Pallial Cavity Research Articles

On reproduction in the Pacific boreal limpet Erginus (Problacmaea) puniceus Lindberg, 1988 (Patellogastropoda: Rhodopetalidae)

ABSTRACT Fifty years ago, it was reported that individuals of the Pacific boreal limpet Problacmaea (= Erginus) bear a penis for copulation and brood their young in the pallial cavity. These observations were based on light microscopy, but now we reveal new details of the reproductive biology of Erginus (Problacmaea) puniceus with electron microscopy. Gametogenesis is fundamentally similar to other Patellogastropoda, but there are some key differences. Oocytes develop in the ovary, dorsal to the foot in the posterior half of the body, before passing through the oviduct to the pallial cavity, where they are fertilized and brooded. Development is direct with embryos being brooded to the crawl-away juvenile stage. However, sometimes fertilization occurs internally with embryos beginning development in or near the gonad. Free sperm, which were likely autosperm (self) but could have been allosperm (cross), were found near developing oocytes in the gonad. Spermiogenesis results in the formation of an enta-quasperm with a cap-like acrosome, a bullet-shaped nucleus and spherical mitochondria in the midpiece. Copulation was not observed, but we confirm the presence of a penis with a dorsal penial groove that lies below the right cephalic tentacle in males, which is typical of functional penises of some molluscs. Males were always smaller, but intermediate-sized individuals were hermaphroditic to different extents. The largest individuals were entirely female, and their penises were smaller and often lacked the penial groove. Thus, E. (Problacmaea) puniceus appears to be a protandrous hermaphrodite, passing from male to female phase. Remnants of the testis persist into the female phase, suggesting that they are protandrous hermaphrodites with overlap, possibly allowing for self-fertilization to occur on occasion. However, the largest females lacked any testis remnants, suggesting instead that the species may be protandrous sequential hermaphrodites.

Anatomy of the pallial cavity and associated organs in three species of Olivella (Mollusca: Neogastropoda: Olividae) from Brazil

ABSTRACT Olivella Swainson, 1831 is a genus of small marine benthic gastropods found worldwide, represented by 117 valid species in 17 subgenera usually defined by conchological features such as colouration, size, shape and shell sculpture. Despite some conchological research on species in the family Olividae Latreille, 1825, the soft anatomy of Olivella species is still poorly studied. The present study aims to describe and compare the morphology of the pallial cavity and its adjacent structures in three species of Olivella from the Brazilian coast: Olivella (Olivella) floralia (Duclos, 1844), Olivella (Olivella) nivea (Gmelin, 1791), and Olivella (Niteoliva) minuta (Link, 1807). We suggest that some conchological (e.g. reabsorption of the columella or not; presence or absence of the operculum) and soft anatomical (e.g. placement of the posterior mantle tentacle, morphology of osphradium and reproductive system) features are useful to better distinguish between the subgenera Olivella and Niteoliva. Such characters have a potential role in taxonomic decisions and hypotheses regarding subgenera and a better understanding of evolutionary relationships within Olivella.

The taxonomic position of brooding limpets of the genera Erginus and Rhodopetala (Patellogastropoda)

Limpets of the genera Erginus Jeffreys, 1877 (previously in Lottiidae) and Rhodopetala Dall, 1921 (previously in Acmaeidae), unlike other patellogastropods, brood larvae and juveniles in the modified pallial cavity. A phylogenetic analysis using three mitochondrial gene markers (cytochrome c oxidase subunit I, 16S rRNA, and 12S rRNA) has shown that Rhodopetala rosea (Dall 1872) and four Erginus species form a highly supported clade that cannot be assigned to Acmaeidae or Lottiidae. The transition from external fertilization and pelagic development to internal fertilization with brooded larvae and juveniles in the special pallial cavity occurred in the evolution of patellogastropods only once. The genera Erginus and Rhodopetala belong to Rhodopetalidae Lindberg, 1981 stat. nov. (= Erginidae Chernyshev 2018 syn. nov.) elevated from subfamily Rhodopetalinae to family status. Erginus puniceus Lindberg, 1988a is restored from synonym of Erginus sybariticus (Dall 1871) for both typical purple forms and the ‘sybariticus’ forms with small shell.

Redescription of Rhinus ciliatus (Gastropoda: Simpulopsidae), An Endemic Species from the Atlantic Rainforest in Brazil

The genus Rhinus Martens, 1860, is represented in Brazil by about twenty species, which are predominantly found in the Atlantic rainforest, an endangered ecosystem with extraordinary biodiversity and high endemism. There is a dearth of detailed morphological data for most species of the genus Rhinus, and the anatomy of only a few species has been described. Rhinus ciliatus, an endemic species from southwestern Brazil, is known by few conchological traits and scarce anatomical data from the reproductive system and pallial cavity. In this study, we redescribe the shell morphology and soft body anatomy of Rhinus ciliatus in detail and compare the new data with known traits of other closely related species. Rhinus ciliatus is diagnosed by the following features: (i) transition from protoconch to teleoconch well marked; (ii) shell ovate-conic, accuminate; (iii) aperture sub-ovate, lip simple; (iv) kidney with granulated lamellae; and (v) marginal teeth with blunt spatula-shaped mesocones. The record of spermatophores for the genus is provided here for the first time.

Phylogenomic resolution of the root of Panpulmonata, a hyperdiverse radiation of gastropods: new insight into the evolution of air breathing.

Transitions to terrestriality have been associated with major animal radiations including land snails and slugs in Stylommatophora (>20 000 described species), the most successful lineage of 'pulmonates' (a non-monophyletic assemblage of air-breathing gastropods). However, phylogenomic studies have failed to robustly resolve relationships among traditional pulmonates and affiliated marine lineages that comprise clade Panpulmonata (Mollusca, Gastropoda), especially two key taxa: Sacoglossa, a group including photosynthetic sea slugs, and Siphonarioidea, intertidal limpet-like snails with a non-contractile pneumostome (narrow opening to a vascularized pallial cavity). To clarify the evolutionary history of the panpulmonate radiation, we performed phylogenomic analyses on datasets of up to 1160 nuclear protein-coding genes for 110 gastropods, including 40 new transcriptomes for Sacoglossa and Siphonarioidea. All 18 analyses recovered Sacoglossa as the sister group to a clade we named Pneumopulmonata, within which Siphonarioidea was sister to the remaining lineages in most analyses. Comparative modelling indicated shifts to marginal habitat (estuarine, mangrove and intertidal zones) preceded and accelerated the evolution of a pneumostome, present in the pneumopulmonate ancestor along with a one-sided plicate gill. These findings highlight key intermediate stages in the evolution of air-breathing snails, supporting the hypothesis that adaptation to marginal zones played an important role in major sea-to-land transitions.

The Ostrea chilensis pallial cavity: nursery, prison, and time machine

The Ostrea chilensis pallial cavity: nursery, prison, and time machine

Computed Microtomography (Micro-CT) in the Anatomical Study and Identification of Solenogastres (Mollusca)

Solenogastres are vermiform marine molluscs characterised by an aculiferous mantle, a longitudinal ventral pedal groove and a terminal or subterminal pallial cavity. Their classification is based in part on the type of mantle sclerites, but identification to even the family level generally requires the study of internal anatomical characters. Taxonomically important internal characters include those related to radular structure, the type of ventrolateral glandular organs of the pharynx and the reproductive system, among others. In order to study their internal anatomical organisation, according to the classical reconstruction method, serial histological sections of specimens are made, from which the 2D internal anatomy of the specimen can be reconstructed manually. However, this is a time-consuming technique that results in destruction of the specimen. Computed microtomography or micro-CT is a non-destructive technique based on the measurement of the attenuation of X-rays as they pass through a specimen. Micro-CT is faster than histology for studying internal anatomy and it is non-destructive, meaning that specimens may be used for e.g., DNA extraction or retained as intact vouchers. In this paper, the utility of micro-CT for studying taxonomically important internal anatomical structures was assessed. Results of the 3D anatomical study of the soft parts of four specimens of three species using micro-CT are presented: Proneomenia sluiteriHubrecht, 1880, Dorymenia menchuescribanaeGarcía-Álvarez et al., 2000 and Anamenia gorgonophilaKowalevsky, 1880. Micro-CT enabled detailed study of most taxonomically important anatomical characters, precise measurements of structures, and observation of the relative position of organs from a variety of angles. However, it was not possible to observe the radula and some details of the ventral foregut organs could not be discerned. Despite these limitations, results of this study highlight micro-CT as a valuable tool to compliment histology in the study of solenogaster anatomy and in non-destructively identifying animals to the family and even genus-level.

When size matters: the first comprehensive anatomical study of a species of "Condylocardiidae", an extremely miniaturized bivalve.

‘Miniaturization’ is a widespread phenomenon among the Metazoa. In the molluscan class Bivalvia, records of miniaturization are numerous. Among the Archiheterodonta, Warrana besnardi (Klappenbach, 1963) has attracted attention for its tiny size, which does not exceed 1.5 mm in shell length, and because it belongs to a group with limited anatomical information and often-debated status, the “Condylocardiidae” (which recent molecular studies place deeply nested within the family Carditidae). All species of Warrana Laseron, 1953 are small-bodied, and so miniaturization presumably occurred from a large-bodied ancestor within the Carditidae sensu lato. South American W. besnardi is here studied in detail. Its small size and the enlargement of the anterodorsal region during growth, reflects (and likely led) to infaunal habit, living as a burrowing bivalve that passively feeds on deposit particles entering the pallial cavity anteriorly. Mantle glands, previously reported as a common feature of other archiheterodonts, are missing in W. besnardi, but spongiform tissue in the antero-ventral portion of the mantle lobes presumably represents a blood sinus that might compensate for the great reduction of the ctenidia. Lecithotrophy is reported, with yolky oocytes bearing a thick non-cellular capsule layer; brooding was not observed, and it is here hypothesized that the extreme miniaturization, with the great reduction of ctenidia, is responsible for a shift in the reproductive mode of condylocardiids, contrasting with the commonly reported ovoviviparity of the carditids.

Behavior of organic acids content of pallial cavity fluid in the Manila clam Ruditapes philippinarum under hypoxia in the aquaculture ground

Behavior of organic acids content of pallial cavity fluid in the Manila clam <I>Ruditapes philippinarum</I> under hypoxia in the aquaculture ground

Updating hosts and distribution range of the pea crab Pinnotheres bicristatus (Brachyura: Pinnotheridae)

Small crabs belonging to the family Pinnotheridae are characterized by living inside mainly bivalves. In European waters the recently-described pea crab Pinnotheres bicristatus increased to five the known number of pinnotherid species. The know distribution of the recently-described pea crab Pinnotheres bicristatus encompassed the area between the Gulf of Cádiz (NE Atlantic) and the western Alboran Sea (SW Mediterranean). The species was so far reported to occur in the pallial cavity of the common saddle oyster, Anomia ephippium, between 11 and 52 m depth. During two years, a total of 43 specimens of Pinnotheres bicristatus were collected in two different projects/surveys along the Mediterranean coasts of the Iberian Peninsula, thus enlarging its known occurrence to the eastern Alboran Sea and the NW Mediterranean, at depths between 37 and 71 m. We also report a new bivalve host for the species, the flat oyster Ostrea edulis, and population structure information of these new records. As a conclusion, this study considerably extends both in latitude and longitude, as well as in depth, the known geographical distribution of P. bicristatus.

The blue mussel inside: 3D visualization and description of the vascular-related anatomy of Mytilus edulis to unravel hemolymph extraction

The blue mussel Mytilus edulis is an intensely studied bivalve in biomonitoring programs worldwide. The lack of detailed descriptions of hemolymph-withdrawal protocols, particularly with regard to the place from where hemolymph could be perfused from, raises questions regarding the exact composition of aspirated hemolymph and does not exclude the possibility of contamination with other body-fluids. This study demonstrates the use of high resolution X-ray computed tomography and histology combined with 3D-reconstruction using AMIRA-software to visualize some important vascular-related anatomic structures of Mytilus edulis. Based on these images, different hemolymph extraction sites used in bivalve research were visualized and described, leading to new insights into hemolymph collection. Results show that hemolymph withdrawn from the posterior adductor muscle could be extracted from small spaces and fissures between the muscle fibers that are connected to at least one hemolymph supplying artery, more specifically the left posterior gastro-intestinal artery. Furthermore, 3D-reconstructions indicate that puncturing hemolymph from the pericard, anterior aorta, atria and ventricle in a non-invasive way should be possible. Hemolymph withdrawal from the heart is less straightforward and more prone to contamination from the pallial cavity. This study resulted simultaneously in a detailed description and visualization of the vascular-related anatomy of Mytilus edulis.

Microbial Inhibition by Bacteria Isolated from Pallial Cavity Fluids and Associated Mucus of the Eastern Oyster Crassostrea virginica (Gmelin)

Thirteen aerobic, mesophilic marine bacterial strains were isolated from the pallial (mantle) cavity fluids and associated mucus of the eastern oyster Crassostrea virginica Gmelin. All strains were Gram-negative and identified to genus using 16S RNA gene sequence analysis. Each isolated strain was tested for its ability to inhibit growth of six Gram-negative and five Gram-positive bacterial tester strains, as well as the yeast Candida albicans, using an in vitro agar diffusion screening method to detect antimicrobial activity (Romenenko et al. 2008). All of the marine bacteria isolated from the oyster pallial cavity fluids showed some ability to inhibit tester strains. Two isolates, F (red) and M, inhibited the greatest variety of indicator strains and produced the largest zones of inhibition. Gram-negative indicator strains were more susceptible to antimicrobial activity of pallial fluid isolates than Gram-positive strains. None of the isolated bacteria was shown to inhibit C. albicans. In addition, targeted 16S metagenome libraries from the Chesapeake Bay were screened for the presence of bacteria isolated from this study. Results indicate that there are commonalities between bacteria associated with oysters from Long Island Sound and the Chesapeake Bay systems.

The genus Dallocardia (Mollusca: Bivalvia: Cardiidae) in the Southwestern Atlantic Ocean

Fil: Signorelli, Javier Hernan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Instituto de Biologia de Organismos Marinos; Argentina

Female–embryo relationships in Ostrea chilensis: brooding, embryo recognition, and larval hatching

Flat oysters brood their embryos and larvae in the female pallial cavity, and the previous work has examined their relationship to the gill/mouth complex. However, the details of this relationship are unclear. By transplanting embryos and using endoscopy, the capacity for embryonic recognition in brooding oysters, Ostrea chilensis, and the ability to clear the pallial cavity of dead embryos were studied. The oysters were collected in 2016 and 2017 in the Quempillen estuary in southern Chile (41°52′S, 73°46′W). Non-brooding and smaller oysters (males) did not retain transplanted embryos in their pallial cavities. Brooding oysters retained transplanted foreign embryos and larvae, which developed along with a female’s own larvae. Dead larvae were detected by brooding oysters and ejected from the pallial cavity in pseudofeces. This was effective but not efficient; females frequently rejected some of their own veligers together with the dead larvae. Brooding females likely recognized dead larvae by their inactivity. At hatching, brooded larvae were released in several short pulses by maternal pumping, which ejected larvae at mean speeds of 178.6 ± 56.6 mm s−1, considerably greater than larval swimming speeds (0.32 ± 0.24 mm s−1) or female counter-currents (0.67 ± 0.42 mm s−1). It remains unknown whether the presence of embryos and larvae in the pallial cavity over the extended brooding period of ~ 8 weeks in O. chilensis contributes to the hatching process in some way.

Antimicrobial Activity in the Pallial Cavity Fluids of the Ribbed Mussel Geukensia Demissa from a Highly Impacted Harbor in Western Long Island Sound

Fluid and its associated mucus from the pallial (mantle) cavity of the ribbed mussel Geukensia demissa (Dwillyn) from Black Rock Harbor, Bridgeport, CT, inhibited the growth of both Gram-positive (Staphylococcus aureus) and Gramnegative (Escherichia coli) bacteria in antimicrobial assays. A significant reduction in size after 24 h was noted in E. coli grown in the presence of ribbed mussel fluid. Mussel-soluble lysozyme levels in the pallial cavity fluid averaged 0.019 + 0.018 relative fluorescence units/mg protein, and no seasonal pattern of lysozyme activity was found (P = 0.522). During the course of the study, copper concentrations ranged from 0.09 to 0.37 ppm and zinc concentrations from 0.17 to 0.66 ppm in the pallial cavity fluid. These values were only slightly higher than the concentrations of these metals found in seawater samples taken at the site, indicating only very low levels of sequestration of heavy metals by G. demissa in the pallial fluid cavity. A comparable study of oysters (Crassostrea virginica) from the same site found lysozyme levels 10 times higher and zinc concentrations two orders of magnitude greater than in that in mussels reported here (Brousseau et al. 2014). These results suggest substantial interspecies variation in profiles of defensive agents involved in antimicrobial activities of marine bivalves and highlight the need for additional studies to characterize these differences.

Phenotypic features of Helicina variabilis (Gastropoda: Neritimorpha) from Minas Gerais, Brazil

Helicina variabilis Wagner, 1827 (Neritimorpha, Helicinidae) is redescribed based on a sample collected in Nanuque, northern Minas Gerais, Brazil. The species description, previously based only on the shell, is expanded to the phenotypic features. The study revealed absorption of the internal shell whorls; a diaphragm muscle connected to the floor of the pallial cavity; a monoaulic pallial oviduct, with the female genital aperture inside the anal aperture, and the lack of a seminal receptacle and provaginal sac; and the pleural ganglia of the nerve ring connected with each other. The significance of these findings is discussed in the light of current taxonomic and phylogenetic knowledge.

The importance of population density and inter-individual distance in conserving the European oysterOstrea edulis

Fertilization success will determine the rate at which a population can expand and is especially important when considering small, establishing or enduring communities. Introduced species frequently fail to establish reproductively functional populations due to strong Allee effects associated with low densities. The native European oyster,Ostrea edulisbroods its fertilized eggs in the pallial cavity for a period of 8–10 days before releasing the larvae. It is considered a partial broadcast spawner and was used as a model species to assess the importance of Allee effects such as inter-individual distance on reproductive success. Distances between individual oysters within test plots in areas of known oyster density were used in conjunction with standardized brood size (n larvae g−1total wet weight) to assess fertilization success. A significant, positive relationship was observed between brood size and oyster density. Oysters with a nearest neighbour ≤1.5 m were found to brood significantly more larvae than individuals with nearest neighbours ≥1.5 m. Therefore, high density sites need to be maintained to ensure the recovery and enhancement of this OSPAR Convention recognized species in decline.

Metal interactions between the polychaete Branchipolynoe seepensis and the mussel Bathymodiolus azoricus from Mid-Atlantic-Ridge hydrothermal vent fields

The vent blood-red commensal polynoid polychaete Branchipolynoe seepensis is commonly found in the pallial cavity of the vent mussel Bathymodiolus azoricus, the dominant bivalve species along the Mid-Atlantic-Ridge (MAR) and is known to be kleptoparasitic. Mussels were collected from three hydrothermal vent fields in the MAR: Menez Gwen (850 m depth, MG2, MG3 and MG4), Lucky Strike (1700 m depth, Montségur-MS and Eiffel Tower-ET) and Rainbow (2300 m depth). Polychaetes were absent in all Menez Gwen vent mussels, while the highest percentage was detected in mussels from Lucky Strike, where more than 70% of the mussels had at least one polychaete in their mantle cavity, followed by Rainbow with 33% of mussels with polychaetes. Total metal concentrations (Ag, Cd, Co, Cu, Fe, Mn, Ni and Zn) were determined in polychaetes whole body and in the mussel tissues (gills, digestive gland and mantle). To understand the possible metal interactions between symbiont and host, the activity of antioxidant defence (catalase (CAT), metallothioneins (MTs)), biotransformation enzymes (glutathione-s-transferases (GST)) activities and lipid peroxidation (LPO) were determined in polychaete whole soft tissues and in mussel tissues (gills, digestive gland and mantle). Metal concentrations in polychaetes and mussels tissues indicated that the accumulation patterns were species specific and also influenced by, and possibly dependent upon, the inter- and intra-variation of vent physico-chemistry between hydrothermal fields. Despite not detecting any strong correlations between metal and enzymes activities in polychaetes and mussels, when in presence of polychaetes, mussels presented less metal concentrations in the gills and digestive gland and lower activity of enzymatic biomarkers. This leads to infer that the polychaete plays a role on the detoxification process, and the interaction between the polychaete mussel association is probably an adaptation to metals concentrations at the vent sites.

Isolation-hypoxia and re-oxygenation of the pallial cavity of female Crepipatella dilatata during estuarine salinity changes requires increased glyoxylase activity and antioxidant metabolism to avoid oxidative damage to female tissues and developing embryos

The estuarine slipper limpet Crepipatella dilatata is a gastropod that can survive prolonged periods of low salinities (< 24 PSU) caused by tidal changes and/or prolonged periods of rain. During low salinity events, C. dilatata can isolate its body from the outside environment, by sealing its shell against the substrate on which it grows. Prolonged isolation periods from the surrounding environment can greatly lower available oxygen levels inside of the pallial cavity, impacting on the physiology of both females and their incubated encapsulated embryos. When salinity levels return to normal, isolation is terminated and the inflow of seawater results in re-oxygenation. In this study we show that when re-oxygenation of the pallial cavity takes place, oxidative damage, in the form of increased levels of lipid peroxides and protein carbonyls, occurs in both maternal tissues and in incubated embryos. To avoid terminal oxidative damage both females and their embryos increase their levels of the glyoxalase pathway enzymes (GLX-I and GLX-II) and general antioxidant metabolism (SOD, CAT, GR, GPOX and GST). As a result the levels of oxidative damage decline to basal levels within 24 h of reoxygenation. Thus the combination of isolation, a behavioural strategy, combined with encapsulation of embryos and a capacity to up regulate relatively rapidly the glyoxylase pathway and general antioxidant metabolism, play major roles in facilitating the survival of C. dilatata in the small estuaries of Southern Chile.

Embryo brooding and its effect on feeding in the bivalve Gaimardia bahamondei Osorio &amp; Arnaud, 1984

Gaimardia bahamondei is a small gonochoric bivalve which lives attached to subtidal algae. Females brood their embryos in the suprabranchial region of the pallial cavity, in close proximity to the gill filaments. We found no significant difference in clearance rate between males (non-brooders) and females (brooders), regardless of the numbers of embryos in the brood, suggesting that the presence of embryos does not interfere with particle capture by the brooding female. Embryos did not ingest microalgae, indicating that they do not compete with the female for food during incubation. These observations contrast with published data on other brooding bivalves in which particle retention by the adult is reduced during brooding, and the embryos may capture particles suspended in the pallial cavity. These differences among bivalve taxa in the effects of brooding on physiological processes in the female are attributable to distinct morphological adaptations of the gill for brooding.