Mode Of Larval Development Research Articles

Contrasting the development of larval and adult body plans during the evolution of biphasic lifecycles in sea urchins.

Biphasic lifecycles are widespread among animals, but little is known about how the developmental transition between larvae and adults is regulated. Sea urchins are a unique system for studying this phenomenon because of the stark differences between their bilateral larval and pentaradial adult body plans. Here, we use single-cell RNA sequencing to analyze the development of Heliocidaris erythrogramma (He), a sea urchin species with an accelerated, non-feeding mode of larval development. The sequencing time course extends from embryogenesis to roughly a day before the onset of metamorphosis in He larvae, which is a period that has not been covered by previous datasets. We find that the non-feeding developmental strategy of He is associated with several changes in the specification of larval cell types compared to sea urchins with feeding larvae, such as the loss of a larva-specific skeletal cell population. Furthermore, the development of the larval and adult body plans in sea urchins may utilize largely different sets of regulatory genes. These findings lay the groundwork for extending existing developmental gene regulatory networks to cover additional stages of biphasic lifecycles.

Shell color polymorphism in marine gastropods.

Marine gastropods are characterized by an incredible variation in shell color. In this review, we aim to introduce researchers to previous studies of shell color polymorphism in this group of animals, trying to provide an overview of the topic and highlighting some potential avenues for future research. For this, we tackle the different aspects of shell color polymorphism in marine gastropods: its biochemical and genetic basis, its patterns of spatial and temporal distribution, as well as its potential evolutionary causes. In particular, we put special emphasis on the evolutionary studies that have been conducted so far to reveal the evolutionary mechanisms responsible for the maintenance of shell color polymorphism in this group of animals, as it constitutes the least addressed aspect in existing literature reviews. Several general conclusions can be drawn from our review: First, natural selection is commonly involved in the maintenance of gastropod color polymorphism; second, although the contribution of neutral forces (gene flow-genetic drift equilibrium) to shell color polymorphism maintenance do not seem to be particularly important, it has rarely been studied systematically; third, a relationship between shell color polymorphism and mode of larval development (related to dispersal capability) may exist. As for future studies, we suggest that a combination of both classical laboratory crossing experiments and -Omics approaches may yield interesting results on the molecular basis of color polymorphism. We believe that understanding the various causes of shell color polymorphism in marine gastropods is of great importance not only to understand how biodiversity works, but also for protecting such biodiversity, as knowledge of its evolutionary causes may help implement conservation measures in those species or ecosystems that are threatened.

Correlated evolution of larval development, egg size and genome size across two genera of snapping shrimp

Across plants and animals, genome size is often correlated with life-history traits: large genomes are correlated with larger seeds, slower development, larger body size and slower cell division. Among decapod crustaceans, caridean shrimps are among the most variable both in terms of genome size variation and life-history characteristics such as larval development mode and egg size, but the extent to which these traits are associated in a phylogenetic context is largely unknown. In this study, we examine correlations among egg size, larval development and genome size in two different genera of snapping shrimp, Alpheus and Synalpheus, using phylogenetically informed analyses. In both Alpheus and Synalpheus, egg size is strongly linked to larval development mode: species with abbreviated development had significantly larger eggs than species with extended larval development. We produced the first comprehensive dataset of genome size in Alpheus (n=37species) and demonstrated that genome size was strongly and positively correlated with egg size in both Alpheus and Synalpheus. Correlated trait evolution analyses showed that in Alpheus, changes in genome size were clearly dependent on egg size. In Synalpheus, evolutionary path analyses suggest that changes in development mode (from extended to abbreviated) drove increases in egg volume; larger eggs, in turn, resulted in larger genomes. These data suggest that variation in reproductive traits may underpin the high degree of variation in genome size seen in a wide variety of caridean shrimp groups more generally.

Fine-scale morphological, genomic, reproductive, and symbiont differences delimit the Caribbean octocorals Plexaura homomalla and P. kükenthali

Octocorals are conspicuous members of coral reefs and deep-sea ecosystems. Yet, species boundaries and taxonomic relationships within this group remain poorly understood, hindering our understanding of this essential component of the marine fauna. We used a multifaceted approach to revisit the systematics of the Caribbean octocorals Plexaura homomalla and Plexaura kükenthali, two taxa that have a long history of taxonomic revisions. We integrated morphological and reproductive analyses with high-throughput sequencing technology to clarify the relationship between these common gorgonians. Although size and shape of the sclerites are significantly different, there is overlap in the distributions making identification based on sclerites alone difficult. Differences in reproductive timing and mode of larval development were detected, suggesting possible mechanisms of pre-zygotic isolation. Furthermore, there are substantial genetic differences and clear separation of the two species in nuclear introns and single-nucleotide polymorphisms obtained from de novo assembled transcriptomes. Despite these differences, analyses with SNPs suggest that hybridization is still possible between the two groups. The two nascent species also differed in their symbiont communities (genus Breviolum) across multiple sampling sites in the Caribbean. Despite a complicated history of taxonomic revisions, our results support the differentiation of P. homomalla and P. kükenthali, emphasizing that integrative approaches are essential for Anthozoan systematics.

Egg masses and larval development of the Antarctic cephalaspidean snail Waegelea antarctica (Cephalaspidea: Antarctophilinidae), with notes on egg masses of the related Antarctophiline alata

ABSTRACT We describe, for the first time, egg masses and larval developmental mode of a recently described Antarctic philinoid snail, Waegelea antarctica. Egg masses resembled the gelatinous, attached masses of many temperate philinoid species and contained very large offspring that hatched as developmentally advanced veligers with many juvenile features. Like other Antarctic heterobranch egg masses, development in the masses of W. antarctica appeared to be largely synchronous despite low internal oxygen levels. Hatched larvae could both swim and crawl, and we did not observe metamorphosis over several days. Molecular barcoding using cytochrome c oxidase subunit I (COI) showed an almost perfect (<0.002% difference) match between our specimens from McMurdo Sound in the Ross Sea and a single sequence from a specimen collected >8,000 km away in the Weddell Sea, suggesting either high realized larval dispersal or a recent range expansion. We also describe the egg mass of the related Antarctophiline alata (identified using COI barcoding) from the Ross Sea, which differed from published descriptions in having considerably smaller embryos.

Species level identification of Antillogorgia spp. recruits identifies multiple pathways of octocoral success on Caribbean reefs

Successful recruitment is critical to the maintenance and resilience of populations and may be at the core of the transition from scleractinian- to octocoral-dominated faunas on some Caribbean reefs. For sessile invertebrates, recruitment incorporates the composite effects of larval supply, settlement and survival. The relative success of these processes differs between species, and successful recruitment may be achieved through different life history strategies. Recruitment of six abundant and widespread Antillogorgia spp. was assessed at six sites on Little Bahama Bank from 2009–2012. Identification of recruits to species level, based on microsatellite analyses, revealed differences in recruitment and survival between species, sites and years. The broadcast spawning species, A. americana and A. acerosa, had low rates of early recruitment and post-settlement survival. Higher levels of recruitment success were achieved among brooding and surface brooding species following somewhat different patterns of early recruitment and survival. The internal brooder A. hystrix had the highest recruitment at five of the sites, but low survival dramatically reduced its abundance and after a year it had similar densities as the surface brooding species, A. elisabethae and A. bipinnata. The brooders have smaller colonies and produce fewer larvae than the broadcast spawning species, but they release competent larvae, which may account for their higher recruitment rates. The Antillogorgia illustrate the diversity of successful reproductive strategies exhibited by octocorals, and differences in the life history strategies among these congeners are best characterized by their mode of larval development.

Paleoecology and paleobiogeography of the Cenomanian-Turonian bivalves from the Southern Galala Plateau (Eastern Desert, Egypt)

Fifty-three bivalve species from the Cenomanian-Turonian strata in the Southern Galala Plateau (Eastern Desert, Egypt) were used to identify major factors controlling their regional and global distribution. Non–metric multidimensional scaling (NMDS) indicated that rock type is a major factor controlling the bivalve distribution, while other biotic parameters such as life habit and mobility level have a minor role. Although the diversity and density of bivalves have a punctuated pattern, a general trend of increasing diversity from the Cenomanian onward was observed. In contrast to the Cenomanian, mobile and infaunal species have dominated the Turonian in a low-energy deeper marine environment with an oligotrophic regime. The lower diversity, the rarity of infaunal taxa, in addition to abundant authigenic minerals (glauconite/pyrite) and oyster bivalves in the Cenomanian point to a high-stress environment, where dysoxia at (or just below) the sediment/water interface may exclude the infaunal taxa. Analysis of the geographic distribution of the identified taxa indicates no significant difference between the Middle East and other mega-provinces. The planktotrophic larval development mode of most bivalve taxa (e.g., oysters and heterodonts) and the opening of seaways associated with the global Cenomnian/Turonian flooding may have resulted on wider geographic dispersion and mixing of faunal communities among the different provinces.

Habitat availability determines distribution patterns of spionid polychaetes (Annelida: Spionidae) around Tokyo Bay

An investigation of the distribution and habitat utilization of spionid polychaetes in Tokyo Bay revealed eight shell-boring and 18 non-boring (interstitial, epifaunal, and infaunal) species, of these 11 species were recorded in the area for the first time. Most of the boring and interstitial species, which are associated with mollusc shells, were mainly distributed in exposed environments favoured by their host species outside Tokyo Bay. Only two boring species, Polydora websteri and Polydora haswelli preferred the enclosed waters of Tokyo Bay. Epifaunal and infaunal species were mainly distributed in the sandy and/or muddy sediment within Tokyo Bay. A widespread or localized distribution pattern within species was observed corresponding to the larval developmental mode. We concluded that habitat availability determines distribution patterns of spionid polychaetes around Tokyo Bay. Novel habitats for Boccardiella hamata, Boccardia proboscidea, Carazziella spongilla, and Polydora cornuta were recorded. Boccardia pseudonatrix, which was recorded for the first time from Japan with clear locality information, is considered to be a potential alien species.

Towards a 'Sea-Level Sensitive' dynamic model: impact of island ontogeny and glacio-eustasy on global patterns of marine island biogeography.

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed 'Sea-Level Sensitive' dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeography with patterns of glacio-eustasy, merging concepts from areas as diverse as taxonomy, biogeography, marine biology, volcanology, sedimentology, stratigraphy, palaeontology, geochronology and geomorphology. Fundamental to the SLS model is the dynamic variation of the littoral area of volcanic oceanic islands (defined as the area between the intertidal and the 50-m isobath) in response to sea-level oscillations driven by glacial-interglacial cycles. The following questions are considered by means of this revision: (i) what was the impact of (global) glacio-eustatic sea-level oscillations, particularly those of the Pleistocene glacial-interglacial episodes, on the littoral marine fauna and flora of volcanic oceanic islands? (ii) What are the main factors that explain the present littoral marine biodiversity on volcanic oceanic islands? (iii) How can differences in historical and ecological biogeography be reconciled, from a marine point of view? These questions are addressed by compiling the bathymetry of 11 Atlantic archipelagos/islands to obtain quantitative data regarding changes in the littoral area based on Pleistocene sea-level oscillations, from 150 thousand years ago (ka) to the present. Within the framework of a model sensitive to changing sea levels, we discuss the principal factors affecting the geographical range of marine species; the relationships between modes of larval development, dispersal strategies and geographical range; the relationships between times of speciation, modes of larval development, ecological zonation and geographical range; the influence of sea-surface temperatures and latitude on littoral marine species diversity; the effect of eustatic sea-level changes and their impact on the littoral marine biota; island marine species-area relationships; and finally, the physical effects of island ontogeny and its associated submarine topography and marine substrate on littoral biota. Based on the SLS dynamic model, we offer a number of predictions for tropical, subtropical and temperate volcanic oceanic islands on how rates of immigration, colonization, in-situ speciation, local disappearance, and extinction interact and affect the marine biodiversity around islands during glacials and interglacials, thus allowing future testing of the theory.

Phenotypic and life-history diversification in Amazonian frogs despite past introgressions

The advent of genomics in phylogenetics and population genetics strengthened the perception that conflicts among gene trees are frequent and often due to introgression. However, hybridization occurs mostly among species that exhibit little phenotypic differentiation. A recent study delineating species in Anomaloglossus, a frog genus endemic to the Guiana Shield, identified an intriguing pattern in the A. baeobatrachus species complex. This complex occurs in French Guiana and Amapá (Brazil) and comprises two sympatric phenotypes contrasting not only in body size, habitat, and advertisement call, but also in larval development mode (endotrophic vs exotrophic tadpoles). However, molecular and phenotypic divergences are, in some cases, incongruent, i.e specimens sharing mtDNA haplotypes are phenotypically distinct, suggesting a complex evolutionary history. Therefore, we genotyped 106 Anomaloglossus individuals using ddRADseq to test whether this phenotype/genotype incongruence was a product of phenotypic plasticity, incomplete lineage sorting, multiple speciation events, or admixture. Based on more than 16,000 SNPs, phylogenetic and population genetic approaches demonstrated that exotrophic populations are paraphyletic. Species tree and admixture analyses revealed a strikingly reticulate pattern, suggesting multiple historical introgression events. The evolutionary history of one exotrophic population in northern French Guiana is particularly compelling given that it received genetic material from exotrophic ancestors but shows very strong genetic affinity with the nearby endotrophic populations. This suggests strong selection on larval development and mating call after secondary contact and hybridization. The case of A. baeobatrachus represents a striking example of introgression among lineages that are phenotypically distinct, even in their larval development mode, and highlights how high-resolution genomic data can unravel unexpectedly complex evolutionary scenarios.

Coral reproduction at Hall Bank, a high latitude coral assemblage in Western Australia

Research on coral reproduction has increased dramatically in recent times; however, there remain significant regions, in particular high latitude reefs, where research is limited. For example, the reproductive biology of species in the coral assemblage at Hall Bank, a high latitude site (32 degrees S) in southern Western Australia, remain unknown. Here, reproductive traits and the likely time of spawning for 12 of the approximately 16 species that occur at Hall Bank were established using histology between March 2009 and March 2011 at 7 discrete time points. Peak reproductive activity most likely occurs in February, as 7 of the 10 species sampled in this month had colonies with mature gametes. The sexuality, mode of larval development and transmission of symbionts were, as expected, consistent with previous work. The reproductive biology of the corals at Hall Bank is consistent with other regions of the Indo-Pacific, supporting the hypo thesis that reproductive traits such as sexuality and mode of larval development are evolutionarily conserved and do not vary biogeographically.

De novo transcriptome assembly and developmental mode specific gene expression of Pygospio elegans.

Species with multiple different larval developmental modes are interesting models for the study of mechanisms underlying developmental mode transitions and life history evolution. Pygospio elegans, a small, tube-dwelling polychaete worm commonly found in estuarine and marine habitats around the northern hemisphere, is one species with variable developmental modes. To provide new genomic resources for studying P. elegans and to address the differences in gene expression between individuals producing offspring with different larval developmental modes, we performed whole transcriptome Illumina RNA sequencing of adult worms from two populations and prepared a de novo assembly of the P. elegans transcriptome. The transcriptome comprises 66,233 unigenes, of which 33,807 contain predicted coding sequences, 26,448 have at least one functional annotation, and 3,076 are classified as putative long non-coding RNAs. We found more than 8,000 unigenes significantly differentially expressed between adult worms from populations producing either planktonic or benthic larvae. This comprehensive transcriptome resource for P. elegans adds to the available genomic data for annelids and can be used to uncover mechanisms allowing developmental variation in this and potentially other marine invertebrate species.

Population and reproductive dynamics of the polychaete Pygospio elegans in a boreal estuary complex

AbstractPygospio elegans is an opportunistic, wide‐spread spionid polychaete that reproduces asexually via fragmentation and can produce benthic and pelagic larvae, hence combining different developmental modes in one species. We documented the density, size distribution, and reproductive activity of P. elegans at four sites in the Danish Isefjord‐Roskilde Fjord estuary complex, where all modes of reproduction were reported. We compared population dynamics of this species to environmental parameters such as salinity, temperature, and sediment characteristics (grain size, sorting, porosity, water content, organic content, C/N). We observed that new cohorts—resulting either from sexual or asexual reproduction—appeared in spring and fall, and old ones disappeared in late summer and winter. Sexual reproduction occurred from September until May, and although their timing was variable, there were two reproductive peaks at three sites. At those sites, we also observed a switch in larval developmental mode. Asexual reproduction peaked in April. While the seasonal dynamics can be related to temperature to a large extent, the differences in population dynamics among sites also correlated with sediment structure and salinity. Populations from sites with coarse and heterogeneous sediment had high levels of sexual reproduction. At the site with lower salinity, intermediate and benthic larvae were present during winter in contrast to pelagic larvae found at the other sites. However, we could not identify one clear environmental factor determining the mode of development. At present, it remains unclear to what degree genetic background contributes to mode of development. Hence, whether the differences in developmental mode are the result of genetically different cohorts will be further investigated.

Dispersal and genetic structure of Boccardia polybranchia and Polydora hoplura (Annelida: Spionidae) in South Africa and their implications for aquaculture

Dispersal and observed genetic structure of sessile marine invertebrates such as the alien polydorid polychaete, Polydora hoplura, which is associated with cultured molluscs, may be influenced by biogeographic barriers and human-mediated dispersal. To test this hypothesis, we compared the population genetic structure of P. hoplura to that of Boccardia polybranchia since both species have similar larval developmental modes (and consequently natural dispersal potential) and distribution ranges in southern Africa. However, since B. polybranchia is not a pest, its population structure should reflect the effects of only biogeographic barriers on natural dispersal. Boccardia polybranchia was collected from five wild sites along the South African coast, and P. hoplura from seven wild sites and four oyster farms; two each were on-shore and off-shore. Analyses of mtDNA Cyt b sequence data indicate two distinct lineages for B. polybranchia, supporting Cape Point as a biogeographic barrier to the dispersal of larvae. In contrast, no distinct geographic lineages were identified for P. hoplura occurring in the wild, and haplotype sharing suggest possible cross infestation between farm and nearby wild sites. At farms the genetic diversity of P. hoplura is lower but also more structured, suggesting separate anthropogenic introductions at each site possibly from genetically distinct source populations. Furthermore, more limited genetic sharing was detected between worms from on-shore and nearby wild sites, whereas the opposite was observed for off-shore farms and associated wild sites. This suggests that populations in on-shore farms are more contained with most of the individuals carrying parasites corresponding to the source of introduction while those on off-shore farms display much more genetic exchange with wild populations. Thus oysters in off-shore facilities are probably more vulnerable to infestation by polydorid pests than are those in on-shore facilities. Statement of relevanceMovement of oysters spreads associated pests

DNA Methylation and Potential for Epigenetic Regulation in Pygospio elegans.

Transitions in developmental mode are common evolutionarily, but how and why they occur is not understood. Developmental mode describes larval phenotypes, including morphology, ecology and behavior of larvae, which typically are generalized across different species. The polychaete worm Pygospio elegans is one of few species polymorphic in developmental mode, with multiple larval phenotypes, providing a possibility to examine the potential mechanisms allowing transitions in developmental mode. We investigated the presence of DNA methylation in P. elegans, and, since maternal provisioning is a key factor determining eventual larval phenotype, we compared patterns of DNA methylation in females during oogenesis in this species. We demonstrate that intragenic CpG site DNA methylation and many relevant genes necessary for DNA methylation occur in P. elegans. Methylation-sensitive AFLP analysis showed that gravid females with offspring differing in larval developmental mode have significantly different methylation profiles and that the females with benthic larvae and non-reproductive females from the same location also differ in their epigenetic profiles. Analysis of CpG sites in transcriptome data supported our findings of DNA methylation in this species and showed that CpG observed/expected ratios differ among females gravid with embryos destined to different developmental modes. The differences in CpG site DNA methylation patterns seen among the samples suggest a potential for epigenetic regulation of gene expression (through DNA methylation) in this species.

The effect of temperature on the evolution of per offspring investment in a globally distributed family of marine invertebrates (Crustacea: Decapoda: Lithodidae).

Within the marine environment, per offspring investment (POI) is associated with modes in larval development; an increase in POI has often been described with a decrease in temperature, as evidenced along latitudinal clines. However, the environmental drivers of POI remain largely hypothetical and have not yet been tested within an evolutionary context. Here, we test the hypothesis that developmental temperature is linked to POI within a globally distributed and diverse family of benthic crustaceans, the Lithodidae, also known as stone or king crab. To do this, we examine variations in egg diameter—a proven corollary of POI—within the Lithodidae. Based on a rare case of well-construed phylogeny, we test the relationship between egg diameter and two aspects of the maternal physical environment: water depth and temperature. We observe a significant relationship between decreasing environmental temperature and an increase in POI within genera of lithodid crabs, and independent of depth. There is a clear correlation of high levels in POI with a decrease in temperature in lithodid crab genera currently inhabiting the deep sea, all of which follow a food-independent (lecithotrophic) mode of larval development. In contrast, lithodid genera thriving in the warmer waters of shallow (continental shelf) seas follow a feeding (planktotrophic) mode in larval development. We conclude that temperature is an important factor governing POI, and discuss its importance in the evolution of larval lecithotrophy in marine invertebrates.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-015-2776-8) contains supplementary material, which is available to authorized users.

The evolution of larval developmental mode: insights from hybrids between species with obligately and facultatively planktotrophic larvae.

Life history characteristics play a pervasive role in the ecology and evolution of species. Transitions between feeding and non-feeding larval development have occurred many times in both terrestrial and marine phyla, however we lack a comprehensive understanding of how such shifts occur. The sea biscuits Clypeaster rosaceus and Clypeaster subdepressus employ different life history strategies (facultatively feeding larvae and obligately feeding larvae, respectively) but can hybridize. In this study, we examined the development of hybrid larvae between these two species in order to investigate the inheritance of larval developmental mode. Our results show that both reciprocal hybrid crosses developed via the feeding mode of their maternal species. However, as feeding larvae can obtain both energy and hormones from algal food, we tested how hormones alone affected development by setting up a treatment where we added exogenous thyroid hormone, but no food. In this treatment the offspring of all four crosses (two homospecific and two heterospecific crosses) were able to metamorphose without algal food. Therefore we hypothesize that although hybrid developmental mode was inherited from the maternal species, this result was not solely due to energetic constraints of egg size.

Observations on the composition and larval developmental modes of polydorid pests of farmed oysters (Crassostrea gigas) and abalone (Haliotis midae) in South Africa

This study provides preliminary insights into how the culture method of molluscs and the larval developmental mode of pest polydorids may determine which species become pests. A total of 10 species were identified on oysters and abalone in offshore and oysters in onshore culture on the west coast of South Africa. One-factor PERMANOVA showed that abalone and oysters cultured offshore housed similar communities of worms, but that they differed significantly from the communities housed by oysters cultured onshore. Oysters from onshore were infested mainly by Polydora hoplura, but also by Polydora cf. websteri and Boccardia pseudonatrix. All these species produce adelphophagic larvae or a mixture of these and planktotrophic larvae. Adelphophagic larvae usually only emerge soon before they settle, which would probably enhance their ability to recruit locally and establish local populations. By contrast, worms from molluscs grown offshore were infested by high abundances of P. hoplura and lower abundances of up to five more species per individual host. All hatched broods observed with these female P. hoplura contained planktotrophic larvae which have a long planktonic phase before settling. This would presumably enhance their ability to reach hosts in the offshore.

Deconstructing environmental predictability: seasonality, environmental colour and the biogeography of marine life histories.

Environmental predictability is predicted to shape the evolution of life histories. Two key types of environmental predictability, seasonality and environmental colour, may influence life-history evolution independently but formal considerations of both and how they relate to life history are exceedingly rare. Here, in a global biogeographical analysis of over 800 marine invertebrates, we explore the relationships between both forms of environmental predictability and three fundamental life-history traits: location of larval development (aplanktonic vs. planktonic), larval developmental mode (feeding vs. non-feeding) and offspring size. We found that both dispersal potential and offspring size related to environmental predictability, but the relationships depended on both the environmental factor as well as the type of predictability. Environments that were more seasonal in food availability had a higher prevalence of species with a planktonic larval stage. Future studies should consider both types of environmental predictability as each can strongly affect life-history evolution.

Correlated evolution between mode of larval development and habitat in muricid gastropods.

Larval modes of development affect evolutionary processes and influence the distribution of marine invertebrates in the ocean. The decrease in pelagic development toward higher latitudes is one of the patterns of distribution most frequently discussed in marine organisms (Thorson's rule), which has been related to increased larval mortality associated with long pelagic durations in colder waters. However, the type of substrate occupied by adults has been suggested to influence the generality of the latitudinal patterns in larval development. To help understand how the environment affects the evolution of larval types we evaluated the association between larval development and habitat using gastropods of the Muricidae family as a model group. To achieve this goal, we collected information on latitudinal distribution, sea water temperature, larval development and type of substrate occupied by adults. We constructed a molecular phylogeny for 45 species of muricids to estimate the ancestral character states and to assess the relationship between traits using comparative methods in a Bayesian framework. Our results showed high probability for a common ancestor of the muricids with nonpelagic (and nonfeeding) development, that lived in hard bottoms and cold temperatures. From this ancestor, a pelagic feeding larva evolved three times, and some species shifted to warmer temperatures or sand bottoms. The evolution of larval development was not independent of habitat; the most probable evolutionary route reconstructed in the analysis of correlated evolution showed that type of larval development may change in soft bottoms but in hard bottoms this change is highly unlikely. Lower sea water temperatures were associated with nonpelagic modes of development, supporting Thorson's rule. We show how environmental pressures can favor a particular mode of larval development or transitions between larval modes and discuss the reacquisition of feeding larva in muricids gastropods.