Body Shape Variation Research Articles

Body shape variation between farms of tilapia (Oreochromis sp.) in Colombian Andes using landmark based geometric morphometrics

Tilapia is the most economically important fish in the aquaculture of different countries from the Americas. This species exhibits morphological plasticity under different conditions. In this study, we used landmark-based geometric morphometric to describe the shape variation of two red and one Nile tilapia farmed populations in Colombian Andes. We recorded significant morphological differences between all studied farms ( P < 0.001, in the multivariate analysis of variance). In this way, individuals from the Nile tilapia farms were more elongated and had a more ventral position of the posterior extreme of the orbit and the insertion of pectoral fin than red tilapias. Moreover, the Nile group showed a shorter space between the mouth profile and the posterior extreme of the orbit, compared to red groups. On the other hand, individuals from farm red 2 were deep bodied and had a smaller head compared to tilapias from farm red 1. Our results provide evidence that tilapias from different farms in Colombian Andes display differences in body shape, and can be applied to selective breeding programs after establishing the contribution of genetic and environmental effects on tilapia shape as well as the preferences of consumers for the body shape of the species.

100-year time series reveal little morphological change following impoundment and predator invasion in two Neotropical characids.

Human activities are dramatically altering ecosystems worldwide, often resulting in shifts in selection regimes. In response, natural populations sometimes undergo rapid phenotypic changes, which, if adaptive, can increase their probability of persistence. However, in many instances, populations fail to undergo any phenotypic change, which might indicate a variety of possibilities, including maladaptation. In freshwater ecosystems, the impoundment of rivers and the introduction of exotic species are among the leading threats to native fishes. We examined how the construction of the Panama Canal, which formed Lake Gatun, and the subsequent invasion of the predatory Cichla monoculus influenced the morphology of two native fishes: Astyanax ruberrimus and Roeboides spp. Using a 100‐year time series, we studied variation in overall body shape over time (before vs. after impoundment and invasion) as well as across space (between an invaded and an uninvaded reservoir). In addition, we examined variation in linear morphological traits associated with swim performance and predator detection/avoidance. Notwithstanding a few significant changes in particular traits in particular comparisons, we found only limited evidence for morphological change associated with these two stressors. Most observed changes were subtle, and tended to be site‐ and species‐specific. The lack of a strong morphological response to these stressors, coupled with dramatic population declines in both species, suggests they may be maladapted to the anthropogenically perturbed environment of Lake Gatun, but direct measures of fitness would be needed to test this. In general, our results suggest that morphological responses to anthropogenic disturbances can be very limited and, when they do occur, are often complex and context‐dependent.

Vertebral evolution and ontogenetic allometry: The developmental basis of extreme body shape divergence in microcephalic sea snakes.

Snakes exhibit a diverse array of body shapes despite their characteristically simplified morphology. The most extreme shape changes along the precloacal axis are seen in fully aquatic sea snakes (Hydrophiinae): "microcephalic" sea snakes have tiny heads and dramatically reduced forebody girths that can be less than a third of the hindbody girth. This morphology has evolved repeatedly in sea snakes that specialize in hunting eels in burrows, but its developmental basis has not previously been examined. Here, we infer the developmental mechanisms underlying body shape changes in sea snakes by examining evolutionary patterns of changes in vertebral number and postnatal ontogenetic growth. Our results show that microcephalic species develop their characteristic shape via changes in both the embryonic and postnatal stages. Ontogenetic changes cause the hindbodies of microcephalic species to reach greater sizes relative to their forebodies in adulthood, suggesting heterochronic shifts that may be linked to homeotic effects (axial regionalization). However, microcephalic species also have greater numbers of vertebrae, especially in their forebodies, indicating that somitogenetic effects also contribute to evolutionary changes in body shape. Our findings highlight sea snakes as an excellent system for studying the development of segment number and regional identity in the snake precloacal axial skeleton.

Flow gradient drives morphological divergence in an Amazon pelagic stream fish

Body shape and size variations are common in stream fishes, and morphological differences can have either a genetic or non-genetic basis. Flow has been indicated as one of the causes of intraspecific variation, and shifts in stream-fish body morphology are related to swimming performance and to individual fitness. Although populations in lotic versus lentic habitats have been compared, the effects of a flow gradient on fish shape are little studied. We tested differences in size, body shape and caudal-peduncle morphology of a pelagic fish that inhabits streams with different velocities in two basins, using geometric morphometrics to evaluate shifts in body morphology. Fish from lower-flow velocities had larger bodies that were deeper posteriorly; fish from higher-flow velocities were smaller and more streamlined. Shape variation among specimens was significantly influenced by the local velocity, with similar responses in fish body shape in the different basins. We showed that selective pressures generated by flow velocities affect fish shape in the same way in both basins. Fish body size, shape and caudal-peduncle morphology affect swimming performance, which could influence the energy costs for survival. Our results with a small pelagic characid help to elucidate questions on morphological predictions for fishes across flow regimes.

A New Non-Invasive Technique for Temporarily Tagging Coral Reef Fishes

The ability to identify individuals is important for the success of many behavioral and ecological studies. In fishes, there is a lot of variation in body size, shape, skin thickness, behavior, and ecology, which means that any given marking/ tagging method may not work well for all species. For the Humbug Damselfish Dascyllus aruanus, a widely used model species of coral-reef fish, we found that standard tagging methodologies (e.g., phenotypic variation, beads and PVC tags, fluorescent elastomer injections) were ineffective as they could not be applied to the fish or easily detected by observers or from videos. In response, we developed a new method to temporarily tag D. aruanus using colored plastic films and topical surgical glue. These films were easily detectable both directly by human observers and indirectly by video/photo-cameras. We tested the efficacy of this new method by examining the survival time of the tags at various positions on the body. Our results showed that the optimal tag locations were dorsal anterior (with a median attachment time of 53 hours) and dorsal middle (with a median attachment time of 49 hours). Total length of fish was not a significant predictor of tag life. In sum, we demonstrate an effective new method for temporarily tagging a widely studied coral reef fish. This method could be applied to other fishes and aquatic organisms (e.g., amphibians) in both marine and freshwater ecosystems.

Sexual size and shape dimorphism in two ground beetle taxa, Carabus (Procrustes) coriaceus cerisyi and C. (Morphocarabus) kollari praecellens (Coleoptera: Carabidae) - A geometric morphometric approach

We investigated morphometric variation in size and shape of the head, pronotum, and abdomen between the taxa and sexes of two ground beetles, Carabus coriaceus cerisyi Dejean, 1826 and C. kollari praecellens Palliardi, 1825. These two taxa differ in overall size, and both of them are characterized by significant sexual size dimorphism. In many taxa, allometry, the relationship between changes in shape and changes in size, can be a major component of intra- and interspecific variation in body shape. In the present study, we applied landmark-based geometric morphometrics to explore allometric and non-allometric components of shape variation between the taxa and more importantly between sexes within the taxa. We were able to show that the differences of shape between the taxa cannot be explained by allometric changes, as allometry explains only a small amount of total shape variation between the taxa, which was expected due to the fact that the taxa belong to separate subgenera. Between the sexes, on the other hand, allometry contributes largely to the variation, particularly in abdomen shape. However, the differences of head and pronotum shape between the sexes cannot be entirely explained in terms of allometric scaling. Our results indicate that allometry contributes largely to differences of body shape between the sexes, while differences between the taxa are influenced by other factors and processes.

Sponge and mollusk associations in a benthic filter-feeding assemblage in the middle and lower Xingu River, Brazil

During a pilot survey, sponges and mollusks were sampled from the bottom of the middle Xingu River (rapids) and lower Xingu River (ria) via hand-picking in shallows and trawling and surface-supplied dives in deeper waters. The survey revealed a benthic community composed of eight sponge species in four genera and three families, and added six species to the Xingu Basin fauna. Sponges exhibited distinct variation in body shape corresponding to local environmental conditions such as water depth, current velocity and available substrates. Sponges inhabiting rocky bottoms in swift currents (rapids) typically formed crusts. Those in the deeper, calmer waters of the ria attained massive and elaborate forms while attached to infaunal bivalves. Oncosclera navicella and Drulia cristata exhibited crusts and massive forms as adaptations to rapids and ria, respectively. In the middle to lower Xingu, sponges encrusted the shells of eleven species of bivalves (seven infaunal, three epifaunal, and one infaunal/epifaunal) and one infaunal/epifaunal gastropod. Bivalves provide key substrates for supporting sponges above the sand, mud and detritus of the Xingu ria. Potential impacts of the Belo Monte Dam complex on the sponge fauna of the middle Xingu rapids are discussed.

Ancient and contingent body shape diversification in a hyperdiverse continental fish radiation.

The characiform fishes of the Neotropics and Africa radiated remarkably in ecomorphology, but the macroevolutionary processes responsible for their biodiversity remain unexplored, and the degree to which their continental diversification parallels classic adaptive radiations remains untested. We reconstruct their diversification using a new fossil-calibrated molecular phylogeny, dietary information, and geometric morphometrics. Though body shape diversified early in a manner consistent with an ancient continental adaptive radiation, trophic shifts did not always coincide with shape changes. With the notable exception of piscivores, lineages that converged in diet did not converge closely in body shape. Shifts in habitat or other variables likely influenced body shape evolution in addition to changes in diet, and the clade's history departs from many classic adaptive radiations in lakes or on islands, in which trophic convergence drives morphological convergence. The contrast between the Neotropical radiation's exhaustive exploration of morphospace and the more restrained diversification in Africa suggests a major role for contingency in characiform evolution, with the presence of cypriniform competitors in the Old World, but not the New, providing one possible explanation. Our results depict the clearest ecomorphological reconstruction to date for Characiformes and set the stage for studies further elucidating the processes underlying its diversification.

Structure and connectivity of bluemouth, Helicolenus dactylopterus, populations in the NE Atlantic and Mediterranean

The bluemouth, Helicolenus dactylopterus (Delaroche 1809), is a marine demersal fish that is widely distributed in the Atlantic and the Mediterranean. It is targeted by longline fisheries around the Iberian Peninsula and it is a common by-catch associated with many demersal fisheries. However, limited information exists about the population structure in the NE Atlantic and Mediterranean. Thus, the bluemouth population structure in these regions was studied using a landmark-based geometric morphometric analysis. The purpose was to assess body shape variation among bluemouth and determine putative populations and their relationships. Three populations were identified in the western Mediterranean: two populations in the Alboran basin and another in the north-western basin (Balearic Sea and Catalonian coast). The population from the central Mediterranean did not seem to be effectively connected to the populations in the western Mediterranean. In the NE Atlantic, our results showed that at least four different bluemouth populations exist in the following areas: Galicia-Cantabrian Sea, Peniche (Portugal), the Gulf of Cadiz and the Porcupine Bank. A connection between bluemouth from the NE Atlantic and Mediterranean was observed, making unlikely that the Strait of Gibraltar acts as a barrier isolating Atlantic and Mediterranean bluemouth populations. The results of this study provide evidence that different bluemouth populations exist, which is relevant for stock assessment and management of this species.

Morphometric differentiation and gene flow in emerald shiners (Notropis atherinoides) from the lower Great Lakes and the Niagara River

Abstract Differences in habitat (e.g., water velocity, prey, and predator regimes) are a driving force causing adaptive divergence among fish populations. This study used geometric shape analysis to assess morphological differences among emerald shiner (Notropis atherinoides) populations inhabiting the Niagara River, Lake Erie, and Lake Ontario. It was expected that emerald shiners inhabiting the two lakes would have more robust bodies and smaller heads, while river emerald shiners were expected to display more fusiform bodies with larger heads. The results of this study indicate that emerald shiners from Lake Erie and the Niagara River had a more robust form on average than individuals from Lake Ontario. Specifically, emerald shiners collected from Lake Ontario displayed more streamlined bodies and larger heads than emerald shiners collected from Lake Erie and the Niagara River. In addition, this divergence in body shape has apparently occurred despite the lack of distinct genetic differentiation as measured with microsatellite variation. Our results suggest that differences in water velocity alone may not be responsible for phenotypic variation in body shape among these emerald shiner populations, and other factors such as differences in prey or predator regimes are likely involved.

An Integrated Vision-Based Approach for Efficient Human Fall Detection in a Home Environment

Falls are an important healthcare problem for vulnerable persons like seniors. Response to potential emergencies can be fastened timely detection and classification of falls. This paper addresses the detection of human falls using relevant pixel-based features reflecting variations in body shape. Specifically, the human body is divided into five partitions that correspond to five partial occupancy areas. For each frame, area ratios are calculated and used as input data for fall detection and classification. First, the detection of falls is addressed from a statistical point of view as an anomaly detection problem. Towards this end, an integrated approach merging a detection step with a classification step is proposed for enabling efficient human fall detection in a home environment. In this regard, an effective fall detection approach using generalized likelihood ratio (GLR) scheme is designed. However, a GLR scheme cannot discriminate between true falls and like-fall events, such as lying down. To mitigate this limitation, the support vector machine algorithm has been successfully applied on features of the detected fall to recognize the type of fall. Tests on two publicly available datasets show the effectiveness of the proposed approach to appropriately detecting and identifying falls. Compared with the neural network, k -nearest neighbor, decision tree and naive Bayes procedures, the two steps approach achieved better detection performance.

Developmental morphology and growth patterns of laboratory-reared giraffe cichlid, Nimbochromis venustus Boulenger, 1908

The giraffe cichlid Nimbochromis venustus Boulenger, 1908 is a well-known species in aquarium trade. The laboratory-reared electric giraffe cichlid was studied in terms of early morphological development and allometric growth pattern from hatching until the juvenile stage i.e.51 dph. Total length increased linearly from hatching until 51 dph, with a high regression coefficient. The yolk sac exhaustion completed throughout 15 days. Significant morphological and morphometric variations occurred before the yolk sac absorption and early juvenile stage by evolving the anterior and posterior body section which improve swimming ability and food capturing. Positive growth coefficient of the body and trunk lengths were occurred after inflexion point coinciding with development of digestive system function. Eye diameter showed negative allometry at the inflexion point of 9.3 mm, continuing with positive growth rate until day 51. Body shape variation in early life history revealed consequent development in anterior and posterior body section in preflexion phase and development of body and trunk length in post flexion phase to support high survival of larvae. The present study emphasizes ontogenic study of different species to interpret biology and ecology of fish in association with evolutionary biology.

Variations in body shape of mountain habitat specialist Carabus croaticus and its sister species Carabus caelatus (Coleoptera: Carabidae) populations across Dinaric Alps

There are abundant phenotypic variations of Carabus croaticus Dejean 1826, an endemic species of the Dinaric Alps, and its sister species Carabus caelatus Fabricius 1801, resulting in taxonomic inflation at intraspecific level, synonymy and inconsistency between relevant catalogues and checklists. The main aims of this research were to explore population structure based on morphology and geographic patterns of phenotypic variability, and compare the results with taxa described by nonmetric visual comparisons of morphological traits. Our study included 224 specimens of C. croaticus and 192 specimens of C. caelatus, covering most of their distributional range. Shapes of the pronotum and head were analysed using geometric morphometrics (GMM). Principal component and canonical variate analyses were used to characterize the main features of shape variation between populations and mountain ranges. GMM delimitated interspecific morphological variations but at the intraspecific level it showed many overlaps within populations for both species. Conducting the morphological analyses for the first time on most of the described phenotypic variants of studied species, we wanted to provide a new evidence for the possible solution of the taxonomic relations within these two endemic species by measuring body shape variability, and thus to enable a better understanding of the evolutionary processes in the Dinaric Mountains.

Diet and body shape among populations of Bryconamericus iheringii (Otophysi: Characidae) across the Campos Sulinos ecosystem

ABSTRACT Alterations in natural landscapes, mainly caused by anthropic pressures, have been threatening the world’s biomes, including aquatic environments and its biota. This study describes the diet of Bryconamericus iheringii, and how its body shape relates to environmental variables in populations of 22 streams. A wide array of food items were found, mainly composed of allochthonous plants (50.5%) and autochthonous invertebrates (25.2%). Even though food items remained almost the same, the predominant food group significantly differed among streams, mainly in relation to environmental characteristics. There was variation in body shape primarily associated with body depth and length of the pre-dorsal region; however, these differences did not correspond with streams. PLS-CA analyses indicated that environmental characteristics, such as substrate type, percentage of marginal vegetation have some influence over food items availability but not on body shape. This may be because B. iheringii is a non-specialist species capable of prey switching based on availability due to an intermediate body shape suited for generalist feeding habits.

Shape and size variation of Jenynsia lineata (Jenyns 1842) (Cyprinodontiformes: Anablepidae) from different coastal environments

A key question in ecological speciation is to understand the causes and consequences of phenotypic divergence among populations. In this work, we analyzed the body shape and size variation in Jenynsia lineata across different coastal habitats along the Atlantic coast of South America. We hypothesized that J. lineata presents morphological variations to inhabit contrasting environments and that these adaptations are sex specific. We analyzed 13 populations from five coastal habitats, using linear and geometric morphometry, and tested the correlation of body shape variation with environmental variables to understand which environmental factors may influence body shape and size variation. Jenynsia lineata showed differences in body shape and size among populations, and these differences are specific to each sex. While females showed a variation in the caudal peduncle correlated with water current, we did not find such trait variation and correlation in males. Alternatively, individuals from marine rocky pools have a convex body curvature along the dorsal profile and larger body sizes, in both sexes. With these results, we describe the shape and size morphological variation of J. lineata and discuss this uncommon habitat-dependent sexual dimorphism in a Neotropical livebearer fish.

Latitudinal phenotypic variation in the southernmost trichomycterid, the catfish Hatcheria macraei: an amalgam of population divergence and environmental factors

Abstract Body shape and meristic characters are highly variable phenotypic aspects in fish, and in most cases are related to phylogeography, environmental factors and life history patterns. Our main goals here were to evaluate morphological and meristic characters in five populations of the catfish Hatcheria macraei living at different latitudes across Patagonia, and to assess the importance of environmental and phylogenetic variables in determining body shape. The present study reveals great morphological variation among populations distributed along the latitudinal gradient. We found that the highest levels of variation in external morphological features were in peduncle height, dorsal fin length and anus position. This variation in body shape, quantified by geometric morphometrics, was mostly explained by the phylogenetic relationship between populations, stream gradient and spawning temperature. In contrast, the meristic characters, such as vertebral and fin ray numbers, except for dorsal fin ray number, were negatively related to latitude and positively to spawning temperature.

Vision-Based Human Action Classification Using Adaptive Boosting Algorithm

Precise recognition of human action is a key enabler for the development of many applications, including autonomous robots for medical diagnosis and surveillance of elderly people in home environment. This paper addresses the human action recognition based on variation in body shape. Specifically, we divide the human body into five partitions that correspond to five partial occupancy areas. For each frame, we calculated area ratios and used them as input data for recognition stage. Here, we consider six classes of activities namely: walking, standing, bending, lying, squatting, and sitting. In this paper, we proposed an efficient human action recognition scheme, which takes advantages of the superior discrimination capacity of adaptive boosting algorithm. We validated the effectiveness of this approach by using experimental data from two publicly available databases fall detection databases from the University of Rzeszow’s and the Universidad de Malaga fall detection data sets. We provided comparisons of the proposed approach with the state-of-the-art classifiers based on the neural network, $K$ -nearest neighbor, support vector machine, and naive Bayes and showed that we achieve better results in discriminating human gestures.

A quantitative approach to determine the taxonomic identity and ontogeny of the pycnodontiform fish Pycnodus (Neopterygii, Actinopterygii) from the Eocene of Bolca Lagerstätte, Italy.

BackgroundThe pycnodontiform fish Pycnodus is one of the representatives of the highly diverse actinopterygian fish fauna from the early Eocene Bolca Lagerstätte, representing one of the youngest and thus last occurrences of this extinct neopterygian clade. This genus has historically been used as a wastebasket taxon in regards to poorly known pycnodontiform fossils. Authors have argued over the specific status of the Bolca Lagerstätte Pycnodus in terms of how many species are contained within the genus with some arguing for multiple species and others suggesting lumping all Bolca specimens together into one species.MethodsHere, we use a quantitative approach performing biometric and geometric morphometric analyses on 52 specimens of Pycnodus in order to determine if the morphological variability within the sample might be related to inter- or intraspecific variation.ResultsThe analyses revealed that the variations of body shape, morphometric and meristic characters cannot be used to distinguish different morphotypes. On the contrary, our results show a remarkable link between shape and size, related to ontogeny.DiscussionDifferences in body shape of small (juvenile) and large (adult) individuals is probably related to different microhabitats occupation on the Bolca reef with juveniles sheltering within crevices on the reef and adults being more powerful swimmers that swim above the coral. Taxonomically, we suggest that the Bolca Pycnodus should be referred to strictly as Pycnodus apodus as this was the name given to the holotype. Additionally, an overview of species assigned to Pycnodus is given.

The effect of ontogeny on estimates of KNM-WT 15000's adult body size

The Homo erectus specimen KNM-WT 15000 has played a critical role in our understanding of body size evolution. New interpretations suggest that KNM-WT 15000 had a younger age-at-death and a more rapid ontogenetic trajectory than previously suggested. Recent fossil discoveries and new interpretations suggest a wide range of body size and shape variation in H. erectus. Based on these new insights, we argue that KNM-WT 15000's adult stature and body mass could have been much smaller than has been traditionally presented in the literature. Using chimpanzee and modern human growth trajectories, we bracketed the range of possibilities for KNM-WT 15000's adult body size between 160.0 and 177.7 cm (5′3″–5′10″) for stature and 60.0 and 82.7 kg (132–182 lbs.) for body mass. These estimates put KNM-WT 15000 near the mean rather than among the largest known H. erectus specimens.

Body-shape diversity in Triassic–Early Cretaceous neopterygian fishes: sustained holostean disparity and predominantly gradual increases in teleost phenotypic variety

AbstractComprising Holostei and Teleostei, the ~32,000 species of neopterygian fishes are anatomically disparate and represent the dominant group of aquatic vertebrates today. However, the pattern by which teleosts rose to represent almost all of this diversity, while their holostean sister-group dwindled to eight extant species and two broad morphologies, is poorly constrained. A geometric morphometric approach was taken to generate a morphospace from more than 400 fossil taxa, representing almost all articulated neopterygian taxa known from the first 150 million years—roughly 60%—of their history (Triassic‒Early Cretaceous). Patterns of morphospace occupancy and disparity are examined to: (1) assess evidence for a phenotypically “dominant” holostean phase; (2) evaluate whether expansions in teleost phenotypic variety are predominantly abrupt or gradual, including assessment of whether early apomorphy-defined teleosts are as morphologically conservative as typically assumed; and (3) compare diversification in crown and stem teleosts. The systematic affinities of dapediiforms and pycnodontiforms, two extinct neopterygian clades of uncertain phylogenetic placement, significantly impact patterns of morphological diversification. For instance, alternative placements dictate whether or not holosteans possessed statistically higher disparity than teleosts in the Late Triassic and Jurassic. Despite this ambiguity, all scenarios agree that holosteans do not exhibit a decline in disparity during the Early Triassic‒Early Cretaceous interval, but instead maintain their Toarcian‒Callovian variety until the end of the Early Cretaceous without substantial further expansions. After a conservative Induan‒Carnian phase, teleosts colonize (and persistently occupy) novel regions of morphospace in a predominantly gradual manner until the Hauterivian, after which expansions are rare. Furthermore, apomorphy-defined teleosts possess greater phenotypic variety than typically assumed. Comparison of crown and stem teleost partial disparity indicates that, despite a statistically significant increase in crown teleost disparity between the Late Jurassic and earliest Cretaceous, stem teleosts remained important long-term contributors to overall teleost disparity during this time.