ON THE DEVELOPMENT OF THE NEMERTEANMICRURA AKKESHIENSIS*,†

Iwata, Fumio

doi:10.1111/j.1440-169x.1958.tb00150.x

Cited by 30 publications

(34 citation statements)

References 2 publications

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“…Ten years ago only three pilidiophoran species were known to have lecithotrophic development: Lineus viridis (encapsulated Desor's larva), its sibling species L. ruber (similarly encapsulated, but adelphophagous), and Micrura akkeshiensis (planktonic planula-like Iwata's larva) (Iwata 1958;Schmidt 1964). However, accumulating evidence suggests that this type of development may be much more common among the Pilidiophora.…”

Section: Pilidiophoramentioning

confidence: 99%

From trochophore to pilidium and back again - a larva’s journey

Maslakova¹,

Hiebert²

2014

Int. J. Dev. Biol.

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Nemerteans, a phylum of marine lophotrochozoan worms, have a biphasic life history with benthic adults and planktonic larvae. Nemertean larval development is traditionally categorized into direct and indirect. Indirect development via a long-lived planktotrophic pilidium larva is thought to have evolved in one clade of nemerteans, the Pilidiophora, from an ancestor with a uniformly ciliated planuliform larva. Planuliform larvae in a member of a basal nemertean group, the Palaeonemertea, have been previously shown to possess a vestigial prototroch, homologous to the primary larval ciliated band in the trochophores of other spiralian phyla, such as annelids and mollusks. We review literature on nemertean larval development, and include our own unpublished observations. We highlight recent discoveries of numerous pilidiophoran species with lecithotrophic larvae. Some of these larvae superficially resemble uniformly ciliated planuliform larvae of other nemerteans. Others possess one or two transverse ciliary bands, which superficially resemble the prototroch and telotroch of some spiralian trochophores. We also summarize accumulating evidence for planktotrophic feeding by larvae of the order Hoplonemertea, which until now were considered to be lecithotrophic. We suggest that 1) non-feeding pilidiophoran larval forms are derived from a feeding pilidium; 2) such forms have likely evolved many times independently within the Pilidiophora; 3) any resemblance of such larvae to the trochophores of other spiralians is a result of convergence and that 4) the possibility of planktotrophy in hoplonemertean larvae may influence estimates of pelagic larval duration, dispersal, and population connectivity in this group.

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Section: Pilidiophoramentioning

confidence: 99%

From trochophore to pilidium and back again - a larva’s journey

Maslakova¹,

Hiebert²

2014

Int. J. Dev. Biol.

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“…According to other authors the dermal muscles and the outer longitudinal layer are derived from the proximal layer of the imaginal disks, while the inner circular and longitudinal muscles are derived from the underlying mesenchymal cells (Bürger 1894 ;Salensky 1912 ). A similar origin of muscle layers has been reported in the Iwata larva of Micrura akkeshiensis , although the sequence of formation of muscle layers is reversed: fi rst, the inner longitudinal and circular layers are formed, while outer longitudinal and dermal muscles have not been seen until 39 days after metamorphosis (Iwata 1958 ). Recent fl uorescent labeling studies have revealed that the sequence of formation of muscle layers is uniform in all species studied.…”

Section: Body Wall Musculaturementioning

confidence: 71%

“…Furthermore, in the Iwata larva, the number of imaginal disks is restricted to fi ve, a pair of frontal head disks, a pair of posteroventral trunk disks, and an unpaired posterior dorsal disk, all of which form from invaginations of the larval epidermis. An anterior-posterior sequence of their formation is likely (Iwata 1958 ).…”

Section: Aberrant Pilidiophoran Larvaementioning

confidence: 98%

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Nemertea

Döhren¹

2015

Evolutionary Developmental Biology of Invertebrates 2

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“…The larva of C. ochracea develops cilia and hatches prior to the onset of gastrulation. The same has been described in the pilidiophoran species Micrura alaskensis while in other palaeonemertean and pilidiophoran larvae hatching has been described to take place after gastrulation [4,16,17,24,28,33]. In newly hatched embryos of C. ochracea an apical tuft of longer cilia has not yet formed.…”

Section: Comparative Aspects Of Larvae In Paleonemerteamentioning

confidence: 78%

First record on the development of the larva of the basally branching nemertean species Carinina ochracea (Palaeonemertea)

Döhren

2016

Helgol Mar Res

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Nemertea are a clade of unsegmented, vermiform, mostly marine Spiralia. While it is generally accepted that Nemertea develop via a pelagic larval stage there is considerable uncertainty about its characteristic, ancestral features. The uncertainty is mainly due to highly disparate larval types in the derived clade Neonemertea and the scarce information on the larval types of Palaeonemertea, the basal-most branching clade of Nemertea. To remedy this shortage of data the early larval development of a member of the palaeonemertean genus Carinina, Carinina ochracea, is described for the first time. Congruently to what has been described in other palaeonemertean species the larva of C. ochracea is uniformly ciliated along with an apical tuft of elongated cilia housed in an epidermal depression, the apical pit. A pair of frontal epidermal invaginations present bilaterally of the apical pit has been shown in other palaeonemertean larvae as well. Following gastrulation the blastopore is shifted to the ventral side of the body to become the mouth opening. A pair of simple unbranched nephridia that is situated on both sides of the mouth opening completes the list of structures documented for palaeonemertean larvae. Formation of the anal opening was not observed during this study. The presence of a single pigmented ventral eye was hitherto reported from the larva of Carinoma species only. The presented results complement the record of larval types found in Palaeonemertea and will serve as a reference for subsequent studies on the development of internal structures in palaeonemertean species.

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ON THE DEVELOPMENT OF THE NEMERTEANMICRURA AKKESHIENSIS*^,^†

Cited by 30 publications

References 2 publications

From trochophore to pilidium and back again - a larva’s journey

From trochophore to pilidium and back again - a larva’s journey

Nemertea

First record on the development of the larva of the basally branching nemertean species Carinina ochracea (Palaeonemertea)

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