Larval activity levels and delayed metamorphosis affect post-larval performance in the colonial, ascidian Diplosoma listerianum

It is becoming widely recognized that extending the larval period of marine invertebrates, especially of species with non-feeding larvae, can affect post-larval performance. As these carry-over effects are presumed to be caused by the depletion of larval energy reserves, we predicted that the level of larval activity would also affect post-larval performance. This prediction was tested with the cosmopolitan colonial ascidian Diplosoma listerianum in field experiments in southern Australia. Diplosoma larvae, brooded in the parent colony, are competent to settle immediately after spawning, and they remain competent to metamorphose for > 15 h. Some larvae were induced to metamorphose 0 to 6 h after release, whilst others were induced to swim actively by alternating light and dark periods for up to 3 h prior to metamorphosis. Juvenile colonies were then transplanted to a subtidal field site in Port Phillip Bay and left to grow for up to 3 wk. Extending the larval period and increasing the amount of swimming both produced carry-over effects on post-larval performance. Colonies survived at different rates among experiments, but larval experience did not affect survival rates. Delays in metamorphosis and increased swimming activity did, however, reduce colony growth rates dramatically, resulting in 50% fewer zooids per colony. Moreover, such colonies produced initial zooids with smaller feeding structures, with the width of branchial baskets reduced by 10 to 15%. These differences in branchial basket size persisted and were still apparent in newly budded zooids 3 wk after metamorphosis. Our results suggest that, for D. listerianum, larval maintenance, swimming, and metamorphosis all use energy from a common pool, and increases in the allocation to maintenance or swimming come at the expense of post-larval performance.

Variation in the dispersal potential of non-feeding invertebrate larvae: the desperate larva hypothesis and larval size

For many species of marine invertebrates, variability in larval settlement behaviour appears to be the rule rather than the exception. This variability has the potential to affect larval dispersal, because settlement behaviour will influence the length of time larvae are in the plankton. Despite the ubiquity and importance of this variability, relatively few sources of variation in larval settlement behaviour have been identified. One important factor that can affect larval settlement behaviour is the nutritional state of larvae. Non-feeding larvae often become less discriminating in their 'choice' of settlement substrate, i.e. more desperate to settle, when energetic reserves run low. We tested whether variation in larval size (and presumably in nutritional reserves) also affects the settlement behaviour of 3 species of colonial marine invertebrate larvae, the bryozoans Bugula neritina and Watersipora subtorquata and the ascidian Diplosoma listerianum. For all 3 species, larger larvae delayed settlement for longer in the absence of settlement cues, and settlement of Bugula neritina larvae was accelerated by the presence of settlement cues, independently of larval size. In the field, larger W subtorquata larvae also took longer to settle than smaller larvae and were more discriminating towards settlement surfaces. These differences in settlement time are likely to result in differences in the distance that larvae disperse in the field. We suggest that species that produce non-feeding larvae can affect the dispersal potential of their offspring by manipulating larval size and thus larval desperation.

Sources of variation in larval quality for free-spawning marine invertebrates: Egg size and the local sperm environment

There has been growing interest in the effects of variation in larval quality on the post-larval performance of adult marine invertebrates. Variation in egg/larval size is an obvious source of variation in larval quality but sources of variation have received little attention. For broadcast spawners, larval size may vary according to the local sperm environment but the generality of this result is unclear. Here, we show that, for a solitary ascidian, a polychaete and an echinoid, larval size is affected by the concentration of sperm present during fertilization. Larvae that are produced at high sperm concentrations are smaller than larvae that are produced from eggs exposed to low sperm concentrations. We also show that for three ascidians and an asteroid, egg size increases with maternal body size. These differences in larval size are likely to affect larval and subsequent adult performance in the field. Given that sperm concentrations in the field can fluctuate widely, it is likely that larval quality in free-spawning marine invertebrates will also vary widely.

When the going gets rough: effect of maternal size manipulation on larval quality

Variation in larval size has been shown to be an important factor for the post-metamorphic performance of marine invertebrates but, despite its importance, few sources of this variation have been identified. For a range of taxa, offspring size is positively correlated with maternal size but the reasons for this correlation remain unclear. We halved the size of colonies in the bryozoan Bugula neritina 1 wk prior to reproduction (but during embryogenesis) to determine if larval size is a fixed or plastic trait. We manipulated colonies in such a way that the ratio of feeding zooids to reproductive zooids was constant between treatment and control colonies. We found that manipulating colony size strongly affects larval size; halved colonies produced larvae that were similar to13% smaller than those produced by intact colonies. We entered these data into a simple model based on previous work to estimate the likely post-metamorphic consequences of this reduction in larval size. The model predicted that larvae that came from manipulated colonies would suffer similar to300% higher post-metamorphic mortality and similar to50% lower fecundity as adults. Colonies that are faced with a stress appear to be trading off current offspring fitness to maximize their own long-term fitness and this may explain previous observations of compensatory growth in colonial organisms. This study demonstrates that larval size is a surprisingly dynamic trait and strong links exist between the maternal phenotype and the fitness of the offspring. The performance of settling larvae may be determined not only by their larval experience but also by the experience of their mothers.

Revision of the larval morphology (Zoea I) of the family Hippolytidae (Decapoda, Caridea), with a description of the first stage of the shrimp Hippolyte obliquimanus Dana, 1852

The aim of this study was to summarize the available data on larval morphology of the first zoea of the family Hippolytidae and describe the first zoeal stage of H. obliquimanus from two geographically distinct populations, Brazilian and Caribbean in order to discuss inter- and intraspecific variability. Ovigerous females of Hippolyte obliquimanus were collected at Cahuita (Limon, Costa Rica) and at Ubatuba (Sao Paulo, Brazil). We compiled the published descriptions of all available hippolytid Zoea I (66 spp., 21%), and all zoeae share several characteristics. However, such morphological features cannot be used to distinguish the first zoeae of Hippolytidae from other caridean larvae. Historically, the presence of an exopodal seta at the maxillule and the absence of the anal spine/papilla have been considered as characteristic for the Zoea I of the genus Hippolyte. The results of our revision, however, did not support these conclusions: although H. obliquimanus showed an exopodal seta at the maxillule, four congeners did not bear such structure; moreover, H. obliquimanus as well as one other congener have an anal spine/papilla. All morphological characters observed in the first zoeal stage of H. obliquimanus are shared with others species of the family Hippolytidae. Intraspecific variability in Hippolyte obliquimanus was detected in one morphological aspect: the first zoea had four denticles on the ventral margin of the carapace in the Brazilian population, while specimens from the Costa Rican population had three.

Na,K-ATPase activity and epithelial interfaces in gills of the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae)

Diadromous freshwater shrimps are exposed to brackish water both as an obligatory part of their larval life cycle and during adult reproductive migration; their well-developed osmoregulatory ability is crucial to survival in such habitats. This study examines gill microsomal Na,K-ATPase (K-phosphatase activity) kinetics and protein profiles in the freshwater shrimp Macrobrachium amazonicum when in fresh water and after 10-days of acclimation to brackish water (21 parts per thousand salinity), as well as potential routes of Na(+) uptake across the gill epithelium in fresh water. On acclimation, K-phosphatase activity decreases 2.5-fold, Na,K-ATPase alpha-subunit expression declines, total protein expression pattern is markedly altered, and enzyme activity becomes redistributed into different density membrane fractions, possibly reflecting altered vesicle trafficking between the plasma membrane and intracellular compartments. Ultrastructural analysis reveals an intimately coupled pillar cell-septal cell architecture and shows that the cell membrane interfaces between the external medium and the hemolymph are greatly augmented by apical pillar cell evaginations and septal cell inviginations, respectively. These findings ire discussed regarding the putative movement of Na(+) across the pillar cell interfaces and into the hemolymph via the septal cells, powered by the Na,K-ATPase located in their invaginations. (C) 2008 Elsevier Inc. All rights reserved.

Variable effects of larval size on post-metamorphic performance in the field

Larval quality may be capable of explaining much of the variation in the recruitment and subsequent population dynamics of benthic marine invertebrates. Whilst the effects of larval nutritional condition on adult performance have received the most attention, recent work has shown that larval size may also be an important and ubiquitous source of variation in larval quality. We examined the effects of variation in larval size on the post-metamorphic survival and growth of Watersipora subtorquata in 2 very different habitats - experimental substrata and pier pilings. We found strong effects of larval size on colony performance, although these varied among experiments. For colonies on experimental substrata, larval size positively affected adult survival and, initially, growth. However, after 3 wk in the field, there was no relationship between larval size and colony size, possibly because colonies were completely surrounded by newly settled organisms. Larval size also positively affected post-metamorphic growth of colonies on pier pilings, but, surprisingly, colonies that came from larger larvae had lower survival than colonies from smaller larvae. Overall, variation in larval size will strongly affect the recruitment and subsequent performance of adults in this species, although this may vary among different habitats. This study highlights the importance of examining the effects of larval quality on adult performance in as realistic conditions as possible, because of the strong interaction between larval size effects and the environment.

Differential adjustment in gill Na(+)/K(+)- and V-ATPase activities and transporter mRNA expression during osmoregulatory acclimation in the cinnamon shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae)

We evaluate osmotic and chloride (Cl(-)) regulatory capability in the diadromous shrimp Macrobrachium amazonicum, and the accompanying alterations in hemolymph osmolality and [Cl(-)], gill Na(+)/K(+)-ATPase activity, and expression of gill Na(+)/K(+)-ATPase alpha-subunit and V-ATPase B subunit mRNA during salinity (S) acclimation. We also characterize V-ATPase kinetics and the organization of transport-related membrane systems in the gill epithelium. Macrobrachium amazonicum strongly hyper-regulates hemolymph osmolality and [Cl(-)] in freshwater and in salinities up to 25 parts per thousand S. During a 10-day acclimation period to 25 parts per thousand S, hemolymph became isosmotic and hypo-chloremic after 5 days, [Cl(-)] alone remaining hyporegulated thereafter. Gill Na(+)/K(+)-ATPase alpha-subunit mRNA expression increased 6.5 times initial values after 1 h, then decreased to 3 to 4 times initial values by 24 h and to 1.5 times initial values after 10 days at 25 parts per thousand S. This increased expression was accompanied by a sharp decrease at 5 h then recovery of initial Na(+)/K(+)-ATPase activity within 24 h, declining again after 5 days, which suggests transient Cl(-) secretion. V-ATPase B-subunit mRNA expression increased 1.5-fold within 1 h, then reduced sharply to 0.3 times initial values by 5 h, and remained unchanged for the remainder of the 10-day period. V-ATPase activity dropped sharply and was negligible after a 10-day acclimation period to 21 parts per thousand S, revealing a marked downregulation of ion uptake mechanisms. The gill epithelium consists of thick, apical pillar cell flanges, the perikarya of which are coupled to an intralamellar septum. These two cell types respectively exhibit extensive apical evaginations and deep membrane invaginations, both of which are associated with numerous mitochondria, characterizing an ion transporting epithelium. These changes in Na(+)/K(+)- and V-ATPase activities and in mRNA expression during salinity acclimation appear to underpin ion uptake and Cl(-) secretion by the palaemonid shrimp gill.

The relative energetic costs of the larval period, larval swimming and metamorphosis for the ascidian Diplosoma listerianum

Variation in larval quality has been shown to strongly affect the post-metamorphic performance of a wide range of marine invertebrate species. Extending the larval period of non-feeding larvae strongly affects post-metamorphic survival and growth in a range of species. These 'carry-over' effects are assumed to be due to changes in larval energetic reserves but direct tests are surprisingly rare. Here, we examine the energetic costs ( relative to the costs of metamorphosis) of extending the larval period of the colonial ascidian Diplosoma listerianum. We also manipulated larval activity levels and compared the energy consumption rates of swimming larvae and inactive larvae. Larval swimming was, energetically, very costly relative to either metamorphosis or merely extending the larval period. At least 25% of the larval energetic reserves are available for larval swimming but metamorphosis was relatively inexpensive in this species and larval reserves can be used for post-metamorphic growth. The carry-over effects previously observed in this species appear to be nutritionally mediated and even short (< 3 h) periods of larval swimming can significantly deplete larval energy reserves.

A new species of Phylloicus Muller, 1880 (Trichoptera: Calamoceratidae), from southeastern Brazil, including descriptions of larval and pupal stages

The cosmopolitan family Calamoceratidae Ulmer, 1906, has 8 living genera, among them Phylloicus Muller, 1880, with species distributed from South to Central America. This genus is characterized by its dark-colored adults (brown to black) with diurnal to crepuscular habits. In this paper, the adults, pupae, and larvae of Phylloicus camargoi n. sp. are described and illustrated. The new species is easily diagnosed by male tergum X bearing a short, digitate, setose, basodorsal process; 2 short, digitate, hairless, lateral processes; and 2 pairs of very short processes on the posterior margin: a pair of digitate, hairless, posterolateral processes, and a pair of posteromesal processes. Additional diagnostic characters are the presence of 3 color bands on the forewings, 2 golden longitudinal bands and a white transversal one.

Less inhibited with age? Larval age modifies responses to natural settlement inhibitors

As larvae of marine invertebrates age, their response to settlement cues can change. This change can have significant consequences to both the ecology of these organisms, and to their response to antifouling coatings. This study examines how larval age affects the settlement response of larvae to two naturally derived settlement inhibitors, non-polar extracts from the algae Delisea pulchra and Dilophus marginatus, the former of which contains compounds that are in commercial development as antifoulants. Two species of marine invertebrates with non-feeding larvae were investigated: the bryozoans Watersipora subtorquata and Bugula neritina. Larval age strongly affected larval settlement, with older larvae settling at much higher rates than younger larvae. Despite having strong, inhibitory effects on young larvae, the non-polar extracts did not inhibit the settlement of older larvae to the same degree for both species studied. The results show that the effects of ecologically realistic settlement inhibitors are highly dependent on larval age. Given that the age of settling larvae is likely to be variable in the field, such age specific variation in settlement response of larvae may have important consequences for host-epibiont interactions in natural communities.

A Mox homeobox gene in the gastropod mollusc Haliotis rufescens is differentially expressed during larval morphogenesis and metamorphosis

We have isolated a homeobox-containing cDNA from the gastropod mollusc Haliotis rufescens that is most similar to members of the Mox homeobox gene class, The derived Haliotis homeodomain sequence is 85% identical to mouse and frog Mox-2 homeodomains and 88.9% identical to the partial cnidarian cnox5-Hm homeodomain. Quantitative reverse transcription-polymerase chain reaction analysis of mRNA accumulation reveals that this gene, called HruMox, is expressed in the larva, but not in the early embryo, Transcripts are most prevalent during larval morphogenesis from trochophore to veliger. There are also transient increases in transcript prevalence 1 and 3 days after the intitiation of metamorphosis from veliger to juvenile. The identification of a molluscan Mox homeobox gene that is more closely related to vertebrate genes than other protostome (e.g. Drosophila) genes suggests the Mox class of homeobox genes may consist of several different families that have been conserved through evolution, (C) 1997 Federation of European Biochemical Societies.

Molecular cloning, sequencing, and expression analysis of presenilin cDNA from Schistosoma mansoni

Presenilins (PS) are integral membrane proteins involved, among other functions, in regulated intramembrane proteolysis. In this study, we report the identification and characterization of a complementary DNA from Schistosoma mansoni exhibiting a significant homology to human and nonvertebrate presinilins. S. mansoni contained a 1,485 bp open reading frame encoding a predicted protein of 494 amino acids. Alignment of predicted amino acid sequence of S. mansoni with PS (SmPS) from other species revealed up to 40% similarity shared among the investigated organisms. In addition, phylogenetic analyses demonstrated SmPS being closely related to its orthologues found in Schistosoma japonicum and Caenorhabditis elegans. Expression analysis of SmPS using quantitative real-time PCR revealed that the transcript is up-regulated in the egg stage. We hypothesize that the high level of SmPS in the S. mansoni embryo correlates to an important role during cellular signaling associated to larval development. To our knowledge, this study represents the first attempt to investigate the existence and abundance of PS from a helminth parasite.

Representational Difference Analysis (RDA) reveals differential expression of conserved as well as novel genes during caste-specific development of the honey bee (Apis mellifera L.) ovary

In highly eusocial insects, such as the honey bee, Apis mellifera, the reproductive bias has become embedded in morphological caste differences. These are most expressively denoted in ovary size, with adult queens having large ovaries consisting of 150-200 ovarioles each, while workers typically have only 1-20 ovarioles per ovary. This morphological differentiation is a result of hormonal signals triggered by the diet change in the third larval instar, which eventually generate caste-specific gene expression patterns. To reveal these we produced differential gene expression libraries by Representational Difference Analysis (RDA) for queen and worker ovaries in a developmental stage when cell death is a prominent feature in the ovarioles of workers, whereas all ovarioles are maintained and extend in length in queens. In the queen library, 48% of the gene set represented homologs of known Drosophila genes, whereas in the worker ovary, the largest set (59%) were ESTs evidencing novel genes, not even computationally predicted in the honey bee genome. Differential expression was confirmed by quantitative RT-PCR for a selected gene set, denoting major differences for two queen and two worker library genes. These included two unpredicted genes located in chromosome 11 (Group11.35 and Group11.31, respectively) possibly representing long non-coding RNAs. Being candidates as modulators of ovary development, their expression and functional analysis should be a focal point for future studies. (C) 2011 Elsevier Ltd. All rights reserved.