Insemination by a kiss? Interactive 3D-microanatomy, biology and systematics of the mesopsammic cephalaspidean sea slug Pluscula cuica Marcus, 1953 from Brazil (Gastropoda: Euopisthobranchia: Philinoglossidae)

Brenzinger, Bastian; Padula, Vinícius; Schrödl, Michael

doi:10.1007/s13127-012-0093-3

Cited by 24 publications

(14 citation statements)

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“…We are not aware of further records of double connectives among the remaining Euthyneura or acteonids, and only few euopisthobranchs have been indicated to possess the double connective, i.e. Runcina [81] and possibly Pluscula [26]. It remains unclear whether these double roots per se are homologous, since it is so far not clear which nerve tracts originally fused (or divided) to form the double roots; ontogenetic data on this particular phenomenon are entirely lacking.…”

Section: Discussionmentioning

confidence: 99%

“…More similar to the condition found in Helminthope , the nudibranch Pseudovermis Périaslavzeff, 1891 appears to possess numerous smaller ganglia along the sides of its ‘acorn-shaped’ snout [81,89]. Since the ganglia are supplied by sensory nerves, they were argued to be part of an enhanced sensory apparatus, facilitating food detection or path finding among three-dimensional interstitial pore spaces [26]. …”

Section: Discussionmentioning

confidence: 99%

“…They belong to at least six independent lineages of seaslugs including some rhodopemorphs, aeolidioidean nudibranchs, cephalaspideans, sacoglossans, and most acochlidians (e.g. [20-26]). Diversity can be expected to be much higher and undescribed species can commonly be found in sand samples from poorly studied areas – these being most of the world [27,28].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…a considerably modified Tectibranchia in the sense of Cuvier (1817b), share a cuticularised oesophagus. Cephalaspidea, previously assumed to be among the most basal opisthobranchs with putatively plesiomorphic habitus, appear to be a derived taxon with derived features, such as head shields (Brenzinger et al 2013b). Panpulmonata (6) have a procerebrum (or rhinophoral nerves) with double roots (Brenzinger et al 2013a).…”

Section: Molecular Approachesmentioning

confidence: 99%

“…in seminal analyses by Valdés and Gosliner (2001) and Valdés (2002a)], while actually phanerobranch lineages may split off a cryptobranch stemline (see Martynov et al 2009. The history of lineages that were assigned to and removed from the Cephalaspidea was reviewed by Brenzinger et al (2013b), and basal sacoglossan systematics by Kohnert et al (2013). The classification by Bouchet and Rocroi (2005) is still in use but, once established, it was challenged immediately by upcoming molecular systematic approaches.…”

Section: The Thankless Task Of Presenting a Classification Of Opisthomentioning

confidence: 99%

Flashback and foreshadowing—a review of the taxon Opisthobranchia

et al. 2013

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Opisthobranchia have experienced an unsettled taxonomic history. At the moment their taxonomy is in state of dramatic flux as recent phylogenetic studies have revealed traditional Opisthobranchia to be paraphyletic or even polyphyletic, allocating some traditional opisthobranch taxa to other groups of Heterobranchia, e.g. Pulmonata. Here we review the history of Opisthobranchia and their subgroups, explain their traditionally proposed relationships, and outline the most recent phylogenetic analyses based on various methods (morphology, single gene and multiple gene analyses, as well as genomic data). We also present a phylogenetic hypothesis on Heterobranchia that, according to the latest results, represents a consensus and is the most probable one available to date. The proposed phylogeny supports the Acteonoidea outside of monophyletic Euthyneura, the basal euthyneuran split into Nudipleura (Nudibranchia plus Pleurobranchoidea) and the recently established taxon Tectipleura. The latter divides into the Euopisthobranchia, containing most of the major traditional opisthobranch clades, and the Panpulmonata, with a mix of the former opisthobranch, putative allogastropod and pulmonate taxa. This "new euthyneuran tree" rejects the traditional taxa Opisthobranchia and Pulmonata, and, in particular, has profound implications for preconceived textbook scenarios of opisthobranch and pulmonate evolution, which must now be reconsidered. In the absence of systematic barriers, research communities-which have traditionally investigated marine and non-marine heterobranchs separately-need to interact and finally merge for the sake of science.

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Anatomy and ultrastructure of the tropical sponge Cladocroce caelum (Haplosclerida, Demospongiae)

Hora

Cavalcanti

Lanna

2018

Journal of Morphology

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The main characteristic of sponges (Porifera) is the presence of the aquiferous system-a system formed by canals and choanocyte chambers, in which the sponges carry out most of their physiological functions. Despite of the importance for the biology of the group, the knowledge about this structure is still incipient, even when morphological investigations are taken in account.Here, we investigated the anatomy and ultrastructure of the tropical demosponge Cladocroce caelum (Haplosclerida, Demospongiae) using light and electron microscopy. In the studied region, specimens of this species were repent or repent-branched, possessing one to several oscula. A uniform and reduced atrium was found just below each osculum. There was a thin ectosome and the choanosome presented meager mesohyl, but a high number of choanocyte chambers. The choanocyte chambers were rounded, and, as in other haplosclerids, they are found separated from the mesohyl by endopinacocytes, "hanging" in the inhalant canals. Even though the utility of the general organization of the aquiferous system has been advocated as a possible tool to understand the phylogeny of the group, we found that these characters might not be as useful as expected. The size of the particles ingested by the sponge and the amount of bacteria to sustain their bodies are discussed. In addition, we found that the density of choanocyte chambers was reduced when the specimens were carrying out the spermatogenesis, indicating that the reproduction may impair the filtering activity of the sponge. Our findings consist in a first step to better comprehend the physiology, development, and adaptation to the environmental conditions where the species is found.

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Insemination by a kiss? Interactive 3D-microanatomy, biology and systematics of the mesopsammic cephalaspidean sea slug Pluscula cuica Marcus, 1953 from Brazil (Gastropoda: Euopisthobranchia: Philinoglossidae)

Cited by 24 publications

References 70 publications

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

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

Flashback and foreshadowing—a review of the taxon Opisthobranchia

Anatomy and ultrastructure of the tropical sponge Cladocroce caelum (Haplosclerida, Demospongiae)

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