Ecomorphological comparisons of sagittae in Mullus barbatus and M. surmuletus

For both Mullus barbatus and M. surmuletus , the relationship between sagitta area (O), sulcus acusticus area (S) throughout postlarval growth was characterized by their negative allometric growth. The adjusted mean S: O ratio differed between the two species. This may be associated with the difference in size and shape of the sagittae, a difference in somatic growth, and differences in food and spatial niches. The inner ear of Mullus cannot be considered as specialized and the interaction of stimuli detected by the sensory barbels and the inner ear together could be a compensatory mechanism that helps in the food search.     

Morphological variation of hypaxial musculature in salamanders (Lissamphibia: Caudata)

Despite the acknowledged importance of the locomotory and respiratory functions associated with hypaxial musculature in salamanders, variation in gross morphology of this musculature has not been documented or evaluated within a phylogenetic or ecological context. In this study, we characterize and quantify the morphological variation of lateral hypaxial muscles using phylogenetically and ecologically diverse salamander species from eight families: Ambystomatidae (Ambystoma tigrinum), Amphiumidae (Amphiuma tridactylum), Cryptobranchidae (Cryptobranchus alleganiensis), Dicamptodontidae (Dicamptodon sp.), Plethodontidae (Gyrinophilus porphyriticus), Proteidae (Necturus maculosus), Salamandridae (Pachytriton sp.), and Sirenidae (Siren lacertina). For the lateral hypaxial musculature, we document 1) the presence or absence of muscle layers, 2) the muscle fiber angles of layers at mid‐trunk, and 3) the relative dorsoventral positions and cross‐sectional areas of muscle layers. Combinations of two, three, or four layers are observed. However, all species retain at least two layers with opposing fiber angles. The number of layers and the presence or absence of layers vary within species (Necturus maculosus and Siren lacertina), within genera (e.g., Triturus), and within families. No phylogenetic pattern in the number of layers can be detected with a family‐level phylogeny. Fiber angle variation of hypaxial muscles is considerable: fiber angles of the M. obliquus externus range from 20–80°; M. obliquus internus, 14–34°; M. transversus abdominis, 58–80° (acute angles measured relative to the horizontal septum). Hypaxial musculature comprises 17–37% of total trunk cross‐sectional area. Aquatic salamanders show relatively larger total cross‐sectional hypaxial area than salamanders that are primarily terrestrial. J. Morphol. 241:153–164, 1999. © 1999 Wiley‐Liss, Inc.     

Innervation zones location and optimal electrodes position of obliquus internus and obliquus externus abdominis muscles

The assessment of abdominal muscles has became popular in recent years because the study of “core muscles” is now considered a pivotal approach for a number of fields. The purpose of this study was to describe the innervation zone (IZ) locations and optimal electrode sites in two core muscles: the obliquus externus (OE) and the obliquus internus (OI) abdominis muscles. Twenty healthy male subjects were recruited and the IZ location was studied during a submaximal isometric contraction using multichannel surface EMG.The optimal electrode position for OI was found to be 2 cm lower the most prominent point of the anterior superior iliac spine, just medial and superior to the inguinal ligament. The optimal electrode position for OE was found to be 14 cm from the median line, lower the level of 1 cm above umbilicus, parallel to the line extending from the most inferior point of the costal margin to the opposite pubic tubercle (almost 45° with respect to the median line).Findings showed that for OI and OE muscles it is possible to provide indications for a muscle belly area suited for proper positioning of at least an electrode pair.     

经豚鼠下鼓道口记录耳蜗电图

豚鼠是听觉机能研究最常应用的动物,在其颅骨的鼓泡上,有一卵圆形的小孔,称为下鼓道口,在此插入电极,可抵鼓岬部,能够很好地记录出耳蜗电图。此方法简便、可靠,不需要打开乳突,是从鼓岬部记录耳蜗电图的一种新途径,在听觉机能研究及生理学实验教学中具有广泛的应用价值。     

Organs of hearing and equilibrium during ontogenesis of mammals

The peripheral part of acoustic analyzer was studied during pre-and postnatal development of mammals. The main trends of structural evolution of the outer, middle, and inner ear were followed in representatives of different ecological groups during postnatal development. The use of ecologomorphological approach made it possible to establish that specific structural features of the hearing organ in different mammals are determined by adaptation to specific acoustic properties of the environment. It was shown that morphofunctional adaptations directed at optimization of acoustic sensitivity in different environmental conditions were leading in the hearing organ evolution. Comparative-embryological studies of the peripheral part of acoustic system made it possible to determine the stages of formation of individual structures and establish general patterns of prenatal development of the organs of hearing and equilibrium in different mammals.     

Changes in otolith area: sensory area ratio with body size and depth

Synopsis The ratio between the sensory areas of the sulcus acusticus and the sagittal otolith (S : O ratio) in the species Merluccius capensis and M. paradoxus was analyzed using a digital image processing system. Sagittal growth in both species is negatively allometric with respect to total fish length but is more negative in the deeper-dwelling species, Merluccius paradoxus. In contrast, the sulcus acusticus undergoes a relative increase in size, that is, the S : O ratio increases with fish length. There was a clear relationship between the increase in the S : 0 ratio and depth.