THE ETHOLOGY OF THE SYNAPTID HOLOTHURIAN, OPHEODESOMA SPECTABILIS

1966 ◽  
Vol 44 (3) ◽  
pp. 457-482 ◽  
Author(s):  
Michael Berrill

Opheodesoma spectabilis commonly occurs in aggregations in the alga Sargassum echinocarpus, a source of shade from which it scrapes adhering detritus, and which allows the dense populations necessary for efficient spawning. The animal is photonegative and moves away from a strong light source. Ocelli provide information on the direction and intensity of sunlight. Statocysts, aided by tactile sensitivity, maintain dorsoventral equilibrium."They may also inhibit unwarranted rapid locomotion. The animal shows no gravity orientation. All sensory receptors are most concentrated in the region of the tentacle crown, and their interaction in controlling the animal's reactions implies considerable central integration of stimuli. The three primary muscular activities are the rhythmic contraction and extension of the tentacles, used in feeding and for slow locomotion; peristalsis of the body wall, involved in rapid locomotion; and the contraction, bending, and reextension of the anterior portion of the body. These activities may vary in rate and amplitude and occur independently or in any combinations. Their initiation and coordination are under central nervous control. Opheodesoma spectabilis has a diurnal rhythm of behavior, reaching an activity peak during the early evening hours and apparently directly dependent on changes in light intensity. Spawning occurs during the summer months.

1948 ◽  
Vol 22 (3-4) ◽  
pp. 219-225 ◽  
Author(s):  
Satya Narayan Singh

The writer in 1934 briefly described this nematode which was collected from the common musk-shrew at Hyderabad Deccan, creating for its reception the new genus and species Gastronodus strasseni. The following account deals with the anatomy of the worm and the close relationship which exists between the genera Gastronodus Singh and Spirocerca Railliet and Henry, 1911.This worm is of common oċcurrence in the musk-shrew, Crocidura caerulea, at Hyderabad and it forms largo nodules on the stomach walls of the host. In certain cases smaller nodules were also found in the mesentery. These are medium sized worms and when freshly extracted appear blood red in colour. The body is coiled and generally flexed at the extremities. In males and young adult females the body is of almost uniform diameter with blunt anterior and posterior ends, whereas in fully grown and gravid females the posterior 2/3 of the body is distinctly thicker than the anterior portion. The males are slender and smaller than the females. The cuticle is thick and bears fine transverse striations which are set quite close together. Irregular transverse wrinkles are also present on the body wall. The cervical papillae are located at the level of the nerve-ring and have the appearance of fine bristles.


1951 ◽  
Vol 28 (1) ◽  
pp. 51-56
Author(s):  
G. P. WELLS ◽  
ELINOR B. ALBRECHT

1. Arenicola ecaudata differs not only in structure, but in mode of life, from A. marina. Our results indicate that there are also great differences in behaviour physiology. 2. The brainless isolated extrovert of ecaudata traces a continuous, or nearly continuous, background of activity, upon which prominent spells of vigorous rhythmic contraction appear at intervals of the order of 30-40 min. Similar spells are sometimes shown by the corresponding preparation from marina, whose characteristic f cycle can be regarded as produced by the organization of the back-ground activity of ecaudata into vigorous and regularly spaced outbursts. 3. There is little evidence of a pacemaker role of the oesophagus in ecaudata. If the movements of the extrovert and body wall are simultaneously recorded, they generally exhibit correlated outbursts of variable and fluctuating pattern, and very unlike the behaviour of the brainless extrovert. Similar outbursts are shown by the body wall after severance of its connexion with the extrovert. They are probably of central nervous origin.


Author(s):  
J. A. C. Nicol

Some preliminary observations on luminescence in polynoid worms have been presented in a previous paper (Nicol, 1953). These animals produce light in scales (elytra) which cover the dorsal surface of the body. The source of the light lies in a layer of unicellular epithelium on the lower surface of the scale. Histologically, this tissue consists of columnar cells (photocytes), characterized by the presence of coarse eosinophilic granules in the cytoplasm. The nervous supply of the elytrum derives from a nerve trunk which ascends the stalk or elytrophore and proceeds to a ganglion in the centre of the scale. From this ganglion nerves radiate peripherally and proceed to the photocytes, and to sensory receptors on the dorsal surface and at the margin of the scale (Bonhomme, 1942).


1997 ◽  
Vol 17 (4) ◽  
pp. 617-624 ◽  
Author(s):  
Philippe Moerman ◽  
Chris Van Geet ◽  
Hugo Devlieger
Keyword(s):  

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 483-498
Author(s):  
J Ahnn ◽  
A Fire

Abstract We have used available chromosomal deficiencies to screen for genetic loci whose zygotic expression is required for formation of body-wall muscle cells during embryogenesis in Caenorhabditis elegans. To test for muscle cell differentiation we have assayed for both contractile function and the expression of muscle-specific structural proteins. Monoclonal antibodies directed against two myosin heavy chain isoforms, the products of the unc-54 and myo-3 genes, were used to detect body-wall muscle differentiation. We have screened 77 deficiencies, covering approximately 72% of the genome. Deficiency homozygotes in most cases stain with antibodies to the body-wall muscle myosins and in many cases muscle contractile function is observed. We have identified two regions showing distinct defects in myosin heavy chain gene expression. Embryos homozygous for deficiencies removing the left tip of chromosome V fail to accumulate the myo-3 and unc-54 products, but express antigens characteristic of hypodermal, pharyngeal and neural development. Embryos lacking a large region on chromosome III accumulate the unc-54 product but not the myo-3 product. We conclude that there exist only a small number of loci whose zygotic expression is uniquely required for adoption of a muscle cell fate.


1985 ◽  
Vol 260 (22) ◽  
pp. 12228-12233 ◽  
Author(s):  
H Takahashi ◽  
H Komano ◽  
N Kawaguchi ◽  
N Kitamura ◽  
S Nakanishi ◽  
...  

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.


Parasitology ◽  
1965 ◽  
Vol 55 (1) ◽  
pp. 173-181 ◽  
Author(s):  
D. L. Lee

The cuticle of adults ofNippostrongylus brasiliensishas been described using histological, histochemical and ultrastructural techniques.The cuticle has the following layers: an outer triple-layered membrane; a single cortical layer; a fluid-filled layer which is traversed by numerous collagen fibrils; struts which support the fourteen longitudinal ridges of the cuticle and which are suspended by collagen fibrils in the fluid-filled layer; two fibre layers, each layer apparently containing three layers of fibres; and a basement lamella.The fluid-filled layer contains haemoglobin and esterase.The muscles of the body wall are attached to either the basement lamella or to the fibre layers of the cuticle.The mitochondria of the hypodermis are of normal appearance.The longitudinal ridges of the cuticle appear to abrade the microvilli of the intestinal cells of the host.Possible functions of the cuticle are discussed.I wish to thank Dr P. Tate, in whose department this work was done, for helpful suggestions and criticism at all stages of this work, and Mr A. Page for technical assistance. I also wish to thank Professor Boyd for permission to use the electron microscope in the Department of Anatomy.


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