Depth regulation in parenchymella larvae of a demosponge:relative roles of skeletogenesis, biochemical changes and behavior

Maldonado, Manuel; George, Sophie B.; Young, Craig M.; Vaquerizo, Isabel

doi:10.3354/meps148115

Cited by 36 publications

(49 citation statements)

References 20 publications

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“…Despite the fact that sensory organs and/or nervous integration remain unknown in Porifera, it has traditionally been thought that sponge larvae use both gravity and light stimuli for orientation during dispersal and settlement (Fell 1974(Fell , 1989, and references therein). Recent studies have shown, however, a reduction in the buoyancy of the sponge larva with increasing age (Maldonado et al 1997). Because thls mechanism plays an important role in passively moving late-stage larvae towards the bottom when the time of settlement approaches, it is unlikely that larvae a r e capable of a n active geotactic response.…”

Section: Introductionmentioning

confidence: 97%

Microrefuge exploitation by subtidal encrusting sponges:patterns of settlement and post-settlement survival

Maldonado¹,

Uriz²

1998

Mar. Ecol. Prog. Ser.

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The larvae of many sessile marine invertebrates are able to locate and settle selectively in physical microrefuges where the survival of the post-larval stage may be enhanced. However, it has been suggested that clonal encrusting organisms with unlimited attachment to the substratum do not rely heavily on microrefuges for post-larval survival, since they quickly outgrow refuges and then suffer partial rather than total mortality. Consequently, the larva of such organisms is predicted to show little selectivity at the time of settlement. This prediction, verified for some bryozoans and ascidians, has also been extrapolated to sponges despite the fact that there IS virtually no field information on patterns of settlement and post-settlement mortal~ty in t h~s group. In the present study, we investigated patterns of settlement and juvenile mortality in 2 common Mediterranean encrusting sponges, Crambe crambe and Scopalina lophyropoda. We placed a set of grooved plates (providing microrefuges for larval settlement) and a set of smooth plates (without refuges) in the natural community, mapped larval settlement on plates at 3 d intervals, and recorded the fate of each settled larva for 10 wk. The total number of larvae of C. crambe that settled on the plates was significantly h~gher than that of S lophyropoda, and both species settled preferentially in the microrefuges of the grooved plates. On each of the grooved plates, larvae settled preferentially on the shaded sides of outer ndges, avoiding equivalent ridge sldes that were highly exposed to light. This pattern suggests that microrefuges are located by larvae on the basis of photic cues. The analysis of survival time revealed that survival of post-larval stages protected in grooves was higher in both species compared to unprotected post-larvae. The survival curve of the juveniles did not clearly follow an exponential model. Survival decreased more or less rapidly for the first 2 mo, but the chance of mortality was not markedly higher 1 wk after settlement than during subsequent weeks. Because we could not exert control over the various coincidental mortality factors that affected the sponges settled on the experimental plates, we tested the following hypotheses in the laboratory: (1) that the abundant echinoderms inhabiting these assemblages cause significant mortality by both unselective ingestion and abrasion, and (2) that microrefuges substantially reduce sponge vulnerability to this mortality factor. In this experiment, we investigated differences in mortality among small sponges as a function of microhabitat exploitation (sponges protected in grooves versus unprotected sponges on smooth surfaces) and the presence/absence of potential predators (the sea urchin Paracentrotus lividus, the starfish Echinaster sepositus). It was found that E. seposjtus caused negligible mortality, irrespective of sponge mlcrohabitat. In contrast, P. livjdus caused significant mortality, indicating that bulldozing by urchins may have substantial negative effects on sponge...

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Section: Introductionmentioning

confidence: 97%

Microrefuge exploitation by subtidal encrusting sponges:patterns of settlement and post-settlement survival

Maldonado¹,

Uriz²

1998

Mar. Ecol. Prog. Ser.

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“…However, the role of spicules in embryos and larvae is largely unknown, although it has been proposed that they provide protection and confer other advantages during larval and post-larval development (Woollacott 1990;Woollacott 2003). Maldonado et al (1997) was the first to provide a possible ecological and functional role of larval spicules, and hypothesise that these control larvae buoyancy. Sigmadocia caerulea larvae sank more rapidly with age, implying that larvae density might be affected by the increasing number of spicules as ciliary activity was halted for the experiment (Maldonado et al 1997).…”

Section: Discussionmentioning

confidence: 99%

“…3.6). Within the larval stage, sclerocytes are mainly localised at the posterior pole along the AP axis, region where larval spicules are distributed and which may allow larvae to orientate themselves (Leys 2003;Maldonado et al 1997;Woollacott 1993). …”

Section: Discussionmentioning

confidence: 99%

“…Maldonado et al (1997) was the first to provide a possible ecological and functional role of larval spicules, and hypothesise that these control larvae buoyancy. Sigmadocia caerulea larvae sank more rapidly with age, implying that larvae density might be affected by the increasing number of spicules as ciliary activity was halted for the experiment (Maldonado et al 1997). Indeed, length of cilia has been reported to affect the swimming speed of larvae, as larvae possessing a posterior ring with long cilia tend to swim faster (Woollacott 1990;Berquist et al 1970;Konstantinova 1966).…”

Section: Discussionmentioning

confidence: 99%

“…Fabrication and secretion of spicules can occur at different developmental stages of the sponge, either during embryogenesis, larval phase and metamorphosis, through to the development of the juveniles and growth of the adult. However, specific details on the ontogenetic basis of spicule formation are scant (Berquist and Sinclair 1968;Leys 2003;Maldonado et al 1997;Woollacott 1990). Therefore, to better understand the process of spiculogenesis during natural sponge development-embryonic, larval and post-larval stages -using a sexual reproductive system, spicule formation and silicatein expression were analysed in the demosponge A. queenslandica.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of silicatein gene expression and spicule formation in the demosponge Amphimedon queenslandica

Gauthier¹

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The skeletal elements in most sponges are siliceous spicules. These are fabricated into species-specific sizes and shapes. Demosponges, in particular, have specialised cells called sclerocytes that possess the unique ability to synthesise biosilica and these spicules.Underlying the diversity of demosponge spicules morphology is a conserved protein, called silicatein. This thesis aims to investigate the process of spiculogenesis in the different developmental stages of the demosponge Amphimedon queenslandica, and the evolution and developmental expression of the silicatein gene family in relation to spicule formation.A. queenslandica is the only sponge species to have its genome fully sequenced, assembled and annotated, and currently is one of the best models to study sponge development (Srivastava et al. 2010). This species broods embryos year-round, facilitating the access to Conservation of gene structure and exon length in silicatein and cathepsin L genes suggests that these genes have preserved an ancestral gene structure common to both gene families in both marine and freshwater sponges.Using in situ hybridisation, I demonstrated that silicatein genes are expressed during A. queenslandica early embryonic development, with genes being expressed exclusively in sclerocytes. Analysis of gene expression levels through embryogenesis and metamorphosis, using RNA-Seq performed on a pool of same stage individuals, revealed that all silicatein-like genes are differentially expressed throughout development, and the expression of silicatein genes occurs prior to spicule formation. However, some silicatein-like gene expression levels and spicule number do not appear to be tightly correlated.

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Siliceous spicules and skeleton frameworks in sponges: Origin, diversity, ultrastructural patterns, and biological functions

Uriz

Turon

Becerro

et al. 2003

Microscopy Res & Technique

218

161

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Silica deposition is a fundamental process in sponges. Most sponges in the Classes Demospongiae and Hexactinellida secrete siliceous elements, which can subsequently fuse, interlock with each other, or form three-dimensional structures connected by spongin. The resulting skeletal frameworks allow sponges to grow upwards and facilitate water exchange with minimal metabolic cost. Several studies on sponge skeletogenesis have been published. We are beginning to understand the mechanisms of spicule secretion and the role of spicules and skeletal frameworks in the biology, ecology, and evolution of sponges. Molecular techniques and ecological experiments have demonstrated the genetic control of the process and the contribution of environmental factors to the expression of a sponge spicule, respectively. However, other classic topics such as the role of membranes in silicon transport or whether spicules are formed in situ or secreted anywhere in the sponge mesohyl and then transported to the skeletal framework require further investigation. We review the process of silica deposition in sponges at the molecular and cellular levels, as well as the biological and ecological functions of spicules and skeletons. The genetic control of spicule shapes makes them useful in the reconstruction of sponge phylogeny, although recent experiments have demonstrated the influence of environmental factors in modulating spicule size, shape, and the presence or absence of one or more spicule types. The implications of such variations in sponge taxonomy may be important. Besides supporting sponge cells, spicules can help larvae stay buoyant while in the plankton or reach the bottom at settlement, enhance reproduction success, or catch prey. Conversely, the role of spicules and skeletons in deterring predation has not been demonstrated. Knowledge of several aspects is still based on a single or a few species and extrapolations should be made only with caution. With the advent of new molecular techniques, new lines of research are presently open and active in this field.

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Depth regulation in parenchymella larvae of a demosponge:relative roles of skeletogenesis, biochemical changes and behavior

Cited by 36 publications

References 20 publications

Microrefuge exploitation by subtidal encrusting sponges:patterns of settlement and post-settlement survival

Microrefuge exploitation by subtidal encrusting sponges:patterns of settlement and post-settlement survival

Analysis of silicatein gene expression and spicule formation in the demosponge Amphimedon queenslandica

Siliceous spicules and skeleton frameworks in sponges: Origin, diversity, ultrastructural patterns, and biological functions

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