Newt Larvae Research Articles

The desmosome: fine structural studies with freeze-fracture replication and tannic acid staining of sectioned epidermis.

Desmosomes of larval and post-metamorphic newt epidermis have been studied by freeze-fracture replication both with and without prior glutaraldehyde fixation. Characteristic particles of a diameter (70-130 A) similar to that of typical membrane associated particles are found clustered on the exposed internal faces of adherent desmosomal membranes. They remain attached to the B-face in unfixed material, but occupy the desmosomal A-face after fixation. Membrane associated particles of nondesmosomal surfaces are found predominantly on the A-face in both fixed and unfixed epidermis. Suitably oriented replicas of unfixed desmosomes reveal profiles of apparent fine filaments extending from the region of tonofilament loops through the desmosomal plaque to traverse the cytoplasmic leaflet of the plasmalemma. They can be traced onto the B-face. Their position correlates to fine linear profiles noted in tannic acid/glutaraldehyde-fixed and sectioned desmosomes. The possibility that these represent a mechanism for anchorage of tonofilaments to the plaque and to the membrane is discussed. These and other fine structural features are compared and contrasted to the properties of hemidesmosomes described in the preceding report.

Integumentary Effects of Prolactin in the Lower Vertebrates

Prolactin was first known as a stimulator of mammary secretion. It has since been found to induce secretion in the sebaceous glands of the mammal as well. It likewise stimulates secretory activity in the avian cropsac and in the mucous glands of fishes and of amphibians when thyroid hormone is also present. Prolactin has mitogenetic effects on a variety of structures including the amphibian stratum corneum and induces growth of the tail fin in larval anurans and in both larval and adult newts. Prolactin causes the regression of cornified tubercles in the skin of the newt yetsynergizes with androgen in the presence of the thyroid hormone to induce the formation of keratinized nuptial pads. A similar synergism between prolactin and steroidal hormones produces avian incubation patches. There is indication that prolactin may facilitate the growth of hair in mammals but detailed information is lacking. Effects on pigmentation are attributed to prolactin in two fishes.

The diet and dentition of Smooth newt larvae (Triturus vulgaris)

This paper describes the dentition and diet of a population of Smooth newt larvae. The development of the teeth and their increase in number with age are discussed. The number of teeth on all five tooth‐bearing bones appear to be controlled by a single developmental system. Young larvae eat chydorids, daphniids and cyclopoid copepods; after they reach a total length of about 15 mm, chironomid larvae comprise the greater part of the diet. In the study population, ostracods were not eaten, and cannibalism was not observed. There was no tendency for larger larvae to select larger individuals of a given species of prey.It is suggested that the exponential rate of growth in weight forces larvae of more than about 15 mm total length to switch from passive to active hunting. This enables them to catch larger prey, at the expense of incurring a higher rate of mortality. This increase in mortality is associated with a reduction in the variation of morphological characters, including dentition, which is thought to be caused by natural selection. The function of different components of the dentition are discussed. It was found that larvae of a given age which have more teeth than average have in their guts fewer prey than average, and an explanation is suggested.

The Reduction of Morphological Variation in Natural Populations of Smooth Newt Larvae

The Reduction of Morphological Variation in Natural Populations of Smooth Newt Larvae

Stimulation of lens regeneration from the newt dorsal iris when implanted into the blastema of the regenerating limb

Dorsal iris from the eyes of adult Notophthalmus viridescens was transplanted into the blastema of regenerating limbs, subcutaneously in the limb or shoulder region, into the dorsal fin of larval newts and into the hindbrain of larval Ambystoma maculatum. The iris implants into the blastema regenerated lens vesicles or lenses with fibers in 40–75% of the cases. Multiple lenses were found in a few instances. No lenses developed from iris implants into the dorsal fin. Twenty percent of subcutaneous implants of iris formed lenses or lens vesicles, but lens regeneration from implants into the brain occurred only rarely. Denervation of the limb at the time of iris transplantation into the blastema greatly reduced the number of lenses regenerated. Studies on nerve fiber distribution in dorsal fin, subcutaneous areas, and denervated and innervated regenerating limbs, using the Bodian method, showed a general correlation between density of nerve fibers in the implant site and the incidence of lens regeneration from iris implants into that site. These results provide some evidence for a trophic action of nerve fibers on lens regeneration from the iris.

The control of alternating coordination of limb pairs in the newt (Triturus vulgaris).

Various lengths of the body includingthe limb-moving spinal cord segments of young newt larvae were grafted into the side of hosts of the same age. Neural connections did not develop between hosts and

Response of newt larvae to x-irradiation.

Graded doses of from 200 to 2000 rad of x-rays were administered to premetamorphic Taricha torosa larvae of various ages. General stunting, specific malformation, pigmentary damage, and a very shortened life-span occurred at all doses. There is an age-dependent dose response; some animals exposed to 200 and 600 rad survived to complete metamorphosis. Evidence is presented supporting a view that postmetamorphic epidermal melanocytes may be derived largely by division of an unpigmented progenitor cell type.

The fine structure of skeletal muscle triad junctions

Triad junctions in skeletal muscle of young newts and adult frogs have been examined after a wide variety of fixation procedures. When collidine-osmium is employed, the T-tubules of younger larval newt muscle appear as dilated channels which retain normal junctional relations with adjacent terminal cisterns. In older muscle, or after other fixation techniques, the T-tubule is narrow. This latter condition is less useful for analysis of junctional morphology, particularly when sections parallel to and including the junction are utilized. The images (including stereo electron micrographs) suggest that a given triad junction contains a gap distance of about 150 A bridged by an array of cementing materials. “Dimples” in the terminal cistern membrane bring it into tight or close junctional proximity to the T-tubule membrane. The overall appearance resembles an intermediate junction within which small foci of tight or close junctional contact exist. Evidence of direct pore-like membrane continuities between T-tubules and terminal cisterns was not observed.

Myofibrillogenesis and Z-band differentiation.

AbstractDeveloping myotubes in skeletal muscle tissue from the limbs of larval newts have been examined with respect to the ultrastructure and sequence of events accompanying myofibril formation. A population of filaments having a diameter of 100 Å is found to occur throughout and beyond the period of myofibrillogenesis. This population is in addition to developing actin and myosin filaments and probably does not contribute directly to myofibril formation. Rather it may represent a cytoskeletal network which ultimately becomes principally disposed around and at right angles to older myofibrils at the level of their Z‐bands.Assembly of thick and thin filaments into myofibrils seems to occur, in this muscle, predominantly near the periphery of the cell with registration of these components into A‐, I‐, and Z‐bands being accomplished as they assume progressively more internal locations. Z‐bands appear to develop by coalescence of Z‐bodies which in turn are earlier related to skeins of fine filamentous material which commonly occupy the most peripheral cytoplasm of these and other mesenchymally derived cells. Fine structural details of these skeins, Z‐bodies, and Z‐bands have been analyzed with regard to the several prevailing concepts of Z‐band architecture. An hypothetical sequence for myofibril formation and Z‐band differentiation is presented which takes into account several observations and relates them to the looping filament configuration previously proposed for mature Z‐band structure.

Responses of tissues from larval newts to implantation into adult hosts

Trunk and tail parts from larvae of Triturus virdescens were implanted into pockets made in the trunk epaxial musculature of adult animals of the same species. Histological observations were made on these grafts at intervals up to 60 days and at eight months following implantation. During the first few days after implantation the small, fragile grafts were distorted and compressed by the mechanical restrictions of host tissues, but they began to increase in size and rigidity by 20 days and eventually some reached sizes that exceeded considerably those of equivalent trunk and tail parts in intact control larvae. Differential responses to the host environment were seen among the various tissues of the grafts. As growth proceeded, the proportion of cartilage and bone relative to the other tissues increased. Gut, gut derivatives, nerve cord, and kidney showed initial growth but usually underwent later degenerative changes and declined in relative mass. Muscle and connective tissue did not show degenerative changes but did not increase significantly in mass. Limb-like protuberances and (in a single graft) a mass of well differentiated testicular tissue were seen. No metastases or infiltrating growths occurred.

Responses of tissues from larval newts to implantation into adult hosts.

AbstractTrunk and tail parts from larvae of Triturus virdescens were implanted into pockets made in the trunk epaxial musculature of adult animals of the same species. Histological observations were made on these grafts at intervals up to 60 days and at eight months following implantation. During the first few days after implantation the small, fragile grafts were distorted and compressed by the mechanical restrictions of host tissues, but they began to increase in size and rigidity by 20 days and eventually some reached sizes that exceeded considerably those of equivalent trunk and tail parts in intact control larvae. Differential responses to the host environment were seen among the various tissues of the grafts. As growth proceeded, the proportion of cartilage and bone relative to the other tissues increased. Gut, gut derivatives, nerve cord, and kidney showed initial growth but usually underwent later degenerative changes and declined in relative mass. Muscle and connective tissue did not show degenerative changes but did not increase significantly in mass. Limb‐like protuberances and (in a single graft) a mass of well differentiated testicular tissue were seen. No metastases or infiltrating growths occurred.

Plagitura intermedia sp. n. (Trematoda : Plagiorchiidae) from the Common Newt, Notophthalmus viridescens viridescens

Plagitura intermedia sp. n., a new plagiorchiid trematode, is described from the common newt, Notophthalmus v. viridescens, collected in Bear Lake, Shawnee State Park, Ohio. In general arrangement of the gonads, P. intermedia is similar to P. parva, the smaller of the two previously named species, but three to four times larger in size. Immature specimens are reported which are larger than the maximum size reported for either P. parva or P. salamandra. Cuticular spines extend posteriorly for three-quarters of the body length, rather than one-third as in the other species. Many trematodes of the genus Plagitura were taken from the small intestines of more than 100 adult Notophthalmus viridescens viridescens collected in Bear Lake, Shawnee State Park, Ohio; none were found in 25 larval newts, or in seven red efts. Some specimens were considerably larger than the maximum size of the two described species, P. parva Stunkard, 1933 and P. salamandra Holl, 1928, both of which were also identified from the same locality. The large worms are three to four times as long as P. parva, but are similar to that species in general arrangement of the gonads. Worms were studied alive in amphibian Ringer's solution, and also as permanent whole mounts. Worms were fixed, under light pressure, in Bouin's fixative, and stained in Semichon's acetic carmine, Ehrlich's hematoxylin, Delafield's hematoxylin, or Gower's carmine. Plagitura intermedia sp. n.

A quantitative study of forelimb innervation in relation to regenerative capacity in the larval, land stage, and adult forms of Triturus viridescens.

AbstractThe nerve fibers present at the amputation surface of the upper arm of the land stage and larval newt were counted and compared with values previously published by one of us on the adult. When expressed per unit area of surface, it was observed that the limb of the larva and the small land forms is more highly innervated than that of the adult. The values were 75.5, 47.6, and 27.7 fibers per (100 μ)2 respectively for the larval, small land stage, and adult animals. The number of fibers per unit area of the larger land forms resembled that for the adult showing that the innervation ratio stabilizes at a time before the animal returns to water.Calculations were also made of the number of motor and sensory fibers in the individual brachial nerves of the younger animals. Assuming the same quantitative threshold of nerve fibers is required to evoke regeneration of the limb in the young animal as is needed in the adult, it was possible to predict the effectiveness of each nerve and nerve component in supplying the neural requirement for regeneration. For example, we found that nerve 5, ineffective in itself to cause regeneration in adults, should evoke regrowth in younger forms, particularly in larvae. The predicted results correspond with experimental ones already published in the literature. The quantitative studies reported herewith are evaluated and discussed against the background of the important action of the nerve in regeneration of a body part.

The fine structure of the adepidermal reticulum in the basal membrane of the skin of the newt, Triturus.

The unique reticulum in the basal membrane of the adult newt's skin consists of a series of nodular swellings from which there radiate fibers. Electron micrographic studies showed that the nodules consist of layers of fibrillae arranged approximately and irregularly at right angles to one another. Some are packed to form a capsule; still others extend into the internodular zone to form the radiating fibers. The fibrils are banded and are revealed best after fixation with potassium permanganate. The reticulum is compared with that of the larval newt and the frog tadpole. The epidermal side of the reticulum is bounded by a membrane separated from the plasma wall of the epidermal cell by a clear space. These we have termed adepidermal membrane and space, and have compared them with similar structures in larvae.

Mitogenetic analysis of the protein substrate of protoplasm

It has been shown, by means of mitogenetic spectrum analysis that during the proliferative stage of cells (yeast, newt larvae, newborn guinea pigs), and in proliferating tissues of adult animals (guinea pig labial epithelium, rabbit cornea) there is relatively little interlinking of cytoplasmic peptide chains. This is shown by the relative narrowness of the spectral bands due to the functional groups R−C=O and R−C6H4OH. Where active proliferation has ceased, the peptide chains are interlinked by weak molecular bonds, giving rise to two-and three-dimensional structures.

The temporary inactivation of newt larvae by benzimidazole and its alkyl derivatives

Benzimidazol und einige von seinen Alkylderivaten inaktivieren Molch-Larven schon in kleinen Konzentrationen. In verdünnte Holtfreter-Lösung zurückgebrachte Tiere gewinnen ihre normale Aktivität schnell wieder. Der zeitweilige Beweglichkeitsverlust scheint analog dem bei Säugetieren durch Benzimidazol erzeugten.

Neoteny with Goitre in Triturus helveticus

ABSTRACT A population of newts from a pond near Crail, Fife, was found to contain neotenic and goitrous specimens of Triturus helveticus in 1951 and 1952 but not in 1953 and 1954. This is a unique record of goitre among amphibians. The thyroid glands of normal adult and neotenic non-goitrous T. helveticus are paired spheroidal or ellipsoidal bodies whose longest dimension varies between 300 and 700 ft. They consist of a few large follicles. The thyroid glands of the goitrous neotenic specimens may be as much as 4 mm. long. They are extremely hyperplastic and hyperaemic and for the most part consist of follicles smaller than those charac- teristic of normal newt thyroids. These goitrous thyroids produce major displacement of other structures in the throat region but do not invade other tissues. It is suggested that the goitres result from the exposure of overwintering newt larvae to the ‘brassica factor’ carried to the pond in the faeces of rabbits feeding on turnips and kale in neighbouring fields.

Newt Larvæ in Brackish Water

MR. ERIC HARDY, in referring1 to Miss Helen Spurway' s observation of newt larvae in brackish water2, states that “the brackish 'slacks' or pools between the west Lancashire coastal dunes from Aihsdale to Formby have long been inhabited by breeding specimens of the common smooth newt, common frog, common toad and natterjack toad”. C. T. Green, in his Flora3, states that “both salt and freshwater plants live in separate, though adjoining areas. The salt and the fresh water here have been readily distinguished by taking their specific gravity”.

A New Ambystomid Salamander Adapted to Brackish Water

THE presence of common salt in water, in any considerable quantity, renders it unfit for the development of the eggs and larvae of amphibians. Marine waters have consequently proved a strong barrier to the distribution of this group of animals. A very few amphibians have eggs and larvae capable of development in waters having some quantity of sodium chloride in solution, while many species appear to develop in alkaline waters of varying concentration. A. S. Pearse (1911) found tadpoles in water in crab holes which were covered daily by the tide water from Manila Bay. In consequence the water had a fairly strong salt concentration. Pearse does not mention the species, but I presume it to be Rana moodiei Taylor, since I have found its tadpoles near Manila, in brackish water in crab holes, though above the tidemark. On one occasion I captured an adult on the edge of the beach, from under a piece of coral, where it sat partially submerged. One might suspect that certain species with a wide archipelagic distribution might be more tolerant of sodium chloride concentrations than continental forms. The presence of larval newts in brackish water was recently reported in England (Spurway, 1943, and Hardy, 1943). Weismann (1878) was under the impression that the habitat of Siredon mexicana is brackish water. I believe that this is an error, since both Lake Xochomilco and Chalco are fresh water lakes (Chalco is now almost entirely drained and cultivated). It is true that there are bodies of brackish water in the Valle de Mexico but Siredon mexicana is not to be found in them. I do not believe any of these bodies of brackish water have other ambystomids. The discovery by Mr. Dyfrig McHattie Forbes of a salamander living in the saline waters of Lake Alchichica, Puebla, Mexico, is thus of especial interest and importance. It proves to be a species differing from other known forms, and is described below. Laguna Alchichica is one of a series of three small lakes in the high plateau region lying to the northwest of the great volcano Citlaltepetl (Orizaba). The region about them is flat and all seem to have been formed by a sinking of the surface crust. They do not seem to be crater lakes. The lakes differ in level, in the salt content of their waters, and in their fauna and flora. The actual depth of the water is not known in any of them. Laguna Quecholac and Laguna de la Mina Preciosa contain potable fresh water. They support a heavy growth of rushes about their edges, with many algae in the water. Each lake has, at least, one species of fish, and one salamander. Laguna Alchichica, with water distinctly salty to the taste, has no fresh water rushes or algae, and only submerged seaweedlike plants were observed, growing on rocks. There is a single species of fish,1 and the salamander here described.

The Feeding Habits of Larval Newts with Reference to Availability and Predilection of Food Items

EcologyVolume 21, Issue 3 p. 351-356 Article The Feeding Habits of Larval Newts with Reference to Availability and Predilection of Food Items W. J. Hamilton, Jr, W. J. Hamilton, JrSearch for more papers by this author W. J. Hamilton, Jr, W. J. Hamilton, JrSearch for more papers by this author First published: 01 July 1940 https://doi.org/10.2307/1930843Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume21, Issue3July 1940Pages 351-356 RelatedInformation