Pen Shell Pinna Nobilis Research Articles

The Predation of Pinna nobilis (Mollusca) Juveniles by the Spiny Sea Star Marthasterias glacialis (Echinodermata) in the Sea of Marmara

The critically endangered bivalve species, the pen shell Pinna nobilis, has been suffering from an epidemic disease in the Mediterranean Sea, and its populations have totally disappeared in many areas across the basin. The Sea of Marmara’s populations of the pen shell, which were previously assumed to have remained unaffected by the epidemic disease because of the special hydrographical condition of the sea (brackish water), have been devastated after the catastrophic mucilage event suddenly outburst in November 2020 in the region. The settlement of healthy juvenile specimens of the species was frequently observed in the area after the mucilage event. However, an unexpected predator of juvenile specimens of the pen shell, the spiny sea star Marthasterias glacialis, was encountered in the area in January 2023. Two cases were observed and the spiny sea star has a capability of crashing one valve of the sea-pen through which it consumes its flesh. This predation might have the potential to affect populations of P. nobilis, which has been struggling to survive in the region after its mass mortality due to the mucilage event. Such data are of utmost importance to imply effective conservation planning for the sustainability of the remaining populations of the pen shell in the region.

First detection of Pinna nobilis infection by Haplosporidium pinnae in the sanctuary area of Thau lagoon, France

The noble pen shell Pinna nobilis is an endemic and emblematic giant bivalve whose populations have been recently affected by a mass mortality event (MME), primarily due to the spread of the pathogen Haplosporidium pinnae. Since the beginning of the MME in Spain in 2016, nearly one hundred percent of monitored open sea water populations have been decimated around the Mediterranean Sea. The only refuge areas with living P. nobilis populations were found in coastal lagoons. Today, the Thau lagoon in France is home to a vitally important population of P. nobilis and was thought to be safe from the parasite. Here, we report the first molecular detection of H. pinnae (isolate PN1) in tissue samples of moribund individuals from Thau lagoon.

Evaluation of Physiological State of Pen Shell Pinna nobilis (Linnaeus, 1758) by a Non-Invasive Heart Rate Recording under Short-Term Hyposalinity Test.

A non-invasive laser fiber-optic method based on infrared sensors for heart rate (Hr) recording was applied to assess the physiological condition of Pinna nobilis. During 2017, the specimens of P. nobilis were sampled at three sites within the Boka Kotorska Bay, Montenegro and used for ex situ experiments with short-term reduction/restoration of ambient salinity to evaluate their physiological adaptive capacity based on heart rate recovery time (Trec). Mean Trec for specimens from Sv. Nedjelja (reference site), Dobrota and Sv. Stasije were 72 ± 3, 91 ± 7 and 117 ± 15 min, while the coefficients of variation (CV) were 0.12, 0.13 and 0.17, respectively. Resting heart rate (Hrrest) and Trec showed statistically significant differences between the groups of mussels from Dobrota and Sv. Stasije in comparison to the reference site. Statistically significant correlations were observed between Trec and shell length/width, which was not the case in comparison between Hrrest and shell length/width. The lower adaptive capacity within the P. nobilis specimens from Dobrota and Sv. Stasije in comparison to the reference site could occur due to stress induced by deterioration of environmental conditions, which could have led to impairment of the physiological state of the mussels evaluated by Hr. All the specimens of P. nobilis survived the experimental treatments; afterwards, they were successfully transplanted at the Dobrota site. The experimental unit with sensor technology applied in this study can provide Hr recording in real time and could have an application in monitoring the physiological/health state of P. nobilis individuals maintained in aquaria.

Exploring coexistence mechanisms in a three-species assemblage

Interactions among species are essential in shaping ecological communities, although it is not always clear under what conditions they can persist when the number of species involved is higher than two. Here we describe a three-species assemblage involving the seagrass Cymodocea nodosa, the pen shell Pinna nobilis and the herbivore sea urchin Paracentrotus lividus, and we explore the mechanisms allowing its persistence through field observations and manipulative experiments. The abundance of pen shells was higher in seagrass beds than in bare sand, suggesting a recruitment facilitation. The presence of sea urchins, almost exclusively attached or around pen shells, indicated habitat facilitation for sea urchins, which overgrazed the meadow around the pen shells forming seagrass-free halos. Our results suggest that this system persists thanks to: (i) the behavioral reluctance of sea urchins to move far from pen shells, making their impact on seagrass strictly local, (ii) the sparse distribution of pen shells and (iii) the plant's resistance mechanisms to herbivory. Unpacking these mechanisms allows a better understanding of how ecological communities are assembled.

New insights about Haplosporidium pinnae and the pen shell Pinna nobilis mass mortality events

Since early autumn 2016, Mass Mortality Events (MME) have drastically impacted the population of the fan mussel Pinna nobilis in the Mediterranean Sea. Haplosporidium pinnae, a newly described Haplosporidian species, has been considered the causative agent of the mortality outbreaks in association to opportunistic bacterial pathogens. In the present study, we first reported a cytological description of H. pinnae in moribund specimens of P. nobilis which were collected in the Gulf of Taranto (Ionian Sea, Italy) during summer 2018. Different life-cycle stages of the parasite, including uni- and binucleate cells, small plasmodia, big multinucleate plasmodia and sporocysts with spores, were detected in all the examined animals and most of the parasite cells were present in gills, mantle and digestive gland, while the spores were found only in the latter organ. Histology and molecular biology were also performed, confirming the nature of the infectious agent, as already reported in the area. Additionally, molecular study revealed the presence of bacteria from the Mycobacterium ulcerans - M. marinum complex but no evident macroscopical or microscopical lesions, just as no bacteria referred to Mycobacterium were observed by histology. In conclusion, the present study aimed to provide further contributions to the understanding of the mortality of P. nobilis, pointing to the role of the cytological method of investigation both for diagnostic and epidemiological purposes, and discussing the current epidemic situation in the Adriatic sea.

Use of Local Ecological Knowledge on the Natural Recruitment of Bivalve Species of Commercial Exploitation in a Natura Area

The current study provides valuable insight into the ecological risks and decline of the bivalve fishery and biodiversity in the Amvrakikos Gulf over the last 50 years through a triangulation of information from in situ surveys and expert judgment, supplemented with historical archives. In situ sampling showed that bivalve species composition was a typical composition of benthic fauna consisting of the olive green cockle, Cerastoderma glaucum, the grooved carpet shell, Ruditapes decussatus, and the Mediterranean mussel, Mytilus galloprovincialis. Interviews confirmed the dramatic decrease in the abundance of striped venus clam, Chamelea gallina, and noble pen shell Pinna nobilis, both of which might be attributed to human-induced impacts, habitat degradation and climate change. Official data depicted a gradual reduction of bivalve catches since 1980 and massive degradation of the resources after 2000. As a result, the bivalve fishery was abandoned, having a negative impact on the local socio-economic community. The present study fills in a gap in knowledge for preserving species biodiversity that is critical to the health of the coastal environments.

An incubation water eDNA method for a non-destructive rapid molecular identification of Pinna nobilis and Pinna rudis bivalve juveniles

The pen shell Pinna nobilis is critically endangered due to a disease that has affected all open water populations since late 2016. Collection of early spats is considered a fundamental step for pen shell conservation. However, the identification between P. nobilis and P. rudis juveniles by morphology is a very difficult task. Furthermore, due to the small size of juveniles and high sensitivity to handling, the sampling for this purpose must not damage individuals. As a consequence, the application of molecular techniques for conservation strategies to identify threatened and endangered bivalve species is every day more and more necessary.In this study, we present the development of a multiplex-PCR procedure for the rapid identification of two Pinna species from eDNA water samples. Using species-specific primers, designed in the rRNA16S and rRNA12S mitochondrial genes, identification of species was obtained by cellular or extracellular DNA dissolved in water and differentiated based on the size of the amplified DNA fragments.• Development of a molecular multiplex-PCR procedure for the rapid identification of two Pinna species from eDNA water samples• Using specie-specific primers, the different species can be differentiated basing on the size of the amplified DNA fragments• This technique removes many of the limitations commonly associated with sampling of threatened and endangered juvenile bivalves for conservation strategies (sampling does not damage individuals).

Modelling parasite-produced marine diseases: The case of the mass mortality event of Pinna nobilis

The state of the art of epidemic modelling in terrestrial ecosystems is the compartmental SIR model and its extensions from the now classical work of Kermack–Mackendrick. In contrast, epidemic modelling of marine ecosystems is a bit behind, and compartmental models have been introduced only recently. One of the reasons is that many epidemic processes in terrestrial ecosystems can be described through a contact process, while modelling marine epidemics is more subtle in many cases. Here we present a model describing disease outbreaks caused by parasites in bivalve populations. The SIRP model is a multicompartmental model with four compartments, three of which describe the different states of the host, susceptible (i.e. healthy), S, infected, I, and removed (dead), R, and one compartment for the parasite in the marine medium, P, written as a 4-dimensional dynamical system. Even if this is the simplest model one can write to describe this system, it is still too complicated for both direct analytical manipulation and direct comparison with experimental observations, as it depends on four parameters to be fitted. We show that it is possible to simplify the model, including a reduction to the standard SIR model if the parameters fulfil certain conditions. The model is validated with available data for the recent Mass Mortality Event of the noble pen shell Pinna nobilis, a disease caused by the parasite Haplosporidium pinnae, showing that the reduced SIR model is able to fit the data. So, we show that a model in which the species that suffers the epidemics (host) cannot move, and contagion occurs through parasites, can be reduced to the standard SIR model that represents epidemic transmission between mobile hosts. The fit indicates that the assumptions made to simplify the model are reasonable in practice, although it leads to an indeterminacy in three of the original parameters. This opens the possibility of performing direct experiments to be able to solve this question.

The First Occurrence of the Pen Shell Pinna nobilis (Linnaeus, 1758) in the Samandağ coast, the northeastern Mediterranean

Pinna nobilis is distributed in the northwest area of the Mediterranean and the Aegean Sea. In this study, on 9 September 2020, one specimen of Pinna nobilis, the pen shell, was observed during scuba diving at a depth of 16 m off Samandag coast (36.259444° N, 35.810111° E), the northeastern Mediterranean Sea. In this study, we observed for the first time P. nobilis from the Mediterranean Coast of Turkey, the Samandag coast. In this region, the presence of P. nobilis has never been previously recorded, and this new record confirms the presence of a new location in the Mediterranean Sea.

First insight into the whole genome shotgun sequence of the endangered noble pen shell Pinna nobilis: a giant bivalve undergoing a mass mortality event

ABSTRACT The noble pen shell Pinna nobilis is a Mediterranean endemic and emblematic giant bivalve. Already considered by the late 20th century to be an endangered species, it is facing a dramatic and rapidly expanding epizooty that has decimated populations since mid-2016. The ecological importance of P. nobilis has prompted important investigations for conservation purposes. Here, we report a first analysis of the whole genome sequencing of this animal. This was performed on an Illumina HiSeq X platform using a single paired-end library of short fragments (2 × 150 bp). The de novo contig assembly had a total size of 584 Mb (96,738 contigs, N50 = 7.6 kb, with 0.4% of ambiguous nucleotides), representing 77.5% of the predicted genome size of 754 Mb. The P. nobilis genome is highly AT-rich, with a GC content of 35.6%. At 1%, heterozygosity was in the range of other bivalves with sequenced genomes. Over one-third (36.2%) of the genome consisted of repeated elements with a surprising larger number of short interspersed nuclear elements compared to other molluscan genomes. We were also able to reconstruct the full mitochondrial genome (c. 19 kb, with 12 protein-coding genes, 2 rRNA and 22 tRNA genes). In the context of the epizootic outbreak affecting P. nobilis, a first insight into the innate immune and stress-related genes found in the sequence is provided.

Dynamic energy budget of endemic and critically endangered bivalve Pinna nobilis: A mechanistic model for informed conservation

The noble pen shell Pinna nobilis L. is the largest, endemic, critically endangered, and protected bivalve of the Mediterranean Sea. Effective conservation and management strategies for this species highly depend on understanding how environmental change and anthropogenic pressures impact its physiology and thereby ecological function, population persistence, and survival. Dynamic Energy Budget (DEB) theory offers a valuable mechanistic modelling framework for capturing how an organism acquires and utilizes available energy for growth, maturation, development and reproduction throughout its life cycle, while accounting for environmental conditions. In this study we parameterized and compared two types of DEB models using limited literature data: a standard model that accounts for morphological metamorphosis only, and a model that through metabolic acceleration between birth and metamorphosis captures physiological changes occurring in the larval life stage. The model with metabolic acceleration performed better, successfully simulating life history traits, growth, and reproduction of P. nobilis. We used the model to predict how food availability implemented through functional response affects growth, maturation, and reproduction of the species throughout its lifespan. We found that (i) abundant food had little effect on the size at maturation, (ii) maximum fecundity at ultimate age doubled compared to typically lower food availability in the wild, (iii) puberty could not be reached below the food availability corresponding to functional response value of 0.164, and (iv) energy allocated to reproduction was positively correlated with both bivalve size and food availability. Accounting for allometric growth observed in P. nobilis did not affect the findings, prompting us to recommend that isometric growth be assumed when modelling the bivalve using DEB. The model presented here is the first full-life cycle bioenergetic model made for P. nobilis. It can be used standalone for predicting energy budget of individuals at specific environmental conditions, or as a building block for modeling populations and ecosystems under various environmental scenarios. The model can readily incorporate other environmental factors relevant to changes in physiology and energy allocation, such as oxygen and pH.

Tracking a mass mortality outbreak of pen shell Pinna nobilis populations: A collaborative effort of scientists and citizens

A mass mortality event is devastating the populations of the endemic bivalve Pinna nobilis in the Mediterranean Sea from early autumn 2016. A newly described Haplosporidian endoparasite (Haplosporidium pinnae) is the most probable cause of this ecological catastrophe placing one of the largest bivalves of the world on the brink of extinction. As a pivotal step towards Pinna nobilis conservation, this contribution combines scientists and citizens’ data to address the fast- and vast-dispersion and prevalence outbreaks of the pathogen. Therefore, the potential role of currents on parasite expansion was addressed by means of drift simulations of virtual particles in a high-resolution regional currents model. A generalized additive model was implemented to test if environmental factors could modulate the infection of Pinna nobilis populations. The results strongly suggest that the parasite has probably dispersed regionally by surface currents, and that the disease expression seems to be closely related to temperatures above 13.5 °C and to a salinity range between 36.5–39.7 psu. The most likely spread of the disease along the Mediterranean basin associated with scattered survival spots and very few survivors (potentially resistant individuals), point to a challenging scenario for conservation of the emblematic Pinna nobilis, which will require fast and strategic management measures and should make use of the essential role citizen science projects can play.

A mycobacterial disease is associated with the silent mass mortality of the pen shell Pinna nobilis along the Tyrrhenian coastline of Italy

Disease is an increasing threat for marine bivalves worldwide. Recently, a mass mortality event (MME) impacting the bivalve Pinna nobilis was detected across a wide geographical area of the Spanish Mediterranean Sea and linked to a haplosporidian parasite. In 2017–2018, mass mortality events affecting the pen shell Pinna nobilis were recorded in two different regions of Italy, Campania and Sicily, in the Tyrrhenian Sea (Mediterranean Sea). Histopathological and molecular examinations of specimens showed the presence of Haplosporidium sp. in only one specimen in one area. Conversely, in all of the surveyed moribund animals, strong inflammatory lesions at the level of connective tissue surrounding the digestive system and gonads and linked to the presence of intracellular Zhiel-Neelsen-positive bacteria were observed. Molecular analysis of all of the diseased specimens (13) confirmed the presence of a Mycobacterium. Blast analysis of the sequences from all of the areas revealed that they were grouped together with the human mycobacterium M. sherrisii close to the group including M. shigaense, M. lentiflavum and M. simiae. Based on pathological and molecular findings, it is proposed that a mycobacterial disease is associated with the mortality episodes of Pinna nobilis, indicating that, at this time, Haplosporidium sp. is not responsible for these events in Campanian and Sicilian waters.

Pen shell Pinna nobilis L. (Mollusca: Bivalvia) from different peculiar environments: adaptive mechanisms of osmoregulation and neurotransmission

The pen shell Pinna nobilis (Linnaeus, 1758) is the largest endemic bivalve mollusc of the Mediterranean Sea, listed as an endangered species in the European Union. Because no information is available about the adaptation of pen shells to different habitats, herein the fundamental conditions of adaptation of P. nobilis to peculiar natural environments, such as the Strait of Messina (SM) and the meromictic Faro Lake (FL; Sicily, Italy), were explored by assessing the morphology, mucous production, osmoregulation and neurotransmission of their gills. Although gills of the pen shells from both sites exhibited a regular morphology, a higher presence of acid mucous cells was detected in P. nobilis from FL than SM, as well as higher levels of osmolytes but without interfering the osmoregulatory processes. About the functioning of gills, the cholinergic (i.e. acetylcholine and AChE) neuronal system was unaltered between individuals from the two sites, whereas the GABAergic neurotransmission (i.e. 4-aminobutyrate or GABA) was significantly augmented in gills of P. nobilis from FL than SM. This may be an adaptive response to hypoxic conditions in FL, as supported by the increased hypoxia-inducible factor (HIF-1α) in gills of pen shells from FL than SM. Noteworthy, this study reports for the first time the presence of the GABA neurotransmitter within the metabolite profile, obtained by application of a protonic Nuclear Magnetic Resonance (1H NMR)-based metabolomics approach, of a marine bivalve. Therefore, GABA may be suggested as a metabolite biomarker in pen shells. Overall, findings from this study provide new insights on the behavioural and adaptive responses of the pen shell Pinna nobilis settled in different peculiar environments.

Mega-litter and remediation: the case of Mar Piccolo of Taranto (Ionian Sea)

According to the United Nations Environment Programme/Mediterranean Action Plan (UNEP/MAP), marine litter is one of the main causes of marine pollution in the Mediterranean Sea and one of the most important threats for its biodiversity. In addition, it is a critical issue with significant implications from an ecological point of view, as well as for human health and safety. The present study provides a focus concerning the mega-litter in a semi-enclosed basin, the Mar Piccolo of Taranto (Southern Italy, Ionian Sea). In this basin, characterized by a suite of anthropic impacts, a specific protocol for the mega-litter removal has been developed according to the Special Commissioner for remediation of the Site of National Interest of Taranto. The application of such protocol proved to be effective in limiting the removals’ secondary effects on the biodiversity and on the environment as a whole, allowing a sustainable removal of marine mega-litter. A critical part of such protocol resulted in the translocation of species of conservation interest present on the debris, particularly considering the rich population of the pen shell Pinna nobilis thriving in the area. A total of 7107 specimens were translocated, showing low mortality percentage and high survival rates during 9 months of monitoring.

Genetic and oceanographic tools reveal high population connectivity and diversity in the endangered pen shell Pinna nobilis

For marine meta-populations with source-sink dynamics knowledge about genetic connectivity is important to conserve biodiversity and design marine protected areas (MPAs). We evaluate connectivity of a Mediterranean sessile species, Pinna nobilis. To address a large geographical scale, partial sequences of cytochrome oxidase I (COI, 590 bp) were used to evaluate phylogeographical patterns in the Western Mediterranean, and in the whole basin using overlapping sequences from the literature (243 bp). Additionally, we combined (1) larval trajectories based on oceanographic currents and early life-history traits and (2) 10 highly polymorphic microsatellite loci collected in the Western Mediterranean. COI results provided evidence for high diversity and low inter-population differentiation. Microsatellite genotypes showed increasing genetic differentiation with oceanographic transport time (isolation by oceanographic distance (IBD) set by marine currents). Genetic differentiation was detected between Banyuls and Murcia and between Murcia and Mallorca. However, no genetic break was detected between the Balearic populations and the mainland. Migration rates together with numerical Lagrangian simulations showed that (i) the Ebro Delta is a larval source for the Balearic populations (ii) Alicante is a sink population, accumulating allelic diversity from nearby populations. The inferred connectivity can be applied in the development of MPA networks in the Western Mediterranean.

Reproductive investment of the pen shell Pinna nobilis Linnaeus, 1758 in Cabrera National Park (Spain)

The spawning period can be a period of particular vulnerability for a species. In hermaphroditic species like the long-lived pen shell Pinna nobilis different costs could be associated with female, male or hermaphrodite stages. Here we evaluate gonad development in a population with few anthropogenic pressures and describe the timing and succession of developmental stages, determine the ratio of the sexes and the condition of the animals. We assess resource mobilisation and associated costs through the relationship between stable isotopes and condition indexes with reproductive parameters and evaluate the role of the adductor muscle as storage organ used in gonad maturation. In our study area only one spawning season is observed, starting in May and peaking in June-July. The onset of spawning coincides with water temperatures of 20 °C. Condition indexes drop during the spawning period and recover afterwards to reach pre-spawning values in November. Stable isotope signals are negatively related to the gonadal condition index, while the CN ratio shows a positive correlation with the same index. Additionally, the muscle condition index sharply decreases after the start of the spawning season, which suggests that P. nobilis uses the reserves stored in the adductor muscle for reproduction as in other Pinnidae species. Reproductive indices and stable isotopes ratios indicate ‘capital breeding’ as reproductive strategy of the pen shell. Decreased muscle force could mean a higher vulnerability during the summer period, coinciding with the peak in recreational activities involving poaching and anchoring.

First haplosporidan parasite reported infecting a member of the Superfamily Pinnoidea (Pinna nobilis) during a mortality event in Alicante (Spain, Western Mediterranean).

Several stages of a haplosporidan parasite, including spores, were detected infecting three out of four specimens of the Pen Shell Pinna nobilis from the coast of Alicante (Western Mediterranean). A mortality event initiated few weeks before the sampling. The infection was systemic in the connective tissue, with free uni-nucleate stages and early plasmodia, whereas sporulation process took place in the digestive tubules disrupting them. Morphological details, by light and transmission electron microscopy, and PCR amplification confirmed that the parasite belongs to the haplosporidan group. Spores were pleomorphic, usually elongated ovoid, with round to elongated haplosporosomes-like in the sporoplasma. The operculum was situated in the apical zone of the wall, with an external lid, and the nucleus tended to be eccentric in the basal zone. Spore ornamentation was not observed. The single uninfected specimen appeared to be healthy. This is the first report of a haplosporidan parasite infecting a member of the Superfamily Pinnoidea and this is the first histopathological study of a mortality event in the endangered and protected P. nobilis.

Host specificity and feeding in European pea crabs (Brachyura, Pinnotheridae)

Pinnotherids, or pea crabs, are symbionts of invertebrates used for shelter and as food source. Feeding strategies and morphological adaptations to food uptake are important to understand host relations and how the host specificity is determined. We herein re-examine the host range of pinnotherids based on long-term collections from different localities in European waters. Both species of Pinnotheres are restricted to bivalves. Pinnotheres pisum infests mussels, oysters, the noble pen shell Pinna nobilis and other bivalves. Pinnotheres pectunculi is symbiotic with Glycymeris glycymeris and several other species of venerids. Nepinnotheres pinnotheres infests ascidians and Pinna nobilis. Observations on feeding in Pinnotheres reveal how mucus strings are brushed from the host gills with a setal comb in the chelipeds, which we describe by using scanning electron microscopy. Our observations on feeding structures are discussed in relation to the host specificity of each species and compared to other pinnotherid taxa, taking additional factors of host choice into account.

Engineering effect of Pinna nobilis shells on benthic communities

Summary Within the framework of the possibility of using the Mediterranean pen shell Pinna nobilis in restoration and conservation plans of benthic habitats, an in situ experiment was conducted using empty P. nobilis shells. The latter were transplanted in a bare soft-bottomed area and their associated fauna were followed along 120 days and compared at different temporal points and with the assemblages living in the surrounding soft-sediment area. Compared to soft-sediment communities, an evidently increasing succession of species richness, abundance, and diversity descriptors (Shannon-Wiener H ′ and Pielou's evenness J ′) was observed with the community inhabiting empty Pinna shells. Among the forty-five (45) species found in association with the transplanted empty shells, seventeen (17) were found constantly in the three temporal points; the other twenty-eight (28) species appeared in the samples collected in the second and/or third sampling time. While motile and sessile species associated to Pinna shells showed an increasing pattern of appearance and abundance along the experiment time, those of soft sediment remained almost constant. The comparison between Pinna shells and soft-sediment associated communities showed that the species richness was slightly different between the two different sample types (49 for soft sediment versus 45 for empty Pinna shells); however the total abundance was found more important with empty Pinna shells. The results obtained herein argue in favor of the important engineering effect of P. nobilis in soft benthic habitats and therefore for the necessity of its conservation.