Meristic and morphometric variation in the silver perch, Leiopotherapon plumbeus (Kner, 1864), from three lakes in the Philippines

A number of researchers have applied multivariate methods to elucidate the population structure of fishes. In this study, we also used multivariate techniques to examine meristic and morphological variations in the silver perch, Leiopotherapon plumbeus (Kner, 1864), from three Philippine lakes, namely, Laguna de Bay, Sampaloc Lake, and Taal Lake. We also aimed to determine whether or not there are meristic and morphological differences among the populations of silver perch from the three lakes, considering that this fish species was introduced from Laguna de Bay into Sampaloc Lake and Taal Lake in the late 1950s and early 1970s, respectively. A total of 710 specimens from four different sites were used in the study: 155 each from Binangonan and Tanay areas of Laguna de Bay and 200 each from Sampaloc Lake and Taal Lake. Based on analysis of variance, eight meristic and 26 transformed morphometric characters were selected for subsequent analyses. Nineteen (19) principal components extracted from the 34 significant variables accounted for 82.3% of the variation in the original variables. Factor analysis using varimax rotation produced four factors: factor 1 was dominated by fin measurements while the highest loadings for factor 2 were gill raker counts. Factors 3 and 4 were dominated by various body and head measurements. Cluster analysis showed specimens from Sampaloc Lake and Taal Lake in one group, while majority of the specimens from Binangonan and Tanay are in another cluster. This suggests a closer morphological similarity between specimens from Sampaloc and Taal. Discriminant analysis gave relatively high correct classification rates (76.13–95.50%). Lower gill raker count was the most discriminating variable. Since both the silver perch from Sampaloc Lake and Taal Lake were introduced from Laguna de Bay, the observed clustering and morphological variation could be attributed to similarities and differences in the lake environments. Laguna de Bay is a shallow eutrophic lake, while Sampaloc Lake and Taal Lake are deep lakes. Further studies, however, are needed to determine which of the myriad of biological and/or physico–chemical factors might have the greatest influence on the observed morphological divergence between the source population and transplanted populations that we found in our study.     

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.     

Morphological differences among three color morphotypes of Sebastes inermis (Scorpaenidae)

 Morphological differences among three color morphotypes occurring almost sympatrically (A, reddish type; B, blackish type; C, brownish type) of Sebastes inermis are clarified. Twenty-six morphometric characters and seven meristic characters were examined on about 20 specimens of each morphotype, 15 of the morphometric characters differing significantly. Principal component analysis (PCA) of the morphometric characters showed morphotype C to differ from the other two morphotypes. Canonical discriminant analysis (CDA) of the morphometric characters showed clear separation of each morphotype. Four meristic characters also differed significantly. Modes of pectoral fin ray counts of morphotypes A, B, and C were 15, 16, and 17, respectively, and the modes of anal fin ray counts of morphotypes B and C were 7 and 8, respectively. Many individuals of morphotype A had seven or eight anal fin rays. These differences suggested that the three morphotypes may be reproductively isolated from each other. Received: October 15, 2001 / Revised: March 14, 2002 / Accepted: April 9, 2002     

Variation of stone sculpin <Emphasis Type="Italic">Paracottus knerii</Emphasis> (Cottidae,Scorpaeniformes) of Baikal and waters of Baikal region

Sixteen samples of the stone sculpin Paracottus knerii from Baikal Lake, Angara River, and seven water bodies of the Baikal and Angara basins are studied. Variation of the morphometric and meristic characters is considered. It is found that the variation of a number of characters is biotopically conditioned and directed at fish adaptation to deepwater and dwelling in the conditions of rapid current. There are also the characters whose variation does not show any regularity, and it is a consequence of the discontinuity of range of the species. It is shown that the individual pairs of populations have differences in a number of characters, and these differences conform to the subspecies (CD > 1.28) and species levels (presence of hiatus). However all such pairs are connected by “ring overlaps,” thus, it is not possible to consider them as independent taxa.     

大眼华鳊和伍氏华鳊的形态差异及其物种有效性

分别对大眼华鳊和伍氏华鳊 137尾标本 7个可数性状和 18个可量性状进行主成分分析 ,以探讨这两个种之间的形态差异及其物种有效性。研究结果显示 :无论是在可数性状上还是可量性状上 ,大眼华鳊和伍氏华鳊之间的形态差异并不显著 ,而且大眼华鳊大陆的标本和台湾的标本无明显的不同。此表明 ,大眼华鳊和伍氏华鳊应该为同一个种。根据国际动物命名法规 ,伍氏华鳊应是大眼华鳊的次定同物异名。     

Morphometric variation among river sturgeons (Scaphirhynchus spp.) of the Middle and Lower Mississippi River

Pallid sturgeon (Scaphirhynchus albus) captured in the Middle and Lower Mississippi River (i.e. below St. Louis, MO, USA) are morphologically very similar to shovelnose sturgeon (Scaphirhynchus platorynchus). Available empirical data are limited to a few studies based on low sample sizes from disjointed populations. Geneticists are currently searching for markers that will differentiate the two species, but the need for unequivocal species‐specific field characters remains. Continuation of commercial fishing for shovelnose sturgeon in some states necessitates an immediate means for accurate field identifications. Previous studies of lower basin river sturgeon classified individuals with simple morphometric character indices and interpreted intermediacy as interspecific hybridization. In this study, morphometric variation among Scaphirhynchus specimens from the Middle and Lower Mississippi River is examined for evidence of hybridization. Data are compared for large (>250‐mm standard length) hatchery‐reared and wild pallid specimens and wild shovelnose specimens. Specimens are compared using two morphometric character indices, two morphometric/meristic character indices and principal components analysis. Results indicate substantial morphological variation among pallid sturgeon below the mouth of the Missouri River. The amount of variation appears to decrease downstream in the Mississippi River. Sheared principal components analysis of morphometric data shows complete separation of shovelnose and pallid sturgeon specimens, whereas character indices indicate overlap. Both character indices and sheared principal components analysis demonstrate that pallid sturgeon in the Lower Mississippi River are morphologically more similar to shovelnose sturgeon than are pallids from the Upper Missouri River. This similarity, explained in previous studies as hybridization, may be the result of latitudinal morphometric variation and length‐at‐age differences between populations of the upper and lower extremes of the range.     

Morphometric and meristic characteristics of two groups ofLethenteron reissneri

Morphometric and meristic characteristics were compared between two genetically divergent groups ofLethenteron reissneri, collected from Hokkaido and Honshu islands, Japan. Whereas significant differences were found in some morphometric and meristic characters, the ranges overlapped somewhat in all of the characters examined between the two groups. Thus, it was difficult to distinguish exactly between the two groups using only the morphological characters. In sympatric populations of the two groups, no significant differences were found in almost all of the morphometric and meristic characters examined. The two groups ofL. reissneri, which are reproductively isolated from each other, should be regarded as sibling species. Assortative mating, based on morphological features, appears unlikely as the reproductive isolating mechanism between the two groups.     

Comparative analysis of alternative statistical models for differentiation of herring stocks based on meristic characters

A basic stock assessment problem is the mixing and separation of herring populations in their specific areas. Within the transition zone between the North and the Baltic seas (Skagerrak, Kattegat, The Sound) a mixing of two herring populations ( Clupea harengus L.) temporarily takes place. One major component stems from the Baltic Sea (spring spawner), and the other from the North Sea (autumn spawner); each stock exhibits different meristic characteristics. In order to separate the two herring populations, 'pure' learning samples of meristic characters were created in 1995 as differential variables. Mainly gained during two research surveys at two geographically remote areas where a mixing of herring components was relatively unlikely, these learning samples were considered as representative for one or the other herring population. This paper compares the current (ICES) separation approach for herring stock assessment with two alternative methods wherein vertebra counts (vc) are used as meristic characters. The two proposed methods are (a) an inverted variance weighted linear model, and (b) a separation rule based on a quadratic discriminant analysis. The paper summarizes and discusses the results of predicting fractions of the two herring components derived from all three separation models. The underlying example data set stems from a 1991–97 routine Swedish survey in the transition zone. In comparison, the quadratic discriminant analysis separation model was identified as superior to the two other methods. Furthermore, the model suggests a higher degree of mixing of the two herring stocks in the transition area than was previously thought; inter-annual changes in the geographical distribution of the two populations are suggested as being less variable than previously assumed.     

Variation patterns of bilateral characters: variation among characters and among populations in the White Sea herring, Clupea pallasi marisalbi (Berg) (Clupeidae, Teleosti)

Phenotypic variation in two populations of the White Sea herring Clupea pallasi marisalbi (Berg) (spring spawners and summer spawners), based on 21 meristic and 21 morphometric bilateral characters, has been studied. Total phenotypic variance was partitioned into a within-individual or stochastic component (fluctuating asymmetry) and an among-individual or factorial component, reflecting heterogeneity among individuals and resulting from the diversity of genotypes and environments. Both standardized stochastic and factorial components show clear negative correlations with means across characters. Negative correlation of the factorial components with means is in contradiction to the commonly accepted explanation of negative means-standardized variances association. Slopes of regression of standardized stochastic variances on means in meristic characters was significantly higher in summer spawners than in spring spawners, and results in discordance of stochastic variance across characters: it is higher in spring spawners for low and average variability characters and does not differ for both populations for high variability characters. The populations do not show notable differences in variation of morphometric characters. Consideration of other available data on these populations, such as spawning behaviour and salinity resistance of larvae, suggests that the lower slope of regression of stochastic variances on means is associated with the reduced viability of spring spawners     

我国华鳊属鱼类形态差异及其物种有效性的研究

为探讨华鳊属鱼类种间和种内居群间的形态差异及其物种有效性,采用多变量形态度量,结合传统分类方法,获得该属鱼类不同地理居群共224尾标本的32个测量性状和7个可数性状数据,并做主成分分析。在可数性状上,海南华鳊各居群间无差异,但明显不同于其他种类;四川华鳊与大眼华鳊差别明显,与伍氏华鳊之间也存在较大程度的差异;大眼华鳊的乌江和珠江居群之间存在显著差异,而伍氏华鳊各地理居群差异不明显。在可量性状上,四川华鳊和大眼华鳊的乌江居群都明显区别于其他种或居群,而大眼华鳊的珠江居群与伍氏华鳊之间以及海南华鳊各居群之间没有明显差异。对上述结果分析认为：四川华鳊和海南华鳊为两个有效的物种;大眼华鳊的乌江标本是一个未被描述的物种,而珠江居群和伍氏华鳊各居群应属同一个种。     

Morphologic comparisons of hatchery-reared specimens of Scaphirhynchus albus, Scaphirhynchus platorynchus, and S. albus × S. platorynchus hybrids (Acipenseriformes: Acipenseridae)

Extensive habitat modifications within the Mississippi and Missouri rivers have presumably interfered with the reproductive isolating mechanisms between the endangered pallid sturgeon, Scaphirhynchus albus, and the sympatric shovelnose sturgeon, Scaphirhynchus platorynchus, causing hybridization between these two species. Several character indices were developed to assist fisheries biologists in identifying specimens of S. albus, S. platorynchus, and their putative hybrids. The indices have numerous assumptions, including that pure strains of both parental species are within the sample analyzed and that hybrids are morphologically intermediate relative to their parents. If these indices have produced inaccurate identifications, then previous work on Scaphirhynchus studies in the Mississippi and Missouri rivers are questionable, including status surveys, captive propagation efforts, or the harvesting of tissues for genetic studies. In this study we tested indices by examining progeny of ‘known’ pallid, shovelnose, and hybrid sturgeon propagated, raised, and preserved at hatcheries. These 60 specimens [78–600 mm standard length (SL)] were propagated with breeding stock from the upper Missouri River drainage, where hybridization between these two species presumably does not occur. Existing indices did not correctly identify small (<250 mm SL) or a combination of small and large (>250 mm SL) sizes of S. albus, S. platorynchus, and their hybrids. Indices worked fairly well in identifying large S. platorynchus, but not in differentiating large S. albus from hybrids. We used principal components analysis (PCA) as an alternative approach to character indices. No a priori knowledge of the identity of the specimen is required with this multivariate technique, which avoids potential circular reasoning present in indices. We were able to completely or almost completely separate both sturgeon species and their hybrids by extracting principal components from a correlation matrix of 13 meristic characters in a standard PCA and extracting size‐corrected principal components from a covariance matrix of 51 morphometric variables using a sheared PCA. Additionally, we demonstrated that first generation hybrids were intermediate with respect to their parental species. Multivariate analyses with a reduced character set of six meristic and 12 morphometric variables also led to accurate and reliable specimen identification. Head spines and numerous qualitative characters are also extremely useful in differentiating between Scaphirhynchus species and their hybrids. In addition to all morphometric characters, some meristic characters and the degree of head spine fusion vary significantly with SL of sturgeons. Recording appropriate data from released specimens, including photovouchers, and making this information available is essential for researchers to have any scientific or legal basis for genetic or any other studies involving these sturgeons.     

Taxonomic status of the six-band morph of Cyphotilapia frontosa (Perciformes: Cichlidae) from Lake Tanganyika, Africa

Six- and seven-band morphs have been identified in a cichlid, Cyphotilapia frontosa, that is endemic to Lake Tanganyika. These color morphs have allopatric distributions; the six-band morph is widespread in the northern half of the lake while the seven-band morph is restricted to Kigoma on the east coast of the lake. Because no specimens of the seven-band morph have been available for taxonomic study except for the holotype of C. frontosa, the taxonomic status of these morphs has not been discussed. In a recent survey at the lake, 21 specimens of the seven-band morph were collected. A comparison of these with existing collection specimens of the six-band morph showed significant differences in morphometric and meristic characters; however, because all characters largely overlapped between these morphs, they are regarded as conspecific.     

Morphometric and meristic variation in Galician threespine stickleback populations,northwest Spain

Synopsis We evaluated morphological differentiation among populations of threespine stickleback, Gasterosteus aculeatus, from the Limia and Miño basins (Galicia, NW Spain), the river Karup (Denmark) and Aiguamolls de l’Empordà (Girona, northeast Spain), using multivariate analysis of morphometric and meristic characters. Multivariate discriminant analysis and hierarchical cluster analysis uncovered significant differences among the four main groups, between the two groups from Galicia and among populations within the Miño basin. The stickleback from Galicia differed from the Danish group in head and body armour characters. Between the Miño and Limia groups, we found differences in both head and body proportions as well as in number of gill rakers. Within the Miño basin populations varied with respect to head and body armour traits and the number of lower gill rakers. Clustering analysis divided these populations into two groups based on the latter trait: fish from the upper section of river Miño and tributaries (a lower number of lower gill rakers) and fish from the central and lower reaches of the river. Overall, morphometric traits were more useful than meristic ones; however, the two types of data provided congruent information about the morphological differentiation of stickleback populations.     

Geographic variation in the molecular,morphological and reproductive characters of the ayuPlecoglossus altivelis (plecoglossidae) in the Japan-Ryukyu Archipelago

In an attempt to clarify geographic variation in the ayuPlecoglossus altivelis, the molecular, morphological and reproductive characters of populations from various localities in the Japan-Ryukyu Archipelago were examined. An electrophoretic analysis of enzymes encoded by 18–28 loci and univariate and multivariate analyses of 12 meristic and 17 morphometric characters indicated that there are two distinct groups of ayu in the archipelago: that of the Japan Islands and that of the Ryukyu Islands. Within the Japan Islands group, a landlocked population of Lake Biwa was found to diverge somewhat from other amphidromous populations genetically and morphologically. The Lake Biwa population was noted as being by far the most fecund, departing from a north-south cline of fecundity observed in amphidromous populations. Though no virtual divergence was observed among amphidromous populations in the Japan Islands in molecular data, divergence among these populations was considerable in morphological and fecundity data. Differences in geographic variation patterns are attributed to qualitative differences inherent in molecular and organismal characters: organismal characters are responsive to selection and also directly altered by environmental influences in part but molecular characters are hardly so. The evolution of different characters may have proceeded at different rates among geographic populations of ayu.     

Morphological characteristics of an introduced threespine stickleback,Gasterosteus aculeatus,from Hasse Lake,Alberta: a first occurrence in the interior plains of North America

Synopsis Threespine stickleback, Gasterosteus aculeatus, are thought to have been introduced into Hasse Lake, Alberta, where they were discovered in 1980. The population has grown in numbers since 1980 and by 1981 was more abundant than the native brook stickleback, Culaea inconstans. This population is the first to be found in the interior plains of North America, and it occurs at a higher elevation than any other Canadian population. The source of this introduced population is unknown. Significant differences among four years were found in several meristic and morphometric characters but no significant trends during 1980–1983 were found. Most characters were well within the range of other populations of the species.     

Continental and ecological variance components of European and North American Atlantic salmon (Salmo salar) phenotypes

Juvenile Atlantic salmon ( Salmo salar ) meristic and morphometric characteristics were examined from 47 European and North American river populations. The relative importance of continental origin, stream gradient, overall temperature regime, and seasonal temperatures in explaining the phenotypic variation of these populations was evaluated using multi-way ANOVA. Ecological factors explained a greater percentage of the variance than continental origin for both meristic and morphometric characters. Stream gradient was the most important factor explaining morphometric variation and April-May mean temperature was the most important factor explaining meristic variation.     

Extant and extinct forms of arctic charr Salvelinus alpinus (L.) complex from the Leprindo lake system (Transbaikalia): Differentiation in life history, morphology, and genetics

Interconnected lakes Bol’shoe Leprindo and Maloe Leprindo in Transbaikalia hosted large (extinct) and dwarf charr forms. Rarely “small” individuals intermediate in size between these forms are caught. In order to assess morphological, ecological, and genetic differentiation of sympatric charr forms and parapatric charr populations we studied their meristic and morphometric characters, feeding, breeding, and growth; we also investigated variation at 8 microsatellite loci using DNA isolated both from contemporary and historic samples. Profound differences were found between large and dwarf charr in growth rate, feeding (piscivores and highly specialized zooplanktivores, respectively), spawning time, and morphology. Dwarf charr from the two lakes demonstrate minor differences in morphology and growth rate. “Small” individuals are morphologically similar with dwarf charr and spawn together with them, they are recruited from dwarf form in late ontogeny as the result of transition to piscivorous feeding and growth acceleration. Microsatellite analysis showed that: (1) large and dwarf charr forms display high degree of genetic differentiation and reproductive isolation; (2) dwarf charr from interconnected lakes belong to different isolted populations; (3) “small charr” are genetically identical with dwarfs. The degree of ecomorphological and genetic differentiation between large and dwarf forms places charr from Leprindo Lakes among the most strongly differentiated Arctic charr forms’ flocks known at the vast range of S. alpinus complex.     

Geographic variation in Austrolebias luteoflamulatus Vaz‐Ferreira, Sierra & Scaglia (Cyprinodontiformes, Rivulidae)

The morphological variation in the annual killifish Austrolebias luteoflamulatus was studied using meristic and pigmentation characters analysed with univariate and multivariate analysis, and morphometric characters analysed with a geometric morphometry approach (thin plate spline). The results showed that morphological variation in this species was associated with a geographical pattern. In the case of meristic and pigmentation characters, the strongest distinction occured in males, while females were more similar among different drainages. Males from Rocha (eastern Uruguay) exhibited the greatest differences from the others. The number of dorsal fin rays and bars on the flanks were the characters that contributed most to this segregation. When morphometrics were considered, the three populations analysed could be distinguished well from each other in both sexes. Some of the characters that contributed to this pattern were dorsal fin origin, position of eyes and length of snout. Since pigmentation characteristics and some characters of the dorsal fin in males were involved in the differences observed, sexual selection could have played an important role in the differentiation of populations of this species. Since Austrolebias luteoflamulatus has a restricted geographical distribution, conservation of this species should include consideration of these populations individually since they might represent different evolutionary units.     

A new species of <Emphasis Type="Italic">Penopus</Emphasis> (Teleostei: Ophidiidae) from the Ryukyu Trench,the West Pacific,with remarks on <Emphasis Type="Italic">Penopus microphthalmus</Emphasis>

The bathyal genus Penopus (Ophidiidae) is revised based on 23 specimens. One specimen from the Ryukyu Trench represents a new species, Penopus japonicus. The remaining 22 specimens were found on both sides of the Atlantic Ocean, and neither 28 meristic and morphometric characters nor several morphological characters show any differences between the two populations. This supports Séret (1988), who considered Penopus macdonaldi Goode and Bean 1896 a junior synonym of Penopus microphthalmus (Vaillant 1888). The new Japanese species can be separated from the Atlantic species by having fewer rays in the dorsal (117 vs. 135–158) and anal (89 vs. 106–122) fins, the squamation of the head restricted to the middle part of the preopercle versus the squamation covering the dorsum, preopercle and the opercle in part, a distinct spine behind the posterior nostril versus the spine hardly visible and 9 spines on the hind margin of the preopercle versus 4–7 spines.