Body Form, Locomotion and Foraging in Aquatic Vertebrates

Four functional categories are denned to embrace the range oflocomotor diversity of aquatic vertebrates; (1) body/caudalfin (BCF) periodic propulsion where locomotor movements repeat,as occurs in cruising and sprint swimming; (2) BCF transientpropulsion where kinematics are brief and non-cylic, as occursin fast-starts and powered turns; (3) median and paired fin(MPF) propulsion, with very diverse fin kinematics, used inslow swimming and precise maneuver; (4) occasional propulsionor "non-swimming." Specialization in any one of these categoriescompromises performance in one or more of the others, therebyreducing locomotor diversity and hence behavioral options. Foodcharacteristics influencing the role of locomotion in searchand capture are; (1) distribution in space and/or time and (2)evasive capabilities. BCF periodic swimmers take food that iswidely dispersed in space/time; BCF transient swimmers consumelocally abundant evasive items and MPF swimmers consume non-evasivefood in structurally complex habitats. Locomotor specialistsunder-utilize smaller food items in exposed habitats. This resourceis exploited by smaller fish, which are locomotor generalistsbecause of predation pressures. For such locomotor generalists,locomotor adaptations for food capture are of diminished importanceand other adaptations such as suction and protrusible jaws infish are common.     

漫谈鲨鱼

鲨鱼是一类结构完美而特殊的动物,适应能力极强。虽然多数种类1次产仔的数量不多,但由于其后代得到较好的保护,成活率较高。随着人们对鲨鱼认识的不断提高,逐渐发现鲨鱼有很高的利用价值。     

Sharks in danger

Many shark populations are in danger of extinction as a direct result of man's activities. A change in attitude and a greater understanding of species' requirements are needed to prevent further destruction and replenish numbers, thus sustaining trade, fisheries and sport activity.     

Feeding Mechanisms in Sharks

Although many sharks have a rather general vertebrate body plan,they display a number of specializations for feeding that beliethe notion that they are "primitive." These specializationsinclude a battery of highly developed exteroceptive systemssuch as vision, olfaction, acoustico-lateralis sense and electroreception;and a cranial morphology that has been molded into a numberof functionally adaptive forms. These forms result in grasping,sucking, crushing, gouging, cutting and filtering systems offeeding. With relatively few exceptions elasmobranch feedingmechanisms share such features as subterminal or inferior mouths,a dynamic tooth replacement system, hyostylic jaw suspensionand a kinetic, protractile upper jaw. The importance of eachof these components is discussed. The evolution of the highdiversity of mechanical feeding systems in such a small groupof vertebrates has probably been facilitated by the morphologicalsimplicity of the basic feeding mechanism. This radiation wasaccomplished by modifications in jaw length, the length andsupporting angle of the hyomandibula, the size of the gape,dentition and changes in the relative size of the cranial musculature.The evolutionary pattern of shark feeding mechanisms is complex,there being several examples of both parallelism and convergence.A long-jawed, grasping form (similar to, but not identical withChlamydoselachus) is here considered primitive. From a subsequentbenthic sucking and grasping ancestor, similar in many respectsto some living batoids,radiated crushing, ray-like forms; cutting,squaloid forms; and gouging, lamniform and carcharhiniform types.From the latter developed sucking and grasping, or crushingforms such as modern orectolobiforms, triakids and heterodontiformsharks. From several levels (primary crushing, secondary crushingand gouging) there emerged filter-feeding forms representedtoday by mobulids, rhiniodontids and cetorhin.     

Specializations of the Body Form and Food Habits of Snakes

Viperid snakes have stouter bodies, larger heads, and longerjaws than snakes in other families; there are no major differencesbetween the two subfamilies of vipers in these features. A suiteof morphological characters that facilitates swallowing largeprey finds its greatest expression among vipers, but certainelapid and colubrid snakes have converged upon the same bodyform. The number of jaw movements required to swallow prey islinearly related to the size of a prey item when shape is heldconstant. Very small and very large prey are not disproportionatelydifficult for a snake to ingest. Vipers swallow their prey withfewer jaw movements than do colubrids or boids and can swallowprey that is nearly three times larger in relation to theirown size. Proteolytic venom assists in digestion of prey, andmelanin deposits shield the venom glands from light that woulddegrade the venom stores. Ancillary effects of the morphologicalfeatures of vipers, plus the ability to ingest a very largequantity of food in one meal, should produce quantitative andqualitative differences in the ecology and behavior of vipersand other snakes.     

Phyletic Relationships of Living Sharks and Rays

A set of hypotheses are developed for the origin of living sharksand rays and the interrelationships of their major groups, usingsome methods of cladistic analysis to relate groups with sharedderived characters. Comparative studies on living sharks andrays combined with new data on fossil sharks suggests that theliving groups ultimately stem from a common ancestral groupof "neoselachian" sharks with many modern characters. Reinterpretationsof "amphistyly" in modern sharks is presented on new data.     

Human Locomotion

The development of bipedal plantigrade progression is a purely human, and apparently learned, accomplishment. Experimental findings confirm the hypothesis that the human body will integrate the motion of various segments of the body and control the activity of muscles to minimize energy expenditure.Movements which are integrated for this purpose include vertical displacement of the body, horizontal rotation of the pelvis, mediolateral pelvic tilt, flexion of the knee, plantar flexion of the ankle and foot, lateral displacement of the torso and rotation of the shoulder girdle.Raising and lowering the body results in gains and losses of potential energy, and acceleration and deceleration result in gains and losses of kinetic energy. The motions are so co-ordinated that a transfer of energy back and forth from kinetic to potential occurs during walking, which tends to minimize total energy expenditure as well as muscle work.     

Theropod Locomotion

Theropod (carnivorous) dinosaurs spanned a range from chicken-sizedto elephant-sized animals. The primary mode of locomotion inthese dinosaurs was fairly conservative: Theropods were erect,digitigrade, striding bipeds. Even so, during theropod evolutionthere were changes in the hip, tail, and hindlimb that undoubtedlyaffected the way these dinosaurs walked and ran, a trend thatreached its extreme in the evolution of birds. Some derivednon-avian theropods developed hindlimb proportions that suggesta greater degree of cursoriality than in more primitive groups.Despite this, fossilized trackways provide no evidence for changesin stride lengths of early as opposed to later non-avian theropods.However, these dinosaurs did take relatively longer strides—atleast compared with footprint length—than bipedal ornithischiandinosaurs or ground birds. Judging from trackway evidence, non-aviantheropods usually walked, and seldom used faster gaits. Thelargest theropods were probably not as fleet as their smallerrelatives.     

Locomotion and posture in Lagothrix lagotricha

This long-term study of woolly monkey (Lagothrix) locomotor and postural behaviour employs methods identical to those used during a previous study of the locomotion and posture of two species of Ateles, allowing a detailed comparison between the two genera, which are strong competitors in extensive parts of the Amazon basin and northern Andes. As in Ateles, Lagothrix locomotion can be divided into five patterns, based on limb usage: quadrupedal walking and running, suspensory locomotion, climbing, bipedalism (very rare in wild woolly monkeys) and leaping. Lagothrix differs from Ateles primarily in its greater reliance on quadrupedal locomotion during both travel and feeding and on its de-emphasis of the use of suspensory locomotion as compared to Ateles, while the use of climbing and leaping is roughly equal in the two genera. Lagothrix exhibits more generalised (primitive) locomotive behaviour in accordance with its morphology, in comparison to the more specialised Ateles. The generic differences reflect differences in habitat use and particularly foraging ecology.     

Functions of Scales and Photophores in Mesopelagic Luminescent Sharks

In sharks bioluminescence is only known from the family Squalidae. It evolved independently in two out of six squalid subfamilies, Dalatiinae and Etmopterinae. The distribution of photophores was mapped in several species. It is suggested that in the Dalatiinae, which do not school, but migrate vertically, luminescence serves as ventral countershading. The Etmopterinae school and feed close to the bottom. Their luminescence is an aid in schooling. Four different placoid scale patterns are found in luminescent sharks and they allow to accommodation the photophores in the skin.     

Seasonal and Ontogenetic Changes in Movement Patterns of Sixgill Sharks

Background

Understanding movement patterns is fundamental to population and conservation biology. The way an animal moves through its environment influences the dynamics of local populations and will determine how susceptible it is to natural or anthropogenic perturbations. It is of particular interest to understand the patterns of movement for species which are susceptible to human activities (e.g. fishing), or that exert a large influence on community structure, such as sharks.

Methodology/Principal Findings

We monitored the patterns of movement of 34 sixgill sharks Hexanchus griseus using two large-scale acoustic arrays inside and outside Puget Sound, Washington, USA. Sixgill sharks were residents in Puget Sound for up to at least four years before making large movements out of the estuary. Within Puget Sound, sixgills inhabited sites for several weeks at a time and returned to the same sites annually. Across four years, sixgills had consistent seasonal movements in which they moved to the north from winter to spring and moved to the south from summer to fall. Just prior to leaving Puget Sound, sixgills altered their behavior and moved twice as fast among sites. Nineteen of the thirty-four sixgills were detected leaving Puget Sound for the outer coast. Three of these sharks returned to Puget Sound.

Conclusions/Significance

For most large marine predators, we have a limited understanding of how they move through their environment, and this clouds our ability to successfully manage their populations and their communities. With detailed movement information, such as that being uncovered with acoustic monitoring, we can begin to quantify the spatial and temporal impacts of large predators within the framework of their ecosystems.     

Locomotion of Spirilla

The hydromechanics of spirilla locomotion is analyzed by considering the balance of both rectilinear and angular momenta of the surrounding viscous fluid which is otherwise at rest. The physical model of Spirillum adopted for the present analysis consists of a rigid helical body with flagella attached to both ends of the helix. The motion is supposed to be activated first by the polar flagella, both rotating in the same sense, thus causing the helical body to rotate in the opposite sense in angular recoil, which in turn pushes the body forward in response to the balance of linear momentum of the surrounding fluid. The sweeping back of the polar flagella during forward motion is ascribed to a certain bending flexibility of the flagella and of their conjunction with the body. Based on this model some quantitative results for Spirillum movement are predicted, and are found to be consistent with existing experimental data.