Free-living Forms Research Articles

The Use of Peracetic Acid to Obtain Germfree Invertebrate Eggs for Gnotobiotic Studies

Embryonated eggs of Heterakis gallinae, Blatella germanica, Artemia salina and Drosophila melanogaster were successfully rendered germfree by treatment with low concentrations of peracetic acid. Methods for growing the three free-living forms are described. Rigorous methods were employed to test for the absence of bacteria as well as PPLO and viruses. The viability of the eggs was not impaired, and no damage to the embryos by the disinfecting agent was observed. Peracetic acid shows promise in decontaminating a wide spectrum of parasite eggs for gnotobiotic studies.

The Evolution of the Ascaridoidea

author rejects the generally accepted view of the terrestrial origin of the Ascaridoidea from the Rhabditoidea by way of the Oxyuroidea, in which the direct life history is regarded as the primitive pattern of transmission. He advocates instead a marine origin and argues that the lips, esophagus, and excretory system of the ascaridoids can be equally well derived from such free-living marine forms as Enoplus, and he regards terrestrial forms as a secondary radiation. According to this view, forms having three hosts (an invertebrate paratenic host, with the second-stage larva in tissues; a small predatory vertebrate with the third-stage larva in its tissues, and a dominant predatory vertebrate harboring the fourth-stage larva and the adult) are the most primitive, and those having two and one are progressively more adaptive. direct life history of such one-host ascaridoids as those of man, horse, and pig represent adaptations to the absence or loss of the predatory habit on the part of the host. These speculations, as well as the history of the classification of the group, are treated in detail. starting point of this review is Chitwood's statement (Chitwood, 1950, p. 195), regarding his views on the origin of the Ascaridoidea. In essence this statement proposed that: (a) they arose from a primarily terrestrial stem, probably from the Rhabditoidea through the Oxyuroidea, (b) the marine forms arose as a secondary radiation through fish traveling up rivers from the sea, (c) that the direct (monoxenous) life-history pattern is more primitive than the indirect (heteroxenous) pattern which arose secondarily. It is probably true to say that these views were to some extent influenced by the fact that most of the previous investigations relating to the life history of the ascaridoid nematodes had been directed to the large roundworms of man and domestic animals. These findings had made such an impact on contemporary parasitologists that the direct life history was regarded as an established pattern for the whole group. This may partly explain why the indirect life-history pattern, involving one or more intermediate hosts, as demonstrated for * Dr. Sprent prepared this lecture on the occasion of his receipt of the Henry Baldwin Ward Medal. Because of its length, the address was presented as the first paper on the Symposium: Future of Nematology, Thursday morning, 14 June 1962, at 8:30 Am. A briefer response, which will be printed later in the Journal, was made at the time of the award. marine ascaridoids by Wiilker (1929), was regarded as a secondary development. In the past 12 years there has been at least a partial change of viewpoint regarding the evolution of the ascaridoids. It is intended in this paper to outline the developments which have influenced this change. Broadly speaking, three main types of investigation have contributed: (1) elucidation of life-history patterns in individual species, (2) morphological observations on the group as a whole, and (3) discussions on the phylogenetic significance of certain morphological features and life-history patterns. In the first category we must acknowledge the contribution of Tiner (1949) who first demonstrated the role of intermediate hosts in the life history of ascaridoids of terrestrial mammals. This discovery focused attention on a number of isolated observations, which together indicated that the indirect life history is much more widespread among the group than was previously realized. Accumulation of this evidence was considerably facilitated by the publication of The Ascaridata of Animals and Man by Mozgovoy (1953). This two-volume compilation in Russian, besides being the first comprehensive account of the ascaridoids, included a number of observations on life histories which had been undertaken in the Soviet Union and were not hitherto readily accessible.

Nature of Swarming in Nematodes

THE phenomenon of swarming in Tylenchorhynchus species and other nematodes1,2, under investigation for the past three years in Louisiana State University laboratories, has been related experimentally to physiological state, cuticle property and species specificity of plant parasitic and free-living forms.

Insect habitats in Antarctica

About fifty species of terrestrial arthropods have been collected in Antarctica; these include mites, ticks, springtails, sucking lice, biting lice and flies. The mites include both free-living and parasitic forms, the springtails and flies are free-living, and the ticks and lice are parasitic. The ticks, parasitic mites, and biting lice are associated with birds, and the sucking lice with seals. The number of species are about equally divided between free-living and parasitic forms. The ability of insects and mites to survive the very low winter temperatures and frequent strong winds of Antarctica is of considerable interest; judged in relation to commonly accepted ideas of tolerance, the environment is extremely forbidding.

Respiration inChondracanthus Zeide la Roche (Copepoda)

In spite of the keen interest evinced in the taxonomy of the parasitic copepods, there is little information on their metabolic rate, though the respiration of free-living forms has been studied by such workers as Marshall & Orr (1955, 1957), Clarke & Bonnett (1939), Zeuthen (1947), Raymont & Gauld (1951), Gauld & Raymont (1953) and Conover (1956). Since the rate of oxygen consumption is a reflexion of the metabolic rate of an animal, it was felt that a study of the rate of oxygen consumption of a copepod parasite would be of interest.Chondracanthus zeiDe la Roche, 1811, is easily available and large.

EVIDENCE FOR A SWARMING SUBSTANCE WHICH STIMULATES COLONY FORMATION IN THE DEVELOPMENT OF PEDIASTRUM DUPLEX MEYEN

1. The characteristics of growth and reproduction in P. duplex Meyen have been studied in non-bacteria-free cultures using large inocula of 5 cc. of stock culture for every 50 cc. of fresh medium.2. It has been found that colonies grown under these conditions exhibit two phases of development: A latent period in which no colony production or swarming takes place but during which the colonies grow, and a period of active swarming or burst phase during which all the cells of the starting colonies give rise to new colonies.3. It has also been shown that a heat-stable substance is present in aged medium which can, through an effect other than pH, alter the time at which colony production begins, the number of colonies produced and the size of these colonies in terms of cell numbers.4. It is suggested that the length of the latent period of development is determined by the time required for this substance to reach a threshold concentration. The possible importance of such a substance to free-living forms of Pe...

On the Odd, or Tissue-Paper, Beetle Supposed to be Thylodrias Contractus (Coleoptera: Dermestidae)

This odd scavenger is a minute dermestid beetle breeding annually and subsisting only on dried animal matter, in association with man. It probably degenerated into its present wingless and almost grublike form from a winged, free-living form, and became dependent for survival upon constant replenishment of waste animal food about the permanent den of some predator, perhaps man, in arid, cool-temperate Asia. It is recorded from Tiflis, Transcaucasia 1839, Provinces of Astrakhan and Turkestan 1894, New York 1903, Milwaukee 1908, St. Petersburg, Russia 1909, Egypt 1921, Canada 1932, Chicago 1933, and Texas and Minnesota 1939. It is probably now cosmopolitan but is not so recorded, as few observers recognize its inconspicuous adults. Discrepancies in recorded and actual characters leave its identification as Thylodrias contractus still uncertain, but the names Ignotus aenigmaticus and Hospitopterus efflatouni have been given to our pest, and the emendation Thelydrias was proposed to supplant Thylodrias . More than 40 years' experience with and interest in this museum pest which now infests houses, prompts the following discussion. Adoption of “tissue-paper beetle” as its common name would be unfortunate, since it is based on a misconception arising from the finding of stray individuals crawling onto this conspicuous background from their actual breeding place. Tissue paper seems to be of no importance in its ecology. A bibliography is appended.

Staining Nuclei and Chromosomes in Protozoa

Technics for free-living forms such as Paramecium and for parasitic forms such as the opalinid ciliates are described.Paramecium: Fix paramecia in hot Schaudinn's fluid containing 5% of glacial acetic acid for 5-15 minutes. (A hot water bath for maintaining the proper temperature of the fixative is described.) Dehydrate up to 83% alcohol. Mount the specimens on albuminized cover glasses. (A table for mounting animals on cover glasses is described.) Apply a thin layer of collodion to the cover glass to prevent the loss of the specimens during the subsequent handling. Pass through descending grades of alcohol to water. Mordant in 4% iron alum for 24 hours. Stain in 0.5% hematoxylin for 24 hours. Destain in saturated aqueous picric acid. Rinse in tap water, expose to ammonia vapor for a second, and then rinse again in tap water. Wash in running water for 1 hour. Dehydrate. Clear, then mount in damar.Opalinid Ciliates: Make smears on cover glasses and fix them while wet. If the opalinids are to be subsequentl...

The Invertebrata: a Manual for the Use of Students

THIS volume has been prepared for the use of students who have completed a year's study of zoology and are entering upon an advanced course. The book opens with an admirable introduction to the study of the structure and biology of the Protozoa, after which follows the systematic consideration of the four main sub-divisions, including a scheme of classification and references to the special points exhibited by representative examples. This chapter is especially praiseworthy for the attention devoted to free-living forms. The student tends to stress the parasitic Protozoa and this account provides a most useful corrective, and he who reads and digests this chapter of 109 pages will have acquired a sound and balanced basis of knowledge of the Protozoa.

Cylindrogaster coprophaga gen. et sp. nov. A Nematode found in a Culture of Fæces from a Wild Brown Rat

Free-living nematodes commonly occur in cultures of fæces, and as Looss (1911) showed years ago they have frequently been mistaken for the developmental stages of parasitic nematodes. For this reason it is important that detailed knowledge of the morphology of such free-living forms should be available. With this end in view the following illustrated account of what appears to be a new genus of nematode has' been prepared. The worms occurred originally in a culture of the fæces of a brown rat, Rattus norvegicus, made for the study of the free-living stages of the Strongyloides of the rat; and as after detailed study it has been found impossible to find any existing description of nematodes which agree with the structural appearances shown by the worms, it has been decided to create a new genus for their reception.

Cultural Amœbæ from the Intestine of Man

I SHOULD like to thank your reviewer for his commendatory remarks in NATURE of December 21, 1916, on the account of the parasitic Protozoa which I contributed to the “Animal Parasites of Man.” Without in any way wishing to raise a discussion, I think it should be pointed out, in respect to his statement about Amoeba limax, that much information concerning these cultural organisms that may occur in the human intestine will be found under the designation “cultural amœbæ” on pp. 42, 618, 742 and 743 of my work. As your reviewer rightly infers, A. limax is not now strictly the name of a single species, but rather of a group or type of free-living forms which show differences among themselves, but can be cultivated on artificial media. It is not easy to point out marked differential characters between them and Entamœbæ, especially after consideration of the work of Drs. Williams and Calkins, to which reference is made by me on p. 42 and pp. 742 and 743 of the book.

A NEW GENUS OF PARASITIC GASTROPODS

A number of gastropods are known, living parasitically upon the body of certain echinoderms, which retain the shell and typical internal organization so that their systematic position is readily established. On the other hand several endoparasitic species exist which have become so highly modified that they stand in much the same relation to the free-living forms as Sacculina to the typical cirripedes. Owing to the lack of any detailed information relating to their ontogenetic development the relationship of such forms is highly problematical. And furthermore it is difficult to accurately follow the stages of the phylogenetic metamorphosis which the body has undergone, and accordingly to establish the homologies of some of the principal organs. Schiemenz' in a very suggestive paper has attempted to construct a hypothetical animal connecting the least modified species like Sty'ifer on one hand with the highly degenerate types represented by Entoconcha. In several respects the animal here described resembles the hypothetical form and in a measure enables us to follow some of the changes which the more degenerate species have undergone. My attention was attracted to this gastropod by my friend and colleague Dr. W. K. Fisher who discovered it in a species of starfish (Brisinga evermanni Fisher) taken by the U. S. F. C. Str. Albatross in the neighborhood of the Hawaiian Islands (sta. 3467) at a depth of 3 10 fathoms. It occupied the ccelomic cavity close to the base of one of the arms, producing a marked distention (Fig. 2, P1. I.) of the body wall. The animal was un-

Biological Notes

MLTAMORPHOSIS IN NEMATODES.—Dr. von Linstow sums up our present knowledge as follows:—The Nematelminthes, according to the medium in which the individual developmental stage is passed, present a truly wonderful series of metamorphoses, and no less than fourteen distinct developmental stages may be enumerated. (1) The embryo passes into an adult form direct (without the intervention of a larval stage) in the one medium, and also passes its existence in fresh, salt, or brackish water, in plants, in the earth, or in decaying substances (Dorylaimus, Enoplus, Plectus, Monhystera, Rhabditis, and many other genera). (2) The larvæ live in the earth, the adult form in plants (Tylenchus tritici, T. putrefaciens, Heterodera schachtii). (3) The larvæ live in worms, and on their death and decay pass into the earth, when they assume an adult form (Rhabditis pellio). (4) The Helminth lives bisexual in the earth, the fruitful females enter the bodies of bees, and produce therein offspring (Sphœrularia bombi). (5) The larvæ live in the earth, assuming the adult condition in some animal (Dochmius, Strongylus). (6) The Helminth lives as an hermaphrodite form in some animal, the off-spring develop into bisexual forms in the earth (Rhabdonema, Angiostomum). (7) Some adult forms differentiate free-living forms developing sexually, and also hermaphrodite forms living parasitically in animals (snails, Leptodera appendiculata). (8) The larvæ hatch out in the earth, and then enter some animal, in which they become metamorphosed into hermaphrodite forms (Trichocephalus, Oxyuris). (9) The larvæ live in insects, the adult form in earth or water (Mermis). (10) The larvæ live encapsuled in some animal, and with it pass into the digestive system of some other animal form, in which latter they become adult (Ascaris, Filaria, Cucullanius). (11) For a short time the hermaphrodite form lives in the intestine of some animal, and produces here its larval form, which, penetrating the intestinal walls, makes its way into the muscles, where it becomes encapsuled (Trichina spiralis). (12) The adult form lives in the trachern of birds; the females lay eggs, which contain well-formed embryos, which get expectorated, to once again enter the bird's system with its ordinary nourishment. In the crop and œesophagus of the bird the embryo hatches out, wandering into the bronchæ and air-sacs, from whence the larger larvæ find their way to the tracheæ (Syngamus trachealis). (13) There will be two larval forms, of which the one will be found in Mollusca, and the other in aquatic beetles and water-boatmen, while the adult form lives in water (Gordius aquaticus). (14) There will be two larval forms, of which the one will be found in water, the other in the lung of some Amphibian, from whence it will wander into the intestine of the same animal, where it will develop into an hermaphrodite form (Nematoxys longicauda); this latter form is described and figured.—(Zeitschrift für wissenschaftliche Zoologie, November 24, 1885, Band xlii. Heft 4, p. 715, pl. 28.)

On Naked Fresh-Water Radiolaria

ABSTRACT The distribution of animals in the older strata of the earth’s crust would lead one to assume that fresh-water lakes could not have been inhabited until a late period, and, indeed,’’the distribution of living beings in fresh and salt waters is now very disproportionate. With regard to many orders of the animal kingdom, nature seems to have made some feeble attempts to populate fresh waters, and then to have given up the matter ; with others the distribution in both quarters is tolerably equal, although no very important physiological differences seem to exist; with the majority the sea presents a most decided predominance. Until recently Radiolaria have been found only in the sea, or at least shell-less free-living forms have never yet been observed in fresh water. In the middle of last summer I, to my great surprise, discovered at the same source · three different kinds of creatures which presented decided characters of Radiolaria. As most of the inhabitants of the sea belonging to this order are enclosed in hard porous shells, the examination of their tissue elements is rendered difficult to a great degree ; consequently, the opportunity of examining these free-living forms from fresh water offer a very desirable facility for making a minute investigation.