scholarly journals On the advantages and disadvantages of larval stages in benthic marine invertebrate life cycles

1999 ◽  
Vol 177 ◽  
pp. 269-297 ◽  
Author(s):  
JA Pechenik
Keyword(s):  
Marine Invertebrate ◽  
Life Cycles ◽  
Larval Stages ◽  
Advantages And Disadvantages ◽  
Benthic Marine Invertebrate

scholarly journals Molecular data reshape our understanding of the life cycles of three digeneans (Monorchiidae and Gymnophallidae) infecting the bivalve, Donax variabilis: it’s just a facultative host!

Parasite ◽  
2021 ◽  
Vol 28 ◽  
pp. 34
Author(s):  
Kristina M. Hill-Spanik ◽  
Claudia Sams ◽  
Vincent A. Connors ◽  
Tessa Bricker ◽  
Isaure de Buron
Keyword(s):  
Gulf Of Mexico ◽  
Intermediate Host ◽  
Atlantic Coast ◽  
The United States ◽  
Life Cycles ◽  
Intermediate Hosts ◽  
Larval Stages ◽  
Complete Life Cycle ◽  
Morphological Criteria ◽  
Donax Variabilis

The coquina, Donax variabilis, is a known intermediate host of monorchiid and gymnophallid digeneans. Limited morphological criteria for the host and the digeneans’ larval stages have caused confusion in records. Herein, identities of coquinas from the United States (US) Atlantic coast were verified molecularly. We demonstrate that the current GenBank sequences for D. variabilis are erroneous, with the US sequence referring to D. fossor. Two cercariae and three metacercariae previously described in the Gulf of Mexico and one new cercaria were identified morphologically and molecularly, with only metacercariae occurring in both hosts. On the Southeast Atlantic coast, D. variabilis’ role is limited to being a facultative second intermediate host, and D. fossor, an older species, acts as both first and second intermediate hosts. Sequencing demonstrated 100% similarities between larval stages for each of the three digeneans. Sporocysts, single tail cercariae, and metacercariae in the incurrent siphon had sequences identical to those of monorchiid Lasiotocus trachinoti, for which we provide the complete life cycle. Adults are not known for the other two digeneans, and sequences from their larval stages were not identical to any in GenBank. Large sporocysts, cercariae (Cercaria choanura), and metacercariae in the coquinas’ foot were identified as Lasiotocus choanura (Hopkins, 1958) n. comb. Small sporocysts, furcocercous cercariae, and metacercariae in the mantle were identified as gymnophallid Parvatrema cf. donacis. We clarify records wherein authors recognized the three digenean species but confused their life stages, and probably the hosts, as D. variabilis is sympatric with cryptic D. texasianus in the Gulf of Mexico.

Life Cycles

2001 ◽  
Author(s):  
Jan A. Pechenik
Keyword(s):  
Life Cycle ◽  
Genetic Material ◽  
Life Cycles ◽  
Offspring Size ◽  
Free Living ◽  
Complex Life Cycles ◽  
Volume Number ◽  
Larval Stages ◽  
Underlying Mechanisms ◽  
Life Cycle Evolution

I have a Hardin cartoon on my office door. It shows a series of animals thinking about the meaning of life. In sequence, we see a lobe-finned fish, a salamander, a lizard, and a monkey, all thinking, “Eat, survive, reproduce; eat, survive, reproduce.” Then comes man: “What's it all about?” he wonders. Organisms live to reproduce. The ultimate selective pressure on any organism is to survive long enough and well enough to pass genetic material to a next generation that will also be successful in reproducing. In this sense, then, every morphological, physiological, biochemical, or behavioral adaptation contributes to reproductive success, making the field of life cycle evolution a very broad one indeed. Key components include mode of sexuality, age and size at first reproduction (Roff, this volume), number of reproductive episodes in a lifetime, offspring size (Messina and Fox, this volume), fecundity, the extent to which parents protect their offspring and how that protection is achieved, source of nutrition during development, survival to maturity, the consequences of shifts in any of these components, and the underlying mechanisms responsible for such shifts. Many of these issues are dealt with in other chapters. Here I focus exclusively on animals, and on a particularly widespread sort of life cycle that includes at least two ecologically distinct free-living stages. Such “complex life cycles” (Istock 1967) are especially common among amphibians and fishes (Hall and Wake 1999), and within most invertebrate groups, including insects (Gilbert and Frieden 1981), crustaceans, bivalves, gastropods, polychaete worms, echinoderms, bryozoans, and corals and other cnidarians (Thorson 1950). In such life cycles, the juvenile or adult stage is reached by metamorphosing from a preceding, free-living larval stage. In many species, metamorphosis involves a veritable revolution in morphology, ecology, behavior, and physiology, sometimes taking place in as little as a few minutes or a few hours. In addition to the issues already mentioned, key components of such complex life cycles include the timing of metamorphosis (i.e., when it occurs), the size at which larvae metamorphose, and the consequences of metamorphosing at particular times or at particular sizes. The potential advantages of including larval stages in the life history have been much discussed.

scholarly journals Silent oceans: ocean acidification impoverishes natural soundscapes by altering sound production of the world's noisiest marine invertebrate

2016 ◽  
Vol 283 (1826) ◽  
pp. 20153046 ◽  
Author(s):  
Tullio Rossi ◽  
Sean D. Connell ◽  
Ivan Nagelkerken
Keyword(s):  
Ocean Acidification ◽  
Sound Production ◽  
Marine Invertebrate ◽  
Empirical Test ◽  
Sound Level ◽  
Similar Reduction ◽  
Snapping Shrimp ◽  
Larval Stages ◽  
Coastal Marine ◽  
Ecological Importance

Soundscapes are multidimensional spaces that carry meaningful information for many species about the location and quality of nearby and distant resources. Because soundscapes are the sum of the acoustic signals produced by individual organisms and their interactions, they can be used as a proxy for the condition of whole ecosystems and their occupants. Ocean acidification resulting from anthropogenic CO 2 emissions is known to have profound effects on marine life. However, despite the increasingly recognized ecological importance of soundscapes, there is no empirical test of whether ocean acidification can affect biological sound production. Using field recordings obtained from three geographically separated natural CO 2 vents, we show that forecasted end-of-century ocean acidification conditions can profoundly reduce the biological sound level and frequency of snapping shrimp snaps. Snapping shrimp were among the noisiest marine organisms and the suppression of their sound production at vents was responsible for the vast majority of the soundscape alteration observed. To assess mechanisms that could account for these observations, we tested whether long-term exposure (two to three months) to elevated CO 2 induced a similar reduction in the snapping behaviour (loudness and frequency) of snapping shrimp. The results indicated that the soniferous behaviour of these animals was substantially reduced in both frequency (snaps per minute) and sound level of snaps produced. As coastal marine soundscapes are dominated by biological sounds produced by snapping shrimp, the observed suppression of this component of soundscapes could have important and possibly pervasive ecological consequences for organisms that use soundscapes as a source of information. This trend towards silence could be of particular importance for those species whose larval stages use sound for orientation towards settlement habitats.

Responses of a benthic marine invertebrate to γ-irradiated sediment

Nature ◽  
1977 ◽  
Vol 270 (5638) ◽  
pp. 595-596 ◽  
Author(s):  
E. A. DEANS ◽  
J. G. ANDERSON ◽  
P. S. MEADOWS
Keyword(s):  
Marine Invertebrate ◽  
Benthic Marine Invertebrate

scholarly journals Comparative description and ossification patterns of Dendropsophus labialis (Peters, 1863) and Scinax ruber (Laurenti, 1758)(Anura: Hylidae)

2017 ◽  
Author(s):  
Angélica Arenas Rodríguez ◽  
Juan Francisco Rubiano ◽  
Julio Mario Hoyos
Keyword(s):  
Comparative Studies ◽  
Skeletal Development ◽  
Spinal Column ◽  
Transverse Process ◽  
Life Cycles ◽  
Larval Stages ◽  
Staining Techniques ◽  
Ossification Sequences ◽  
Comparative Description ◽  
Ossification Sequence

Although comparative studies of anuran ontogeny have provided new data on heterochrony in the life cycles of frogs, most of them have not included Colombian species. Using different staining techniques, we describe the cranial and poscranial elements development in two hylid species, Scinax ruber and Dendropsophus labialis, providing new data for more comprehensive ontogenetic studies in Neotropical frogs. We examined specimens from Gosner stages 25 to 45. We found differences in the infrarostral and suprarostral cartilages, optic foramen, planum ethmoidale, and the gill apparatus. In the ossification sequence, one of the first elements to ossify were the transverse process of spinal column and atlas in both species, and the parasphenoid in the skull. New descriptions of skeletal development and ossification sequences of larval stages of these two species, especially data concerning the postcranium, contribute with useful information for analysis of sequential heterochrony, because although the hylids are widely known, there are few works (15 of 700 species) about ossification sequence that include the whole skeleton.

scholarly journals Identification of the Neuropeptide Precursor Genes Potentially Involved in the Larval Settlement in the Echiuran Worm Urechis unicinctus

2020 ◽  
Author(s):  
Xitan Hou ◽  
Zhenkui Qin ◽  
Maokai Wei ◽  
Zhong Fu ◽  
Ruonan Liu ◽  
...  
Keyword(s):  
De Novo ◽  
Marine Invertebrate ◽  
Larval Settlement ◽  
Life Cycles ◽  
Apical Organ ◽  
Neurosecretory System ◽  
Environmental Cues ◽  
Urechis Unicinctus ◽  
Neuroendocrine Mechanisms ◽  
Settlement And Metamorphosis

Abstract Background: In marine invertebrate life cycles, which often consist of planktonic larval and benthonic adult stages, settlement of the free-swimming larva to the sea floor in response to environmental cues is a key life cycle transition. Settlement is regulated by a specialized sensory–neurosecretory system, the larval apical organ. The neuroendocrine mechanisms through which the apical organ transduces environmental cues into behavioral responses during settlement are not fully understood yet.Results: In this study, a total of 54 neuropeptide precursors (pNPs) were identified in the Urechis unicinctus larva and adult transcriptome databases using local BLAST and de novo prediction, of which 10 pNPs belonging to the ancient eumetazoa, 23 pNPs belonging to the ancient bilaterian, 3 pNPs belonging to the ancient protostome, 10 pNPs exclusive in lophotrochozoa, 3 pNPs exclusive in annelid, and 5 pNPs only found in U. unicinctus. Furthermore, four pNPs (MIP, FRWamide, FxFamide and FILamide) which may be associated with the settlement and metamorphosis of U. unicinctus larvae were verified successfully by qRT-PCR. Whole-mount in situ hybridization results showed that all the four pNPs were expressed in the region of the apical organ of the larva, and the positive signals were also detected in the ciliary band and abdomen chaetae. We speculated that these pNPs may regulate the movement of larval cilia and chaeta by sensing external attachment signals.Conclusions: This study represents the first comprehensive identification of neuropeptides in Echiura, and would contribute to a complete understanding on the roles of various neuropeptides in larval settlement of most marine benthonic invertebrates.

Bringing the User into the Project Development Process

2011 ◽  
pp. 105-113 ◽  
Author(s):  
Daniel W. Surry
Keyword(s):  
Project Management ◽  
System Development ◽  
Life Cycles ◽  
It Project Management ◽  
Comprehensive Overview ◽  
Technology Project ◽  
Advantages And Disadvantages ◽  
Agile Methodologies ◽  
Information Technology Project ◽  
Information Technology Project Management

This chapter will discuss more than 20 system development life cycles (SDLC) found in the Information Technology project management arena, whereby, a comprehensive overview of the SDLCs history as well as the trigger that instigated its development would be laid out. Subsequently, the chapter will discuss the advantages and disadvantages of using SDLC, whereby the chapter will explain where and when to use which SDLC. As such, the chapter will classify the different SDLCs into three non-exclusive categories: Traditional methodologies, agile methodologies, spiral methodologies and other types of methodologies that used in IT project Management.

scholarly journals Agile Software Development: Methodologies and Trends

2020 ◽  
Vol 14 (11) ◽  
pp. 246
Author(s):  
Samar Alsaqqa ◽  
Samer Sawalha ◽  
Heba Abdel-Nabi
Keyword(s):  
Software Development ◽  
Agile Software Development ◽  
Life Cycles ◽  
Agile Development ◽  
Advantages And Disadvantages ◽  
Modern Business ◽  
Software Development Methodologies ◽  
Agile Software ◽  
The Cost ◽  
Business Requirements

<p>Software engineering is a discipline that undergone many improvements that aims to keep up with the new advancements in technologies and the modern business requirements through developing effective approaches to reach the final software product, agile software development is one of these successful approaches. Agile software development is a lightweight approach that was proposed to overcome the convolutional development methods’ limitations and to reduce the overhead and the cost while providing flexibility to adopt the changes in requirements at any stage, this is done by managing the tasks and their coordination through a certain set of values and principles.</p><p>In this work, a comprehensive review that outlines the main agile values and principles, and states the key differences that distinguish agile methods over the traditional ones are presented. Then a discussion of the most popular agile methodologies; their life cycles, their roles, and their advantages and disadvantages are outlined. The recent state of art trends that adopts agile development especially in cloud computing, big data, and coordination are also explored. And finally, this work highlights how to choose the best suitable agile methodology that must be selected according to the task at hand, how sensitive the product is and the organization structure.</p>

scholarly journals Correlated and decoupled evolution of adult and larval body size in frogs

2020 ◽  
Vol 287 (1933) ◽  
pp. 20201474
Author(s):  
Tung X. Phung ◽  
João C. S. Nascimento ◽  
Alexander J. Novarro ◽  
John J. Wiens
Keyword(s):  
Body Size ◽  
Phylogenetic Signal ◽  
Life Cycles ◽  
Major Group ◽  
Adult Size ◽  
Larval Body ◽  
Larval Stages ◽  
Rates Of Evolution ◽  
Adult Body ◽  
Body Sizes

The majority of animal species have complex life cycles, in which larval stages may have very different morphologies and ecologies relative to adults. Anurans (frogs) provide a particularly striking example. However, the extent to which larval and adult morphologies (e.g. body size) are correlated among species has not been broadly tested in any major group. Recent studies have suggested that larval and adult morphology are evolutionarily decoupled in frogs, but focused within families and did not compare the evolution of body sizes. Here, we test for correlated evolution of adult and larval body size across 542 species from 42 families, including most families with a tadpole stage. We find strong phylogenetic signal in larval and adult body sizes, and find that both traits are significantly and positively related across frogs. However, this relationship varies dramatically among clades, from strongly positive to weakly negative. Furthermore, rates of evolution for both variables are largely decoupled among clades. Thus, some clades have high rates of adult body-size evolution but low rates in tadpole body size (and vice versa). Overall, we show for the first time that body sizes are generally related between adult and larval stages across a major group, even as evolutionary rates of larval and adult size are largely decoupled among species and clades.

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