Section 3 Summary—Larval Transport, Settlement, and Metamorphosis

2018 ◽  
Keyword(s):  
Marine Invertebrates ◽  
Adult Stage ◽  
Sensory Ecology ◽  
Life Cycles ◽  
Larval Transport ◽  
Broadcast Spawning ◽  
Developmental Transition ◽  
Ecological Aspects ◽  
Settlement And Metamorphosis

Life cycles for broadcast-spawning marine invertebrates are characterized by a pelagic (larval) and benthic (juvenile and adult) stage, which are differentiated by the process of settlement and metamorphosis. While settlement and recruitment are concepts that primarily deal with the ecological aspects of this transition, they are often accompanied by a drastic morphological and developmental transition. Larval transport, the means of reaching suitable settlement sites, is difficult to study, but insights from genetics, behavior, sensory ecology, and oceanography have provided important insights....

I Feel That! Fluid Dynamics and Sensory Aspects of Larval Settlement across Scales

2018 ◽  
Keyword(s):  
Fluid Dynamics ◽  
Marine Invertebrates ◽  
Larval Settlement ◽  
External Environment ◽  
Life Cycles ◽  
Decision Making Process ◽  
Larval Biology ◽  
Sea Floor ◽  
External Cues ◽  
Juvenile Habitat

A commonality among oceanic life cycles is a process known as settlement, where dispersing propagules transition to the sea floor. For many marine invertebrates, this transition is irreversible, and therefore involves a crucial decision-making process through which larvae evaluate their juvenile habitat-to-be. In this chapter, we consider aspects of the external environment that could influence successful settlement. Specifically, we discuss water flow across scales, and how larvae can engage behaviors to influence where ocean currents take them, and enhance the likelihood of their being carried toward suitable settlement locations. Next, we consider what senses larvae utilize to evaluate their external environment and properly time such behavioral modifications, and settlement generally. We hypothesize that larvae integrate these various external cues in a hierarchical fashion, with differing arrangements being employed across ontogeny and among species. We conclude with a brief discussion of the future promises of larval biology, ecology, and evolution.

Speciation of cestoda. Evidence for two sibling species in the complex Bothrimonus nylandicus (Schneider 1902) (Cestoda: Cyathocephalidea)

Parasitology ◽  
1988 ◽  
Vol 97 (1) ◽  
pp. 139-147 ◽  
Author(s):  
F. Renaud ◽  
C. Gabrion
Keyword(s):  
Sibling Species ◽  
Definitive Host ◽  
Parasite Species ◽  
Adult Stage ◽  
Life Cycles ◽  
The Other ◽  
Congeneric Species ◽  
Biochemical Genetic ◽  
Autumn And Winter ◽  
Biological Differences

SUMMARYUsing biochemical genetic methods, we have distinguished 2 sibling species in the complex Bothrimonus nylandicus (Schneider, 1902), which infest 2 congeneric species of sole (Solea lascaris and Solea impar) on European coasts (Atlantic and Mediterranean). Neither of the parasite species is specific for either of the sole species, but one of them is present all year round, whereas the other is absent in the autumn and winter and only appears in the spring, subsequently disappearing at the end of the summer. Only S. impar lives in the Mediterranean, and is equally infested by both cestodes, whereas both species occur in the Atlantic and each of them is preferentially infested by 1 species of cestode. The shortness of the adult stage of the parasite in the definitive host and the presence of 2 life-cycles associated with competition between the 2 hosts in the Atlantic could be responsible for the biological differences observed and for maintaining the sibling species in sympatry.

scholarly journals Bacterial Nucleobases Synergistically Induce Larval Settlement and Metamorphosis in the Invasive MusselMytilopsis sallei

2019 ◽  
Vol 85 (16) ◽  
Author(s):  
Jian He ◽  
Qi Dai ◽  
Yuxuan Qi ◽  
Pei Su ◽  
Miaoqin Huang ◽  
...  
Keyword(s):  
Marine Invertebrates ◽  
Larval Settlement ◽  
Aquatic Systems ◽  
Substrate Selection ◽  
Content Type ◽  
Dreissenid Mussels ◽  
Settlement And Metamorphosis ◽  
Environmental Bacteria ◽  
Fouling Organisms ◽  
Chemical Mediators

ABSTRACTMarine bacterial biofilms have long been recognized as potential inducers of larval settlement and metamorphosis in marine invertebrates, but few chemical cues from bacteria have been identified. Here, we show that larval settlement and metamorphosis of an invasive fouling mussel,Mytilopsis sallei, could be induced by biofilms of bacteria isolated from its adult shells and other substrates from the natural environment. One of the strains isolated,Vibrio owensiiMS-9, showed strong inducing activity which was attributed to the release of a mixture of nucleobases including uracil, thymine, xanthine, hypoxanthine, and guanine into seawater. In particular, the synergistic effect of hypoxanthine and guanine was sufficient for the inducing activity ofV. owensiiMS-9. The presence of two or three other nucleobases could enhance, to some extent, the activity of the mixture of hypoxanthine and guanine. Furthermore, we determined that bacteria producing higher concentrations of nucleobases were more likely to induce larval settlement and metamorphosis ofM. salleithan were bacteria producing lower concentrations of nucleobases. The present study demonstrates that bacterial nucleobases play an important role in larval settlement and metamorphosis of marine invertebrates. This provides new insights into our understanding of the role of environmental bacteria in the colonization and aggregation of invasive fouling organisms and of the metabolites used as chemical mediators in cross-kingdom communication within aquatic systems.IMPORTANCEInvasive species are an increasingly serious problem globally. In aquatic ecosystems, invasive dreissenid mussels are well-known ecological and economic pests because they appear to effortlessly invade new environments and foul submerged structures with high-density aggregations. To efficiently control exotic mussel recruitment and colonization, the need to investigate the mechanisms of substrate selection for larval settlement and metamorphosis is apparent. Our work is one of very few to experimentally demonstrate that compounds produced by environmental bacteria play an important role in larval settlement and metamorphosis in marine invertebrates. Additionally, this study demonstrates that bacterial nucleobases can be used as chemical mediators in cross-kingdom communication within aquatic systems, which will enhance our understanding of how microbes induce larval settlement and metamorphosis of dreissenid mussels, and it furthermore may allow the development of new methods for application in antifouling.

Fine structure of Metchnikovella incurvata Caullery and Mesnil 1914 (microsporidia), a hyperparasite of gregarines Polyrhabdina sp. from the polychaete Pygospio elegans

Parasitology ◽  
2013 ◽  
Vol 140 (7) ◽  
pp. 855-867 ◽  
Author(s):  
Y. Y. SOKOLOVA ◽  
G. G. PASKEROVA ◽  
Y. M. ROTARI ◽  
E. S. NASSONOVA ◽  
A. V. SMIRNOV
Keyword(s):  
Electron Microscopy ◽  
Marine Invertebrates ◽  
Light And Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Life Cycles ◽  
Single Family ◽  
Host Cytoplasm ◽  
History Of ◽  
Multinuclear Cells

SUMMARYClass Rudimicrosporea Sprague 1977, with its single family Metchnikovellidae, comprises hyperparasites of gregarines from the guts of marine invertebrates. Metchnikovellids remain poorly studied in spite of their significance to the evolutionary history of microsporidia; their ultrastructure and life cycles require further investigation. Here we present results of the light- and electron-microscopy study of Metchnikovella incurvata Caulleri and Mesnil 1914, isolated from lecudinid gregarines, parasitizing polychaetes Pygospio elegans in the White Sea littoral zone, and yet described only on the light-microscopic level. The life cycle of this microsporidium includes 2 sporogonies: free (FS) and sac-bound (SBS). In FS, sporonts develop into multinuclear cells (sporogonial plasmodia), which generate sporoblasts and free spores residing in direct contact with the host cytoplasm. Electron microscopy revealed their metchnikovellidean structure: a horseshoe-shaped nucleus, short manubrium perpendicular to the long axis of the spore, and a polar cap in a separate membrane container. Merogony was not observed. The earliest stages of SBS were chains of binucleate cells. They underwent a series of nuclear and cell divisions, produced extracellular envelopes, and split into boomerang-shaped spore sacs, containing up to 16 spores each. Ultrastructure and sizes of sac-bounded spores were similar to those of free-living ones. An amended diagnosis of M. incurvata is provided.

scholarly journals Rethinking competence in marine life cycles: ontogenetic changes in the settlement response of sand dollar larvae exposed to turbulence

2015 ◽  
Vol 2 (6) ◽  
pp. 150114 ◽  
Author(s):  
Jason Hodin ◽  
Matthew C. Ferner ◽  
Gabriel Ng ◽  
Christopher J. Lowe ◽  
Brian Gaylord
Keyword(s):  
Life Histories ◽  
Immature Stage ◽  
Life Cycles ◽  
Sand Dollar ◽  
Ontogenetic Changes ◽  
Marine Animals ◽  
Settlement And Metamorphosis ◽  
Two Phases ◽  
Pass Through ◽  
Dendraster Excentricus

Complex life cycles have evolved independently numerous times in marine animals as well as in disparate algae. Such life histories typically involve a dispersive immature stage followed by settlement and metamorphosis to an adult stage on the sea floor. One commonality among animals exhibiting transitions of this type is that their larvae pass through a ‘precompetent’ period in which they do not respond to localized settlement cues, before entering a ‘competent’ period, during which cues can induce settlement. Despite the widespread existence of these two phases, relatively little is known about how larvae transition between them. Moreover, recent studies have blurred the distinction between the phases by demonstrating that fluid turbulence can spark precocious activation of competence. Here, we further investigate this phenomenon by exploring how larval interactions with turbulence change across ontogeny, focusing on offspring of the sand dollar Dendraster excentricus (Eschscholtz). Our data indicate that larvae exhibit increased responsiveness to turbulence as they get older. We also demonstrate a likely cost to precocious competence: the resulting juveniles are smaller. Based upon these findings, we outline a new, testable conception of competence that has the potential to reshape our understanding of larval dispersal and connectivity among marine populations.

Sperm environment affects offspring quality in broadcast spawning marine invertebrates

2002 ◽  
Vol 5 (2) ◽  
pp. 173-176 ◽  
Author(s):  
Dustin John Marshall ◽  
Craig Andrew Styan ◽  
Michael James Keough
Keyword(s):  
Marine Invertebrates ◽  
Offspring Quality ◽  
Broadcast Spawning

scholarly journals High potential for formation and persistence of chimeras following aggregated larval settlement in the broadcast spawning coral, Acropora millepora

2011 ◽  
Vol 279 (1729) ◽  
pp. 699-708 ◽  
Author(s):  
E. Puill-Stephan ◽  
M. J. H. van Oppen ◽  
K. Pichavant-Rafini ◽  
B. L. Willis
Keyword(s):  
Marine Invertebrates ◽  
Larval Settlement ◽  
Early Life History ◽  
Experimental Conditions ◽  
Broadcast Spawning ◽  
Acropora Millepora ◽  
Reef Corals ◽  
Life History Stages ◽  
Potential Benefits ◽  
High Level

In sessile modular marine invertebrates, chimeras can originate from fusions of closely settling larvae or of colonies that come into contact through growth or movement. While it has been shown that juveniles of brooding corals fuse under experimental conditions, chimera formation in broadcast spawning corals, the most abundant group of reef corals, has not been examined. This study explores the capacity of the broadcast spawning coral Acropora millepora to form chimeras under experimental conditions and to persist as chimeras in the field. Under experimental conditions, 1.5-fold more larvae settled in aggregations than solitarily, and analyses of nine microsatellite loci revealed that 50 per cent of juveniles tested harboured different genotypes within the same colony. Significantly, some chimeric colonies persisted for 23 months post-settlement, when the study ended. Genotypes within persisting chimeric colonies all showed a high level of relatedness, whereas rejecting colonies displayed variable levels of relatedness. The nearly threefold greater sizes of chimeras compared with solitary juveniles, from settlement through to at least three months, suggest that chimerism is likely to be an important strategy for maximizing survival of vulnerable early life-history stages of corals, although longer-term studies are required to more fully explore the potential benefits of chimerism.

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