Comparative morphology and scale formation in four species ofOncorhynchus during early life

Morphological divergence including scale formation in alevin and juvenile stages of masu (Oncorhynchus mason), coho (O. kisutch), chum (O. keta) and pink (O. gorbuscha) salmons reared in freshwater was investigated. Chum and coho salmons developed faster than the other species when raised at constant water tempertaure. Growth decreased suddenly at emergence from the gravel bed in all the four species. Morphology changed significantly from hatch through emergence to squamation. Two distinct morphological types were identified: the rotund type (masu and coho), and the streamlined type (chum and pink salmons). The former had well-developed parr marks, a deeper body and caudal peduncle, and higher relative growth coefficients, while the latter had parr marks which appeared only temporarily or never appeared, a slimmer body and caudal peduncle, and a more gradual and continuous change in morphology. Coho and chum developed squamation and formed circuli on scales considerably earlier than masu and pink salmons.     

Scale morphology of greater lizardfish Saurida tumbil (Bloch, 1795) (Pisces: Synodontidae)

A comparative study comprising scale morphology and squamation of Saurida tumbil was conducted to identify the most useful scale and squamation characters within the different body regions and length groups and to clarify their significance for future systematic studies. The presence of the caudal pores is documented for the first time in teleosts. In addition, the presence of crenae and spines formed by posterior orientation and projection of circuli is recorded for the first time in a member of the Synodontidae. Scales of S. tumbil show some characters that are either never seen or they are exceedingly rare in scales of other teleosts. These are: two types of scalar denticles, denticles in the inter-circular area, and twin or Siamese scales. Several other scale characters have shown a consistent variation in different body regions and in fishes from different length groups. These are: focus position; bilobate rostral field edge; presence of three radii; long, narrow and separated crenae; papillae-form, crowded scalar denticles with posterior directed spines; the number of scale rows between anterior end of the dorsal fin and the lateral line.     

Growth inacanthodes (acanthodii: pisces) data and implications

Body proportions did not change during ontogeny and were very similar in most, if not all,Acanthodes species. The length/width ratio of circumorbital bones decreased during growth. The mandibular-splint-length/prepectoral-length and mandibular-splint-length/total-specimen-length ratios remained stable throughout life. The pectoral girdle grew isometrically with the pectoral spine. Large scapulocoracoids could not have borne suprascapulae relatively as large as the small scapulocoracoids, and, therefore, negative allometry is indicated for the suprascapula. The scale size relative to the total specimen size is remarkably similar in all the species studied. The rates of squamation development, on the other hand, differ considerably in species from different stratigraphic levels. In the tail, the scale zones 1,3, and 4 are present in even the smallest known specimens. The epichordally situated scales of zones 2 and 2” appeared only later in ontogeny. With the exception of the scale cover and possibly the tesserae on the head, the components of the exoskeleton are fully developed in even the smallest available specimens (ca. 50 mm long), in which no trace of ossification of the endoskeleton can be detected. The first component of the endoskeleton to ossify was the scapulocoracoid. The ossification of the labyrinth, co-ossification of divisions of the jaws, and development of the squamation all commenced, and were completed, earliest in ontogeny of the oldest (Namurian) species and latest in ontogeny of the youngest (Autunian) species considered in this study. This implies a regressive trend which is further evidenced by a tendency in ontogeny toward the loss of posterior rows of gillrakers. At least four species ofAcanthodes co-existed at Lebach. The entire material ofAcanthodes from Lebach needs to be re-examined in a manner suited for resolving the taxonomic situation, i. e. more quantitatively, which will also describe the ontogenetic development of the species present. The branchiostegal rays and gill-rakers ofAcanthodes are exoskeletal. The mandibular splint is a serial homologue of the ceratohyal branchiostegals, i. e. the dermal component of the ceratomandibular.     

Ontogenetic causes and mechanisms for formation of differences in number of fish scales

Fish squamation is developed in late ontogeny. Therefore, the conditions of development significantly affect its characteristics (number of scales). This study is aimed at considering the influence of external and internal factors on variation of the number of scales in fish. Acceleration of development results in decrease of the number of scales, while it increases with retardation. Experiments on regulation of thyroid status of fish showed that the certain mechanism of alteration of the number of scales is related with heterochrony, such as a shift of the timing of squamation. Accelerated development is caused by early scale development at smaller body length, while retarded development is characterized with later scale development and at greater body length. Data considering heterochrony as the possible reason for differences in the number of scales in related fish species are represented. Moreover, alterations of the distance between scales (morphogenetic count) can serve as another alteration mechanism of the number of scales in fish (especially phyletically distant species).     

Comparative squamation of the lateral line canal pores in sharks

The current study collected the first quantitative data on lateral line pore squamation patterns in sharks and assessed whether divergent squamation patterns are similar to experimental models that cause reduction in boundary layer turbulence. In addition, the hypothesis that divergent orientation angles are exclusively found in fast‐swimming shark species was tested. The posterior lateral line and supraorbital lateral line pore squamation of the fast‐swimming pelagic shortfin mako shark Isurus oxyrinchus and the slow‐swimming epi‐benthic spiny dogfish shark Squalus acanthias was examined. Pore scale morphology and pore coverage were qualitatively analysed and compared. In addition, pore squamation orientation patterns were quantified for four regions along the posterior lateral line and compared for both species. Isurus oxyrinchus possessed consistent pore scale coverage among sampled regions and had a divergent squamation pattern with multiple scale rows directed dorsally and ventrally away from the anterior margin of the pore with an average divergent angle of 13° for the first row of scales. Squalus acanthias possessed variable amounts of scale coverage among the sampled regions and had a divergent squamation pattern with multiple scale rows directed ventrally away from the anterior margin of the pore with an average angle of 19° for the first row of scales. Overall, the squamation pattern measured in I. oxyrinchus fell within the parameters used in the fluid flow analysis, which suggests that this pattern may reduce boundary layer turbulence and affect lateral line sensitivity. The exclusively ventral oriented scale pattern seen in S. acanthias possessed a high degree of divergence but the pattern did not match that of the fluid flow models. Given current knowledge, it is unclear how this would affect boundary layer flow. By studying the relationship between squamation patterns and the lateral line, new insights are provided into sensory biology that warrant future investigation due to the implications for the ecology, morphology and sensory evolution of sharks.     

Homatula laxiclathra (Teleostei: Balitoridae), a new species of nemacheiline loach from the Yellow River drainage in Shaanxi Province, northern china

Homatula laxiclathra, new species, is here described from the Wei-He of the Yellow River drainage in Shaanxi Province, northern China. It is similar to H. berezowskii, H. longidorsalis, and H. variegata in the shared possession of a shallower body with a uniform depth, a character distinguishing all of them from all other congeners, but differs from these three species in the width of vertical brown bars on the caudal peduncle. This new species, along with H. berezowskii, differs from H. longidorsalis, and H. variegata in head length, caudal-peduncle depth, length of the dorsal adipose creast of the caudal peduncle, body squamation, and intestinal coiling. Homatula laxiclathra and H. berezowskii are further distinct in the caudal-fin shape and interorbital width.     

Scale Growth and Squamation Chronology for the Laboratory-Reared Hermaphroditic Fish <Emphasis Type="Italic">Rivulus marmoratus</Emphasis> (Cyprinodontidae)

Scale morphology, growth and the squarnation chronology are described for the hermaphroditic fish Rivulus marmoratus reared in the laboratory. The scales are round or oval shaped cycloid type, and their sizes are about 0.3–1.0 mm in diameter. The number of ridges increases more rapidly relative to the body growth of the fish in early stages, but this increase is proportionate to growth subsequently. Three loci of scale development have been identified. The scales first appeared on the center of the parietal region at 8 days after hatching. The second locus of scale formation was on the lateral line of the posterior end of the caudal peduncle. A third locus was later observed on the lower right corner of the operculum: The final squamation was completed at 6 weeks after hatching.     

A review of the <Emphasis Type="Italic">Gerres subfasciatus</Emphasis> complex from the Indo-West Pacific,with three new species (Perciformes: Gerreidae)

Gerres japonicus Bleeker, 1854, and Gerres subfasciatus Cuvier in Cuvier and Valenciennes, 1830, are redescribed, and Gerres akazakii sp. nov. (Japanese endemic), Gerres ryukyuensis sp. nov. (Okinawa I., Japan), and Gerres shima sp. nov. (Indo-Malayan region, including the Andaman Sea, Southeast Asia, southern China and Taiwan, and Ryukyu Is., Japan) are described. Gerres ovatus Günther, 1859, and Gerres kapas Bleeker, 1854, are recognized as junior synonyms of G. subfasciatus and Gerres oyena (Forsskål, 1775), respectively. All species (except G. oyena) have a small (<170?mm in standard length: SL), moderately deep (depth 36–48% SL), body with dark vertical bars, dorsal fin rays X, 9 or IX, 10, and 31/2 or 41/2 scale rows between the 5th dorsal fin spine base and lateral line, defined as the G. subfasciatus complex. The five species can be variously differentiated from each other by dorsal head squamation, and differing meristic, morphometric, and color characters. They are generally distributed sympatrically in the Indo-West Pacific. Other nominal species of uncertain status or relationship are discussed.     

Making teeth to order: conserved genes reveal an ancient molecular pattern in paddlefish (Actinopterygii)

Ray-finned fishes (Actinopterygii) are the dominant vertebrate group today (+30 000 species, predominantly teleosts), with great morphological diversity, including their dentitions. How dental morphological variation evolved is best addressed by considering a range of taxa across actinopterygian phylogeny; here we examine the dentition of Polyodon spathula (American paddlefish), assigned to the basal group Acipenseriformes. Although teeth are present and functional in young individuals of Polyodon, they are completely absent in adults. Our current understanding of developmental genes operating in the dentition is primarily restricted to teleosts; we show that shh and bmp4, as highly conserved epithelial and mesenchymal genes for gnathostome tooth development, are similarly expressed at Polyodon tooth loci, thus extending this conserved developmental pattern within the Actinopterygii. These genes map spatio-temporal tooth initiation in Polyodon larvae and provide new data in both oral and pharyngeal tooth sites. Variation in cellular intensity of shh maps timing of tooth morphogenesis, revealing a second odontogenic wave as alternate sites within tooth rows, a dental pattern also present in more derived actinopterygians. Developmental timing for each tooth field in Polyodon follows a gradient, from rostral to caudal and ventral to dorsal, repeated during subsequent loss of teeth. The transitory Polyodon dentition is modified by cessation of tooth addition and loss. As such, Polyodon represents a basal actinopterygian model for the evolution of developmental novelty: initial conservation, followed by tooth loss, accommodating the adult trophic modification to filter-feeding.     

Post-fire regeneration patterns in the eastern Iberian Peninsula

Post-fire regeneration patterns (plant cover and richness) in the Valencia region (eastern Iberian Peninsula) are studied by analysing data from two different samplings after two periods of large fires (1991 and 1994). Emphasis is given to comparing different environmental conditions (thermo-Mediterranean vs. meso-Mediterranean; south facing vs. north facing slopes) and different bedrock types (limestone vs. marls). Results suggest that the highest post-fire cover and species richness is reached in thermo-Mediterranean conditions on limestone, and the main species are the resprouters Quercus coccifera and Brachypodium retusum. North-facing sites have higher plant cover than south-facing ones, and most life forms (trees, shrubs, grasses) have higher cover in these sites. Species richness is higher on north-facing sites than on the south-facing ones at the small scale (1 to 200 m²), but differences were not significant at the highest scale studied (1 000 m²). Plant species richness with increasing sampling area follows the classical log-log relationship; however, when species are segregated by life forms (woody species and herbs), different species-area relationships were found.     

A histologic survey of diencephalic circumventricular organs in teleosts with special reference to osteoglossomorphs

Diencephalic circumventricular organs of various teleosts were studied histologically. Special attention was paid to osteoglossomorphs. The neurohypophysis of osteoglossomorphs (Arapaima, Notopterus, Xenomystus, andGymnarchus) is well differentiated into the median eminence and the neural lobe. The pituitary organization of these species is an intermediate between that of holosteans and of more advanced teleosts. The saccus vasculosus is absent inPantodon andGymnarchus, but it is well developed inNotopterus andXenomystus. The light microscopically discernible pineal is absent inGymnarchus: this may be the only species that lacks the pineal among teleosts. The paraphysis is found in various species including most osteoglossomorphs and some perciforms. In advanced teleosts such as gobiids and tetraodontids, the saccus dorsalis and velum transversum are absent, but the diencephalic choroid plexus is well developed instead. Some evolutionary trends are apparent in the occurrence and organization of these circumventricular organs among teleosts.     

Scale formation in selected fundulid and cyprinodontid fishes

Patterns of scale formation (onset, points of origin, completion, and spatial pattern) were examined for six species of killifishes in two families (Cyprinodontidae: Cyprinodon variegatus, and Fundulidae: Fundulus confluentus, F. heteroclitus, F. luciae, F. majalis, and Lucania parva) to determine if the patterns are another useful indicator for the transition from the larval to juvenile periods. In some species, the patterns were very similar, with scale formation originating on/near the caudal peduncle, then the dorsal surface of the head (in fundulids only), and later on the lateral surfaces of the head, and on the ventral surface of the trunk at the level of the pectoral fin. The timing of scale formation, relative to fish size, was later than or overlapped with other morphological characters (e.g., fin ray formation, juvenile/adult body shape) often used to mark the larval/juvenile transition. The onset of scale formation, across all species, occurred between 8 and 13 mm TL. Completion of scale formation occurred between 18 and 23 mm TL. At completion, scales covered 86–99% of the trunk and head. Completion of scale formation in these fishes is one of the last external morphological changes to occur during the larval to juvenile transition. For these species, and other flatfishes we have examined in detail, it appears that scale formation may be useful in helping to define the end of the larval period and the beginning of the juvenile period. Further studies, of divergent groups of teleosts, are necessary to determine if this length-based approach has broad validity.     

Feeding Site Selection by Frog-Biting Midges (Diptera: Corethrellidae) on Anuran Hosts

A critical challenge of obtaining a blood meal resides in selecting a feeding site at the host. We investigate the feeding sites of species of frog-biting midges (Corethrella spp) on túngara frogs, Engystomops pustulosus (Cope), and two species of treefrogs, Dendropsophus ebraccatus (Cope) and Dendropsophus microcephalus (Cope). To investigate the differences in midge feeding sites, we performed field observations, histological sections of the frogs and examined the mouthparts of the midges. Feeding sites are predicted by the vascular properties of the skin in different body areas of the frogs. According to optimal foraging theory, the midges should feed on host body areas that maximize blood intake. Contrary to optimal foraging theory predictions, however, their feeding sites correspond to body areas with high intensity host defensive behavior.     

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.     

How life history affects threat status: Requirements of two Onobrychis-feeding lycaenid butterflies, Polyommatus damon and Polyommatus thersites, in the Czech Republic

Comparisons of related species differing in conservation status may offer insights into causes of species declines. We studied egg-laying patterns and landscape occupancy of two sympatric lycaenidae butterflies inhabiting xeric grasslands, vulnerable Polyommatus thersites and critically endangered Polyommatus [Agrodiaetus] damon, both developing on sainfoin, Onobrychis spp. Females of bivoltine P. thersites oviposit on host plant leaves at a relatively low height (??20 cm), in both spring (May?CJune) and summer (July?CAugust) generations. Females of univoltine P. damon (July?CSeptember) oviposit to senescing inflorescences, in significantly higher heights (>30 cm), and the species is hence vulnerable to summer mowing or grazing. On a landscape scale, both species tended to occur at sites with diverse sward management, including temporarily unmanaged patches. In addition, P. damon occurred only in the proximity of other occupied sites. The study documents that grassland management must respect the needs of the most vulnerable species, and because these needs are seldom known, it must maintain a high diversity of conditions within individual sites.     

Modeling the Biogeography of Fossil Baboons

We use a model of modern baboon socio-ecology to explore the behavioral ecology and biogeography of the extinct Plio-Pleistocene baboons (genera Parapapio, Gorgopithecus, Dinopithecus, and Papio). The model is based on the way climate affects the baboons’ time budgets, and focuses on intersite variability in behavior rather than on species-typical patterns of behavior, as most previous approaches have done. We use climate estimates for individual fossil sites based on matching modern habitats using faunal profiles and estimates of individual species’ body masses given in the literature. The model allows us to examine the minimum and maximum sizes of groups that individual species would have been able to support at particular localities, and hence the biogeography of a species on a continental scale. In doing so, the model allows us to examine which variables are most responsible for limiting a species’ ecological and biogeographic flexibility, and through this to explore a species’ capacity for coping with climate change. Feeding time is identified as the main constraint. In general, large-bodied species would have had more difficulty surviving in as wide a range of habitats as smaller-bodied species, and this may explain the limited geographical distribution of large-bodied baboons such as Gorgopithecus and Dinopithecus.     

A multi-scale analysis of breeding site characteristics of the endangered fire salamander (Salamandra infraimmaculata) at its extreme southern range limit

Understanding species’ distributions often requires taking into consideration the characterization of the environment at different spatial scales. The habitat characteristics of the endangered fire salamander, S. infraimmaculata, have received little attention. In this study, at this species’ most peripheral and xeric limit (Mt. Carmel, Israel), we examined predictors of the larval distribution of S. infraimmaculata at aquatic-breeding sites at both local and landscape scales. We investigated the predictive power of environmental variables using two methods: generalized linear models and conditional inference trees (CTREE). Both multi-model approaches yielded similar results. At the local site scale, hydroperiod predicted breeding site use. At the landscape scale, Salamandra presence was best predicted by proximity to other breeding sites. In addition, our study indicates that sites selected for breeding are far from roads and agricultural fields. Overall, this study demonstrates that ultimately, both local and landscape scale predictors are necessary to understand properly a species’ habitat requirements and thus can help in planning future management around the breeding sites.     

Species richness and beta diversity of aquatic macrophytes in a large subtropical reservoir (Itaipu Reservoir, Brazil): the influence of limnology and morphometry

Assessment of the environmental factors that control species richness (S) is a central issue in ecology. In this study, aquatic macrophyte S was estimated in 235 sampling sites distributed in 8 arms of a large (1350 km²) subtropical reservoir (Itaipu Reservoir, Brazil). Morphometric variables (area, shoreline development and length of shoreline, all measured for each arm; n= 8) and environmental variables measured at each sampling site (extinction coefficient of light (k), electrical conductivity, fetch, distance from the main reservoir body; n = 235) were used to predict aquatic macrophyte S at two spatial scales. At arm scale, linear regression analysis indicated that length of shoreline was a better predictor of S than area. At sampling site scale, multiple regression analysis indicated that S was significantly predicted by electrical conductivity, fetch and distance from the main body. However, other relationships with predictive interest was demonstrated by using non-traditional regression approaches. This analysis started by the visual inspection of scatter plots. The bivariate relationship between S and fetch, for example, showed an envelope or a `left triangle' pattern. The relationship between the number of submerged species and k showed an asymmetrical left triangle pattern. Using randomization procedures, it was demonstrated that these patterns were not generated by chance alone. Beta diversity (estimated within the arms) was significantly and positively correlated with spatial environmental variability. Overall, these results indicate that the prediction of aquatic macrophytes assemblage variables in large waterbodies, specially S, is more complex than previous studies have suggested.