The embryonic moult in diplogastrids (Nematoda) – homology of developmental stages and heterochrony as a prerequisite for morphological diversity

Lieven, Alexander Fürst von

doi:10.1016/j.jcz.2005.05.001

Cited by 25 publications

(22 citation statements)

References 17 publications

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“…Although the nematode eggshell is not expected to harden until after being passed through uterine or vaginal sphincters {e.g.. Bird et al, 1993), embryonic development as currently perceived proceeds by cell division without an increase in embryo size (Sulston et al, 1983;Schulze & Schierenberg, 2011). Finally, the demonstrated capability for vivipary tentatively distinguishes Sudhausia n. gen. from most other diplogastrid species, except for Koerneria pararmata (Schneider, 1938) Sudhaus & Fürst von Lieven, 2003(Fürst von Lieven, 2005 and Mehdinema alii Farooqui, 1967(Luong et al, 1999, although more detailed examination of other diplogastrids exhibiting intra-uterine birth (usually endotokia matricida) may reveal further cases of vivipary. However, whereas endotokia matricida in particular is commonly a facultative response to a stressful environment (Johnigk & Ehlers, 1999;Chen & Caswell-Chen, 2004), S. aristotokia n. gen., n. sp.…”

Section: Discussionmentioning

confidence: 99%

Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp. (Nematoda: Diplogastridae): viviparous new species with precocious gonad development

Herrmann

Ragsdale

Kanzaki

et al. 2013

Nematol

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Two new species of diplogastrid nematodes, Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp., were isolated from dung beetles (Coleoptera: Scarabaeidae) in Ghana and South Africa, respectively. Sudhausia n. gen. is circumscribed by stomatal morphology, namely the presence of a tube-shaped gymnostom, a pair of conical subventral denticles in the metastegostom, and a disk-like telostegostom bearing minute conical denticles. Other characters distinguishing the new genus are the presence of a bursa in the male and a vulva lined anteriorly and posteriorly by columns of sac-like cells. The two new species, both of which are hermaphroditic, are distinguished from each other by spicule and gubernaculum morphology, male papillae arrangement, bursal shape, vaginal morphology, and phasmid position. A suite of unusual developmental traits that distinguishes Sudhausia n. spp. includes maturation of the gonad and development of juvenile progeny before moulting to adulthood, a two-fold increase in embryo size during development, and constitutive vivipary. A phylogeny inferred from 11 ribosomal protein-coding genes and a fragment of the small subunit rRNA gene show Sudhausia n. gen. to be divergent from other sequenced diplogastrid taxa, including those characterised by a tube-like stoma. The two new species represent useful new reference points for the study of feeding-structure evolution in Diplogastridae.

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Section: Discussionmentioning

confidence: 99%

Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp. (Nematoda: Diplogastridae): viviparous new species with precocious gonad development

Herrmann

Ragsdale

Kanzaki

et al. 2013

Nematol

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“…Comparing developmental data across different taxa is a process fraught with problems, one of the main ones being the arbitrary nature of classifications such as those based on age, size or stage, instar or stase [14,99-102]. These terms are used to arbitrarily describe a real, developmentally fixed condition, but only at the specific time of observation.…”

Section: Methodsmentioning

confidence: 99%

Unraveling the origin of Cladocera by identifying heterochrony in the developmental sequences of Branchiopoda

2013

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IntroductionOne of the most interesting riddles within crustaceans is the origin of Cladocera (water fleas). Cladocerans are morphologically diverse and in terms of size and body segmentation differ considerably from other branchiopod taxa (Anostraca, Notostraca, Laevicaudata, Spinicaudata and Cyclestherida). In 1876, the famous zoologist Carl Claus proposed with regard to their origin that cladocerans might have evolved from a precociously maturing larva of a clam shrimp-like ancestor which was able to reproduce at this early stage of development. In order to shed light on this shift in organogenesis and to identify (potential) changes in the chronology of development (heterochrony), we investigated the external and internal development of the ctenopod Penilia avirostris and compared it to development in representatives of Anostraca, Notostraca, Laevicaudata, Spinicaudata and Cyclestherida. The development of the nervous system was investigated using immunohistochemical labeling and confocal microscopy. External morphological development was followed using a scanning electron microscope and confocal microscopy to detect the autofluorescence of the external cuticle.ResultsIn Anostraca, Notostraca, Laevicaudata and Spinicaudata development is indirect and a free-swimming nauplius hatches from resting eggs. In contrast, development in Cyclestherida and Cladocera, in which non-swimming embryo-like larvae hatch from subitaneous eggs (without a resting phase) is defined herein as pseudo-direct and differs considerably from that of the other groups. Both external and internal development in Anostraca, Notostraca, Laevicaudata and Spinicaudata is directed from anterior to posterior, whereas in Cyclestherida and Cladocera differentiation is more synchronous.ConclusionsIn this study, developmental sequences from representatives of all branchiopod taxa are compared and analyzed using a Parsimov event-pairing approach. The analysis reveals clear evolutionary transformations towards Cladocera and the node of Cladoceromorpha which correspond to distinct heterochronous signals and indicate that the evolution of Cladocera was a stepwise process. A switch from a strategy of indirect development to one of pseudo-direct development was followed by a shift in a number of morphological events to an earlier point in ontogenesis and simultaneously by a reduction in the number of pre-metamorphosis molts. A compression of the larval phase as well as a shortening of the juvenile phase finally leads to a precocious maturation and is considered as a gradual progenetic process.

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“…(6) Hence heterochrony may be a prerequisite for morphological diversity in this evolutionary branch. Several life history traits make P. pacificus an ideal animal for developmental genetics.…”

Section: Introductionmentioning

confidence: 99%

Pristionchus pacificus: a well‐rounded nematode

2006

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Nematodes pervade Earth's biosphere and occupy innumerable ecological niches. The role of Caenorhabditis elegans as a model for developmental processes has encouraged us to cultivate a second nematode, Pristionchus pacificus, as a comparative counterpoint to address questions in development, behavior and ecology in nematode evolution. We hope that this endeavor, now more than a decade underway, will allow us to project findings onto other comparative models for biological processes. To this end, our laboratory has made an extensive genetic map and mutant screens to understand changes in developmental programs. Recently, we have been capitalizing on the whole genome sequence of P. pacificus to describe more thoroughly the molecular basis for these changes, as well as to better integrate our molecular knowledge with the biodiversity of Pristionchus species.

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The embryonic moult in diplogastrids (Nematoda) – homology of developmental stages and heterochrony as a prerequisite for morphological diversity

Cited by 25 publications

References 17 publications

Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp. (Nematoda: Diplogastridae): viviparous new species with precocious gonad development

Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp. (Nematoda: Diplogastridae): viviparous new species with precocious gonad development

Unraveling the origin of Cladocera by identifying heterochrony in the developmental sequences of Branchiopoda

Pristionchus pacificus: a well‐rounded nematode

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