The embryology of Crepidula

Conklin, Edwin G.

doi:10.5962/bhl.title.22111

Cited by 85 publications

(141 citation statements)

References 0 publications

Supporting

Mentioning

138

Contrasting

Unclassified

Order By: Relevance

“…Neither the development nor the larval morphology of either species differs in any substantive way from that described for the well-known larvae of Crepidula fornicata (Conklin, 1897;Werner, 1955; Fig. 1C).…”

Section: Observations Of Developmentmentioning

confidence: 82%

Molecular Phylogenetic and Embryological Evidence That Feeding Larvae Have Been Reacquired in a Marine Gastropod

Collin

Chaparro

Winkler

et al. 2007

The Biological Bulletin

View full text Add to dashboard Cite

Abstract. Evolutionary transitions between different modes of development in marine invertebrates are thought to be biased toward the loss of feeding larvae. Because the morphology of feeding larvae is complex and nonfceding larvae or encapsulated embryos with benthic development often have simplified morphologies, it is presumed to be easier to lose a larval stage than to reacquire it. Some authors have gone so far as to suggest that feeding larvae, morphologically similar to the ancestral feeding larvae, cannot be reacquired. However, the larval structures of some groups, most notably gastropods, are often retained in the encapsulated embryos of species that hatch as benthic juveniles. Therefore the re-evolution of feeding larvae using the same structures may be possible in these groups. Here we present the first well-substantiated case for the recent re-evolution of feeding larvae within a clade of directdevelopers. DNA sequence data show that Crepipatella fecunda, a species of calyptraeid gastropod with planktotrophic development, is nested within a clade of species with direct development, and that Crepipatella dilatata, a species with direct development, appears to be paraphyletic with respect to C. fecunda. Observation of the embryos of C. dilatata shows that the features necessary for larval feeding and swimming are retained in the encapsulated veligers, suggesting that heterochronic shifts in hatching time and changes in nurse-egg allotment could have resulted in the re-evolution of feeding larvae in this species.

show abstract

Section: Observations Of Developmentmentioning

confidence: 82%

Molecular Phylogenetic and Embryological Evidence That Feeding Larvae Have Been Reacquired in a Marine Gastropod

Collin

Chaparro

Winkler

et al. 2007

The Biological Bulletin

View full text Add to dashboard Cite

show abstract

“…Some species, such as C. fornicata, C. lingulata and C. plana exhibit indirect development with a planktotrophic feeding veliger larvae (Fig. 3D, Conklin, 1897;Werner, 1955;Fretter, 1972;Collin, 2000). On the other hand, species such as C. adunca, and C. convexa exhibit direct development leading to the formation of crawl-away juvenile snails (Conklin, 1897;Moritz, 1939).…”

Section: Abstract: Bilaterian Metazoan Spiral Cleavage Life Histormentioning

confidence: 99%

“…Of course the individual micromeres belonging to each quartet also undergo further divisions as successive quartets are born and early on these divisions also follow the same alternating oblique orientations. These daughter cells are distinguished from one another by a system of successive superscript numbers (see Conklin, 1897). Typically those daughters born towards the animal pole receive a superscript of 1 while those towards the vegetal pole receive a 2 (e.g., 1b 1 and 1b 2 , Fig.…”

Section: General Characteristics Of Various Spiralian Phylamentioning

confidence: 99%

“…3D, Conklin, 1897;Werner, 1955;Fretter, 1972;Collin, 2000). On the other hand, species such as C. adunca, and C. convexa exhibit direct development leading to the formation of crawl-away juvenile snails (Conklin, 1897;Moritz, 1939). Yet others such as Crepipetella dilatata (formerly Crepidula dilatata) and Crepidula cf.…”

Section: Abstract: Bilaterian Metazoan Spiral Cleavage Life Histormentioning

confidence: 99%

“…These cells are set aside relatively early during development. Although these organizer cells reside within the D quadrant, there is a fair degree of heterotopic and heterochronic variation in terms of which particular cell(s) serves Henry et al, 2006, andConklin, 1897) …”

mentioning

confidence: 99%

See 2 more Smart Citations

Spiralian model systems

Henry¹

2014

Int. J. Dev. Biol.

View full text Add to dashboard Cite

The "Spiralia" represent one of the three major clades of bilaterian metazoans. Though members of this clade exhibit tremendous diversity in terms of their larval and adult body plans, many share a highly conserved early pattern of development involving a stereotypic cleavage program referred to as spiral cleavage. This group therefore represents an excellent one in which to undertake comparative studies to understand the origins of such diversity from a seemingly common ground plan. These organisms also present varied and diverse modes in terms of their ecology, development and life history strategies. A number of well established and emerging model systems have been developed to undertake studies at the molecular, genetic, cell and organismal levels. The Special Issue of the Int. J. Dev. Biol. entitled "Spiralian Model Systems" focuses on these organisms and here, I introduce this clade, pointing out different types of studies being undertaken with representative spiralian model systems. KEY WORDS: bilaterian metazoan, spiral cleavage, life history strategyThe Spiralia (Lophotrochozoa)Of the three major clades of bilaterians, the Spiralia (Lophotrochozoa) comprise nearly half of the extant metazoan phyla (see Fig. 1). Despite this fact, the group has received relatively little attention compared to the other two clades, the deuterostomes and ecdysozoans, notably in the areas of genetics, as well as molecular, cellular and developmental biology. This is due in part to the long standing predominance of key experimental models positioned within the Ecdysozoa, (e.g., the fruit fly Drosophila and the nematode, C. elegans), and the Deuterostomia, (e.g., chordates such as the Zebrafish and mouse, as well as a few invertebrate representatives from the Echinodermata).The Spiralia include 14 of roughly 36 metazoan phyla (Fig. 1). The Spiralia include the Lophotrochozoa, and sometimes these terms have been used synonomously. The clade "Lophotrochozoa" was first recognized by Halanych et al., (1995, see also Giribet et al., 2007 Helmkampf et al., 2008a,b;Dunn et al., 2008;Hejnol et al., 2009; Edgecomb et al., 2011) who showed that the Lophophorata (consisting of groups possessing characteristic ciliated feeding structures, such as brachiopods and phoronids), are clearly united with other protostome phyla that include annelids, molluscs, and nemerteans. The Spiralia, however, encompass an even larger group of metazoans, and the exact relationships amongst the Spiralia are, however, not fully resolved. The consensus from recent analyses suggest that there are two large sub-groups (clades). One group is the "Trochozoa," (Roule, 1891), which include Annelida, Int. J. Dev. Biol. 58: 389-401 (2014) doi: 10.1387/ijdb.140127jh Mollusca, Nemertea, as the "Eutrochozoa", together with the "Brachiozoa" (see Cavalier-Smith, 1998), comprised of Brachiopoda and Phoronida, and the "Polyzoa" (Funch and Kristensen 1995;Passamaneck and Halanych 2006; Helmkampf et al., 2008a,b;Edgecombe et al., 2011) consisting of the Bryozoa, E...

show abstract

Development of serotonin-like immunoreactivity in the embryos and larvae of nudibranch mollusks with emphasis on the structure and possible function of the apical sensory organ

1997

View full text Add to dashboard Cite

This investigation provides a light and electron microscopic examination of the development of serotonin-like immunoreactivity and structure of the apical sensory organ (ASO) in embryos and/or larvae of four nudibranch species: Berghia verrucicornis, Phestilla sibogae, Melibe leonina, and Tritonia diomedea. Serotonin-like immunoreactivity is first expressed in somata, dendrites, and axons of a group of five distinct neurons within the ASO. These neurons extend axons into an apical neuropil, a structure that is situated centrally and immediately dorsal to the cerebral commissure. Three of these neurons possess sensory dendrites that extend through the pretrochal epithelium, each supporting two cilia at their distal ends. Later development of serotonin-like immunoreactivity includes 1) axons from the apical neuropil that extend into each of the velar lobes; 2) neuron perikarya in the cerebral and pedal ganglia; 3) axons that extend through the cerebral commissure, cerebral-pedal connectives, pedal commissure, and possibly the visceral loop connective; and 4) axons extending from each pedal ganglion into the larval foot. Ultrastructurally, the ASO can be seen to be composed of three lobes and an apical neuropil that is separately delineated from the cerebral commissure. Four cell types are present within the ASO: ciliary tuft cells, type I and type II parampullary neurons, and ampullary neurons. Immunofluorescence and 3,3' diaminobenzidine tetrahydrochloride (DAB) labeling verify that the serotonergic neurons of the ASO are type I and type II parampullary neurons. The ampullary and type I parampullary neurons possess dendrites that extend through the pretrochal epithelium. These dendrites are partitioned into three bundles, one on either side of the ciliary tuft cells and a third bundle penetrating the pretrochal epithelium centrally between the ciliary tuft cells. One serotonergic type I parampullary neuron is associated with each of these bundles. Two ampullary neurons are associated with each of the lateral dendritic bundles, while the central bundle includes only one. Ultrastructural analyses of serotonergic axonal innervation arising from the ASO agree with those determined from fluorescently labeled material. The structure of the ASO and its associated serotonergic axons suggest that the serotonergic component of this structure senses environmental stimuli affecting velar function, possibly the contractility of muscle fibers in the velar lobes. Similarities and differences among the ASOs of embryos and larvae from various invertebrate phyla may provide useful data that will assist in the reconstruction of phylogenetic relationships.

show abstract

The embryology of Crepidula

Cited by 85 publications

References 0 publications

Molecular Phylogenetic and Embryological Evidence That Feeding Larvae Have Been Reacquired in a Marine Gastropod

Molecular Phylogenetic and Embryological Evidence That Feeding Larvae Have Been Reacquired in a Marine Gastropod

Spiralian model systems

Development of serotonin-like immunoreactivity in the embryos and larvae of nudibranch mollusks with emphasis on the structure and possible function of the apical sensory organ

Contact Info

Product

Resources

About