Tricladida Research Articles

Spatial localization ability of planarians identified through a light maze paradigm.

Spatial localization ability is crucial for free-living animals to fit the environment. As shown by previous studies, planarians can be conditioned to discriminate directions. However, due to their simplicity and primitiveness, they had never been considered to have true spatial localization ability to retrieve locations of objects and places in the environment. Here, we introduce a light maze training paradigm to demonstrate that a planarian worm can navigate to a former recognized place from the start point, even if the worm is transferred into a newly produced maze. This finding identifies the spatial localization ability of planarians for the first time, which provides clues for the evolution of spatial learning. Since the planarians have a primitive brain with simple structures, this paradigm can also provide a simplified model for a detailed investigation of spatial learning.

Squid sucker teeth and cocoons of a terrestrial flatworm: amino acid content of two nano-structurally identical tissues in phylogenetically unrelated taxa

An extraordinary micro-structural similarity between squid sucker teeth and the egg shell of a terrestrial planarian worm has been reported, but to date only the amino acid content of the squid sucker tooth has been available. This prompted us to analyse the amino acid content of the planarian egg shell. Although both share an absence of detectable chitin and metal ions and both possess relatively high amounts of the amino acids GLY and HIS, the planarian egg shell is considerably richer in GLU, LYS and ASP. Most dramatic was the difference in TYR, which was the second most abundant amino acid in the squid, but hardly featured at all in the planarian egg shell. In the light of these new findings the different functional roles that the structures in question play in the lives of the two taxa are discussed. An EDS-analysis revealed clear C, N, and O peaks and additional very small peaks less than 0.1w% suggesting the presence of one or both S and Cl.

NEW PLANARIANS (TURBELLARIA, TRICLADIDA) FROM ISRAEL AND LEBANON

ABSTRACT Two new species of freshwater triclads belonging to the Dugesia gonocephala species group are described, D. golanica n.sp. from northern Israel and D. libanica n.sp. from Becharre in northern Lebanon. D. golanica is characterized by a large, solid, bilobed adenodactyl positioned dorsally and to the right of the pointed penis papilla, while D. libanica has a large, solid, conical-shaped adenodactyl situated dorsally and to the right of the asymmetrical, finger-shaped penis papilla. These two species are clearly related to each other and to D. iranica (Livanov) from Iran and Turkey.

The effects of starvation on the planarian worm Polycelis tenuis Iijima.

Employing a combination of microscopical, biochemical and autoradiographic techniques, the primary effects of starvation on adult polycelis tenuis have been studied. Over a five week period of starvation there is on average a 32% decrease in the size of the organism. This decrease is contributed to by a reduction in mitosis and an increase in cell shrinkage autolysis and death. During starvation (following a sharp rise in RNA synthesis) there is a distinct sequence of events; four peaks of acid phosphatase activity can be resolved. The first is associated with the immediate response of the gastrodermis to feeding; the second (after 6 to 7 days) with increased autophagy and dedifferentiation in the gland cells and with muscle lysis of cells. The third peak (after 14 to 15 days) is contributed to largely by the lysis of cells in the gut and the fourth peak (after 25 to 26 days) is caused by an extensive lysis of the reproductive system. Fine structural changes involving increased intracellular vacuolation, autophagy, crinophagy, atrophy of muscle, increased intercellular space and loss of basement membrane matrix have been related to changes in enzyme pattern. Nerve cells appear unchanged throughout the first five weeks of starvation. Pigment and gland cells loose their characteristic granules, dedifferentiate and become morphologically similar to the undifferentiatied neoblasts. Dedifferentiation and the mechanisms involved in the survival of starvation are discussed.

A Mechanism of Action of Neurotransmitters on the Regeneration of the Planarian WormDugesia tigrina.Role of Acetylcholine as a Negative Feed-back

By means of histochemical and pharmacological analysis it is shown that acetylcholine has an inhibitive effect on regeneration in the planaria Dugesia tigrina. It seems that serotonin and adrenaline on the one hand, and acetylcholine on the other hand, play a role in a mechanism of regulation in which the latter plays a role in a negative feed-back process.

A Mechanism of Action of Serotonin and Nor-Adrenaline on the Regeneration of the Planarian Worm Dugesia tigrina

On the basis of autoradiographical investigations with tritiated serotonin or N adrenaline and histochemical studies, it was possible to describe a mechanism of cell migration in which these biogenic amines play a role in the presence of acid mucopolysaccharides and collagen. They may also have a role by provoking the formation of necrotic areas in which the mucopolysaccharides appear.

Protective Effect of 5-hydroxytryptophan and α-Methyl DOPA against the Inhibitive Effect of Lithium on the Cicatrisation and the Regeneration of the Planarian WormDugesia tigrinaand the HydroidClava squamata

The lithium ion has an inhibitive effect on cicatrisation and regeneration of Dugesia tigrina and Clava squamata while 5-hydroxytryptophan and α-methyl DOPA have a protective one. It seems that these substances as well as the biogenic amines 5-hydroxytryptamine and N-adrenaline play a role during the cell migrations which underly morphogenesis.

Morphogenetic Actions of 5‐hydroxytryptamine and Some Analogous Substances on the Regeneration of the Planarian Worm Dugesia tigrina

AbstractThe effects on regeneration of serotonin and analagous substances such as tryptamine, DMT, bufotenine, melatonin, auxin and gramine were studied on small pieces of D. tigrina. By comparison with results obtained in previous works with DOPA, α methyl DOPA and noradrenaline, and also with substances of the series of tetrahydrocannabinol it is shown that the normal morphogenetic action of the neurohormone is dependant of the presence of a free hydroxyl on a flat ring (phenol or indole) and of a free amine on the lateral chain of the molecule. Essays to detect the mechanism of the morphogenetic action did not allow to give any clear conclusion.

Electron microscopic and optical diffraction studies of negatively stained axial units of certain platyhelminth sperm

Microtubular elements of frog lung-fluke (Haematoloechus medioplexus) and Dugesia tigrina (common planarian worm) sperm were negatively stained and examined by optical diffraction using a helium-neon laser as a light source. The complex central or core element of the axial unit shows a 650 Å repeat along its outer sheath, which is comprised of two helically wound ribbons, and the gyres of the helix are inclined 45°–50°. Doublet tubules of lung-fluke sperm have a typically protofibrillar configuration along their length, while the terminal portion of those of Dugesia sperm have a helical substructure with an 80 Å repeat, and the gyres are inclined 15°–25°. In fundamental substructure, the helical region of doublet tubules of Dugesia is remarkably similar to the cortical singlet microtubules of lung-fluke sperm.

AN ORIENTATIONAL RESPONSE TO WEAK GAMMA RADIATION

1. The common planarian worm, Dugesia dorotocephala, displays a significant orientational response to increase in Cs137 gamma radiation when the increase is no greater than 6 times background.2. The worms are able to distinguish the direction of the weak gamma source, turning away from it, whether it is presented on the right or left side. The response sign is, therefore, the same as that of the response of these negatively phototactic worms to visible light.3. There is a clear compass-directional relationship of the responsiveness to the experimental gamma radiation. A conspicuous negative response is present when the worms are traveling northward or southward in the earth's field with the gamma change in an east-west axis. No statistically significant mean turning response to the gamma radiation is found when the worms are traveling eastward or westward in the earth's field with the gamma change in a north-south axis.4. The previously observed annual fluctuation in the character of the monthly orientati...

Changes in Deoxyribonucleic Acid and Total Nitrogen in Planarian Worms during Starvation

ABSTRACT The changes in total nitrogen and in deoxyribosides (DNA) have been followed during starvation of the planarian worm, Polycelis nigra. It was found that total nitrogen content after 60 days had been reduced to about 14 per cent, of its initial value. It is not possible to exclude with certainty the occurrence of any DNA loss, but it is clear that the loss, if any, is much smaller than the loss in nitrogen. The implications of these results for previous morphological investigations of the effects of starvation on planarian worms are discussed.

Nutritional Value for Planarian Worms of Vitamin Depleted Mammalian Tissues.

The planarian worm has proved itself a useful instrument for demonstrating changes in the composition of mammalian tissues resulting from changing conditions in the animal as a whole. (Bahrs.) This research was undertaken to ascertain what the planarian worm could reveal as to modification of the nutritional value of tissues derived from animals fed diets with and without the recognized vitamins. Guinea pigs and white rats were used to furnish the tissues. The animals received standard basal diets for a month or more. (For diets used, see Table I.) When definite signs of vitamin A deficiency and polyneuritis were apparent in the respective groups of rats, the planarian worm experiments were started. Guinea pigs showed definite signs of scurvy before their tissues were used in the planarian worm experiments. The guinea pigs maintained upon the vitamin D-free diet, of course, appeared entirely normal when their tissues served for the planarian worm diets. Each group of planarian worms (probably Planaria agilis) consisted of 30 newly regenerated worms, all of the same length. Experimental groups were kept in finger bowls of heat-sterilized river water, and maintained at a constant temperature, 23°C-24°C. The worms were fed twice per week on thoroughly mashed tissues of freshly killed guinea pigs or rats, taken from groups fed the specified vitamin diets. They always ate the tissues well. Spleen, lung, liver, heart and in one case kidney cortex were the tissues used.

The Growth-Promoting Power of Egg for Planarian Worms

It has been previously demonstrated by us that an exclusive diet of egg albumin is not capable of promoting growth in Planaria maculata. Although the food is well taken, the worms show progressive decrease in size throughout the experimental period. Upon an exclusive diet of egg yolk the worms may maintain or increase their size for a period of 2 or 3 weeks, but after that time their length becomes progressively less. We have confirmed these results repeatedly with the species of planarian worm (Planaria agilis?) which we are at present using, and have found in addition that a combination of egg yolk with egg albumin produces a diet decidedly superior to either substance used alone. Each group in an experimental series consisted of 30 worms of equivalent size which were fed ad lib. twice a week on the experimental diets. The total length of the worms was found at the beginning of the experiment and at its conclusion and the proportional increase in length was determined. In one experiment of 2 weeks duration kept at room temperature, the group of 30 worms fed upon egg yolk made a gain in total length of 3.9%, while those fed upon a combination of equal parts of egg yolk and albumin gained 20.2% in total length. In another series incubated at a temperature of 27° C. over a 2 week period, egg yolk diet produced an increase in total length of 32%, while a diet of blended egg yolk and albumin in equal parts gave an increase in total length of 51.5%. In a third series pastes were made of 15% liver pulp and 45% starch paste (10%) with the addition of 40% egg yolk or egg albumin or a mixture of equal parts egg yolk and albumin.

Variations in the Growth-Promoting Power, for Planarian Worms, of Digestive Mucosa of Rabbit.

Through the use of the planarian worm as the test animal, according to the method developed by R. Wulzen,1 I have found that different regions of the digestive mucosa of the rabbit cause marked variations in growth when fed to planarian worms.According to this method, the worms were accurately measured at the beginning and at the end of the experiment, the result being the total gain in millimeters of the experimental group. Each experimental group consisted of 30 worms, 6, 7 and 8 mm. in length, and had an average total length of 200 mm. at the beginning of an experiment. Repeated measurements have shown that the total length of an experimental group can be duplicated with no greater error than 1%. The worms were fed twice a week upon portions of the digestive tract from freshly killed rabbits and each portion was placed in the respective bowl in such a manner that the worms could feed only upon the mucous membrane. Six parts of the digestive tract were used, as follows: the posterior half of the oesopha...

Insects and Flowers

THE more definite relationships which subsist between organism and organism, whether it be between the algal and fungal partners of the lichen complex; between the forest tree, the orchid, or the gentian and their respective mycorrhiza; or between the Plan-arian worm Convoluta Roscoffensis and the alga Carteria, all alike bring home to one the delicacy of biotic relationships and the efficiency of whatever be the modus operandi of the evolutionary process. The relation between entomophilous flowers and the insects through the agency of which their pollination is effected constitutes no less remarkable an example of mutual specialisation than those already cited. It is scarcely surprising that the subject has attracted the attention of a considerable number of investigators from the observational period rendered notable by the publications of Koelreuter (1761), Delpino (1867), Mueller (1883), Darwin (1876), Kerner (1876), and Knuth (1898), to the experimental period of modern times initiated by the extensive researches of Plateau (1877-1910), and so ably followed by Lubbock (1882), Frisch (1913-19), Knoll (1919-22), and the work of Clements and Long, which has prompted and is the basis of the present article.1

On the oxygen consumption rate parts of the chick embryo and fragments of the earthworm

In the last few years a considerable number of observations have been made on the respiration rate of regenerating worm fragments, the fertilized egg cell, and growing parts of the embryo. Child (1) as the result of many years’ work in this field has recently put forward an interesting conception of the animal and plant life cycle. In this theory for the first time, an attempt is made to account for development on a straightforward physiological basis. While this hypothesis contradicts many of our current views regarding the significance of the germ cells, reproduction, and inheritance, it certainly brings together under one head more facts than any other theory. Child claims he can demonstrate in all growing organisms certain axial gradients of metabolic activity, which control the appearance of morphological structure. Thus, in Planarian worm fragments the frequency with which the head is regenerated, is a direct function of the axial gradient, which is highest in the head and lowest in the tail region of the worm. To demonstrate the presence of these gradients Child employed weak solutions of KCN, K 2 Mn 2 O 8 and other chemicals. The susceptibility of the living tissues to the action of these agents in a definite manner is taken as evidence of their presence. The question arises do these agents demonstrate gradients of real high and low metabolic activity—or something different? To test this point a large number of determinations have been carried out by Hyman’s (5) on the oxygen consumption of Planarian fragments. The Winkler titration method was used. The results obtained seem to bear out Child’s conclusions based on the direct and indirect susceptibility method in every detail. There are, however, serious objections to the use of the Winkler method of estimating the oxygen consumption of living tissues. In the experiments described in the following paper, I have thought it worth while to reinvestigate the question, using the more direct and accurate manometer method. The following tables give the results of a number of experiments in which the oxygen consumption of head and tail portions of various stages of the chick embryo and the earthworm have been determined in this way. In these measurements rigorous care was taken to avoid sources of error, and every means was adopted of obtaining readings as accurate as possible under the experimental conditions.

An Addition to the British Fauna: (Rhynchodemus Scharffi)

ONE of my students, Mr. G. D. Morison, has brought me a very interesting Planarian worm which he found this morning under rotten wood in a coal-shed in a garden at Chiswick. This is the fourth specimen which he has found in the same place, where they were associated with slugs, upon which they may have been feeding. The other three specimens were found a week ago. A living specimen was measured up to 6 cm. in length when crawling. In this condition the worm is very slender; when contracted it is naturally a good deal thicker and exhibits a transverse wrinkling. The colour in life is usually bright yellow, without pattern, but with a dusky anterior tip bearing the two small eyes close to the extremity. Mr. Morison tells me, however, that one specimen was salmon-pink.

A New British Land Planarian

MR. MORISON'S discovery of the interesting planarian worm (Rhynchodemus Scharffi) in a garden at Chiswick, as described in Prof. Dendy's letter in NATURE of May 5 (p. 298), shows that this species has a wider range than was at first anticipated. As Prof. Dendy states, it was first discovered in a Dublin garden in 1894, but since that date it has turned up in the Royal Botanic Gardens at Glasnevin, Dublin. I thought it had probably been introduced into both localities, but that nevertheless it was indigenous to Ireland.

Note on my former communication on a supposed new species of planarian worm

Note on my former communication on a supposed new species of planarian worm

Note on a species of Planarian worm hitherto apparently not described

Note on a species of Planarian worm hitherto apparently not described