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PubMed2025

Genome Report: De novo genome assembly of the greater Bermuda land snail, Poecilozonites bermudensis (Mollusca: Gastropoda), confirms ancestral genome duplication.

Poecilozonites bermudensis, the greater Bermuda land snail, is a critically endangered species and one of only two extant members in its genus. These snails are one of Bermuda's few endemic animal clades and their rich fossil record was the basis for the punctuated equilibria model of speciation. Once thought extinct, recent conservation efforts have focused on the recovery of the species, yet no genomic information or other molecular sequences have been available to inform these initiatives. We present a high-quality, annotated genome for P. bermudensis generated using PacBio long read and Omni-C short read sequencing. The resulting assembly is approximately 1.36 Gb with a scaffold N50 of 44.t Mb and 31 chromosome-length scaffolds. Nearly 43 percent of the genome was identified as repeat content. This assembly will serve as a resource for the conservation and study of P. bermudensis, and its only close extant and also critically endangered relative, P. circumfirmatus. Additionally, this genome adds to the growing body of data needed for a more complete understanding of gastropod evolution and for evolutionary processes in general.

Annotation↗
PubMed2004

Muscle differentiation in tentacles of Sepia officinalis (Mollusca) is regulated by muscle regulatory factors (MRF) related proteins.

The tentacles of Sepia officinalis are muscular structures that can be quickly everted and 'super-elongated' to capture prey. The speed and super-elongation are achieved by the presence of both cross-striated and helical muscles. In the present study, the complex organization and differentiation of various fibers of the cuttlefish were examined from an early stage of development (stage 26), when the embryo is still inside the egg gel-coating, until the juvenile stage (two weeks after hatching). The muscles start to differentiate centrifugally from the area around the axial nervous system where two types of myoblasts can be recognized. Smooth fibers (referred to here as 'smooth-like' fibers because of their similarity to vertebrate smooth fibers) appear first, then bundles and layers of circomyarian helical and cross-striated fibers differentiate. In Sepia, two muscle-specific transcription factors (MRF), Myf5-like and MyoD-like, have been identified and they are differently expressed during development. Myf5 was detected at first in myoblasts, which give rise to helical smooth-like fibers, while MyoD was expressed later in the other population of myocytes from which circomyarian helical and cross-striated fibers derive. The effective role of these two MRF in tentacle muscle differentiation was confirmed by RNA interference experiments. Injection of double stranded (ds)RNA Myf5 inhibited differentiation of smooth-like fibers, whereas injection of dsRNA MyoD resulted in inhibition of cross-striated and circomyarian helical fibers.

Animals↗
PubMed2004

Differentiation of slow and fast fibers in tentacles of Sepia officinalis (Mollusca).

The tentacles of Sepia officinalis are cylindrical muscular structures that can be quickly everted and elongated to capture prey. The combination of both velocity and extensive elongation of the tentacles is due to the presence of both cross-striated and helical muscles. The complex organization and differentiation of different fibers has been studied in cuttlefish extracted from egg gel coats at different developmental stages, and in completely developed animals. Tentacle muscles start to differentiate centrifugally from the area close to the axial nervous system, where two types of myocytes can be recognized. These populations of myocytes, which may be distinguished morphologically and which express different myosin isoforms, give rise to fast and slow muscles. The presence in molluscs of slow and fast muscles arising from different populations of myocytes, as in vertebrate muscle development, could be considered as an example of evolutionary conservation.

Animals↗
PubMed1973

Genetic variation in a gradient of environmental variability: marine bivalvia (Mollusca).

Six bivalve mollusk species were sampled for genetic variability at two enzyme synthesizing loci. The effective number of alleles and absolute number of alleles decreased with depth of burial within the sediment, intertidally, and with depth of water, subtidally. It is proposed that environmental variability regulates genetic variability at these two loci.

Alleles↗
PubMed1998

Genetic diversity of the biofilm covering Montacuta ferruginosa (Mollusca, bivalvia) as evaluated by denaturing gradient gel electrophoresis analysis and cloning of PCR-amplified gene fragments coding for 16S rRNA.

The shell of the bivalve Montacuta ferruginosa, a symbiont living in the burrow of an echinoid, is covered with a rust-colored biofilm. This biofilm includes different morphotypes of bacteria that are encrusted with a mineral rich in ferric ion and phosphate. The aim of this research was to determine the genetic diversity and phylogenetic affiliation of the biofilm bacteria. Also, the possible roles of the microorganisms in the processes of mineral deposition within the biofilm, as well as their impact on the biology of the bivalve, were assessed by phenotypic inference. The genetic diversity was determined by denaturing gradient gel electrophoresis (DGGE) analysis of short (193-bp) 16S ribosomal DNA PCR products obtained with primers specific for the domain Bacteria. This analysis revealed a diverse consortium; 11 to 25 sequence types were detected depending on the method of DNA extraction used. Individual biofilms analyzed by using the same DNA extraction protocol did not produce identical DGGE profiles. However, different biofilms shared common bands, suggesting that similar bacteria can be found in different biofilms. The phylogenetic affiliations of the sequence types were determined by cloning and sequencing the 16S rRNA genes. Close relatives of the genera Pseudoalteromonas, Colwellia, and Oceanospirillum (members of the gamma-Proteobacteria lineage), as well as Flexibacter maritimus (a member of the Cytophaga-Flavobacter-Bacteroides lineage), were found in the biofilms. We inferred from the results that some of the biofilm bacteria could play a role in the mineral formation processes.

Animals↗
PubMed2003

Sequence analysis of the ribosomal DNA internal transcribed spacer region in some scallop species (Mollusca: Bivalvia: Pectinidae).

The internal transcribed spacer (ITS) region of the ribosomal DNA from the European scallops Aequipecten opercularis, Mimachlamys varia, Hinnites distortus, and Pecten maximus was PCR amplified and sequenced. For each species, three or five clones were examined. The size ranged between 636 and 713 bp (ITS1, 209-276 bp; 5.8S rRNA gene, 157 bp; ITS2, 270-294 bp) and GC content ranged between 47 and 50% (ITS1, 43-49%; 5.8S rRNA gene, 56-57%; ITS2, 44-49%). Variation within repeats was minimal; only clones from M. varia and P. maximus displayed a few variable sites in ITS2. Among scallops, including Chlamys farreri whose ITS sequence appears in databases, significant variation was observed in both ITS1 and ITS2. Phylogenetic analysis using ITS1, ITS2, or both spacer sequences always yielded trees with similar topology. Aequipecten opercularis and P. maximus grouped in one clade and the other three scallops (C. farreri, M. varia, and H. distortus) in another, where M. varia and H. distortus are the more closely related species. These results provide new insights into the evolutionary relationships of scallop species and corroborate the close evolutionary relationship between the tribes Aequipectinini and Pectinini previously deduced from 18S rDNA sequences.

Animals↗
PubMed2024

Complementing aculiferan mitogenomics: comparative characterization of mitochondrial genomes of Solenogastres (Mollusca, Aplacophora).

BACKGROUND: With the advances in high-throughput sequencing and bioinformatic pipelines, mitochondrial genomes have become increasingly popular for phylogenetic analyses across different clades of invertebrates. Despite the vast rise in available mitogenomic datasets of molluscs, one class of aplacophoran molluscs - Solenogastres (or Neomeniomorpha) - is still neglected. RESULTS: Here, we present six new mitochondrial genomes from five families of Solenogastres (Amphimeniidae, Gymnomeniidae, Proneomeniidae, Pruvotinidae, Simrothiellidae), including the first complete mitogenomes, thereby now representing three of the four traditional orders. Solenogaster mitogenomes are variable in size (ranging from approximately 15,000 bp to over 17,000 bp). The gene order of the 13 protein coding genes and two rRNA genes is conserved in three blocks, but considerable variation occurs in the order of the 22 tRNA genes. Based on phylogenetic analyses and reconstruction of ancestral mitochondrial genomes of Aculifera, the position of (1) trnD gene between atp8 and atp6, (2) trnT and P genes between atp6 and nad5, and (3) trnL1 gene between G and E, resulting in a 'MCYWQGL1E'-block of tRNA genes, are all three considered synapomorphies for Solenogastres. The tRNA gene block 'KARNI' present in Polyplacophora and several conchiferan taxa is dissolved in Solenogastres. CONCLUSION: Our study shows that mitogenomes are suitable to resolve the phylogenetic relationships among Aculifera and within Solenogastres, thus presenting a cost and time efficient compromise to approach evolutionary history in these clades.

Genome, Mitochondrial↗
PubMedDate not supplied

[Sarasinula marginata (Semper, 1885) (Mollusca, Soleolifera) from Belo Horizonte (MG, Brasil) as a potential intermediate host of Angiostrongylus costaricensis Morera, Cespedes, 1971].

Specimens of Sarasinula marginata were collected in kitchen and house gardens of Belo Horizonte, Minas Gerais. The susceptibility of these molluscs for Angiostrongylus costaricensis was tested by infecting 15 laboratory--reared slugs (F1). The positivity demonstrated was of 80.0%.

Angiostrongylus↗
PubMedDate not supplied

Natural infection of deroceras laeve (Mollusca: gastropoda) with metastronbylid larvae in a transmission focus of abdominal angiostrongyliasis.

Angiostrongylus costaricensis is a nematode parasitic of rodents. Man may become infected by ingestion of the third stage larvae produced within the intermediate hosts, usually slugs from the family Veronicellidae. An epidemiological study carried out in a locality in southern Brazil (western Santa Catarina State) where these slugs are a crop pest and an important vector for A. costaricensis has documented for the first time the natural infection of Deroceras laeve with metastrongylid larvae. This small limacid slug is frequently found amid the folds of vegetable leaves and may be inadvertently ingested. Therefore D. laeve may have an important role in transmission of A. costaricensis to man.

Animals↗
PubMedDate not supplied

Potentiality of Achatina fulica Bowdich, 1822 (Mollusca: Gastropoda) as intermediate host of the Angiostrongylus costaricensis Morera & Céspedes 1971.

Samples of Achatina fulica were experimentally infected with Angiostrongylus costaricensis larvae, etiological agent of abdominal angiostrongyliasis, showing that A. fulica is susceptible to the parasite. Achatina fulica may be a risk to urbanization of abdominal angiostrongyliasis presumably due to its high proliferation, continuous dispersion and remarkable adaptation in several Brazilian towns.

Angiostrongylus cantonensis↗