Carapace Shape Research Articles

Eucypris fontana(Graf, 1931) (Crustacea, Ostracoda) in permanent environments of Patagonia Argentina: a geometric morphometric approach

Fil: Ramos, Lorena Yesica. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina

Geometry of self righting: the case of Hermann’s tortoises

Armoured animals can easily lose their balance and fall on their back. When overturned, they can be exposed to suboptimal environment conditions, starvation or predation, thus, self-righting has a vital importance. Chelonians’ stiff shells prevent torsion of the torso, thus influence of the dorsum shape on self-righting can be significant. We explored the relationship between duration of active self-righting attempts and shell geometry in Hermann’s tortoises. We used geometric morphometrics and shell shape indices (R index, sphericity and flatness indices) to explore this effect. Our results showed a negative relationship between size and righting performance in both females and males. Enlarged females’ body, and thus reduced agility, could be favoured by fecundity selection. On the other hand, the body size of males is probably affected by sexual selection. Additionally, enlarged flared rear marginal scutes in males negatively affect self-righting. This part of males’ shells could be shaped by the trade-off between self-righting and stability during courtship and mating. However, the relationship between carapace shape and righting performance is not straightforward, as different results were obtained when various shape indices were applied in the analyses. The indices imply that greater curvature of the carapace shape facilitates self-righting in Hermann’s tortoises. Comparison of available literature data and results of this study imply that shell shape across the Testudo genus, except for T. marginata, largely overlaps with shell shape of T. hermanni. Thus, a similar effect of shell shape on self-righting performance could be expected for most of Testudo species.

Morphometric variation in allopatric populations of Aegla platensis (Crustacea: Decapoda: Anomura): possible evidence for cryptic speciation

Aegla platensis is a freshwater crustacean species that forms a nonmonophyletic group, which may indicate that the taxon is composed of cryptic species. Our objective was to test if allopatric populations of A. platensis differ in carapace shape, aiming to clarify the species situation. We used a geometric morphometric approach to analyze the carapace shape of 11 populations of A. platensis, four from Argentina and seven from Brazil. Our results showed that all the populations differ significantly in carapace shape, except two populations from Argentina and two from Brazil. The Argentinean and Brazilian populations formed two separate groups and were separated by high values of shape distance. This suggests the existence of reproductive isolation between the populations from the two groups. Shape distances between populations within each country were lower. Allopatric populations of A. platensis may be isolated from each other by the difficulty of migration, leading to interruption of gene flow and differentiation in carapace shape.

Effects of the evolution of theSerra doMar mountains on the shape of the geographically isolated populations ofAegla schmittiHobbsIII, 1979 (Decapoda:Anomura)

AbstractThe Aeglidae family is a useful model for evaluating the shape variation to present small geographically isolated populations and present a carapace structure that allows precise placement of landmarks. We analysed variations of the size and shape of the carapace of seven populations ofA. schmitti. We used 18 bidimensional anatomical landmarks on the carapace of adult males. Size variation between the populations was analysed through a univariate analysis of variance, while the shape variation was analysed through a multivariate analysis of variance using the configurations aligned by the generalized Procrustes analysis. The ordination of the populations was investigated through a canonical variables analysis. Individuals from the populations differed in the carapace size, in this case, we observed the largest individuals in the Iguaçu river basin, followed by Ribeira do Iguape and the Coastal basin. Carapace shape also differed between the populations ofA. schmitti, with the exception of the Mato Grande and Piraquara rivers: populations from the Iguaçu River presented a larger and rounder carapace when compared with the slenderer carapace of the Coastal basin, and the Ribeira do Iguape animals presented intermediate shapes. Data from the present study show great congruency with the draining pattern and geological history of the region.

Marine pollution effects on the southern surf crab Ovalipes trimaculatus (Crustacea: Brachyura: Polybiidae) in Patagonia Argentina

We compared the carapace shape and thickness as well as the energy density of Ovalipes trimaculatus inhabiting areas comprising a gradient of marine pollution: high, moderate and undetected, in the Nuevo gulf (Patagonia Argentina). The carapace shape was evaluated by means of individual asymmetry scores (=fluctuating asymmetry) whereas the carapace thickness was assessed by measuring the carapace dry weight. The energy density was analyzed through its negative relationship with water content in muscle tissue. The individual asymmetry scores as well as the percentage of water content in muscle tissue were proportional to the marine pollution gradient, whereas the carapaces thickness did not differ among sampling sites. Our results are consistent with previous findings and demonstrate the direct effect of marine pollution on other taxa different from gastropods, cephalopods and polyplacophora and add to long-standing concerns about detrimental effects caused by marine pollution on the benthic community of the Nuevo gulf.

Post-larval developmental dynamics of the Spinicaudatan (Branchiopoda: Diplostraca) carapace

The evolution of reproductive systems is of critical importance to evolution and yet has been difficult to examine using paleontological information. Recent studies on freshwater “clam shrimp” in both extant and fossil populations have demonstrated that sex can be inferred by quantifying morphological differences of the carapaces. However, the extent of morphological continuity between juveniles and mature phenotypes remains unclear, which, if extensive, would confound the determination of sex ratios from fossil specimens. Herein, we report studies of clam shrimp ontogeny using quantitative morphometric techniques to assess carapace shape change through juvenile and early adult development. Intra- and inter-species ontogenetic variance was captured in three species from two families (Limnadiidae, Cyzicidae), three genera (Paralimnadia, Eulimnadia and Cyzicus), and three breeding systems (dioecy, androdioecy and hermaphroditism) using geometric morphometric analyses to identify and characterize discrete phenotypic stages during ontogeny. With this approach, we successfully discriminated juvenile, male and female/hermaphrodite phenotypes. Additionally, we generated models that described the ontogenetic trajectory of carapace shape as species developed into sexually mature phenotypes. These findings verify the ability of these morphometric techniques to distinguish sex ratios using only carapace shape and, thus, validate the use of fossil spinicaudatans for studies of reproductive system evolution in deep time.

Revision of Lissoporcellana streptochiroides (Johnson, 1970) (Crustacea: Decapoda: Anomura: Porcellanidae), with description of a new species of Lissoporcellana Haig, 1978 from Beibu Bay, South China Sea.

A new porcellanid crab, Lissoporcellana demani n. sp. is described based on material from the Beibu Bay in the northern South China Sea. The new species can be distinguished from other congeners by the shape of rostrum, form of fixed finger of smaller cheliped and armature of lateral margins of carapace. The poorly known species L. streptochiroides (Johnson, 1970), which resembles L. demani n. sp. in carapace shape, is redescribed on the basis of examination of the syntypes from Singapore and transferred to Pisidia Leach, 1820.

Clinal variation in carapace shape in the South American freshwater crab,Aegla uruguayana(Anomura: Aeglidae)

South America has been influenced by different geoclimatic events ever since its separation from Africa. The inland water fauna has evolved in response to the changing landscape. Currently, there are indications of variations in populations, occurring to different degrees that would indicate a clinal pattern in morphology. Among South America's fauna, the freshwater anomuran, Aegla, is an enigmatic group as a result of its endemicity and is composed of only one genus. Of all the species in this family, Aegla uruguayana has the broadest distribution. Its native habitats have been influenced by several marine transgressions during the Miocene–Quaternary Periods; thus, it is likely that their current distribution has been more recent. Its habitat spreads across a number of isolated basins and sub-basins that display distinct degrees of isolation/connection, making clinal variation patterns in the morphology of this species possible. The present study aimed to evaluate the pattern of carapace shape variation in A. uruguayana and how it relates to the isolation and/or connection of populations from different basins and sub-basins, allowing the determination of any extant clinal patterns. The specimens studied belong to 25 separate populations, representing all areas in which the species currently exists. A total of 523 crabs were analyzed. We identified 13 landmarks and four semi-landmarks in the carapace. The aeglids were divided into seven size intervals to avoid an allometry effect. In each size category, shape relationships analyzed by principal component analysis suggest a geographical pattern corresponding to the distribution of the populations studied. An evaluation of covariation between body shape and geographical coordinates reveals a strong pattern and shows that population distribution had a significant effect on species morphology. Additionally, according to covariance analysis, the variation in shape was not associated with the environmental variables studied. We observed a clinal pattern throughout the species distribution, which could be attributed to genetic drift. It is possible that this process is being amplified by the geographical isolation of the basins, differences in environmental characteristics, and low dispersal ability. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 914–930.

Body shape and burial behavior of the sand crab Emerita analoga (Stimpson 1857) in a reflective to intermediate morphodynamic range of sandy beaches

Sand crabs belonging to the genus Emerita are the dominant species on sandy beaches of the Pacific and Atlantic coasts of America. The success of this genus has been attributed to the great phenotypic plasticity of life history traits that enables them to cope with swash climate variability from beach to beach. The burrowing rate and variation in carapace shape of Emerita analoga from south-central Chile were studied on a series of five sandy beaches with contrasting reflective-intermediate swash conditions (harsher swash to benign swash). Environmental sampling was carried out monthly from September 2009 to November 2010, while biological experiments were conducted in September and October 2010. A combination of field experiments, geometric morphometric tools and multivariate analysis was used to assess the relationship between burrowing behavior and carapace shape with variables of swash climate. Our results showed that (1) body shape of E. analoga is directly affected by the frequency of effluent line crossing, (2) burrowing rate of E. analoga is affected directly by shape variability, (3) burrowing rate is affected directly and indirectly by the swash climate variables: frequency of effluent line crossing and mean grain size of sediment. Thus, the physical conditions in the intertidal zone may be the main environmental constraints determining cephalothorax shape, with a wider cephalothorax on beaches with finer sand and more benign physical dynamics, and a narrower shape on beaches with coarser sand and harsher physical dynamics. The latter phenotype (narrower shape) probably allows compensating the high difficulty of burying in coarser sediments.

Geometric morphometric analysis of the freshwater prawn Macrobrachium borellii (Decapoda: Palaemonidae) at a microgeographical scale in a floodplain system

AbstractMorphometric studies are useful for delineating the shapes of various populations and species over geographical ranges and as evidence of regional differences in crustaceans. Hydrological fluctuations in a floodplain system modulate the dispersal and presence of decapods among habitats and constitute an important macrofactor that regulate other environmental variables and which could explain the richness, distribution and abundance of organisms that live in these systems. Morphological variations among populations of the freshwater prawn Macrobrachium borellii in a floodplain system at a microgeographical scale were studied using geometric morphometrics. Carapace structure was represented using 16 digitised landmarks. Allometry and sexual dimorphism was tested. Variation in shape was explored via Principal Component Analysis. Canonical Variate Analyses was applied to compare the differences in shape between species’ populations. The correlations and covariations among shapes and hydrometric level, current velocity, geographical location and hydrologic distances were analysed. The average carapace shape was different between sexes in all sites. Populations that were near each other in terms of hydrological distance had similar shapes, but all of the populations differed in shape from the farthest population. The environmental variables were not good predictors of the carapace shape. Instead, the shape was strongly related to the hydrologic distance and geographical location. The swimming characteristics of these prawns and their passive movements, together with the dynamics of a floodplain system, explain the low morphological variation between populations in this study. The dynamic characteristics of the system influence the dispersal of the prawns and allow populations to remain connected.

Intraspecific variation inAegla longirostri(Crustacea: Decapoda: Anomura) revealed by geometric morphometrics: evidence for ongoing speciation?

Genetic divergences among populations of Aegla longirostri suggest that this group may be formed by cryptic species. In this study, we analysed the carapace shape of six populations of A. longirostri from southern Brazil, using a geometric morphometric approach, to better elucidate the species' systematics. Our results were congruent with the genetic data, meaning that genetically differentiated populations were also morphogeometrically differentiated. The geometric morphometric descriptors showed significant differences in carapace shape among all populations. Geographical distance and isolation may be affecting the gene flow between populations, leading to divergence in both genetic and morphometric traits. Our data indicate the possible existence of cryptic species within A. longirostri, or an incomplete process of speciation. Geometric morphometric methods were efficient in differentiating among populations that do not show divergence in diagnostic characters. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 31–39.

Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 20:53-67 (2014) - DOI: https://doi.org/10.3354/ab00545 Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil Kelsey R. Hampton1, Melanie J. Hopkins2, John C. McNamara3, Carl L. Thurman1,* 1Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614-0421, USA 2GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Loewenichstraße 28, 91054 Erlangen, Germany 3Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil *Corresponding author: thurman@uni.edu ABSTRACT: Isolation due to geographical barriers should promote genetic and morphological divergence among populations. Marine currents flowing in opposing directions along landmasses can constitute barriers that isolate populations dependent upon aquatic dispersal. The distribution of fiddler crabs (genus Uca) is regulated primarily by the oceanic transport of their planktonic larvae and by available adult habitat. Along the Brazilian coast of eastern South America, the flow of 2 major oceanic currents separates northern from southern Uca populations, which may promote intraspecific divergence in ‘trans-Brazilian’ species. Populations of 10 Uca species were sampled at 64 locations north and south of the Ponta do Calcanhar, Rio Grande do Norte, Brazil. Carapace shape was assessed using geometric morphometrics to analyze 12 surface landmarks in 1319 female crabs. Carapace shape differs significantly in each species. In morphospace, the carapace forms of the 10 species appear to separate into traditional subgeneric clusters. Within the 8 species exhibiting trans-Brazilian distributions, northern and southern populations show distinct carapace differences. Depending on species, either the hepatic or the branchial region is larger in northern populations. Since significant genetic variability among such populations has not been confirmed, divergence in carapace shape suggests significant ecological modulation of phenotype within each species. Apparently, environmental differences between northern and southern localities exert a greater impact on carapace morphology than impeded gene flow. The drivers underpinning diversification of carapace shape remain unknown, however. KEY WORDS: Brachyura · Fiddler crab · Uca · Structural variation · Landmark analysis · Isolation · Ecophenotypy Full text in pdf format Supplementary material PreviousNextCite this article as: Hampton KR, Hopkins MJ, McNamara JC, Thurman CL (2014) Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil. Aquat Biol 20:53-67. https://doi.org/10.3354/ab00545 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 20, No. 1. Online publication date: January 13, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

Sexual shape dimorphism of the mangrove crab Ucides cordatus (Linnaeus, 1763) (Decapoda, Ucididae) accessed through geometric morphometric.

Sexual dimorphism is often observed in Crustaceans. Considering the great diversity of this subphylum, only few reports are found in the literature and most are mainly based on traditional morphometry. The present study uses geometric morphometrics analysis to identify sexual dimorphism by shape variation in the overexploited semiterrestrial crab Ucides cordatus, species with great social and economic importance in South America. Comparative morphology analyses were performed by using the outer face of the propodus of major cheliped, dorsal and anterior region of carapace shape. Significant differences in shape between sexes were detected in these body areas. The causes of dimorphism presented in this species are not clear but, analogous to other possibly associated species, it may be inferred that the causes are with adaptations to body ability of reproductive potential (females), and of reproductive behaviour and agonistics encounters (males). Additional analyses on courtship displays and other reproductive aspects should provide better comprehension of functionality of this morphological differentiation.

A revision of the Australian species of Lynceus Müller, 1776 (Crustacea: Branchiopoda: Laevicaudata, Lynceidae).

Australia has had two species of Lynceus, L. macleayanus (King, 1855) and L. tatei (Brady, 1886) reported to date, both poorly described and without types, and supposedly both widely distributed. This study establishes neotypes and redescribes each according to modern standards. The present distribution of each is severely restricted by the destruction of temporary aquatic habitats, both in cities and in the country and also misunderstood by the lack of recent collecting in some outlying areas. Detailed study of male first thoracopods, together with an understanding of the form of the head and rostrum, antenna 2 spinal patterns, carapace shape, and the females' lamina abdominalis, most of which are discontinuously variable, has resulted in the delineation of four more species: L. baylyi sp. nov. in desert rockholes of Western Australia; L magdaleanae sp. nov. mainly in deep gnammas of the WA Wheatbelt and Goldfields but also extending into NT, Qld and SA; L. susanneae sp. nov. of rockholes on the Nullarbor Plain, WA; and L. argillaphilus sp. nov. of the coastal Pilbara, WA. Identification keys are provided for all six species, both males and females.

On Callistocypris thailandensis sp. nov. (Ostracoda, Crustacea) from Thailand.

Callistocypris thailandensis sp. nov. is here described from terrestrial habitat in Khao Yai National Park, Nakhon Ratchasima province, Thailand. The new species differs from the other three Callistocypris species in the shape of carapace, the presence of strong longitudinal ridges on the ventral part of the valves and the chaetotaxy of several limbs. Zoogeography and ecology of the genus are briefly discussed.

Repeatability of Habitat-Associated Divergence in Shell Shape of Turtles

Repeated patterns of phenotypic divergence between environments across disparate taxa provide strong evidence for the generation of adaptive phenotypes. Flow velocity is an important selective force in aquatic habitats; however, among vertebrates, the study of its effects on morphology has been limited almost exclusively to fully- aquatic bony fishes. We tested whether three confamilial species of semi-aquatic freshwater turtle (family Emydidae: Graptemys pseudogeographica, Graptemys nigrinoda, and Pseudemys concinna) displayed similar patterns of phe- notypic divergence in carapace shape between fast- and slow-flowing aquatic environments. We used (1) geometric morphometrics to quantify shell shape, (2) multivariate analysis of variance to test the effects of species, sex, and flow, and (3) phenotypic trajectory analysis to compare patterns of divergence for six species-sex groups. We found significant effects on shell shape for all factors. In general, ecomorphs from fast-flowing habitats had flatter shells than those from slow-flowing habitats. Furthermore, results of trajectory analysis indicate that the degree to which, as well as the way in which, ecomorphs differed were concordant across all species. Our findings demon- strate that the effects of flow are not limited to fully-aquatic vertebrates, and provide evidence of the ability of flow to drive repeatable phenotypic divergence in tetrapods.

A new species of sesarmid crab of the genus Chiromantes (Crustacea: Decapoda: Brachyura) from the Ogasawara Islands, Japan.

A new species of sesarmid crab, Chiromantes magnus, is described from the Ogasawara (Bonin) Is., Japan. The new species was previously confused with C. dehaani (H. Milne Edwards, 1853). The different carapace shape, proportionally longer ambulatory legs, large adult size and the distinct live coloration distinguish the new species from its two closest congeners, C. dehaani and C. neglectus (De Man, 1887). Available information indicates that C. magnus n. sp. is endemic to the Ogasawara Is.; there is no evidence of the occurrence of the true C. dehaani in the Ogasawara Is.

Contribution to the knowledge of the genus <i>Vestalenula</i> Rossetti & Martens, 1998 (Crustacea, Ostracoda, Darwinulidae), with the description of a new species, V. carinata n. sp., from the island of Florianópolis, Brazil

The genus Vestalenula is the most species rich in the putative ancient asexual ostracod Family Darwinulidae. Several new Recent species were described from various continents, mostly based on carapace shape and structure. These species were found in a variety of aquatic and (semi-) terrestrial habitats, including springs, streams, interstitial waters, leaf litter in forests and in splash zones of waterfalls. Here, we describe V carinata n. sp. from moist leaf litter, collected from the Brazilian island of Florian6polis. The species belongs to the danielopoli-lineage within the genus because of its elongated internal tooth in the left valve and elongated external keel on the right valve. It can be distinguished from all other species in this group by its size, its L/H ratio and the relative length of the keel. The relationship of this new species to the enigmatic, putative marine species Senidarwinula terraenuxforna Choe, 1988, is discussed. An identification key to species of the genus is provided.

New retroplumid crabs (Crustacea, Brachyura, Retroplumidae Gill, 1894) from the Eocene of Huesca (Aragón, Spain).

Two new brachyurans assignable to the family Retroplumidae Gill, 1894, Serrablopluma diminuta n. gen., n. sp., and Gaudipluma bacamortensis n. gen., n. sp., from the Eocene of northern Spain (Huesca, Aragón), substantially enlarge our current knowledge of the morphological diversity of the family. The material, with well-preserved ventral surfaces, permits the erection of two new genera that can be referred to the family with confidence on the basis of the general carapace shape, narrow front, a reduced last pair of pereiopods and characteristic thoracic sternum (broad, trapezoidal sternites 3, 4, subrectangular sternites 5-7, sternite 8 conspicuously reduced and inclined). Serrablopluma diminuta n. gen., n. sp. co-occurs with two other retroplumids in the most diverse fossil assemblage of that family known to date.

A new species of Megaesthesius Rathbun, 1909 (Crustacea: Brachyura: Chasmocarcinidae) from deep water off Western Australia.

A new species of Megaesthesius Rathbun, 1909, M. westralia, is described from shelf waters off Western Australia. It can be separated from its two congeners by differences in carapace shape and dentition, as well as differences in the male abdomens and gonopods.