Morphological asymmetry and behavioral laterality in the crayfish, Procambarus clarkii

Lateral asymmetry is found widely among vertebrates, but is scarcely observed in invertebrates. Here, morphological asymmetry and behavioral laterality of a wild crayfish, Procambarus clarkii, was investigated. The carapace morphology of crayfish showed left–right differences; in some, the right side of the carapace was larger than the left side, while in others, the left side was larger. A bimodal distribution in the direction of escape behaviors induced by a tactile stimulus was also observed. Experimental crayfish were definitively divided into two groups: individuals that frequently jumped leftward (right type) and those that jumped rightward (left type). Moreover, carapace asymmetry and lateralized escape responses were significantly correlated. These results suggest that crayfish exhibit left–right dimorphism in natural populations. The ecological advantages and maintenance mechanisms underlying these behaviors are also discussed.     

Behavioral laterality and morphological asymmetry in the cuttlefish, Sepia lycidas

Behavioral laterality is widely found among vertebrates, but has been little studied in aquatic invertebrates. We examined behavioral laterality in attacks on prey shrimp by the cuttlefish, Sepia lycidas, and correlated this to their morphological asymmetry. Behavioral tests in the laboratory revealed significant individual bias for turning either clockwise or counterclockwise toward prey, suggesting behavioral dimorphism in foraging behavior. Morphological bias was examined by measuring the curvature of the cuttlebone; in some the cuttlebone was convex to the right (righty), while in others, the cuttlebone was convex to the left (lefty). The frequency distributions of an index of cuttlebone asymmetry were bimodal, indicating that populations were composed of two types of individuals: "righty" and "lefty." Moreover, an individual's laterality in foraging behavior corresponded with the asymmetry of its cuttlebone, with righty individuals tending to turn counterclockwise and lefty ones in the opposite direction. These results indicate that cuttlefish exhibit behavioral dimorphism and morphological antisymmetry in natural populations. The presence of two types of lateral morph in cuttlefish provides new information on the relationship between antisymmetric morphologies and the evolution of individual laterality in behavioral responses in cephalopods. The implications of these findings for the interpretation of ecological meaning and maintenance mechanisms of laterality in cuttlefish are also discussed.     

Morphological observations on the gills of dendrobranchiate shrimps

Gill morphology, traditionally, has played an important role in attempts to reconstruct the phylogenetic history of the Crustacea Decapoda. We examined the gills of dendrobranchiate shrimps (Crustacea, Decapoda, Dendrobranchiata) to test the assumption that all members of the clade have gills that are “dendrobranchiate” (highly branching) in form, from whence the taxon name Dendrobranchiata comes. Currently, the Dendrobranchiata consists of two superfamilies and seven families. Specimens from two genera in each of the known families were examined using light and scanning electron microscopy. Members of the family Luciferidae, all of which lack gills as adults, were not examined. Only one genus was examined for the Penaeidae (because they have been the subject of numerous previous studies) and Sicyoniidae (a monogeneric family). All gills examined have secondary branches that are further subdivided, conforming to existing and rather broad definitions of dendrobranchiate gills. Families with “typical” dendrobranchiate gills, which consist of curved secondary branches that in turn bear branched (dendritic) tubular tertiary elements on their distal surfaces, include the Penaeidae, Aristeidae, and Solenoceridae. In other families, secondary and tertiary gill elements are sometimes quite flattened, and the tertiary elements are not dendritic, giving the gill a distinctly non-dendrobranchiate appearance. Flattened biserial secondary branches and their flattened tertiary elements are particularly obvious in gills of the monogeneric family Sicyoniidae (Sicyonia). Within the family Sergestidae, gills of the genus Sergestes are unusual in having secondary branches that arise from the main gill axis in an alternating pattern; these gills also have distinctly oval tertiary elements that are not further subdivided and are directed basally rather than distally. Another sergestid genus, Petalidium, displays gills that differ from those of Sergestes; in Petalidium the secondary branches also come off the main gill axis in an alternating pattern, but these branches are more widely spaced and have relatively larger and broader tertiary elements when compared with gills of Sergestes. The family Benthesicyemidae also contains species with different gill types; Gennadas is shown to have flattened, plate-like tertiary elements, whereas Benthesicyemus has more typical dendrobranchiate gills. The significance of this variation in gill morphology within families and within the Dendrobranchiata as a whole is unclear at this point; rearrangements of the currently accepted phylogeny and resulting classification based solely on gill morphology are not recommended at this time.     

Morphological and functional asymmetry in alpha-proteobacteria

The release of an increasing number of complete bacterial genomic sequences allows the evolutionary analysis of processes such as regulatory networks. CtrA is a response regulator of the OmpR subfamily, belonging to a complex regulatory network in the dimorphic bacterium Caulobacter crescentus. It coordinates the cell cycle with an asymmetric division, which is part of the adaptation of Caulobacter to poor-nutrient environments. CtrA is only found in alpha-proteobacteria, a group of bacteria encompassing genera with very distinct lifestyles, including host-associated bacteria. Analyses of CtrA regulatory networks and morphological examinations of some alpha-proteobacteria are presented. Our observations suggest that the core of the CtrA regulation network is conserved and that alpha-proteobacteria divide asymmetrically. We propose that the two daughter cells might be differentiated bacteria, each one displaying specific functions.     

Variability of the behavioral laterality in Teleostei (Pisces)

Factors causing variability of behavioral laterality in Teleostei are reviewed. The laterality has been revealed in many fish species belonging to various families. The best ever demonstrated example of the laterality is the different use of the right and left eyes when a fish responds to different visual objects. Magnitude and sign of the laterality differ in fishes of different species, gender, and age. Also, an observed laterality depends on how familiar a stimulus is to fishes and what it means to them, as well as their motivational level and various behavioral traits. Therefore, comparisons of the laterality among different fish species should be based on experimental methods that also take into account those behavioral differences among them that are not directly linked to the laterality.     

Distribution and habitat utilization in two atyid shrimps (Crustacea: Decapoda) in rivers of Nuku-Hiva Island (French Polynesia)

The distribution of Atyoida pilipes (Newport, 1847) and Caridina weberi De Man, 1892 was studied at two spatial scales on Nuku-Hiva Island (Marquesas, French Polynesia). At the stream reach scale, the two species were present at 40 and 39 sites, respectively, out of a total of 49 sites sampled. These two taxa represented more than half of the invertebrates collected at 9 sites. There was no difference in distribution between the species at the reach scale. However, clear differences appeared between the two species at the microhabitat scale. A. pilipes was more abundant in lotic habitats, even waterfalls, while C. weberi was associated with accumulations of leaves in lentic habitats. A. pilipes, particularly males, were tolerant to parameters such as water velocity, leaves, and the presence of algae and rocks. C. weberi had a more restricted altitudinal distribution and were scarce upstream from large waterfalls. These differences were linked to differences in climbing ability rather than the effect of chemical parameters, such as oxygen content. Our results suggest that little competition for space or food resources occurs between the two species. Both are feeding on small detritus particles, but through differing mechanisms and in differing habitats.     

Analysis of quantitative trait loci for behavioral laterality in mice

Laterality is believed to have genetic components, as has been deduced from family studies in humans and responses to artificial selection in mice, but these genetic components are unknown and the underlying physiological mechanisms are still a subject of dispute. We measured direction of laterality (preferential use of left or right paws) and degree of laterality (absolute difference between the use of left and right paws) in C57BL/6ByJ (B) and NZB/BlNJ (N) mice and in their F(1) and F(2) intercrosses. Measurements were taken of both forepaws and hind paws. Quantitative trait loci (QTL) did not emerge for direction but did for degree of laterality. One QTL for forepaw (LOD score = 5.6) and the second QTL for hind paw (LOD score = 7.2) were both located on chromosome 4 and their peaks were within the same confidence interval. A QTL for plasma luteinizing hormone concentration was also found in the confidence interval of these two QTL. These results suggest that the physiological mechanisms underlying degree of laterality react to gonadal steroids.     

Morphological integration of fluctuating asymmetry in the mouse mandible

Morphological integration of fluctuating asymmetry (FA) was assessed for nine mandibular characters in random-bred house mice to test the hypothesis that there should be a significant integration or concordance of FAs at the population level, but not at the individual level. FA estimates for each of the nine characters were made for each of 16 subpopulations (two replicates each for mice varying in sex and age) and their correlations indicated a moderate level of integration (index of integration = 0.42). A matrix permutation test of the differences of the correlations within two (‘incisor’ and ‘muscle’) developmentally different character groups versus correlations between groups was significant, indicating the presence of morphological integration. Kendall's coefficient of concordance also indicated a significant population asymmetry parameter for FAs within the two character groups. Correlations among individual FA estimates were generally lower than those calculated from subpopulations, the index of integration being 0.21. The matrix permutation test failed to show significant morphological integration among individual FAs, but Kendall's coefficient of concordance was significant, indicating the presence of an ‘individual asymmetry parameter’ among the nine characters. Principal components analysis and canonical correlation analysis confirmed the overall higher level of integration of FAs among the subpopulations and within the two character groupings.     

中国非人灵长类物种的行为偏侧研究进展

行为偏侧是指动物进行某一行为时偏好使用某一侧肢体或感觉器官。行为偏侧作为脑偏侧所对应的可观测的行为指标,是动物行为适应性进化的代表性特征之一,它在个体水平上影响着个体适合度,在群体水平上是社会性物种的一种进化稳定策略,具有重要的生态和进化意义。中国非人灵长类资源丰富,而中国非人灵长类的行为偏侧研究起步较晚,始于二十世纪八十年代。本文系统归纳中国非人灵长类物种的行为偏侧研究进展,并基于当前研究现状,为今后发展提出积极建议。     

Morphological asymmetry in dividing retinal progenitor cells

For the understanding of histogenetic events in the 3-D retinal neuroepithelium, direct observation of the progenitor cells and their morphological changes is required. A slice culture method has been developed by which the behavior of single progenitor cells can be monitored. Although it has been believed that each retinal progenitor cell loses its basal process while it is in M phase, it is reported here that the process is retained throughout M phase and is inherited by one daughter cell, which can be a neuron or a progenitor cell. Daughter neurons used an inherited process for neuronal translocation and positioning. In divisions that produced two mitotic daughters, both of which subsequently divided to form four granddaughter cells, only one daughter cell inherited the original basal process while the other extended a new process. Interestingly, behavioral differences were often noted between such mitotic sisters in the trajectory of interkinetic nuclear movement, cell cycle length, and the composition of the granddaughter pair. Therefore, "symmetric" (progenitor --> progenitor + progenitor) divisions are in fact morphologically asymmetric, and the behavior of the mitotic daughters can often be asymmetric, indicating the necessity for studying possible associations between the process inheritance and the cell fate choice.     

Morphological studies of facial skeleton asymmetry in pongidae and hominid primates

On the question of asymmetry in the upper facial skeleton, ten samples of hominoid primates were investigated in a comparative metrical analysis. Generally, there was a slight dominance in the right-handed measurements. With one exception these findings could be confirmed statistically, whereas sexual dimorphism could not be shown to be significant in this respect. The question, whether the differences between right and left measurements show a bimodal distribution and so suggest a certain amount of reversed asymmetry, could not be answered clearly because the sample size was limited. Most of the distributions are explicable in accordance with this assumption.     

Dependence of behavioral responses form during shake-off conditional reflex on laterality of the neocortex

Pattern of discharges and interhemispheric interaction of parietal neurons (somatosensory presentation of the ear) were compared in interstimulus intervals before active shake-off and passive freezing reactions at stimuli after elaboration defensive avoid reflex. Before passive reactions in contrast to active right-side influences on left-side neurons were reinforced with delay to 100 ms, it result in appearence of asymmetry in interhemispheric interaction with right-side dominance. Before passive reactions intensity of delta-frequencies was increased in impulsation of single neurons and in interaction of cells pair. On this evidence the pattern of interhemispheric asymmetry before stimuli can be one of a number of factors, determinant active or passive form of behavioral reactions and also reflective of activation level of neocortex.     

Morphological and behavioral antipredatory adaptations of decapod zoeae

Summary Zoeae of some species of estuarine decapods are retained in the estuary throughout development while others are exported into nearshore coastal waters. The horizontal migrations of decapod zoeae to coastal waters may have evolved to reduce the probability of encountering planktivorous fishes which are most abundant in the estuary. If so, then the morphological vulnerability of zoeae to fish predation should be inversely related to the number of predators occurring where they develop. Six species of estuarine decapod zoeae were offered to Menidia menidia and Fundulus heteroclitus. The behavioral interactions were observed to determine the prey's vulnerability to predation, and the mode of operation and relative effectiveness of their defenses. Feeding trials and behavioral observations both demonstrated that M. menidia 6–16 mm long preferred Uca minax and Callinectes sapidus zoeae, which are exported from the estuary, to Rhithropanopeus harrisii, Sesarma reticulatum and Palaemonetes pugio, which are retained within estuaries. Pinnotheres ostreum zoeae develop in the lower estuary and fish demonstrated an intermediate preference for the zoeae. Menidia menidia 20–40 mm long showed similar preferences for R. harrisii S. reticulatum, P. ostreum and U. minax as did small silversides. Large-mouthed demersal fish, Fundulus heteroclitus 6–10 mm long, also preferred U. minax to R. harrisii, but more readily preyed on zoeae than did M. menidia. The exported species of zoeae have shorter spines and smaller bodies than do retained zoeae, except P. ostreum which is small, spineless and passively sinks when attacked by fish. Other retained species of zoeae also have postcontact behavioral defenses which enhance the effectiveness of their morphological defenses. Zoeae do not evade attacks by fishes, but fishes quickly learned to avoid zoeae, which increases the effectiveness of the zoeae's antipredatory adaptations.     

Morphological stasis and phylogenetic relationships in Tadpole shrimps, Triops (Crustacea: Notostraca)

The tadpole shrimp (Triops) is a well-known 'living fossil' whose fundamental morphology has been unchanged for over 170 million years. Thus, tadpole shrimps are suitable subjects for the study of morphological stasis. We were able to obtain samples of three species of Triops (T. granarius, T longicaudatus and T. cancriformis) from four regions in Japan. Taxonomic species were identified by diagnostic morphology. We inferred phylogenetic relationships between individual samples using mitochondrial 16S rRNA. Carapace shapes were compared among populations using shape coordinate methods. The phylogeny inferred from mtDNA shows that T. granarius is phylogenetically more similar to T. longicaudatus than to T. cancriformis. mtDNA sequences did not differ among the populations of T granarius. However, there were two distinct phylogenetic species within T. longicaudatus. In spite of the similarity in fundamental morphological characteristics among Triops species, mtDNA sequences of Triops showed marked differences among the four phylogenetic species. Among the populations of T. granarius , the carapace shape of the Fukuoka population was significantly different from those of other populations of T. granarius. The carapace shape of the Kagawa population of T. longicaudatus was more similar to those of the Shizuoka and Kagawa populations of T. granarius. The shape of the carapace of T. cancriformis was significantly different from those of T. granarius and T longicaudatus. Thus, taxonomic species, phylogenetic species and populations with similar carapace morphology did not correspond with each other. The present results indicate that most of the morphological change did not occur at the time of speciation (lineage separation) and that morphological stases are important evolutionary patterns, but they are not species-level properties.     

Morphological asymmetry of insular freshwater populations of threespine stickleback

Fluctuating asymmetry (FA), random deviations from perfect symmetry in a bilateral organism, has been widely used as a proxy for developmental instability in stressed populations. In order to test the utility of FA of resident freshwater threespine stickleback (Gasterosteus aculeatus) as a biomonitoring tool for contaminated sites, we compared levels of asymmetry of seven morphological traits of threespine stickleback collected from lakes at three islands with a history of military contamination and three islands with no military history, in the Aleutian Archipelago, Alaska. Traits examined include eye diameter, operculum width, pectoral fin ray number, pectoral fin width, lateral plate number, lateral plate length, and pelvic spine length. All morphometric traits demonstrated some degree of FA or directional asymmetry (DA), but the military history of a lake was not a predictor of the degree or type of asymmetry. Overall, the patterns of asymmetry were similar for all traits, irrespective of military contamination at a lake. Our results demonstrate that the suite of threespine stickleback traits measured are not suitable for examination of FA as a proxy for aquatic pollution in this region. DA also does not appear to be suitable as an indicator of aquatic pollution, but may instead be driven by local ecological factors such as predation.     

Association between the behavioral and neurochemical effects of amphetamine: Hemispheric asymmetry study

Effects of amphetamine on concentrations of dopamine, norepinephrine and serotonin in several monoamine-containing cell body and terminal regions were examined left and right separately in rats. Results suggest that amphetamine reduced the L-R asymmetry of most of these measures, and this effect is more significant in the cell body than in the terminal regions. Behaviorally, amphetamine also decreased L-R asymmetry of the spontaneous turning behavior in rats and this latter effect is most closely associated with the reductions of dopamine and norepinephrine asymmetries in the substantia nigra and reduction of norepinephrine asymmetry in the locus coeruleus.     

Morphological phylogeny of alpheid shrimps: parallel preadaptation and the origin of a key morphological innovation, the snapping claw

The Alpheidae-possibly the most diverse family of recent decapod crustaceans-offers attractive opportunities to study the evolution of many intriguing phenomena, including key morphological innovations like spectacular snapping claws, highly specialized body forms, facultative and obligate symbioses with many animal groups, and sophisticated behaviors like eusociality. However, studies of these remarkable adaptations remain hampered by insufficient phylogenetic information. We present the first phylogenetic hypothesis of relationships among 36 extant genera of alpheid shrimps, based on a cladistic analysis of 122 morphological characters from 56 species, and we use this hypothesis to explore evolutionary trends in morphology and species diversity. Our results strongly supported a monophyletic Alpheidae that included two hitherto difficult-to-place genera (Yagerocaris and Pterocaris). Of 35+ nodes among genera, all were supported by at least one morphological character (24 were supported by two or more) and 17 received greater than 50% jackknife support. Unfortunately, many basal nodes were only weakly supported. Six genera appeared nonmonophyletic, including the dominant genus Alpheus (paraphyletic due to inclusion of one clade with three minor genera). Evolutionary trends in alpheid claw form shed some revealing light on how key innovations evolve. First, several functionally significant features of the cheliped (claw bearing leg) evolved independently multiple times, including: asymmetry, folding, inverted orientation, sexual dimorphism, adhesive plaques that enhance claw cocking, and tooth-cavity systems on opposing claw fingers, a preadaptation for snapping. Many conspicuous features of alpheid claw form therefore appear prone to parallel evolution. Second, although tooth-cavity systems evolved multiple times, a functional snapping claw, which likely facilitated an explosive radiation of over 550 species, evolved only once (in Synalpheus + [Alpheus + satellite genera]). Third, adhesive plaques (claw cocking aids) also evolved multiple times, and within snapping alpheids are associated with the most diverse clade (Alpheus + derivative genera). This pattern of parallel preadaptation-multiple independent evolutionary origins of precursors (preadaptations) to what ultimately became a key innovation (adaptation)-suggests alpheid shrimp claws are predisposed to develop features like tooth-cavity and adhesive plaque systems for functional or developmental reasons. Such functional/developmental predisposition may facilitate the origin of key innovations. Finally, moderate orbital hoods-anterior projections of the carapace partly or completely covering the eyes-occur in many higher Alpheidae and likely evolved before snapping claws. They are unique among decapod crustaceans, and their elaboration in snapping alpheids suggests they may protect the eyes from the stress of explosive snaps. Thus one key innovation (orbital hoods) may have facilitated evolution of a second (snapping claws).