scholarly journals Life cycle of Early Cambrian microalgae from theSkiagia-plexus acritarchs

2010 ◽  
Vol 84 (2) ◽  
pp. 216-230 ◽  
Author(s):  
Małgorzata Moczydłowska
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Biological Species ◽  
Complex Life Cycle ◽  
Early Cambrian ◽  
Closely Related Species ◽  
Vegetative Cells ◽  
Depositional Settings ◽  
Sexual Generation ◽  
Sheath Structure

Light microscopy studies on new materials and museum collections of early Cambrian organic-walled microfossils, informally called acritarchs, provide the observations on phenetic features that permit a comparison to certain Modern microalgae and the recognition of various developmental stages in their life cycle. the microfossils derive from various depositional settings in Estonia, Australia, Greenland, Sweden, and Poland. the exceptionally preserved microfossils reveal the internal body within the vesicle, the endocyst, and the process of releasing the endocyst from the cyst. Vegetative cells, cysts, and endocysts are distinguished, and the hypothetical reconstruction of a complex life cycle with the alternation of sexual and asexual generations is proposed. Acritarchs from theSkiagia-plexus are cysts, and likely zygotes in the sexual generation, which periodically rested as “benthic plankton.” Some microfossils of theLeiosphaeridia-plexus that are inferred to be vegetative cells were planktonic and probably haplobiontic. These form-taxa may belong to a single biological species, or a few closely related species, and represent the developmental stages and alternating generations in a complex life cycle that is expressed by polymorphic, sphaero- and acanthomorphic acritarchs. the morphological resemblance and diagnostic cell wall ultrastructure with the trilaminar sheath structure known from earlier studies suggest that the early Cambrian microfossils are the ancestral representatives and/or early lineages to the Modern class Chlorophyceae and the orders Volvocales and Chlorococcales.

Whirling Disease: Reviews and Current Topics

2002 ◽  
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Small Subunit ◽  
Fish Host ◽  
Complex Life Cycle ◽  
Developmental Cycle ◽  
Myxobolus Cerebralis ◽  
Rdna Sequences ◽  
Complex Development ◽  
The One

<em>ABSTRACT. Myxobolus cerebralis </em>possesses unique phenotypic and genotypic characteristics when compared with other histozoic parasites from the phylum Myxozoa. The parasite infects the cartilage and thereby induces a serious and potentially lethal disease in salmonid fish. Comparisons of the small subunit ribosomal DNA (ssu rDNA) sequences of <em>M. cerebralis </em>to other myxozoans demonstrate that the parasite has evolved separately from other <em>Myxobolus </em>spp. that may appear in cartilage or nervous tissues of the fish host. <em>Myxobolus cerebralis </em>has a complex life cycle involving two hosts and numerous developmental stages that may divide by mitosis, endogeny, or plasmotomy, and, at one stage, by meiosis. In the salmonid host, the parasite undergoes extensive migration from initial sites of attachment to the epidermis, through the nervous system, to reach cartilage, the site where sporogenesis occurs. During this migration, parasite numbers may increase by replication. Sporogenesis is initiated by autogamy, a process typical of pansporoblastic myxosporean development that involves the union of the one cell (pericyte) with another (sporogonic). Following this union, the sporogonic cell will give rise to all subsequent cells that differentiate into the lenticular shaped spore with a diameter of approximately 10 µm. This spore or myxospore is an environmentally resistant stage characterized by two hardened valves surrounding two polar capsules with coiled filaments and a binucleate sporoplasm cell. In the fish, these spores are found only in cartilage where they reside until released from fish that die or are consumed by other fish or fish-eating animals (e.g., birds). Spores reaching the aquatic sediments can be ingested and hatch in susceptible oligochaete hosts. The released sporoplasm invades and then resides between cells of the intestinal mucosa. In contrast to the parasite in the fish host, the parasite in the oligochaete undergoes the entire developmental cycle in this location. This developmental cycle involves merogony, gametogamy or the formation of haploid gametes, and sporogony. The actinosporean spores, formed at the culmination of this development, are released into the lumen of the intestine, prior to discharging into the aquatic environment. The mechanisms underlying the complex development of <em>M. cerebralis</em>, and its interactions with both hosts, are poorly understood. Recent advances, however, are providing insights into the factors that mediate certain phases of the infection. In this review, we consider known and recently obtained information on the taxonomy, development, and life cycle of the parasite.

scholarly journals Dynamics of venom composition across a complex life cycle

2017 ◽  
Author(s):  
Yaara Y. Columbus-Shenkar ◽  
Maria Y. Sachkova ◽  
Arie Fridrich ◽  
Vengamanaidu Modepalli ◽  
Kartik Sunagar ◽  
...  
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Complex Life Cycle ◽  
Nematostella Vectensis ◽  
Life Stages ◽  
Early Life Stages ◽  
Sea Anemones ◽  
Sessile Polyp ◽  
Venom Composition ◽  
Production Dynamics

AbstractLittle is known about venom in young developmental stages of animals. The appearance of stinging cells in very early life stages of the sea anemone Nematostella vectensis suggests that toxins and venom are synthesized already in eggs, embryos and larvae of this species. Here we harness transcriptomic and biochemical tools as well as transgenesis to study venom production dynamics in Nematostella. We find that the venom composition and arsenal of toxin-producing cells change dramatically between developmental stages of this species. These findings might be explained by the vastly different ecology of the larva and adult polyp as sea anemones develop from a miniature non-feeding mobile planula to a much larger sessile polyp that predates on other animals. Further, the results suggest a much wider and dynamic venom landscape than initially appreciated in animals with a complex life cycle.

The life history and ecology of the snow alga Chloromonas polyptera comb. nov. (Chlorophyta, Volvocales)

1983 ◽  
Vol 61 (9) ◽  
pp. 2416-2429 ◽  
Author(s):  
Ronald W. Hoham ◽  
John E. Mullet ◽  
Stephen C. Roemer
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Laboratory Observation ◽  
Vegetative Cells ◽  
Snow Algae ◽  
Algal Succession ◽  
Snow Alga ◽  
Low Levels ◽  
Increasing Temperature ◽  
First Time

Snow algae previously designated as Carteria nivale, Scotiella polyptera, S. polyptera var. polimantii, and S. polyptera var. magellanica were found to be developmental stages of the zygote of Chloromonas polyptera comb. nov. Five species of Scotiella from snow have now been identified as zygotes of different specis of Chloromonas. In this life cycle, biflagellate vegetative cells, zoospores, gametes, and sexual reproduction are reported for the first time. The different forms of the zygote have been reported previously in the literature from several parts of the world, but have been misinterpreted as several distinct taxa of snow algae. The stages in the life cycle of Chloromonas polyptera occur in old, rapidly melting snowbanks, usually less than 30 cm deep. In the same snowbanks, zygotes of C. polyptera germinate later than those reported for Chloromonas nivalis, Chloromonas brevispina, and Chloromonas pichinchae indicating the occurrence of algal succession. Higher light intensity and a more saturated snowbank appear necessary for germination of zygotes of C. polyptera when compared with other species of Chloromonas found in snow. Low levels of carbon dioxide in snow may be limiting for growth of C. polyptera and vegetative cells are sensitive to increasing temperature as observed through laboratory observation. Freezing does not appear to initiate meiosis in the zygotes of C. polyptera as reported for other Volvocalean algae found in snow.

scholarly journals Developmental plasticity and the evolution of animal complex life cycles

2010 ◽  
Vol 365 (1540) ◽  
pp. 631-640 ◽  
Author(s):  
Alessandro Minelli ◽  
Giuseppe Fusco
Keyword(s):  
Life Cycle ◽  
Developmental Plasticity ◽  
Developmental Stages ◽  
Ecological Condition ◽  
Life Cycles ◽  
Complex Life Cycle ◽  
Complex Life Cycles ◽  
Transcription Profiles ◽  
Alternative Phenotypes ◽  
Reproductive Events

Metazoan life cycles can be complex in different ways. A number of diverse phenotypes and reproductive events can sequentially occur along the cycle, and at certain stages a variety of developmental and reproductive options can be available to the animal, the choice among which depends on a combination of organismal and environmental conditions. We hypothesize that a diversity of phenotypes arranged in developmental sequence throughout an animal's life cycle may have evolved by genetic assimilation of alternative phenotypes originally triggered by environmental cues. This is supported by similarities between the developmental mechanisms mediating phenotype change and alternative phenotype determination during ontogeny and the common ecological condition that favour both forms of phenotypic variation. The comparison of transcription profiles from different developmental stages throughout a complex life cycle with those from alternative phenotypes in closely related polyphenic animals is expected to offer critical evidence upon which to evaluate our hypothesis.

scholarly journals Dynamics of venom composition across a complex life cycle

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Yaara Y Columbus-Shenkar ◽  
Maria Y Sachkova ◽  
Jason Macrander ◽  
Arie Fridrich ◽  
Vengamanaidu Modepalli ◽  
...  
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Interspecific Interactions ◽  
Life Stage ◽  
Complex Life Cycle ◽  
Sessile Polyp ◽  
Venom Composition ◽  
Transgenic Tools ◽  
Eggs And Larvae ◽  
Production Dynamics

Little is known about venom in young developmental stages of animals. The appearance of toxins and stinging cells during early embryonic stages in the sea anemone Nematostella vectensis suggests that venom is already expressed in eggs and larvae of this species. Here, we harness transcriptomic, biochemical and transgenic tools to study venom production dynamics in Nematostella. We find that venom composition and arsenal of toxin-producing cells change dramatically between developmental stages of this species. These findings can be explained by the vastly different interspecific interactions of each life stage, as individuals develop from a miniature non-feeding mobile planula to a larger sessile polyp that predates on other animals and interact differently with predators. Indeed, behavioral assays involving prey, predators and Nematostella are consistent with this hypothesis. Further, the results of this work suggest a much wider and dynamic venom landscape than initially appreciated in animals with a complex life cycle.

Ultrastructural analysis of “Sensory” surface nerve endings and “putative” neurotransmitter sites in Schistosoma mansoni Miracidia

1989 ◽  
Vol 47 ◽  
pp. 962-963
Author(s):  
Betty Ruth Jones ◽  
Steve Chi-Tang Pan
Keyword(s):  
Nervous System ◽  
Life Cycle ◽  
Schistosoma Mansoni ◽  
Snail Host ◽  
Complex Life Cycle ◽  
Rational Approach ◽  
Effective Control ◽  
The Social ◽  
Social And Economic Development ◽  
Basic Biology

INTRODUCTION: Schistosomiasis has been described as “one of the most devastating diseases of mankind, second only to malaria in its deleterious effects on the social and economic development of populations in many warm areas of the world.” The disease is worldwide and is probably spreading faster and becoming more intense than the overall research efforts designed to provide the basis for countering it. Moreover, there are indications that the development of water resources and the demands for increasing cultivation and food in developing countries may prevent adequate control of the disease and thus the number of infections are increasing.Our knowledge of the basic biology of the parasites causing the disease is far from adequate. Such knowledge is essential if we are to develop a rational approach to the effective control of human schistosomiasis. The miracidium is the first infective stage in the complex life cycle of schistosomes. The future of the entire life cycle depends on the capacity and ability of this organism to locate and enter a suitable snail host for further development, Little is known about the nervous system of the miracidium of Schistosoma mansoni and of other trematodes. Studies indicate that miracidia contain a well developed and complex nervous system that may aid the larvae in locating and entering a susceptible snail host (Wilson, 1970; Brooker, 1972; Chernin, 1974; Pan, 1980; Mehlhorn, 1988; and Jones, 1987-1988).

scholarly journals Caterpillars of the marsh fritillary butterfly Euphydryas aurinia can extend their life-cycle in Scotland

2021 ◽  
Author(s):  
Neil O. M. Ravenscroft
Keyword(s):  
Life Cycle ◽  
Conservation Status ◽  
Northern Europe ◽  
First Year ◽  
Winter Mortality ◽  
Closely Related Species ◽  
Euphydryas Aurinia ◽  
High Conservation ◽  
The Uk ◽  
Marsh Fritillary

AbstractThe marsh fritillary Euphydryas aurinia is declining across Europe and is of high conservation interest. Its ecology has been defined and its conservation status assessed primarily from the affinities and populations of young caterpillars in the autumn, before hibernation and high winter mortality. The possibility that caterpillars of E. aurinia can overwinter more than once was investigated on the Isle of Islay, Scotland after caterpillars were found to occur at some locations in the spring despite a pre-hibernation absence. Closely-related species in North America and Northern Europe can prolong larval development by diapausing for a year as does E. aurinia in Scandinavia. Measurements of development and manipulations of distribution confirmed that some caterpillars do extend the life-cycle in Scotland and may occur in areas devoid of larvae in their first year. Caterpillars attempting this life-cycle develop slowly in spring, attain the normal penultimate spring instar and then enter diapause while other caterpillars are pupating. They moult just before diapause, construct highly cryptic webs and on emergence the following spring are 5–6 times heavier than larvae emerging in their first spring, or the equivalent of a month or so ahead. They attain a final, extra instar as larvae in their first spring reach the penultimate instar. Knowledge of this life-cycle is confined in the UK to Islay but its occurrence in this mild climate implies that it is more widespread.Implications for insect conservation Conditions that permit long diapause are probably precise and may not be reflected in recognised qualities of habitat. The species may also be present despite a perceived absence in autumn, the standard period for monitoring. Assessments of the prevalence of the life-cycle and its contribution to the persistence of E. aurinia are required. Populations of E. aurinia are known to fluctuate greatly and do occur below the observation threshold for long periods.

scholarly journals Mitochondrial Processes during Early Development of Dictyostelium discoideum: From Bioenergetic to Proteomic Studies

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 638
Author(s):  
Monika Mazur ◽  
Daria Wojciechowska ◽  
Ewa Sitkiewicz ◽  
Agata Malinowska ◽  
Bianka Świderska ◽  
...  
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Coupling Efficiency ◽  
Slime Mold ◽  
Intact Cells ◽  
Life Cycle Stages ◽  
Early Developmental Stages ◽  
Proteomic Study ◽  
And Function ◽  
Early Developmental

The slime mold Dictyostelium discoideum’s life cycle includes different unicellular and multicellular stages that provide a convenient model for research concerning intracellular and intercellular mechanisms influencing mitochondria’s structure and function. We aim to determine the differences between the mitochondria isolated from the slime mold regarding its early developmental stages induced by starvation, namely the unicellular (U), aggregation (A) and streams (S) stages, at the bioenergetic and proteome levels. We measured the oxygen consumption of intact cells using the Clarke electrode and observed a distinct decrease in mitochondrial coupling capacity for stage S cells and a decrease in mitochondrial coupling efficiency for stage A and S cells. We also found changes in spare respiratory capacity. We performed a wide comparative proteomic study. During the transition from the unicellular stage to the multicellular stage, important proteomic differences occurred in stages A and S relating to the proteins of the main mitochondrial functional groups, showing characteristic tendencies that could be associated with their ongoing adaptation to starvation following cell reprogramming during the switch to gluconeogenesis. We suggest that the main mitochondrial processes are downregulated during the early developmental stages, although this needs to be verified by extending analogous studies to the next slime mold life cycle stages.

The developmental stages of Neobrachiella robusta (Wilson, 1912), a parasitic copepod of Sebastes (Teleostei: Scorpaeniformes)

1987 ◽  
Vol 65 (6) ◽  
pp. 1331-1336
Author(s):  
Z. Kabata
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Parasitic Copepod ◽  
Gill Arch ◽  
Gill Rakers ◽  
Copepodid Stage

The morphology of the developmental stages of Neobrachiella robusta (Wilson, 1912) (Copepoda: Siphonostomatoida) is described. The copepod is parasitic on the gill rakers of Sebastes alutus (Gilbert, 1890) (Teleostei: Scorpaeniformes). The life cycle of this copepod consists of a copepodid stage, followed by four chalimus stages and a relatively long preadult stage, which undergoes extensive metamorphosis. The copepods aggregate on the outer row of long gill rakers of the first gill arch, as many as 97% of them being attached to these rakers. Some of the rakers become distorted, but a connection between the presence of N. robusta and these abnormalities could not be established.

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