Scanning Electron Microscope Observations on Some Life History Stages of Carchesium polypinum (Ciliata,Peritrichia)1

SYNOPSIS. Sessile zooids, and mobile telotrochs and microgamonts of Carchesium polypinum (Protozoa, Ciliata, Peritrichia), were examined by scanning electron microscopy. The results were compared to earlier light and electron microscope studies in order to investigate structural changes concerned with adaptation and differentiation. Telotrochs and microgamonts always had a contracted peristome and usually had a long phalange of cilia. Striae around the contracted buccal apparatus in all 3 stages were convoluted and often had thickened margins; those in telotrochs and microgamonts had oral-aboral ectoplasmic cross-connections. Nonbuccal striae of telotrochs and microgamonts varied in structure and height differences between epiplasmic peaks and alveoli surface membranes. The number of striae were constant in all 3 stages. Pellicular pore structure did not vary in any of the stages examined and resembled parasomal sacs located near buccal structures. Fully relaxed sessile zooids had ectoplasmic ridges coursing from polykinety kinetosomes and cilia to an area in front of the ciliated portion of the haplokinety; these ridges were interpreted to be the interkinetal fibers. Telotroch bands of sessile zooids consisted of 2 or 3 parallel ectoplasmic ridges which circled the aboral region and contained structures resembling pores. Telotroch bands in telotrochs and microgamonts had 2 enlarged, parallel ectoplasmic ridges circling the aboral region; telotroch band cilia were found between these ridges. In addition, a fold-like, ectoplasmic structure extended beyond the 2 ridges and was located between the telotroch band cilia and the aboral ridge. The epiplasmic shelf surrounding the stalk in sessile zooids was enlarged in telotrochs, and cilia were seen in the scopula depression. No scopula organelle was seen in any microgamont.     

Telotroch formation, survival, and attachment in the epibiotic peritrich Zoothamnium intermedium (Ciliophora, Oligohymenophorea)

Abstract. Aspects of the life cycle of the peritrich ciliate Zoothamnium intermedium , an epibiont on calanoid copepods in the Chesapeake Bay, were investigated using host and epibiont cultures. Experiments were designed to characterize the formation, survival, and attachment of free-swimming stages (telotrochs) and to assess whether telotrochs preferentially attach to primary ( Acartia tonsa and Eurytemora affinis ) or alternate hosts from the zooplankton community (the rotifer Brachionus plicatilis , barnacle nauplii, polychaete larvae, and a harpacticoid copepod). The results showed that telotroch formation started 2 h after the death of the host, with >90% of the zooids leaving the host carapace within 7 h. Formation of telotrochs was triggered only by the death of the host, failing to occur when the host was injured or unable to swim. Telotrochs failed to attach to non-living substrates and survived for only 14 h in the absence of host organisms, suggesting that members of Z. intermedium are obligate epibionts. Attachment success decreased with telotroch age, indicating that colonization success in nature may strongly depend on the ability to find a suitable host in a short period of time. Individuals exhibited no preferences in colonizing juvenile or adult stages of A. tonsa or E. affinis . While telotrochs were able to colonize barnacle nauplii and the harpacticoid copepod in the absence of individuals of A. tonsa or E. affinis , they did not attach to the rotifers or polychaete larvae. Telotrochs preferentially colonized individuals of A. tonsa when in the presence of other non-calanoid host species.     

A Method for the Synchronous Induction of Large Numbers of Telotrochs in Vorticella convallaria by Monocalcium Phosphate at Low pH

ABSTRACT We have devised a two step method for the synchronous induction of telotrochs in the peritrich ciliate, Vorticella convallaria. The method is easy, reliable, and allows us to study the earliest events of telotroch formation at the ultrastructural, biochemical, and molecular levels. The steps involved are: (1) excising the cell body from the stalk in a large population (7.4 times 10⁴ cells) of EDTA-treated, attached cells by the application of monocalcium phosphate monohydrate solution at pH 3.2, (2) rinsing and suspending the isolated cell bodies in inorganic medium. Within 90 min, 80% of the population forms telotrochs. Analysis of factors that are important for maximum stalk excision and transformation shows that the population must not be older than 2 d and the most effective concentration of monocalcium phosphate is 4.8 mM for a 20 min exposure. The most effective monocalcium phosphate is in the monohydrated form. A pH value of 3.2, produced by the addition of hydrochloric acid in the presence or absence of calcium is not sufficient to initiate stalk excision and telotroch formation. This observation leads us to conclude that stalk excision is dependent on monocalcium phosphate or its hydrolysis products.     

Five New Species of Lagenophrys (Ciliophora,Peritricha, Lagenophryidae) from the United States with Observations on Their Developmental Stages1

Five species of the loricate genus Lagenophrys were found on freshwater hosts and are described for the first time. Lagenophrys dennisi n. sp., L. incompta n. sp., and L. oregonensis n. sp. are ectosymbionts of astacid crayfish. Lagenophrys foxi n. sp and L. missouriensis n. sp. are ectosymbionts of gammarid amphipods. All five species appear to occur only m North America. Protargol preparations of the five species reveal that the peristomial myoneme is much broader and more extensive in telotrochs and metamorphosing individuals than in adults. Darkly staining bands appearing to be somatic myonemes were also seen underneath the surface of the body and in the center of the body of telotrochs and metamorphosing individuals. The telotroch of Lagenophrys is so different from the adult that it constitutes a true larval form rather than a simple dispersal stage. Structural parallels between the telotroch of Lagenophrys and mobiline peritrichs suggest the hypothesis that mobilines evolved from the telotroch of a sessiline pentrich which had first evolved into a true larval form.     

Effect of Algal Exudates on Substratum Selection by Motile Telotrochs of the Marine Peritrich Ciliate Vorticella marina

SYNOPSIS. Several species of marine peritrichs are found as epiphytes on small strands of filamentous green and red algae affixed to the substratum of marine intertidal rock pools. In pools located along the coast of Narragansett Bay, the motile vorticellid telotrochs appear to show a substratum selection for specific algae. Exudation products by marine algae have distinct differences; some Phaeophyta have particularly high values for dissolved organic matter (DOM), and for phenolic compounds. Algal exudates appear to influence population growth of vorticellids. The mean survival percentage of vorticellid populations increased with exposure to exudates from Cladophora gracilis, Polysiphonia harveyi and Polysiphonia lanosa ; and decreased with exposure to those of Ascophyllum nodosum, Fucus spiralis and Scytosiphon lomentaria. Telotroch settlement of Vorticella marina was enhanced by exudates of Cladophora gracilis, Polysiphonia harveyi and Polysiphonia lanosa , but was reduced by exudates of Ascophyllum nodosum , and was prevented by exudates of Fucus spiralis and Scytosiphon lomentaria .
Algal exudates were obtained by allowing photosynthetic activity of the experimental algae for 6 hr. The exudates were filtered and the concentration of DOM, total phenols and carbohydrates determined. The filtered seawater containing the exudate was placed in a box-type plastic dish on which the vorticellids had colonized. Survival percentages and the percentage of population due to telotroch settlement were calculated. This investigation indicates that algal exudates may exert a significant influence on the selection of substrata by vorticellid telotrochs and suggests that the ecologic stability of a given rock pool may be considerably lessened by a high level of Phaeophtya and the consequent reduction of Aufwuchs species.     

Studies on the asexual reproduction in the polystyelid ascidian,Polyzoa vesiculiphora Tokioka

New blastozooids of Polyzoa vesiculiphora, the polysytelid ascidian are produced by pallial budding of three types depending on the method of “isolated bud” formation; stolonic, planktonic and intermediate types. Differences among each type of bud are attributed to behavior of test-vessels composing a part of the bud. Isolated buds produced by each type are essentially equal in terms of their internal structures and their subsequent fate, and develop independently of their parent zooids. New test-vessels originate directly from the epidermis of a “prefunctional zooid,” while the test-vessels derived from the parent zooid finally disintegrate. The new test-vessels extended with branching under the ventral side of a “functional zooid,” ascend to the lateral side of it and participate in bud formation. Budding regions exist in three dimensions on the lateral wall of the mantle of the functional zooid, especially the right posterior part. During the life cycle of one functional zooid, the stolonic type buds appear at early and/or aged stages. Appearances of the stolonic type buds in early stages tend to repress those of the planktonic types. The number of planktonic type buds formed on a functional zooid at the same time is many more than that of the stolonic type. Such budding features are discussed from the viewpoint of behavior of the test-vessel system.     

Functional development of chemosensory systems in the fish ontogeny

Regularities of the functional development of chemosensory systems in the ontogeny of fish has been studied, i.e., the olfactory system, the taste system, and the common chemical sense. The olfactory system begins to function and provides response of juveniles to chemical signals before the taste system. Embryos that have hatched from eggs but that do not yet take food exhibit nonspecialized motor responses to olfactory stimuli already. Immediately after the transition to exogenous feeding, olfactory sensitivity to signals which elicit defensive and feeding behavioral responses begins to form and the ability to differentiate between similar odors develops. The reception of a limited number of taste stimuli occurs in the larvae during the transition to exogenous feeding. With age, the spectrum of effective taste substances expands and the time spent on the definition of palatability by juvenile fishes reduces. Functional development of individual components of the taste system arises heterochronously, i.e., the external (extraoral) form of taste reception arises earlier and more rapidly, and the oral (intraoral) form of taste reception arises slower. No information is available about the functional development of the common chemical sense in the ontogeny of fish. It is assumed that the function of the chemosensory system arises in fish in early larval stages.     

Tropomyosin in peripheral ruffles of cultured rat kidney cells

Tropomyosin distribution has been studied in two normal lines and one transformed line of rat kidney cells during the early phases of substrate attachment and growth. One non-motile normal line, which spreads rapidly after attachment, immediately begins to assemble prominent stress fibers that contain tropomyosin. It displays small peripheral ruffles that are not noticeably stained with anti-tropomyosin. The other normal line is motile and produces large ruffles that are brightly stained with anti-tropomyosin. Large numbers of tropomyosin-positive stress fibers assemble only after the cells stop moving and lose the peripheral ruffles. The transformed line does not assemble stress fibers but does contain large numbers of actin filament bundles in ruffles on the cell surface that are stained with anti-tropomyosin. These observations indicate that cytoskeletal tropomyosin is not restricted in distribution to stress fibers, and may undergo re-organization along with actin during the transition from motile to non-motile behavior.     

The Fine Structure of the Trophont and Stages in Telotroch Formation in Circolagenophrys ampulla (Ciliophora,Peritrichida)1

ABSTRACT. Ultrastructural studies of the trophont of the epizooic loricate peritrich, Circolagenophrys ampulla, show that the body conforms to the basic peritrich pattern. The lorica is dome-shaped, and the trophont is joined to it by attachment organelles. A single row of barren aboral kinetosomes is present. In telotroch formation, as cytokinesis proceeds, a band of aboral kinetosomes develops, running posteroventrally in an arc from the base of the epistomial disc. In one instance, postciliary microtubules were seen associated with the kinetosomes of the adoral polykinety in a dividing organism. In the fully developed telotroch there are several distinctive structures. In the midaboral region there is a scopula with numerous barren kinetosomes in the epiplasm underlying the pellicle. Surrounding the rim of the aboral surface is a tripartite fringe which overlies the base of the aboral ciliary girdle. The outer layer of this fringe contains regularly spaced electron-dense striations and the middle region contains microfilaments. The aboral ciliary girdle forms a complete ring. It is composed of diagonal rows of kinetosomes, 8–9 in each row. Striated fibers run between the rows of kinetosomes. They bend at the ends of the rows and continue for some distance below the outer rim of the aboral surface. Running beside each striated fiber is a band of paracrystalline material. Several distinctive structures are associated with the kinetosomes and striated fibers of the aboral girdle. In the telotroch many of the adoral cilia are absent but the adoral kinetosomes are still present. The possible functions of the specializations of the aboral surface in settlement of the telotroch, and the relationship between telotroch formation and the molting behavior of the crustacean host are discussed.     

Surface contact stimulates the just-in-time deployment of bacterial adhesins

The attachment of bacteria to surfaces provides advantages such as increasing nutrient access and resistance to environmental stress. Attachment begins with a reversible phase, often mediated by surface structures such as flagella and pili, followed by a transition to irreversible attachment, typically mediated by polysaccharides. Here we show that the interplay between pili and flagellum rotation stimulates the rapid transition between reversible and polysaccharide-mediated irreversible attachment. We found that reversible attachment of Caulobacter crescentus cells is mediated by motile cells bearing pili and that their contact with a surface results in the rapid pili-dependent arrest of flagellum rotation and concurrent stimulation of polar holdfast adhesive polysaccharide. Similar stimulation of polar adhesin production by surface contact occurs in Asticcacaulis biprosthecum and Agrobacterium tumefaciens. Therefore, single bacterial cells respond to their initial contact with surfaces by triggering just-in-time adhesin production. This mechanism restricts stable attachment to intimate surface interactions, thereby maximizing surface attachment, discouraging non-productive self-adherence, and preventing curing of the adhesive.     

FEEDING IN PERANEMA TRICHOPHORUM REVISITED (EUGLENOPHYTA)1

Feeding in Peranema trichophorum (Ehrenberg 1838) Stein 1878 was first observed over a century ago, yet there is still contention over how the feeding apparatus is used in feeding. Using video microscopy and scanning microscopy, this study documents two types of feeding. Peranema may engulf prey cells whole. Immotile cells are preferred, but moving cells occasionally are engulfed. Details of the early stages of engulfment are presented using scanning electron microscopy. A second method of feeding begins with the attachment of Peranema to a prey cell. The rods of the feeding apparatus then are repeatedly scraped over the surface of the prey until a tear occurs in the cell. The feeding apparatus is inserted into the opening and the internal cell contents are sucked out. The anterior flagellum is inserted into the prey to help remove the cell's contents.     

The ciliate epibiont Epistylis pygmaeum: selection for zooplankton hosts, reproduction and effect on two rotifers

1. A clonal culture of the peritrich Epistylis pygmaeum was used for all observations and experiments. Motile cells preferentially attached to the eggs of three species of Brachionus but also attached to the body of adult B. angularis. Zooids on the transitory egg substratum developed only short stalks, while those on the body often developed long stalks and branched colonies. Selection for the eggs positions the ciliate near the cloaca, and thus high concentrations of fine particulate material excreted by the host. Settlement on eggs occurred equally well in the light and dark, and on moving and stationary eggs. 2. Motile Epistylis cells attached to a wide variety of rotifer and crustacean zooplankton, but exhibited some pronounced selectivity. They readily settled on the eggs of other rotifers (Epiphanes, Polyarthra), on the carapace of several cladocerans (Ceriodaphnia, Daphnia, Diaphanosoma), and on the egg sacs of a copepod (Tropocyclops). They settled less readily on the bodies of the rotifers Asplanchna and Synchaeta, and rarely or never settled on the rotifer Keratella, the cladocerans Bosmina and Scapholeberis, and the body of the copepod. 3. Epistylis populations initiated with a single zooid on Brachionus increased exponentially and often contained several hundred attached zooids and motile cells after 3 days at 20 °C. Observations of a culture initiated from a single telotroch provided new information about peritrich life cycles: (1) motile cells reproduced themselves at a rapid rate (λ = 4.26 day^?1); (2) telotrochs produced or transformed into swimming zooids and vice versa. Functions of the two types of motile cells remain to be clarified. Telotrochs likely are specialised for finding and attaching to hosts. Swimming zooids can feed and reproduce, producing both their own cell type and telotrochs. Together, they should enhance dispersal and population growth, especially when hosts are rare. 4. Life‐table experiments with two species of Brachionus showed that colonisation by Epistylis had no effect on adult survival but significantly decreased fecundity, by 29% in both cases. Zooids attached to eggs could be a weight burden, increase drag, and possibly inhibit egg development. Those on the body of B. angularis also could interfere with coronal cilia, inhibiting feeding and further slowing locomotion. The ability of E. pygmaeum to select and then interfere with its hosts indicates that this epibiont has the potential to influence the species structure of zooplankton communities.     

The Fine Structure of the Scopula-Stalk Region of Vorticella convallaria

ABSTRACT. We examined by SEM and TEM the stalk-scopular junction, the stalk, and stalk formation in Vorticella convallaria Linnaeus, 1767. The stalk sheath is anchored to the walls of the scopular lip and to the scopular cilia by thin fibrils. Experimental extraction of these fibrils weakens this junction enough to separate the stalk from the cell body. Telotrochs escape from the stalk by means of violent contractions of the cell body, accelerated beating of the trochal band cilia, and twisting of the cell body against the stalk. The edges of the scopular lip spread over the scopular cilia after escape and, in some cases, fuse to enclose the entire, aboral scopular surface in a cupola-like structure. The sessile cells contain fewer and smaller scopular granules than telotrochs. The presence of disintegrating scopular granules in the stalk matrix of some sessile cells suggests that they contain material which is secreted over a period of time to form the stalk. Eruptive formation of the initial adhesive pad and quick elongation of the distal part of the stalk suggests a rapid exocytosis of the larger, more numerous granules of the telotroch. The stalk sheath is formed of fibrils making up complete and incomplete compartments peripherally arranged along the major stalk axis.     

Locomotory and feeding effectors of the tornaria larva of Balanoglossus biminiensis

Lacalli, T. C. and Gilmour, T. H. J. 2001. Locomotory and feeding effectors of the tornaria larva of Balanoglossus biminiensis . — Acta Zoologica (Stockholm) 82 : 117–126
The tornaria ciliary bands and oesophagus were examined ultrastructurally to identify the neural components that control larval behaviour. The circumoral ciliary band is known to be innervated in part by fibres from the apical plate and adoral nerve centres. Within the band itself, however, the only neurones we could find were multipolar cells, an unusual cell type with apical processes that traverse the surface of the band. Similar cells occur in the circumoral bands of echinoderm larvae. The tornaria telotroch has a much larger nerve, but no neurones were found either in the band or nearby, so the source of the fibres in the telotroch nerve remains unknown. In addition to having different innervation, the two bands also respond differently to cholinergic agonists, which elicit telotroch arrests but have no visible effect on the circumoral band. The oesophagus has a well-developed musculature and an extensive nerve plexus. During feeding, the oesophagus repeatedly contracts, forcing excess water out along two lateral channels prior to swallowing. These channels are also sites of gill slit formation, so there is evidently a continuity between the water bypass mechanism of the larva and that of the postmetamorphic juvenile.     

Flagellar attachment and detachment ofCrithidia fasciculata to the gut wall ofAnopheles gambiae

Summary Flagellar attachment to the cuticle lined fore and hindgut ofAnopheles gambiae has been studied. At an attachment site, the flagellar membrane follows the contour of the surface to which it is apposed. In the colon where there is little folding of the gut the flagellum is truncate but in regions where the cuticular lining is highly folded the tip of the flagellum is more variable in shape. Numerous filaments lying beneath the adhering membrane make attachment sites easy to recognise. Although haptomonads lying close to the gut possess a short flagellum, those cells which in heavy infections are separated from the gut wall by severalm develop a much longer organelle in order to reach the cuticular lining.The induction of flagellar detachment by the addition of distilled water begins with the appearance of membrane invaginations at the adhesion site. Some of these invaginations, which appear to take cuticular material with them, develop into vesicles. It appears that this process progressively reduces the area of adhesion so that when flagellar activity begins, detachment is easily effected.     

The ontogeny and maintenance of adult symmetry properties in the ctenophore, Mnemiopsis mccradyi

Ctenophores are biradially symmetrical animals. The body is composed of four identical quadrants which are organized along an oral-aboral axis. Most species have eight comb rows, two tentacles, and an apical organ (located on the aboral surface). During embryogenesis there is a fixed pattern of cleavage, a precocious specification of blastomere developmental potential, and an inability to regulate for portions of the embryo that have been removed. When blastomeres are separated at the two-cell stage each blastomere develops into a "half-animal" with four comb rows, one tentacle, and half an apical organ. In contrast, adult ctenophores regenerate readily. When an adult ctenophore is cut in half to produce "half-animals," in most cases each half regenerates the missing half. In some cases, however, bisected animals remain as "half-animals" which repair the wound site but do not replace all of the missing structures. When animals are cut in half along the tentacular or esophageal axis at different stages of embryogenesis a transition period is detected when the capacity for adult regeneration begins. This transition occurs at the time when the formation of the apical organ is complete and comb row function becomes coordinated. Embryos bisected prior to this time remain as "half-animals" even after growing to large reproductive sizes, while animals bisected after the transition period usually regenerate the missing structures within 2-3 days. When adult "half-animals" (produced by bisection either before or after the transition period) are cut into "quarter-pieces," the pieces regenerate to form either "half-animals" or whole animals. Thus, "half-animals" produced prior to the transition period--although they failed to undergo embryonic regulation--have not irreversibly lost the capacity to form whole animals if challenged to regenerate during adult stages. When aboral blastomeres destined to form the apical organ, tentacles, and comb rows are removed from early cleavage stages (prior to the transition period), the embryo does not form these structures at the appropriate time. However, the resulting deficient adults spontaneously form these structures from remaining blastomere lineages soon after hatching. These experiments suggest that as long as some quadrant-specific cells of the oral pole are present at the time of the transition period, the structures of that quadrant will be spontaneously replaced during the adult period.(ABSTRACT TRUNCATED AT 400 WORDS)     

Freeze-fracture study of the filamentous, segmented microorganism attached to the murine small bowel.

A freeze-fracture study has provided new information about the filamentous, segmented microorganism known to live in the murine small bowel. The intracellular bodies produced by this microbe appear to arise by a modified sporogenesis so that they are enclosed in an envelopment membrane at least prior to release by the filament mother cell. At least some of the intracellular bodies divide while still within the mother cell, suggesting a reproductive role for these structures. The host epithelial membrane remains intact at the site of attachment, but does appear to have a reduced concentration of intramembrane particles. Changes in the host cytoplasm adjacent to the attachment site are documented and interpreted to be a sol-gel transformation which may stabilize the attachment socket.     

The surface topography of <Emphasis Type="Italic">Eudiplozoon nipponicum</Emphasis> (Monogenea) developmental stages parasitizing carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

Using scanning electron microscopy (SEM), the external morphology of all developmental stages (egg, oncomiracidium, diporpa, just fused juvenile and adult) of the parasite, Eudiplozoon nipponicum (Monogenea, Diplozoidae), from the gills of carp was studied. During the ontogeny, the tegument, tegumentary and sensory structures are subsequently developed. The tegument of free swimming oncomiracidium occurs in two types — the ciliated and non-ciliated with numerous uniciliated sensory structures. An attachment apparatus starts to form during the oncomiracidium stage. Further developmental stages are adapted to the environment of the gills. Tegumentary folds become more apparent later in development and assist to the parasite’s attachment. In connection with its reproductive strategy, the two morphological structures of diporpa (ventral sucker and dorsal papilla) appear to play important role. On the gills, two individuals need to meet and these structures mediate the fusion between two diporpae. The hindbody of adult parasite is highly modified for attachment. The haptor, folds and lobular extensions are most developed. The forebody is flexible and able to interact with host gill tissue via the mouth and associated mouth structures. The process of food intake of the parasite was discussed.     

Development of Nonsocial Behaviour in the Asiatic Elephant

The elephant calf, a defended follower is completely dependent on adults till the age of 3 months. It begins to explore and attempts to feed at 3 to 6 months, and then becomes partially independent with some feeding on its own. The characteristics of behavior in adults are examined and the development of this pattern in the calf is traced by analyis of duration, transition and clustering of the behavioural elements. Essential activities like suckling, locomotion and lying down for rest appear soon after birth whereas elements of feeding, grooming and play appear only at a later stage. The calf takes the initiative in suckling and its termination, drinking directly by mouth till the age of 6 months. The first element of feeding appears at about a week in attempts to pick up and hold objects in the trunk. Co-ordination of limb, trunk and mouth movement is achieved by about 1 month. The calf is strong enough to pull out plants by 6 months when independent feeding begins. In about a year feeding, drinking and dusting patterns are well developed.