Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Beak”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1984

[Biomechanics of the skull and the beak in Ramphastos (Ramphastidae, Aves) I. Description of anatomical elements].

The different cranial kinetic systems described in Birds are limited in Ramphastos by the dorsal and backward position of the nostrils, the shape of the fronto-nasal suture, the lateral fit-in between nasal, lacrymal and frontal bones, and the divergent directions of the 2 otic processes of the quadrate, 5 ligaments joint the posterior skull elements to the quadrate and the mandible. Small sesamoid bones strengthen the external jugo-mandibular ligament in its retro-articular portion. The nomenclature of the aponeuroses is not useful by itself to compare the organizations and homology of the diverses muscular layers in the different birds groups. The differences observed in the relative position of the muscular bundles have to be related to the shape and particular relationships between skeletal structures. We have to consider the osteo-muscular systems as a whole and analyse them from a functional viewpoint.

Animals↗
PubMed1994

Organization of 'feeding circuits' in birds: pathways for the control of beak and head movements.

Two sensorimotor 'feeding' circuits and their descending projections are described in the mallard and compared to those in the pigeon. The tactile/trigeminal circuit consists of a pattern of reciprocal connections of the nucleus basalis with the overlying parts of the frontal neostriatum (Nf) and hyperstriatum ventrale (HV). The dorsal zone of Nf projects to the sensorimotor part of archistriatum, to the paleostriatum augmentatum (PA) and to the lateral lobus parolfactorius. A comparable pattern of visual connections has been found: the ectostriatum has reciprocal connections with the intermediate neostriatum (Ni) and HV. Here, too, Ni has projections to archistriatum and probably to PA. Archistriatum is the source of a large descending pathway with, among others, substantial projections to the parvocellular reticular formation of the brain stem. This provides a pathway for telencephalic control of premotor systems of jaw, tongue and neck muscles. The paleostriatal complex is the source of the ansa lenticularis with projections to the nucleus spiriformis lateralis and the nucleus tegmenti pedunculopontinus, both projecting to the deep tectum. This pathway may be important for the control of body position. In the mallard, it includes a substantial trigeminal component that has not been found in the pigeon.

Animals↗
PubMed1989

Complex spermatozoon of the live-bearing half-beak, Hemirhamphodon pogonognathus (Bleeker): ultrastructural description (Euteleostei, Atherinomorpha, Beloniformes).

The spermatozoon of Hemirhamphodon pogonognathus shows modifications that are frequent though not obligate in internally fertilizing sperm, notably elongation of the nucleus and extension of the mitochondria of the midpiece as an elongate sheath around the proximal region of the axoneme. These similarities to poecilid and jenynsid sperm are considered homoplasic. As in the mature sperm of all but one investigated teleost, an acrosome is absent. The elongate, blade-shaped, electron-dense nucleus has a mean length of 3.2 microns; its basal implantation fossa, less than one-tenth of the length of the nucleus, houses the anterior half of the distal and only centriole (of triplet construction with satellite rays), a centriolar plug, and a mass connecting the centriole to the wall of the fossa. A unilateral putative centriole adjunct is present. The anterior region of the axoneme is surrounded by a mitochondrial sleeve, and internal to this, separated by a cisterna, by a submitochondrial sleeve. The mitochondrial sleeve unites posteriorly with the submitochondrial sleeve. Between the submitochondrial sleeve and the axoneme is a space, the cytoplasmic canal, that is open to the exterior posteriorly. The discrete, cristate mitochondria, in their sleeve, are unique in investigated atherinomorph sperm in being bilateral, grouped on only two opposing sides of the axoneme, with an arc-shaped "intermitochondrial link" between. The 9 + 2 flagellum is unique for the Animalia in having 23 radial subplasmalemmal rods, repeated longitudinally (periodicity 0.025 microns) in a quasicrystalline array. Internal fertilization is deduced to have arisen in the Exocoetoidei independently of that in the Cyprinidontiformes.

Animals↗
PubMed2002

Win-shift and win-stay learning in the short-beaked echidna (Tachyglossus aculeatus).

Numerous previous investigators have explained species differences in spatial memory performance in terms of differences in foraging ecology. In three experiments we attempted to extend these findings by examining the extent to which the spatial memory performance of echidnas (or "spiny anteaters") can be understood in terms of the spatio-temporal distribution of their prey (ants and termites). This is a species and a foraging situation that have not been examined in this way before. Echidnas were better able to learn to avoid a previously rewarding location (to "win-shift") than to learn to return to a previously rewarding location (to "win-stay"), at short retention intervals, but were unable to learn either of these strategies at retention intervals of 90 min. The short retention interval results support the ecological hypothesis, but the long retention interval results do not.

Animals↗