Larvae Of Benthic Marine Invertebrates Research Articles

Evaluation of light traps for sampling lobster larvae in the German Bight, North Sea

Biological monitoring of planktonic animals is greatly dependent on the deployment of traps.A variety of specialized traps have been designed for surface plankton and vertebrates. However, certain groups, such as planktonic larvae of benthic marine invertebrates remain underrepresented in sampling efforts. Catching them has proven to be more challenging because of their size, swimming ability, location, and abundance. In the present study a successful light trap for sampling American lobster larvae in New Brunswick, Canada, is evaluated on the island of Helgoland (German Bight, North Sea). Our results showed the traps were successful in catching larvae in laboratory experiments but were unable to catch European lobster larvae in the field. Traps deployed in the field were successful in capturing other benthic and pelagic zooplankton predominantly consisting of crustaceans from the orders: Cumacea, Amphipoda, Mysida and Isopoda. The low density of lobster larvae, the island's topography, and their unique photactic response possibly limited the success rate of the light traps. Future research is needed to construct a specialized trap to sample Helgoland's lobster larvae and provide information on the current larval fitness and population numbers.

Effect of background substrate on recruitment of benthic marine invertebrates to subtidal cobble-filled collectors

The availability of suitable substrate for settlement can alter the behaviour of larvae of benthic marine invertebrates and consequently their settlement patterns. We tested the effect of the background substrate of a site (rocky vs sediment) on recruitment of invertebrates settling into standardized cobble-filled collectors deployed at shallow subtidal sites in the south-western Bay of Fundy, Canada, in 2009 and 2010. The assemblage of invertebrates that settled into the collectors differed significantly in both abundance and species composition between “paired sites” (≈0.003–0.009 km2 in area and 345–861 m apart) with rocky vs sediment background substrate, and markedly less so between paired sites comprised of rocky bottom. Species that are known to be rock-dwelling recruited in greater abundance to cobble-filled collectors at rocky sites, while those known to be sediment-dwelling recruited more to cobble-filled collectors at sediment sites. At the smaller spatial scale of patches of sediment within one site (14–107 m apart), differences in abundance but not species composition were detected between collectors on the two types of background substrate. This study supports the idea that larvae of some species of marine invertebrates respond to substrate at a larger spatial scale than their immediate location of settlement.

The Peril of the Plankton

The pelagic environment is characterized by unevenly distributed resources and risks. Such unpredictability presents adaptive challenges to diverse planktonic organisms including the larvae of benthic marine invertebrates. Estimates of mortality during planktonic development are highly variable, ranging from 0% to 100% per day. Predation is considered a significant source of this mortality, but what explains the variability in estimates of the mortality of marine invertebrate larvae? While differential exposure of larval prey to predators may explain these widely variable estimates, adaptations that reduce vulnerability of marine larvae to predators may also be important. Although there are excellent reviews of predation upon larvae and of larval mortality and defenses, nearly 15 years have elapsed since these topics were formally reviewed. Here, we highlight recent advances in understanding the behavioral, chemical, and morphological defenses that larvae possess and assess their effectiveness in reducing the risk of predation. While recent work confirms that larval mortality is generally high, it also demonstrates that larvae can reduce their risk of predation in several ways, including: (1) temporarily escaping the benthos during vulnerable early stages, (2) producing chemical compounds that reduce palatability, (3) possessing morphological defenses such as spines and shells, and (4) exhibiting induced defensive responses whereby larvae can alter their behavior, morphology, and life histories in the presence of predators. Taken together, these studies indicate that marine invertebrate larvae possess a sophisticated suite of defensive phenotypes that have allowed them to persist in the life cycle of benthic invertebrates for eons.

Go with the flow: tidal import and export of larvae from semi-enclosed bays

There is a growing body of evidence that suggests the effective functioning of marine reserves is dependent on the dispersal and recruitment of larvae. Enhanced production inside reserves is predicted to lead to a net larval export and increased settlement and recruitment outside reserve boundaries. However, larval retention in bays is also well documented. Since bays are increasingly being used as reserve areas, planktonic larvae of benthic marine invertebrates were sampled from two semi-enclosed marine reserves during flood and ebb tides to determine whether these bays are acting as net exporters of larvae. Neither reserve was a net importer or exporter of species richness, larval abundance or diversity, although one reserve showed a small export of species richness during the hours of darkness. Both reserves balanced the net import of some species with a net export of others, which was generally related to adult or larval abundance, although exceptions were found in one reserve. Significant effects of light were found, with the net import or export of some species occurring exclusively during either the hours of daylight or darkness. An increased understanding of larval sink-source dynamics in bays is essential for ensuring their effective use as marine reserves to meet specific conservation needs.

Coastline configuration as a determinant of structure in larval assemblages

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 352:67-75 (2007) - DOI: https://doi.org/10.3354/meps07156 Coastline configuration as a determinant of structure in larval assemblages M. Jessopp1,*, O. R. Mulholland2, R. McAllen1, M. P. Johnson3, T. P. Crowe2, A. L. Allcock3 1Department of Zoology, Ecology and Plant Science, University College Cork, Distillery Fields, North Mall, Cork, Ireland 2School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland 3School of Biology and Biochemistry, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK *Email: mjessopp@gmail.com ABSTRACT: The richness and turnover of coastal larval pools set upper limits for biodiversity in coastal systems. For particular local systems, such as embayments, the characteristics of the local larval pool are determined by the relative contributions of locally produced and external larvae. The balance between these sources partially reflects the extent of tidal exchange and is hence related to system size and flushing time. Larvae of benthic marine invertebrates were sampled from 8 bays along the Irish coast to investigate the effect of coastline configuration on the characteristics of the larval pool. Flushing time explained 34.5% of the variability in species richness from a series of daily samples. Many of the potentially relevant environmental variables are correlated, limiting the potential for individual variables to be examined in isolation. We therefore used a principal components analysis to describe the major patterns in environmental variability across bays. The second principal component separated bays along a gradient of increasing depth, salinity, tidal range and flushing time. Scores along this component were generally better predictors of the larval pool than single variables, explaining as much as 61.2% of the variation in species richness, diversity and similarity between dates. Deeper bays, with more saline water and longer flushing times, tended to have richer and more diverse larval pools, with a greater consistency in species composition between sample dates. No relationship was found between environmental variables and larval abundance. Our results suggest that flushing time, particularly when in combination with topographic variables, chlorophyll, tidal range and salinity, may be a useful predictor for the richness and turnover of local larval pools. KEY WORDS: Flushing time · Larval retention · Larval dispersal · Larval pool Full text in pdf format PreviousNextCite this article as: Jessopp M, Mulholland OR, McAllen R, Johnson MP, Crowe TP, Allcock AL (2007) Coastline configuration as a determinant of structure in larval assemblages. Mar Ecol Prog Ser 352:67-75. https://doi.org/10.3354/meps07156 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 352. Online publication date: December 20, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Effects of depth and microhabitat on growth and survivorship of juvenile corals in the Florida Keys

Despite the well known discrimination among substrata by settling larvae of benthic marine invertebrates, there is limited evidence showing that recruits benefit from the microhabitats selected. To explore the fitness consequences of substrate selection by scleractinian corals, this study was designed to test for selective advantages arising from the microhabitat location of juvenile corals on natural substrata on Conch Reef (Florida Keys). Juvenile corals (ca. 2 to 40 mm diameter) were censused for density and microhabitat at 14, 17, 20 and 26 m depth, and a subset were tagged to mea- sure growth and survivorship. Microhabitats were scored as exposed (upward facing), vertical or cryptic, and the results were analyzed first for all taxa combined, and second by life-history strategy in order to contrast 2 ecologically distinct groups (i.e. brooders versus broadcasters). The majority (> 53%) of juveniles occupied exposed microhabitats at all depths, with the remainder mostly in ver- tical instead of cryptic microhabitats at ≤17 m, and in cryptic instead of vertical microhabitats at ≥20 m depth. Overall, juvenile distribution was unrelated to life history, and the abundance of brood- ers and broadcasters was largely similar across depths (regardless of microhabitat). Despite clear evi- dence of non-random distribution of juvenile corals, their growth and survivorship were statistically indistinguishable among the microhabitats or depths. The disparity between these results and evi- dence that coral larvae actively select specific microhabitats for settlement could reflect (1) a strong size-dependency of the fitness consequences of microhabitat, (2) a consequence of reef degradation such as a modification of the selective value of microhabitats, or (3) reduced exploitation competition for settlement locations caused by low rates of coral recruitment.

Checking the landing zone: do invertebrate larvae avoid settling near superior spatial competitors?

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:239-247 (2004) - doi:10.3354/meps280239 Checking the landing zone: Do invertebrate larvae avoid settling near superior spatial competitors? Stephan G. Bullard1,3, Robert B. Whitlatch1,*, Richard W. Osman2 1Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, USA 2Smithsonian Environmental Research Center, PO Box 28, 647 Contees Wharf Road, Edgewater, Maryland 21037, USA 3Present address: University of Hartford Hillyer College, 200 Bloomfield Av., West Hartford, Connecticut 06117, USA *Corresponding author. Email: robert.whitch@ucom.edu ABSTRACT: It has been hypothesized that larvae of benthic marine invertebrates may reduce their risk of post-settlement competition by avoiding superior competitors during settlement. Few studies, however, have directly compared the levels of larval settlement close to and away from established competitors. We conducted experiments in the New England subtidal to determine whether larvae of fouling organisms would avoid substrata (100 cm2 PVC panels) with established adult colonies of the tunicates Botryllus schlosseri, Botrylloides violaceus, and Diplosoma listerianum compared to control substrata without tunicates. After panels had been exposed for 1 wk in the field, we assessed larval settlement on the entire surface of panels and within 1 cm of established tunicate colonies. We also monitored the fate of larvae that settled near established tunicates to determine if different tunicate species posed different risks of overgrowth to newly settled juveniles. Pair-wise comparisons revealed only 1 significant difference (out of 48 total analyses) when we examined levels of settlement on panels with tunicates relative to bare controls. We also found no significant differences in the number of settlers overgrown by different tunicate species. Thus, our results suggest that invertebrate larvae do not avoid settling near established dominant competitors (i.e. colonial tunicates). These results are in contrast to a previous study which had shown that larvae of competitively inferior species avoided settling near B. schlosseri. KEY WORDS: Ascidians · Competition · Cues · Larvae · Overgrowth · Settlement · Tunicates Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Description of planktonic polychaete larvae from Terre Ad�lie and the Ross Sea (Antarctica)

An analysis was carried out on 51 samples from 32 stations, obtained during the I.C.O.T.A. cruise between 18 January 1996 and 7 February 1996 in the Pointe Geologie Archipelago, Terre Adelie, and on samples obtained by 2 sediment traps deployed in the Ross Sea, within the framework of the Italian C.L.I.M.A. Project. These samples showed the unexpected presence of numerous larvae of benthic marine invertebrates. In addition, larvae from the Ross Sea were examined. Seven phyla with complex life-cycles and at least 18 species of benthic polychaetes were represented. Morphological descriptions by scanning electron microscopy of the most frequent larvae and identification of larval types are provided. Descriptions from the literature of larvae collected in the Antarctic Peninsula were used for comparison. Morphological descriptions do not always lead to identification at the species level; however, these descriptions are indispensable for establishing the geographic distribution of larvae. It has been demonstrated that indirect identification methods relying on the premise that the benthic fauna is entirely known and that sampled larvae belong only to species already known through their benthic adult stage may lead to obvious absurdities. As an ecological consequence, Thorson's rule, according to which indirect development should not be represented and direct development should be dominant at high latitudes, is not supported by our data. A short comparison of the local reproductive pattern with a subantarctic area, the Kerguelen Archipelago, strongly suggests that the absence of planktonic development in this area cannot be explained by Thorson's rule. This rule has been invalidated in more austral zones; the prevalent reproductive pattern in the Kerguelen Archipelago is linked to the very marked advective strength of water flow.

The genetic structure of intertidal populations of two species of nudibranch molluscs with planktotrophic and pelagic lecithotrophic larval stages: are pelagic larvae “for” dispersal?

Planktonic larvae of benthic marine invertebrates may confer larval dispersal and colonization potential on the reproductive adult. Analyses of genetic heterogeneity of local populations provide an indirect means of assessing gene flow and the scale of realized dispersal of larval migrants. Here we compared populations of two species of nudibranchs with long term planktotrophic ( Goniodoris nodosa) and shorter term pelagic lecithotrophic ( Adalaria proxima) veliger stages. Both species have annual life cycles, population turnover is absolute and free-swimming larvae hatch from benthic spawn masses. G. nodosa larvae are pelagic for up to ∼3 months, whereas those of A. proxima can metamorphose within 1–2 d of release although, at least in the laboratory, they may delay metamorphosis for several weeks. The broad ranges of pelagic larval transport potential were estimated at 10 2–10 3 km for G. nodosa and 10 1–10 2 km for A. proxima: significant differentiation of populations of G. nodosa was predicted to occur on a scale of 10 3–10 4 km, whereas for A. proxima differentiation was expected on a scale of perhaps only 10 2–10 3 km. For both species, analyses were undertaken of allozyme variation among sites throughout the 1600 km British Isles range of A. proxima. F-statistic analyses showed no evidence of population differentiation for G. nodosa (11 populations). By contrast, comparable data for 19 populations of A. proxima showed very high levels of differentiation, but no obvious pattern of variation or significant isolation by distance. More detailed sampling of nine populations of A. proxima over a 26.18 km range in W Scotland – in a location characterised by highly dispersive tidal currents – revealed (1) similar levels of differentiation to the 1600 km range, (2) clear distance-related clinal patterns of variation, and (3) a significant inverse relationship between genetic differentiation and geographic distance. For Adalaria proxima there was evidence of significant differentiation of populations on a scale of ≤10 1 km. This was counter to our expectations of larval transport potential for A. proxima and implies that these larvae are behaviourally adapted to avoid dispersal in the water column and thereby recruit locally. Whilst the planktotrophic species, G. nodosa, conformed to our expectations, the clear implication of the data for A. proxima is that possession of a pelagic larval stage does not necessarily facilitate dispersal and colonisation potential for this sedentary invertebrate. Extrapolations and predictions of dispersal potential, and gene flow in natural populations, based on laboratory observations of the larval phase duration may be markedly error-prone.

Variation in Suspension Feeding Rates among Larvae of Some Temperate, Eastern Pacific Echinoderms

Larvae of many echinoderms and other benthic marine invertebrates depend on ciliary suspension feeding for growth and development, but some larvae may be superior feeding devices (with consequences for variation in growth, size, and fitness). I measured differences in feeding performance among larvae of 9 echinoderm species from 4 taxonomic classes (Asteroidea, Ophiuroidea, Holothuroidea, Echinoidea). Maximum clearance rates (relative to size of the feeding structure) of some larvae were much higher than the rates of others, indicating substantial variation in feeding capabilities among larvae of similar size. In order to interpret these differences in feeding capability, I also give some preliminary data on larval form, development, and organic content. Although incomplete in several respects, these data do not indicate a simple relation between larval feeding and growth. This surprising result indicates that functional morphology is not always the most appropriate perspective from which to examine variation in growth and development of planktonic larvae. Additional key words: larval morphology, cilia The feeding planktonic larvae of benthic marine invertebrates are life-history devices for turning eggs into juveniles (Strathmann 1985). Adult females can increase their fecundity by spawning large numbers of relatively small eggs. Small eggs develop into larvae that feed on small suspended particles or other zooplankton, grow, and metamorphose at a large size relative to the contents of an egg. Efficient and rapid growth from a small egg to a large juvenile is an important component of fitness in marine invertebrates with feeding larvae (Havenhand 1995), but some larvae may be more equal to this task than are others. Connections between feeding capability, larval morphology, and components of fitness might be strong but have not been considered in much detail. Differences in larval form may be correlated with differences in feeding capabilities (e.g., McEdward & Strathmann 1987). Despite a large number of studies of larval feeding (reviewed by R. Strathmann 1987; Hart & Strathmann 1995), there is little information that can be used to compare feeding rates or other measures of the feeding capabilities of different larvae (e.g., Pearse et al. 1991). a Present address: Section of Evolution and Ecology, Division of Biological Sciences, University of California, Davis, CA 95616-8755, USA. Here I show that feeding capability varies substantially among larvae of some co-occurring, shallow-water echinoderms from the eastern temperate Pacific. I measured maximum clearance rates for larvae of different sizes and developmental stages for each species, and compared the relationship between larval size and maximum clearance rate among species. I found some large differences in this relationship, which indicate that some larvae are better suspension feeders than are others. These differences were weakly associated with variation in larval body form among echinoderm class-

Distribution of pelagic larvae of benthic marine invertebrates in the Bellingshausen Sea

During November and December 1992, plankton samples were collected using a ring net of mesh size 200 μm vertically hauled through a 600 m water column, at five stations along a transect running north from the Allison Peninsula in the Bellingshausen Sea. Three stations were located over the continental shelf; two of these were ice bound, whilst the third was at the ice edge. Two other stations were in deeper, ice-free water. Sixteen different larval and juvenile types were found representing seven phyla: Echinodermata, Nemertea, Coelenterata, Mollusca, Annelida, Arthropoda and Bryozoa, of which the first two were the most abundant. Larval numbers and types decreased with distance offshore and away from permanent sea ice. The presence of many stages of nemertean larval development within a short time scale, in an area where developmental tends to be slow, suggests that reproduction occurs over an extended period and that the larvae have a long planktonic phase. The increased size of later developmental stages of the nemertean larvae indicates they obtain nutrition within the water column during winter, when little particulate food is present.

Settlement of oyster (Crassostrea virginica) larvae: Effects of water flow and a water‐soluble chemical cue

Although previous evidence indicates that larvae of benthic marine invertebrates can respond to waterborne cues in still water, the importance of waterborne cues in mediating natural settlement out of flowing water has been questioned. Here, we summarize the results of flume experiments demonstrating enhanced settlement of oyster larvae in small target wells (circles of 7‐cm diam) with the release of a waterborne settlement cue compared to identical substrates without the cue. In concurrent still‐water experiments, more oyster larvae settled in solutions of waterborne cue than in seawater controls. Velocity and electrochemical measurements of a conservative tracer verified that at low flow velocities (2 and 6 cm s−1) with U* values <0.25 cm s−1, the waterborne cue was present above the targeted substrate to a height of ≤4 mm. Rapid vertical swimming or sinking in response to the waterborne cue can concentrate larvae in near‐bottom waters and enhance larval settlement. Our investigation provides the first experiimental evidence to demonstrate that dissolved chemical cues can mediate settlement by larvae under hydrodynamic conditions approaching those of natural benthic habitats.

Larval period and its influence on post-larval life history: comparison of lecithotrophy and facultative planktotrophy in the aeolid nudibranch Phestilla sibogae

The variable duration of the pelagic phase of metamorphically competent larvae of benthic marine invertebrates is set by an interaction between environmental factors and larval traits that together influence the chance that a larva will encounter and respond to a suitable settlement site. In the Hawaiian aeolid nudibranch Phestilla sibogae Bergh, an extended competent larval phase resulted in a cascade of negative effects on larval and post-larval life-history traits. When raised as fed (i.e., facultatively planktotrophic) larvae, an extended larval period resulted in lower larval survival, slightly lower metamorphic success, and delayed reproduction. When raised as unfed (i.e., lecithotrophic) larvae, an extended larval period resulted in lower larval and post-larval weights, survival, metamorphic success, and reproductive output, and also resulted in a longer juvenile period and delayed reproduction. The chance nature of locating a settlement site generally spreads these negative effects over all larvae of a cohort, and so balances the relative fitness of the genetic lineages within a population.

Influence of delayed metamorphosis on survival, growth, and reproduction of the marine polychaete Capitella sp. I

In the absence of an appropriate environmental cue, larvae of benthic marine invertebrates typically delay their metamorphosis. Delaying metamorphosis is considered beneficial in promoting placement of offspring into suitable habitats and likely increasing genetic exchange among populations. However, recent studies suggest that delaying metamorphosis can reduce juvenile fitness in some species, by reducing postmetamorphic survivorship or growth rate. The effects of delayed metamorphosis on survival, growth, and reproduction of the marine polychaete Capitella sp. I were tested. The lecithotropic larvae, which are competent to metamorphose within minutes of their release from the parental brood tube, were forced to delay metamorphosis for up to 216 h at 20°C. We induced metamorphosis at intervals by adding azoic sediment, and then reared the juveniles in the laboratory for up to 4 wk. Although survival was significantly reduced ( P < 0.01) when larvae delayed metamorphosis for > 72h, delaying metamorphosis had no convincing effect on postmetamorphic growth rate (μg tissue· day −1), time to first reproductive activity, or fecundity.

Delayed metamorphosis by larvae of benthic marine invertebrates: Does it occur? Is there a price to pay?

Abstract In the laboratory, the swimming larvae of benthic marine invertebrates are generally capable of prolonging their larval period beyond the time that they first become physiologically competent to metamorphose. Larvae seem to differ markedly in their ability to postpone metamorphosis, both interspecifically and intraspecifically. The proportion of this variability that is genetically controlled has not yet been determined; if under genetic control, both pre-competent and competent periods would be subject to selection, although the selective pressures and the physiological or developmental mechanisms through which such pressures might operate remain purely speculative. Limited data strongly suggest that at least a few species delay metamorphosis in the field. The frequency with which they do so, and under what conditions they do so, and for how long, are unexplored questions. Some of these issues can now be explored, with the finding that various inorganic and organic substances can trigger the met...

Molluscan Metamorphosis: A Study in Tissue Transformation

Metamorphosis of the pelagic larvae of benthic marine invertebrates is often a cataclysmic event in which a rapid loss of organs specialized for larval life occurs simultaneously with the renewal or increased rate of development of potential adult organs. In the nudibranch gastropod Phestilla sibogae this change involves loss of the velum, shell, operculum, larval kidney, some retractor muscles, and some of the pedal mucous glands. Exit from the larval shell at metamorphosis is rapid and is correlated with the spread of epidermis from the larval foot over the visceral mass as the visceral mass emerges from the shell aperature. This spreading of epipodial epidermis to cover the entire body has not been previously reported for other nudibranchs. Neither cell proliferation nor active cell motility are responsible for this epidermal migration. Rather it appears that the action of larval muscles pulls the visceral organs out of the shell and simultaneously causes the epipodial epidermis to cover the visceral mass. This epidermis becomes the definitive adult epidermis.