Computer-based 3-dimensional reconstruction of major organ systems of a new aeolid nudibranch subspecies, Flabellina engeli lucianae, from Brazil (Gastropoda: Opisthobranchia)

DaCosta, Simone; Cunha, Carlo M.; Simone, Luiz Ricardo L.; Schrödl, Michael

doi:10.1093/mollus/eym035

Cited by 25 publications

(12 citation statements)

References 20 publications

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“…Neusser et al. , 2006; DaCosta et al. , 2007; Neusser & Schrödl, 2007); scanning and transmission electron microscopy can reveal a number of informative characters, e.g.…”

Section: Discussionmentioning

confidence: 99%

Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)

Schrödl

Neusser

2010

Zoological Journal of the Linnean Society

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The Acochlidia are unique among opisthobranch gastropods in combining extremely high morphological and ecological diversity with modest species diversity. The phylogeny of acochlidians has never been addressed by cladistic means, as their evolution has remained unknown. This study gives a first overview on more than 150 biological and morphological characters that are potentially useful for phylogenetic analysis. Based on 107 characters, a parsimony analysis (PAUP) was performed for all 27 valid acochlidian species together with 11 (plus two) outgroup taxa. The resulting strict consensus tree shows a moderate overall resolution, with at least some bootstrap support for most resolved nodes. The Acochlidia are clearly monophyletic, and originate from an unresolved basal opisthobranch level. The Acochlidia split into the Hedylopsacea (Tantulum (Hedylopsis (Pseudunela (Strubellia ('Acochlidium', 'Palliohedyle'))))) and Microhedylacea (Asperspina (Pontohedyle, 'Parhedyle', 'Microhedyle', (Ganitus, Paraganitus))). The formerly enigmatic Ganitidae, resembling sacoglossan opisthobranchs by having dagger-like rachidian radular teeth, are likely to be highly derived microhedylids. The paraphyly of some of the traditionally recognized family level taxa induced a preliminary reclassification. From the phylogenetic hypothesis obtained, we conclude that the acochlidian ancestor was marine mesopsammic. The colonization of limnic systems occurred twice, independently: first in the Caribbean (with the development of the small interstitial Tantulum elegans), and second in the Indo-Pacific, with a radiation of large-sized benthic acochlidian species. The evolution of extraordinary reproductive features, such as hypodermic impregnation by a complex copulative aparatus in hedylopsaceans, cutaneous insemination via spermatophores in microhedylaceans, and gonochorism in Microhedylidae s.l. (including Ganitidae), is discussed.

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“…Neusser et al. , 2006; DaCosta et al. , 2007; Neusser & Schrödl, 2007); scanning and transmission electron microscopy can reveal a number of informative characters, e.g.…”

Section: Discussionmentioning

confidence: 99%

Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)

Schrödl

Neusser

2010

Zoological Journal of the Linnean Society

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“…In gastropod research, such studies have been published mainly for minute Heterobranchia (e.g. [22,24,46-53]).…”

Section: Introductionmentioning

confidence: 99%

At the limits of a successful body plan - 3D microanatomy, histology and evolution of Helminthope (Mollusca: Heterobranchia: Rhodopemorpha), the most worm-like gastropod

2013

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BackgroundGastropods are among the most diverse animal clades, and have successfully colonized special habitats such as the marine sand interstitial. Specialized meiofaunal snails and slugs are tiny and worm-shaped. They combine regressive features – argued to be due to progenetic tendencies – with convergent adaptations. Microscopic size and concerted convergences make morphological examination non-trivial and hamper phylogenetic reconstructions. The enigmatic turbellarian-like Rhodopemorpha are a small group that has puzzled systematists for over a century. A preliminary molecular framework places the group far closer to the root of Heterobranchia – one of the major gastropod groups – than previously suggested. The poorly known meiofaunal Helminthope psammobionta Salvini-Plawen, 1991 from Bermuda is the most worm-shaped free-living gastropod and shows apparently aberrant aspects of anatomy. Its study may give important clues to understand the evolution of rhodopemorphs among basal heterobranchs versus their previously thought origin among ‘higher’ euthyneuran taxa.ResultsWe describe the 3D-microanatomy of H. psammobionta using three-dimensional digital reconstruction based on serial semithin histological sections. The new dataset expands upon the original description and corrects several aspects. Helminthope shows a set of typical adaptations and regressive characters present in other mesopsammic slugs (called ‘meiofaunal syndrome’ herein). The taxonomically important presence of five separate visceral loop ganglia is confirmed, but considerable further detail of the complex nervous system are corrected and revealed. The digestive and reproductive systems are simple and modified to the thread-like morphology of the animal; the anus is far posterior. There is no heart; the kidney resembles a protonephridium. Data on all organ systems are compiled and compared to Rhodope.ConclusionsHelminthope is related to Rhodope sharing unique apomorphies. We argue that the peculiar kidney, configuration of the visceral loop and simplicity or lack of other organs in Rhodopemorpha are results of progenesis. The posterior shift of the anus in Helminthope is interpreted as a peramorphy, i.e. hypertrophy of body length early in ontogeny. Our review of morphological and molecular evidence is consistent with an origin of Rhodopemorpha slugs among shelled ‘lower Heterobranchia’. Previously thought shared ‘diagnostic’ features such as five visceral ganglia are either plesiomorphic or convergent, while euthyneury and a double-rooted cerebral nerve likely evolved independently in Rhodopemorpha and Euthyneura.

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“…The small body size of marine interstitial species allows for the preparation and analysis of entire specimens via serial semithin histological sections. The successive three‐dimensional reconstruction of organ systems using amira software is a reproducible and very powerful method (DaCosta et al . 2007).…”

Section: Introductionmentioning

confidence: 99%

Heartless and primitive? 3D reconstruction of the polar acochlidian gastropod Asperspina murmanica

2009

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This study re‐examines in detail the microanatomy of the Arctic opisthobranch Asperspina murmanica, the only acochlidian that was described as retaining a well‐developed mantle cavity, and evaluates its supposedly basal position within the Acochlidia. Several specimens were recollected at the type locality in Russia. Spicules and radulae were studied by scanning electron microscopy. Semithin sections were prepared and a computer‐based three‐dimensional reconstruction of all major organ systems was made using amira software. Our results show significant differences from the original description, e.g. the nervous system shows paired rhinophoral and gastro‐oesophageal ganglia and large aggregations of precerebral accessory ganglia, whereas the presence of a postulated posterior genital ganglion can be excluded; the radula is asymmetric; the circulatory system includes a small heart; and the reproductive system comprises a sac‐like ampulla and three female glands. The most surprising discrepancy to the original description refers to the complete absence of any mantle cavity. The gonopore, anus and nephropore open separately to the exterior. Instead of being aberrant or basal, A. murmanica fits well with other Asperspina species and comes closest to the Mediterranean Asperspina rhopalotecta. The monotypic genus/family Minicheviella/Minicheviellidae Starobogatov (1983) is confirmed as a junior synonym of Asperspina/Asperspinidae Rankin (1979).

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Computer-based 3-dimensional reconstruction of major organ systems of a new aeolid nudibranch subspecies, Flabellina engeli lucianae, from Brazil (Gastropoda: Opisthobranchia)

Cited by 25 publications

References 20 publications

Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)

Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)

At the limits of a successful body plan - 3D microanatomy, histology and evolution of Helminthope (Mollusca: Heterobranchia: Rhodopemorpha), the most worm-like gastropod

Heartless and primitive? 3D reconstruction of the polar acochlidian gastropod Asperspina murmanica

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