Trochophore Larva (trochophore + larva)

Distribution by Scientific Domains


Selected Abstracts


Vestigial prototroch in a basal nemertean, Carinoma tremaphoros (Nemertea; Palaeonemertea)

EVOLUTION AND DEVELOPMENT, Issue 4 2004
S. A. Maslakova
Summary Nemerteans have been alleged to belong to a protostome clade called the Trochozoa that includes mollusks, annelids, sipunculids, echiurids, and kamptozoans and is characterized by, among other things, the trochophore larva. The trochophore possesses a prototroch, a preoral belt of specialized ciliary cells, derived from the trochoblast cells. Nemertea is the only trochozoan phylum for which presence of the trochophore larva possessing a prototroch had never been shown. However, so little is known about nemertean larval development that comparing it with development of other trochozoans is difficult. Development in the nemertean clade Pilidiophora is via a highly specialized planktonic larva, the pilidium, and most of the larval body is lost during a drastic metamorphosis. Other nemerteans (hoplonemerteans and palaeonemerteans) lack a pilidium, and their development is direct, forming either an encapsulated or planktonic "planuliform" larva, producing a juvenile without a dramatic change in body plan. We show that early in the development of a member of a basal nemertean assemblage, the palaeonemertean Carinoma tremaphoros, large squamous cells cover the entire larval surface except for the apical and posterior regions. Although apical and posterior cells continue to divide, the large surface cells cleavage arrest and form a contorted preoral belt. Based on its position, cell lineage, and fate, we suggest that this belt corresponds to the prototroch of other trochozoans. Lack of differential ciliation obscures the presence of the prototroch in Carinoma, but differentiation of the trochoblasts is clearly manifested in their permanent cleavage arrest and ultimate degenerative fate. Our results allow a meaningful comparison between the development of nemerteans and other trochozoans. We review previous hypotheses of the evolution of nemertean development and suggest that a trochophore-like larva is plesiomorphic for nemerteans while a pilidium type of development with drastic metamorphosis is derived. [source]


A lophotrochozoan twist gene is expressed in the ectomesoderm of the gastropod mollusk Patella vulgata

EVOLUTION AND DEVELOPMENT, Issue 5 2002
Alexander J. Nederbragt
SUMMARY The twist gene is known to be involved in mesoderm formation in two of the three clades of bilaterally symmetrical animals: viz. deuterostomes (such as vertebrates) and ecdysozoans (such as arthropods and nematodes). There are currently no data on the spatiotemporal expression of this gene in the third clade, the lophotrochozoans (such as mollusks and annelids). To approach the question of mesoderm homology across bilaterians, we decided to analyze orthologs of this gene in the gastropod mollusk Patella vulgata that belongs to the lophotrochozoans. We present here the cloning, characterization, and phylogenetic analysis of a Patella twist ortholog, Pv-twi, and determine the early spatiotemporal expression pattern of this gene. Pv-twi expression was found in the trochophore larva in a subset of the ectomesoderm, one of the two sources of mesoderm in Patella. These data support the idea that twist genes were ancestrally involved in mesoderm differentiation. The absence of Pv-twi in the second mesodermal source, the endomesoderm, suggests that also other genes must be involved in lophotrochozoan mesoderm differentiation. It therefore remains a question if the mesoderm of all bilaterians is homologous. [source]


Laboratory spawning, larval development, and metamorphosis of the limpets Lottia digitalis and Lottia asmi (Patellogastropoda, Lottiidae)

INVERTEBRATE BIOLOGY, Issue 1 2002
Matthew C. Kay
Abstract. This study describes and compares laboratory spawning, larval development, and metamorphosis in the patellogastropod limpets Lottia digitalis and Lottia asmi. Both species were dioecious and freely spawned their gametes, which were fertilized externally. Eggs from L. digitalis and L. asmi averaged 155 and 134 ,m in diameter, respectively. Early cleavage patterns were typical of other patellogastropods. Swimming trochophore larvae had developed , 15 hours after fertilization, and ultimately developed into lecithotrophic veliger larvae that reached metamorphic competence at 5.25,5.5 days after fertilization (13°C). Food particles were frequently visible in the gut of newly metamorphosed individuals one day after settlement, and adult shell growth was typically initiated within 2,4 days of settlement. Small egg size in L. asmi, relative to other eastern Pacific lottiids, may be directly related to the need for high fecundity in this small-bodied species; however, developmental information is available for relatively few lottiid species. Because broadcasting lottiids do not secure egg masses in safe microhabitats for development, this reproductive mode may have been conducive to their ecological radiation into novel habitats. [source]


Developmental stages, larval and post-larval growth of angelwing clam Pholas orientalis

AQUACULTURE RESEARCH, Issue 7 2009
Beewah Ng
Abstract Angelwing clam were induced to spawn by thermal stimulation. Mature eggs measured 50 ,m in diameter. Cell division occurred within 36 min after fertilization. Mobile trochophore larvae were seen after 12 h and larvae developed within 18 h. Reared on a diet of Isochrysis galbana the larvae reached the umbo stage in 6,7 days. On day 10 the foot could be seen and settlement occurred if a suitable substrate was present. The larvae completed metamorphosis into juveniles within 20 days after settling. [source]