Having cake and eating too: The benefits of an intermediate larval form in a brittle star sp. opaque (Ophiuroidea).

Most marine invertebrate larvae either obligately feed or depend on maternally provided reserves during planktonic development. A small number of species have the capacity to do both, in a mode of development known as facultative planktotrophy. We describe facultative feeding in a larva from the Oregon coast, and identify it as being an undescribed species in the genus , which we refer to as sp.

Swimming Kinematics of Cyprids of the Barnacle Balanus glandula.

Larvae of barnacles typically pass through naupliar and cyprid planktonic stages before settlement and metamorphosis. As the final larval stage, cyprids swim much faster than nauplii and in turbulent fluid environments with high shears as they seek habitat. Cyprids swim with six pairs of reciprocating thoracic appendages and use two anterior antennules during settlement.

(Echinodermata: Ophiuroidea) and Bursal Ventilation.

The basket star is an aerobic organism highly dependent on dissolved oxygen in surrounding waters. Previous observations on the anatomy of state that five pairs of ossicles (the radial shields and genital plates) regulate the position of the roof of the body disc and are responsible for flushing seawater into and out of the bursae, though this seems never to have been empirically tested. In the current study, rates of bursal ventilation were investigated in response to an increase in the availability of food and, separately, exposure to hypoxic levels of dissolved oxygen.

Permanently Fused Setules Create Unusual Folding Fans Used for Swimming in Cyprid Larvae of Barnacles.

Many crustacean swimming appendages carry arrays of plumose setae-exoskeletal, feather-like structures of long bristles (setae) with short branches (setules) distributed along two sides. Although closely spaced, setae are not physically interconnected. Setal arrays function during swimming as drag-based leaky paddles that push the organism through water.

How the pilidium larva feeds.

Introduction: The nemertean pilidium is a long-lived feeding larva unique to the life cycle of a single monophyletic group, the Pilidiophora, which is characterized by this innovation. That the pilidium feeds on small planktonic unicells seems clear; how it does so is unknown and not readily inferred, because it shares little morphological similarity with other planktotrophic larvae.

Results: Using high-speed video of trapped lab-reared pilidia of Micrura alaskensis, we documented a multi-stage feeding mechanism.

Low rates of bindin codon evolution in lecithotrophic Heliocidaris sea urchins.

Life-history variables including egg size affect the evolutionary response to sexual selection in broadcast-spawning sea urchins and other marine animals. Such responses include high or low rates of codon evolution at gamete recognition loci that encode sperm- and egg-surface peptides. Strong positive selection on such loci affects intraspecific mating success and interspecific reproductive divergence (and may play a role in speciation).

Dispersal of deep-sea larvae from the intra-American seas: simulations of trajectories using ocean models.

Using data on ocean circulation with a Lagrangian larval transport model, we modeled the potential dispersal distances for seven species of bathyal invertebrates whose durations of larval life have been estimated from laboratory rearing, MOCNESS plankton sampling, spawning times, and recruitment. Species associated with methane seeps in the Gulf of Mexico and/or Barbados included the bivalve "Bathymodiolus" childressi, the gastropod Bathynerita naticoidea, the siboglinid polychaete tube worm Lamellibrachia luymesi, and the asteroid Sclerasterias tanneri. Non-seep species included the echinoids Cidaris blakei and Stylocidaris lineata from sedimented slopes in the Bahamas and the wood-dwelling sipunculan Phascolosoma turnerae, found in Barbados, the Bahamas, and the Gulf of Mexico.

Larval development and metamorphosis of the deep-sea cidaroid urchin Cidaris blakei.

Cidaroids, one of the two major sister clades of sea urchins, first appeared during the lower Permian (ca. 270 mya) and are considered to represent the primitive form of all living echinoids. This study of Cidaris blakei, a deep-sea cidaroid urchin with planktotrophic larvae, provides a description of development from fertilization through early juvenile stages and is the first report of a deep-sea urchin reared through metamorphosis.

Morphological evolution of newly metamorphosed sea urchins--a phylogenetic and functional analysis.

Newly metamorphosed juvenile sea urchins are highly variable across taxa. This contribution documents and illustrates structural, functional, and phylogenetic variation among newly metamorphosed juvenile sea urchins for 31 species from 12 ordinal or familial lineages. The classic juvenile with five primary podia, 20 interambulacral spines, and variable numbers of juvenile spines is found commonly among new metamorphs across lineages, but there are many examples, which depart from this pattern and most likely reflect adaptation to settlement habitats.

The bilaterally asymmetrical larval form of Stomopneustes variolaris (Lamarck).

This study describes the echinopluteus and juveniles of the Indo-Pacific echinoid Stomopneustes variolaris. Late 4-armed larvae had left postoral arms that were longer and more deeply red pigmented than the right arms. Two weeks into development, the sixth pair of arms, the posterolaterals, began to form as these larvae achieved an arbacioid form.

Heat-shock response of the upper intertidal barnacle Balanus glandula: thermal stress and acclimation.

In the intertidal zone in the Pacific Northwest, body temperatures of sessile marine organisms can reach 35 degrees C for an extended time during low tide, resulting in potential physiological stress. We used immunochemical assays to examine the effects of thermal stress on endogenous Hsp70 levels in the intertidal barnacle Balanus glandula. After thermal stress, endogenous Hsp70 levels did not increase above control levels in B.

Linking stages of life history: How larval quality translates into juvenile performance for an intertidal barnacle (Balanus glandula).

Many marine invertebrates with complex life cycles produce planktonic larvae that experience environmental conditions different from those encountered by adults. Factors such as temperature and food, known to impact the larval period, can also affect larval size and consequently the size of newly settled juveniles. After documenting natural variation in the size of cyprids (the final larval stage) of the barnacle Balanus glandula, we experimentally manipulated temperature and food given to larvae to produce cyprids of differing sizes but within the size range of cyprids found in the field.

Offspring size effects mediate competitive interactions in a colonial marine invertebrate.

Over the past 30 years, numerous attempts to understand the relationship between offspring size and fitness have been made, and it has become clear that this critical relationship is strongly affected by environmental heterogeneity. For marine invertebrates, there has been a long-standing interest in the evolution of offspring size, but there have been very few empirical and theoretical examinations of post-metamorphic offspring size effects, and almost none have considered the effect of environmental heterogeneity on the offspring size/fitness relationship. We investigated the post-metamorphic effects of offspring size in the field for the colonial marine invertebrate Botrylloides violaceus.

Macroevolutionary consequences of developmental mode in temnopleurid echinoids from the Tertiary of southern Australia.

Taxonomic revision and cladistic analysis of a morphological dataset for Australian Tertiary temnopleurids resolve the phylogeny of the group and allow the testing of a series of hypotheses about the evolution of larval development and consequences of changes in development. Australian Tertiary temnopleurids encompass all three major developmental types found in marine invertebrates (planktotrophy, lecithotrophy, and brooding). Planktotrophy is plesiomorphic for this clade, and nonplanktotrophic larval development evolved independently at least three times during the Tertiary.

Phylogeny and evolution of developmental mode in temnopleurid echinoids.

The phylogenetic relationships of 24 nominal species of temnopleurid echinoid were established using molecular and morphological data sets. The analysis combined sequence data from mitochondrial 16S rRNA and cytochrome c oxidase subunit I genes and the nuclear 18S-like small subunit rRNA gene with morphological data concerning coronal, lantern, spine, and pedicellarial traits. All four data sets contain similar phylogenetic information, although each provides support at a different taxonomic level.

Functional and Evolutionary Implications of Opposed Bands, Big Mouths, and Extensive Oral Ciliation in Larval Opheliids and Echiurids (Annelida).

Larvae of two annelids, the opheliid Armandia brevis and the echiurid Urechis caupo, captured small particles between opposed prototrochal and metatrochal ciliary bands and also captured large particles with wide ciliated mouths. The body volume of larval A. brevis increased more rapidly than the estimated maximum clearance rate as segments were added.

Energy Use During the Development of a Lecithotrophic and a Planktotrophic Echinoid.

The energy required for development was measured in two closely related echinoids with differing modes of development. Heliocidaris tuberculata hatches from a 95-{mu}m egg (~0.1 {mu}g dry organic mass) and develops via a planktotrophic larva over 21-30 days into a juvenile (5.

EFFECTS OF EGG SIZE ON POSTLARVAL PERFORMANCE: EXPERIMENTAL EVIDENCE FROM A SEA URCHIN.

Many life-history and developmental studies of marine invertebrates assume that eggs of species with nonfeeding larvae are large because they provide materials for rapid development. Using the sea urchin Heliocidaris erythrogramma which has 400 μm eggs and nonfeeding larvae, we removed an acellular, lipid-rich component from the blastula equivalent to ca. 40% of the egg volume and ca.

DEVELOPMENTAL MODE AND SPECIES GEOGRAPHIC RANGE IN REGULAR SEA URCHINS (ECHINODERMATA: ECHINOIDEA).

Among marine benthic organisms, the ability to disperse, primarily during the larval stage, is widely thought to influence the extent of species geographic range. Because related species often differ in their modes of larval development (pelagic, feeding larvae; pelagic, nonfeeding larvae; or brooded development), and these can have dramatically different planktonic intervals, the mode of development may influence geographic range. A global survey of 215 regular echinoids shows that species with pelagic, feeding larvae have significantly larger ranges than those with pelagic, nonfeeding larvae, but there is no difference in ranges between species with pelagic, nonfeeding larvae and those with brooded development.

Larval spicules, cilia, and symmetry as remnants of indirect development in the direct developing sea urchin Heliocidaris erythrogramma.

Nonfeeding larvae of the echinoid Heliocidaris erythrogramma were raised in culture and examined for expression of a larval skeleton and for the arrangement of the ciliated band. Opaque larvae were fixed, cleared, and examined under polarized light for evidence of calcification. By 35 hr after fertilization (at 22 degrees C), a pair of triradiate spicules was present at the posterior end of the larvae.