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Asexual propagation and reproductive strategies

TL;DR: Partial table of contents: Annelida-Clitellata (B. Christensen), Tardigrada (R. Bertolani), Arthropoda-Insecta (J. Muthukrishnan), Echinodermata: Asexual Propagation (P. Mladenov & R. Burke).
Abstract: Partial table of contents: Annelida-Clitellata (B Christensen) Tardigrada (R Bertolani) Arthropoda-Insecta (J Muthukrishnan) Pentastomida (J Riley) Bryozoa Entoprocta (C Nielsen) Brachiopoda (S Chuang) Chaetognatha (A Alvari?o) Echinodermata: Asexual Propagation (P Mladenov & R Burke) Cephalochordata (J Azariah) Indexes
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Journal Article
TL;DR: An overview of the current understanding of the regeneration in echinoderms can be found in this paper, where the main biological aspects of regeneration giving an idea of the state of the art across the phylum in terms of experimental approaches and representative models.
Abstract: Regenerative potential is expressed to a maximum extent in echinoderms. It is a commonphenomenon in all the classes, extensively employed to reconstruct external appendages and internalorgans often subjected to amputation, self-induced or traumatic, rapidly followed by completesuccessful re-growth of the lost parts. Regeneration has been studied in adult individuals as well as inlarvae. In armed echinoderms, regeneration of arms is obviously frequent: in many cases, the detached body fragments can undergo phenomena of partial or total regeneration independently of the donor animal, and, in a few cases (asteroids), the individual autotomised arms can even regenerate to produce new complete adults, offering superb examples of cloning strategies. In the species examined so far most results throw light on aspects related to wound healing, growth, morphogenesis and differentiation, even though in most cases many crucial questions remain unanswered. The present paper provides an overview of the current understanding of the phenomenon and covers the main biological aspects of regeneration giving an idea of the “state of the art” across the phylum in terms of experimental approaches and representative models.

171 citations

Journal ArticleDOI
TL;DR: The 39 kDa protein is an excellent candidate for the rotifer mixis induction signal and has strong similarity to a steroidogenesis-inducing protein isolated from human ovarian follicular fluid.
Abstract: The defining feature of the life cycle in monogonont rotifers such as Brachionus plicatilis (Muller) is alternation of asexual and sexual reproduction (mixis). Why sex is maintained in such life cycles is an important unsolved evolutionary question and one especially amenable to experimental analysis. Mixis is induced by a chemical signal produced by the rotifers which accumulates to threshold levels at high population densities. The chemical features of this signal were characterized using size exclusion, enzymatic degradation, protease protection assays, selective binding to anion ion exchange and C3 reversed phase HPLC columns, and the sequence of 17 N-terminal amino acids. These studies were carried out over two years beginning in 2003 using B. plicatilis Russian strain. When rotifer-conditioned medium was treated with proteinase K, its mixis-inducing ability was reduced by 70%. Proteinase K was added to medium auto-conditioned by 1 female ml−1 where typically 17% of daughters became mictic and mixis was reduced to 1%. A cocktail of protease inhibitors added to conditioned medium significantly reduced degradation of the mixis signal by natural proteases. Conditioned medium subjected to ultrafiltration retained mixis-inducing activity in the >10 kDa fraction, but the <10 kDa fraction had no significant activity. The putative mixis signal bound to an anion exchange column, eluting off at 0.72 M NaCl. These fractions were further separated on a C3 reversed phase HPLC column and mixis-inducing activity was associated with a 39 kDa protein. Seventeen amino acids from the N-terminus have strong similarity to a steroidogenesis-inducing protein isolated from human ovarian follicular fluid. The 39 kDa protein is an excellent candidate for the rotifer mixis induction signal.

146 citations

Journal ArticleDOI
TL;DR: Original data on the mode of cleavage, timing of cellular differentiation, and the mechanisms involved in the organization of differentiated cells to form the metazoan body plan are reviewed.
Abstract: Having descended from the first multicellular animals on earth, sponges are a key group in which to seek innovations that form the basis of the metazoan body plan, but sponges themselves have a body plan that is extremely difficult to reconcile with that of other animals. Adult sponges lack overt anterior–posterior polarity and sensory organs, and whether they possess true tissues is even debated. Nevertheless, sexual reproduction occurs as in other metazoans, with the development of embryos through a structured series of cellular divisions and organized rearrangements of cellular material, using both mesenchymal and epithelial movements to form a multicellular embryo. In most cases, the embryo undergoes morphogenesis into a spatially organized larva that has several cell layers, anterior–posterior polarity, and sensory capabilities. Here we review original data on the mode of cleavage, timing of cellular differentiation, and the mechanisms involved in the organization of differentiated cells to form the ...

91 citations

Book ChapterDOI
01 Jan 2002

46 citations

Journal ArticleDOI
TL;DR: Seasonal samples of all fish species from Lake Moreno were taken to determine the presence of paratenia, to evaluate the status of the hosts and to characterise the transmission of Acanthocephalus tumescens at the component population level.
Abstract: Seasonal samples of all fish species from Lake Moreno were taken in order to determine the presence of paratenia, to evaluate the status of the hosts and to characterise the transmission of Acanthocephalus tumescens (von Linstow, 1896) at the component population level. Prevalence, mean abundance, mean intensity, numbers of gravid females, relative abundance of the different fish species, relative output of eggs and relative flow rates for each host species were computed. Acanthocephalus tumescens showed low host specificity, successfully parasitizing six out of eight fish species present in the lake. No paratenic infection was registered. If prevalence, mean abundance, and number of gravid females are considered, host species can be placed in a continuum from the most to least suitable as follows: Galaxias platei Steindachner, Diplomystes viedmensis (Mac Donagh), Oncorhynchus mykiss (Walbaum), Salvelinus fontinalis (Mitchill), Percichthys trucha (Cuvier et Valenciennes) and Galaxias maculatus (Jenyns). However, when parasite flow rates and egg output were calculated, including relative abundance of each fish species, the continuum was rearranged as follows: P. trucha, O. mykiss, G. platei / G. maculatus, S. fontinalis and D. viedmensis. The first four species would be the main contributors to the population of A. tumescens in this lake, P. trucha being the major one. Different regulatory and non-regulatory mechanisms are suggested.

45 citations