和黑龙江流域的尖吻细鳞鲑(B. lenok lenok)和钝吻细鳞鲑(B. tumensis)的5项可数性状和34项标准化后的比例性状进行统计分析。单因素方差分析结果表明, 尖吻细鳞鲑、钝吻细鳞鲑和秦岭细鳞鲑在32项比例性状和5项可数性状上存在极显著差异(P<0.01); 主成分分析结果显示, 贡献率较大的前3个主成分的累计贡献率为92.779%; 以逐步判别分析方法选用14个判别效果较好的比例性状构建了3个细鳞鲑类群的判别函数, 综合判别率为99.4%。基于欧式距离矩阵法构建的形态学聚类图显示, 秦岭细鳞鲑和尖吻细鳞鲑距离较近, 而与钝吻细鳞鲑距离较远。据Mayr 75%亚种识别和划分规则, 34项比例性状和5项可数性状中, 尖吻细鳞鲑和秦岭细鳞鲑第一鳃弓外鳃耙数目的差异系数大于1.28, 而钝吻细鳞鲑和秦岭细鳞鲑有31项比例性状和2项可数性状的差异系数高于1.28。据分析结果, 结合秦岭细鳞鲑地理隔离的事实及其与尖吻细鳞鲑和钝吻细鳞鲑的形态差异, 推断秦岭细鳞鲑与黑龙江流域内的尖吻细鳞鲑的形态差异程度至少已达亚种水平。     

Combining geometric morphometrics and genetic analysis to identify species of Opisthonema Gill, 1861 in the eastern Mexican Pacific

Studies focusing on the specific identification of the taxonomic cast within the genus Opisthonema are scarce and contradictory, in spite of this species commercial importance and of the potential ecological impact that fisheries may have on the pelagic ecosystem. In this study, the specific composition of thread herrings Opisthonema (O. bulleri, O. medirastre, and O. libertate) in the southeastern region of the Gulf of California was identified using meristic characters, morphometric data, and mtDNA sequences. In this paper we supported the hypothesis that the commercial catch comprises three evolutionary entities with meristic and morphometric differences. The results were based on the number of ceratobranchial gill rakers, the presence of spicules on the gill rakers, the form of insertion of the gill rakers base onto the ceratobranchial segment, the geometric morphometrics of body shape, and the genetic distances from a fragment of Cytochrome Oxidase Subunit I gene (COI) of mtDNA. Specimens of Pacific thread herring were obtained from landings of the small pelagic fleet at Mazatlan, Sinaloa during 2011–2012. Taxonomic categories were assigned to 1060 individuals according to the measurement of meristic characters. A total of 228 thread herrings O. bulleri, (n = 76), O. medirastre (n = 76), and O. libertate (n = 76) were used in the morphometric analysis, and 25 specimens (O. bulleri n = 8, O. medirastre n = 7, and O. libertate n = 10) were used for genetic comparisons. The morphometric results showed differences among the three groups that had been previously identified using meristic characters, giving support to the existence of three discrete morphotypes. The percentage of sequence divergence of the COI gene supports the existence of three clades. Genetic distances were considerably lower within each clade than between clades. The results of this study provide sufficient evidence for the existence of three Pacific thread herring species in the southern Gulf of California.     

Osteology and morphology of the characiform fish Alestes stuhlmanniiPfeffer, 1896(Alestidae) from the Rufiji River basin,East Africa

The osteology of a population of the characiform fish Alestes stuhlmannii, from the Rufiji River basin of Tanzania, is described, and meristic and morphometric data from over 100 specimens, ranging from 15·5 to 218 mm standard length are given. Two allometric changes occur during growth of this fish: both the number of gill rakers and the interorbital width relative to the head length increase with size. There are also changes in tooth form associated with growth in A. stuhlmannii, with the unicuspid teeth of juveniles becoming almost molariform in adults. This change in dentition with age, and therefore size, may have implications for recognizing taxa, some of which (the fossil genera Sindacharax and Bunocharax, and the living dwarf petersiines) have been distinguished by jaw or dental characters.     

Postglacial dispersal of longnose suckers, Catostomus catostomus, in the Mackenzie and Yukon Drainages

The role played by stream transfers and reversals in the postglacial dispersal of fish populations in the Yukon and Mackenzie River drainages of Canada was analysed using genetic and meristic data from longnose sucker (Catostomus catostomus Forrester) populations. The hypothesis the suckers dispersed from the Yukon River into the Mackenzie River via the Peel River was evaluated. Meristic data (gill rakers and lateral line scales) were uninformative for this analysis. Genetic affinity between the Yukon River and upper Peel River populations, and between Mackenzie and lower Peel River populations is suggested by transferrin allele frequencies. These affinities support the view that longnose suckers inhabiting the middle and upper regions of the Peel River are derived from Beringian and Mississippian ancestors, while suckers in the lower Peel are descended from Mississippian stock. Evidence for dispersal by way of the Eagle River was not found. Affinities of sucker populations in other river systems in the region are also described.     

A population analysis of Robertsonian and Ag-NOR polymorphisms in brown trout (Salmo trutta)

An analysis of Robertsonian polymorphism and variation in the number of active NORs has been carried out in several populations of brown trout (Salmo trutta) from Northwestern Spain. The karyotype of this species appears to be soundly established, and essentially no variation has been found in chromosome number. Interindividual and interpopulation variation in arm number was detected, with figures ranging between 100 and 102 among individuals, and between 100.10 and 100.80 among populations. This variation in arm number is solely attributable to the polymorphism of the short arm of the main NOR-bearing pair 11, which can appear from acrocentric to metacentric in different individuals. Most populations analyzed showed the standard distribution of active NORs previously observed in this species. The Miño drainage basin, and specially the Chamoso population, showed a multi-chromosomal distribution of active NORs, with several new locations, always telomeric. In most cases no concordance was observed between previously detected rDNA sites in S. trutta and the new Ag-NOR locations. This fact suggests a transposition mechanism rather than an activation of silent rDNA sites to explain this multichromosomal NOR pattern.     

Morphological variation in a secondary contact between divergent lineages of brown trout (Salmo trutta) from the Iberian Peninsula

The aim of this study was to analyze the morphological variation of brown trout (Salmo trutta) in the Duero basin, an Atlantic river basin in the Iberian Peninsula, where a spatial segregation of two divergent lineages was previously reported, based on isozyme, microsatellite and mtDNA data. In these studies, two divergent pure regions (Pisuerga and Lower-course) and several hybrid populations between them were identified. Morphological variation was evaluated in 11 populations representative of the genetic differentiation previously observed in the Duero basin, using multivariate analysis on 12 morphometric and 4 meristic traits. A large differentiation between populations was observed (interpopulation component of variance: 41.8%), similar to that previously detected with allozymes and microsatellites. Morphometric differentiation was also reflected by the high classification success of pure and hybrid individuals to their respective populations, using multivariate discriminant functions (94.1% and 79.0%, respectively). All multivariate and clustering analyses performed demonstrated a strong differentiation between the pure regions. The hybrid populations, though showing large differentiation among them, evidenced an intermediate position between the pure samples. Head and body shape traits were the most discriminant among the morphometric characters, while pectoral rays and gillrakers were the most discriminant among the meristic traits. These results confirmed the high divergence of the brown trout from the Duero basin and suggest some traits on which selection could be acting to explain the spatial segregation observed.     

Morphological variation of the pikeperch Sander lucioperca (L.) in the southern Caspian Sea, using a truss system

A morphometric truss network system and meristic counts were used to investigate the hypothesis of population fragmentation of pikeperch Sander lucioperca among four major fishing areas in the Caspian Sea drainage. Univariate analysis of variance showed significant differences between the means of the four groups for 20 out of 32 standardized morphometric measurements (27 truss, five traditional characters) and six out of nine meristic counts. The first two canonical discriminant functions accounted for 93 and 92.3% of the total variability in morphometric and meristic characteristics, respectively. A dendogram derived from cluster analysis of Mahalanobis distances and a discriminant analysis among the groups confirmed three distinct populations in these regions, while there was a relatively high degree of overlap between all locations when using meristic characters. The most relevant morphometric characteristics were the measured distances on body heights and the caudal peduncle area. This study indicated that the morphometric truss network system was more adequate than meristic characters for separation among the populations.     

Parallel and nonparallel ecological,morphological and genetic divergence in lake–stream stickleback from a single catchment

Parallel phenotypic evolution in similar environments has been well studied in evolutionary biology; however, comparatively little is known about the influence of determinism and historical contingency on the nature, extent and generality of this divergence. Taking advantage of a novel system containing multiple lake–stream stickleback populations, we examined the extent of ecological, morphological and genetic divergence between three‐spined stickleback present in parapatric environments. Consistent with other lake–stream studies, we found a shift towards a deeper body and shorter gill rakers in stream fish. Morphological shifts were concurrent with changes in diet, indicated by both stable isotope and stomach contents analysis. Performing a multivariate test for shared and unique components of evolutionary response to the distance gradient from the lake, we found a strong signature of parallel adaptation. Nonparallel divergence was also present, attributable mainly to differences between river locations. We additionally found evidence of genetic substructuring across five lake–stream transitions, indicating that some level of reproductive isolation occurs between populations in these habitats. Strong correlations between pairwise measures of morphological, ecological and genetic distance between lake and stream populations supports the hypothesis that divergent natural selection between habitats drives adaptive divergence and reproductive isolation. Lake–stream stickleback divergence in Lough Neagh provides evidence for the deterministic role of selection and supports the hypothesis that parallel selection in similar environments may initiate parallel speciation.     

Divergent selection as revealed by P(ST) and QTL-based F(ST) in three-spined stickleback (Gasterosteus aculeatus) populations along a coastal-inland gradient

Three measures of divergence, estimated at nine putatively neutral microsatellite markers, 14 quantitative traits, and seven quantitative trait loci (QTL) were compared in eight populations of the three-spined stickleback (Gasterosteus aculeatus L.) living in the Scheldt river basin (Belgium). Lowland estuarine and polder populations were polymorphic for the number of lateral plates, whereas upland freshwater populations were low-plated. The number of short gill rakers and the length of dorsal and pelvic spines gradually declined along a coastal-inland gradient. Plate number, short gill rakers and spine length showed moderate to strong signals of divergent selection between lowland and upland populations in comparison between P(ST) (a phenotypic alternative for Q(ST)) and neutral F(ST). However, such comparisons rely on the unrealistic assumption that phenotypic variance equals additive genetic variance, and that nonadditive genetic effects and environmental effects can be minimized. In order to verify this assumption and to confirm the phenotypic signals of divergence, we tested for divergent selection at the underlying QTL. For plate number, strong genetic evidence for divergent selection between lowland and upland populations was obtained based on an intron marker of the Eda gene, of which the genotype was highly congruent with plate morph. Genetic evidence for divergent selection on short gill rakers was limited to some population pairs where F(ST) at only one of two QTL was detected as an outlier, although F(ST) at both loci correlated significantly with P(ST). No genetic confirmation was obtained for divergent selection on dorsal spine length, as no outlier F(ST)s were detected at dorsal spine QTL, and no significant correlations with P(ST) were observed.     

Quantitative Trait Loci Analyses for Meristic Traits in Oncorhynchus mykiss

Meristic trait variation among species and populations has long been used as the basis for identification and classification of fishes. Within Oncorhynchus mykiss, there is considerable variation in meristic characters such as numbers of vertebrae, lateral line scales, fin rays, gill rakers, and pyloric caeca. In our laboratory the Oregon State University (OSU) rainbow trout and the Clearwater River (CW) steelhead trout clonal lines, produced by androgenesis, exhibit significant differences in values for meristic traits, making quantitative trait locus (QTL) analysis of these meristic characters possible. Our objective was to determine the number, location, and effects of QTL associated with meristic characters in order to test two hypotheses: (1) that QTL for different meristic traits co-localize to the same linkage group and (2) that meristic trait QTL co-localize to the same linkage group as a previously identified development rate QTL. Doubled haploid individuals, produced by androgenesis from sperm from an F₁ hybrid between the OSU and CW lines, were used to evaluate the joint segregation of each meristic phenotype and Amplified Fragment Length Polymorphic marker genotypes. Composite interval mapping revealed QTL for six of the seven traits analyzed. One QTL each for scales above the lateral line and for gill rakers co-localized to the same position. Only one QTL for scales above the lateral line co-localized to the same region as that for the development rate QTL, but a greater map resolution is necessary to determine if these loci are truly the same. We failed to detect pleiotropy for most meristic trait QTL. Our results suggest that different major loci are associated with variation in each meristic character and that the expression of these loci may be influenced by maternal and external environmental factors.     

Larval development of the freshwater croaker Pachypops fourcroi (La Cépède 1802) (Perciformes: Sciaenidae)

The larval development of Pachypops fourcroi from the lower Amazon River was described through morphological, meristic and morphometric features. Sixty-five larvae were examined and present a moderate body, slightly elliptical eyes and head ranging from moderate to large. The mouth is initially terminal and becomes subterminal throughout development with three barbels in the mentonian region. The larvae of P. fourcroi can be differentiated from other Sciaenidae in the Amazon basin by the pigmentation pattern, the presence of barbels, head depth, body depth and diameter, and shape of the eye.     

Two new soldierfishes (Beryciformes: Holocentridae:Myripristis) from Japan

Two species of the holocentrid fish genusMyripristis are described as new from Japan, both with a single pair of tooth patches outside the gape at tip of lower jaw, the third anal spine longer than the fourth, and 28–29 lateral-line scales:M. kochiensis from Kashiwa-jima, Kochi Prefecture, previously misidentified asM. murdjan, is distinct in having small scales in axil of pectoral fins, 32–36 gill rakers, interorbital space 4.45–5.1 in head, and lower jaw not strongly projecting when mouth closed;M. greenfieldi, from the Ryukyu Islands and Ogasawara Islands to Kochi Prefecture, previously misidentified asM. woodsi andM. randalli, is distinct in lacking scales in the pectoral axil, having 35–52 cteni on largest body scales, 43–47 gill rakers, and longest dorsal spine 2.0–2.25 in head.     

Morphological variation in diadromous and landlocked populations of the spotted galaxias,Galaxias truttaceus,in Tasmania,south-eastern Australia

Synopsis A comparison of a suite of morphometric measurements and meristic counts of individuals of two landlocked lacustrine and two diadromous riverine populations of Galaxias truttaceus was carried out utilising both univariate and canonical variate analyses. Lacustrine fish had fewer dorsal and anal fin rays than did riverine fish. Differences were not as clear for gill rakers and vertebrae. Comparisons of serial counts were made with two derived lacustrine species, G. auratus and G. tanycephalus, also from Tasmania. Lacustrine G. truttaceus varied in the same direction as the derived species, relative to riverine G. truttaceus. From an analysis of 12 body measurements, the first canonical variate clearly separated lacustrine fish from riverine fish largely based on measurements associated with fins (pre-anal fin length, length of anal base, pre-dorsal fin length, maximum length of dorsal fin and inter-orbital width). An overall value for the correct classification of fish into groups based on locality was 84%. The percentage of fish classified into the wrong habitat (lake or stream) was much less than the percentage classified between localities within habitats. Overall morphological variation was greater between than within habitats. It is suggested that the differences in water movement and food type may in part account for the differences shown and that selective pressures peculiar to the lacustrine environment may be causing the lake populations to diverge from the riverine populations.     

Changes in morphological characteristics of an introduced population of the threespine stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> in Lake Towada,northern Japan

A freshwater population of the threespine stickleback Gasterosteus aculeatus occurs at an elevation of 400m in Lake Towada in the mountains of northern Japan. Morphological characteristics of each sex of this population were studied between 1985 and 1992. The 1985 fishes were larger in standard length than even anadromous populations, as well as all other freshwater populations, so the large body size of this population was unusual for the species. The population was also characterized by large ratios of head length, eye diameter, and gill raker length, and a higher ovary volume in 1992 than in 1985, but it was not readily characterized by meristic characters. The population may have been introduced within the last 20 years (probably in the early 1980s). The large body size of the population may not reflect a defense against predators because coexisting fishes were not important predators on threespine stickleback adults. It is supposed that the change of body size was induced by environmental changes in prey abundance in the lake and/or by the longevity of fishes.     

台湾棘带吸虫囊蚴在鳙鳃丝、鳃耙上的分布

通过对鳙为期16个月的定期取样研究发现,1993年8月到1994年3月,台湾棘带吸虫的囊蚴主要分布在鳃耙上,1994年4月至11月,囊蚴则主要分布在鳃丝上;当鳙体长范围为30-90mm时,囊蚴主要分布在鳃耙上,当体长大于90mm时,囊蚴主要分布在鳃丝上,随着鳙的生长,鳃丝囊蚴所占的比例逐渐增大,从0增加到100%,而鳃耙囊蚴所占的比例逐渐减小,从100%下降到0;不同月份、不同体长组鳙其不同组鳃丝囊蚴分布规律相同,第2组鳃丝囊蚴分布较多,第3、第1、第4组鳃丝囊蚴分布依次减少：其不同组鳃耙囊蚴分布规律也相同,总是第1组鳃耙囊蚴分布较多,其余依次为第2、第3、第4组鳃耙;囊蚴在鳙鳃丝和鳃耙上的分布都呈聚集分布,且聚集的强度随囊蚴内种群密度的增高而增高。