Zoomorphology 

About: Zoomorphology is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Biology & Ultrastructure. It has an ISSN identifier of 0720-213X. Over the lifetime, 1299 publications have been published receiving 23829 citations.

Transmission of force and velocity in the feeding mechanisms of labrid fishes (Teleostei, Perciformes)

Abstract: The feeding mechanisms of four species of the teleostean family Labridae (Cheilinus fasciatus, C. trilobatus, Oxycheilinus bimaculatus, and O. unifasciatus) were modeled using four-bar linkage theory from mechanical engineering. The predictions of four-bar linkage models regarding the kinematics of feeding were compared to the movements observed with high speed cinematography (200 frames/s). A four-bar linkage was an accurate model of the mechanism by which upper jaw protrusion, maxillary rotation, and gape increase occur in each species. A four-bar mechanism of hyoid depression was an accurate predictor of hyoid depression when simultaneous cranial elevation and sternohyoideus contraction were simulated. Morphometrics of the linkage systems of the jaws and hyoid were collected for 12 labrid species. These data were used to calculate the transmission of force and motion through the musculoskeletal linkages. Several measures of mechanical advantage and displacement advantage were compared, including both traditional lever ratios and transmission coefficients of four-bar linkages. Alternative designs of the feeding mechanisms maximize force or velocity for the capture of different prey types. High velocity transmission of both the jaw and hyoid systems is characteristic of those species that feed on evasive prey, whereas species that feed on benthic invertebrates favor increased force transmission in both systems. Quantitative models of biomechanical systems supply criteria for functionally relevant morphometrics, and aid in calculating the capacity for transmission of force and velocity in musculoskeletal systems.

From micropterism to hyperpterism: recognition strategy and standardized homology-driven terminology of the forewing venation patterns in planthoppers (Hemiptera: Fulgoromorpha)

Abstract: Following recent advances in the morphological interpretations of the tegmen basal cell margins in the Paraneoptera, a standardized and homology-driven groundplan terminology for tegmina types, structures and vein patterns in Hemiptera Fulgoromorpha, including fossils, is proposed Each term is listed with a morphological definition, compared and linked to the main systems of planthopper forewing description that have been reviewed The importance of a standardized and homology-driven terminology is stressed to enhance the quality of data in taxonomic descriptions and to strengthen phylogenetic morphological analysis results When the interpretation of the origin of vein branches is render difficult, a three-step strategy for pattern recognition of the vein is proposed based on two principles: (1) vein forks are more informative than topology of the vein branches: a search for homologous areas, the nodal cells in particular, must first guide the recognition rather the number of branches of a vein, and (2) minimum of ad hoc evolutionary events should be invoked in the understanding of a modified vein pattern Examples of some conflicting interpretations of venation patterns in planthoppers are discussed within different families for both extant and extinct taxa For the first time, the concept of brachypterism is defined in a non-relative way independently from other structures, and the new one of hyperpterism is proposed; a reporting system is proposed for each of them

Sample size and sampling error in geometric morphometric studies of size and shape

Abstract: Geometric morphometric studies are increasingly becoming common in systematics and palaeontology. The samples in such studies are often small, due to the paucity of material available for analysis. However, very few studies have tried to assess the impact of sampling error on analytical results. Here, this issue is addressed empirically using repeated randomized selection experiments to build progressively smaller samples from an original dataset of ∼400 vervet monkey (Cercopithecus aethiops) skulls. Size and shape parameters (including mean size and shape, size and shape variances, angles of allometric trajectories) that are commonly used in geometric morphometric studies, are estimated first in the original sample and then in the random subsamples. Estimates are then compared to give an indication of what is the minimum desirable sample size for each parameter. Mean size, standard deviation of size and variance of shape are found to be fairly accurate even in relatively small samples. In contrast, mean shapes and angles between static allometric trajectories are strongly affected by sampling error. If confirmed in other groups, our findings may have substantial implications for studies of morphological variation in present and fossil species. By performing rarefaction analyses like those presented in our study, morphometricians can be easily provided with important clues on how a simple but crucial factor like sample size can alter results of their studies.

The mechanics of cutting and the form of shark teeth (Chondrichthyes, Elasmobranchii)

Abstract: A rich engineering literature exists that is applicable to many aspects of vertebrate jaw mechanics and has been referred to in many studies in this sector. But mechanical engineering technology has provided few theoretical bases that are directly helpful in the study of predator teeth. Hence, analyses of puncturing and slicing functions of these teeth have lacked a firm physical technology as a background. Predator teeth have evolved to pierce and cut animal tissues that are usually compliant in that they readily undergo relatively large deformations under applied stress before they actually yield. The bulk of engineering theory is directed toward such noncompliant materials as wood and metal, the design of tools that cut them, and the mechanics involved in this. The purpose of the present paper is to scan the mechanical implications of different tooth designs, pose hypotheses that relate to primary considerations of the physics of cutting compliant substrates, and offer a preliminary approach that is intended as a useful guide to further studies on sharks and on other vertebrate groups. Thus, in this paper I have attempted to formulate some tentative and preliminary generalizations concerning the mechanics of cutting compliant materials. Then comes a survey of the teeth of a particular group of predators, three families of sharks, in terms of these preliminary formulations. The approach views the shark teeth in isolation from the complex cranial mechanism (presently under study) that functionally integrates with the teeth. Therefore, adaptive conclusions are minimal, because the evolutionary significance of tooth form cannot properly be assessed outside of an integrated study. However, certain correlations do exist between structural tooth characteristics and mechanics. Slender, smooth-edged (or nearly so) teeth can readily pierce prey, but are of less use in slicing it. Such teeth are typical of the lower jaw dentition in many sharks and, in a few species, they are present in both upper and lower jaws. Usually these slender teeth display a reversed curvature at their tips, so that although most of the tooth's crown is curved inward toward the mouth cavity, the tip is turned outward. This outward turning of the tip can enhance the probability of initial prey penetration, without much compromising the prey-retaining properties of the inward curvature of the greater, more proximal portion of the tooth. Many sharks possess upper teeth with serrations along the edges. The serrations vary from one species to another in coarseness and in distribution along tooth edges. Serrated teeth can make greater use of the available biting forces, and they have a greater cutting effect than do smooth-edged teeth. These latter depend upon friction which, because the coefficient friction is always less than 1.0 (often very much less), can make use of only a fraction of the total bite force. However, smooth tooth blades can pierce prey with less resistance and are less prone to binding (becoming immobilized) in the prey tissue. In many shark species serrations are concentrated along the proximal portions of the tooth crown, where the bases of adjacent teeth are in near contact along the jaw margin. In these regions food can be pressed during feeding, resulting in a binding of the teeth in the prey. Release of the binding must be accomplished by cutting the jammed food, to permit clearance of the prey material so it can slip past the tooth rows. The more prominent serrations in such regions may act to puncture and slice the jammed tissue. It is noted that commercial saws are typically designed in various ways to promote clearance between adjacent saw teeth. The pitch or rake of the teeth of sharks is discussed, as is the overall form of the tooth rows along the jaw margins. The relationship between the distribution of teeth along the jaw margins and surface irregularities of the prey surfaces is also considered.

Life-cycle and functional cytology of the hepatopancreatic cells of Astacus astacus (Crustacea, Decapoda)

Abstract: The hepatopancreas of the freshwater crayfish Astacus astacus was reinvestigated by means of light and electron microscopy using refined techniques of tissue preservation. The results contribute significantly to the solution of controversial problems of the decapod hepatopancreas such as cell genealogy, cellular interdependences, elimination of senescent cells and functional interpretation of the cell types. The three mature cell types of the organ, R-, F- and B-cells, are shown to originate independently from embryonic E-cells which are located at the blind-ending tips of the hepatopancreatic tubules. The less abundant M-cells are supposedly of non-hepatopancreatic origin since they are also found in other epithelia of the digestive tract. Differentiating cells can be assigned at an early stage to one of the three hepatopancreatic cell lines if the ultrastructural appearance and distribution pattern of their organelles are used as distinguishing features. The most sensitive markers are the Golgi bodies which have a cell-specific architecture and secretion product not only in mature cells but also in early differentiating stages. Later conversion of one cell type into another, as has often been proposed in literature, does not occur. Senescent cells are preferably expelled from the epithelium at the junction of neighbouring hepatopancreatic tubules and at the antechamber which links the hepatopancreas to the main digestive tract. Cellular discharge in the antechamber occurs by sliding of the oldest parts of the hepatopancreatic epithelium across a particular antechamber epithelium that was thus far unknown. New ultrastructural findings are described with respect to the absorptive apparatus of nutrient absorbing R-cells, the formation of Golgi vesicles and retrieval of membranes in digestive enzyme synthesizing F-cells, and the involvement of Golgi body and endoplasmic reticulum in the formation of heterophagic vacuoles in B-cells. The discovery of these ultrastructural features enables a more sophisticated functional interpretation of the hepatopancreatic cells of Decapoda.