Invasive Gastropod Crepidula Fornicata Research Articles

The dark side of soft tissues: Unexpected inorganic carbonate in the invasive slipper limpet Crepidula fornicata and its implications for stable isotope interpretations.

Stable isotopic analysis is extensively used in trophic ecology. Inorganic carbonates, usually originating from shell fragments, are routinely removed from samples using an acid treatment because they affect δ13 C values. However, acid treatment can also change δ15 N values. For some taxa such as molluscs, the general assumption is that acid pre-treatment is not necessary since their shell is easily dissected from soft tissues and represents the only source of inorganic carbonates. However, other sources of non-dietary carbon (e.g., intracellular inorganic carbon) enriched in13 C thus get overlooked. Soft tissues (foot) of the invasive gastropod Crepidula fornicata of different size classes were analysed for their δ13 C and δ15 N values with and without acid pre-treatment using isotope ratio mass spectrometry. In toto microscopic investigations coupled with acid treatment, scanning electron microscopy and energy-dispersive spectroscopy were used to highlight the presence of inorganic carbonate. A correction model was derived and applied to existing stable isotope data for C. fornicata. We used both seasonal variations in δ13 C signatures and mixing model outputs to assess the error in δ13 C values. Acid pre-treatment had a significant effect on the stable isotope compositions of C. fornicata foot tissue, especially on δ13 C values: isotopic differences increased with size, up to 3‰ for large females. No effect was detected for small (below ~20 mm) and motile males. In toto microscopic analysis revealed the presence of small spherules of inorganic carbonate, hence explaining the differences in δ13 C values. Mixing model outputs and seasonal variation of δ13 C values showed that untreated samples can lead to large misinterpretations about diet proportions and degree of trophic niche overlap, respectively. Spherules of inorganic carbonate in C. fornicata soft tissues are likely to be linked with the motility of this species and their mucus production. We recommend assessing the presence of inorganic carbonate in soft tissue of sessile gastropods.

The seminal receptacle and implications for reproductive processes in the invasive gastropod Crepidula fornicata

The calyptraeid gastropod Crepidula fornicata is the object of considerable research attention, due to its invasive status in the North-Eastern Atlantic, its introduction to habitats throughout the Northern hemisphere, and its scientific interest as a model organism for the study of developmental and reproductive processes in the Metazoa. Since the knowledge concerning the structural foundations for its reproductive processes is surprisingly weak, we investigated the seminal receptacle, a key structure in the reproductive biology of other metazoans, using histology, scanning electron and transmission electron microscopy. The seminal receptacle consists of 9–11 lobes, each subdivided into small, narrow lobules. The inner epithelium of the lobules appears to be highly dynamic, characterised by the perforation and attachment of received spermatozoa, the progressive degeneration of this epithelium, and the concomitant detachment of the spermatozoa. The allocation of spermatozoa to many different lobules, in different phases, may explain the extended reproductive season of C. fornicata, and thereby contribute to its colonizing and invasive success. The same compartmentalisation, as well as the complete covering of the inner epithelium of the lobules by spermatozoa and the large amount of spermatozoan debris in the lumina, suggest that the C. fornicata seminal receptacle may be a site of sperm competition in this polyandrous species.

The invasive gastropod Crepidula fornicata: reproduction and recruitment in the intertidal at its northernmost range in Wales, UK, and implications for its secondary spread

The establishment and spread of a non-native species in an introduced range depends to a large extent on the performance of the species under the prevailing environmental conditions. The spawning, larval and spatfall periods of the invasive gastropod Crepidula fornicata were monitored in the intertidal zone at its northernmost range in Wales, UK, between February 2010 and January 2011. The duration of the reproductive season was similar to that recorded from more southerly European populations. Spawning and larval release occurred throughout most of the year even at low seawater temperatures of 16 °C. Recruitment was low and likely controlled by post-settlement mortality. These observations suggest that C. fornicata’s northwards spread in Welsh waters will not be limited by seawater temperature negatively affecting reproduction, but by processes acting after larval release. These data show the importance of incorporating settlement and post-settlement processes into studies on recruitment success when aiming to predict the potential spread of a potentially harmful invader such as C. fornicata.

Does larval supply explain the low proliferation of the invasive gastropod Crepidula fornicata in a tidal estuary?

Human-mediated transport and aquaculture have promoted the establishment of non-indigenous species in many estuaries around the world over the last century. This phenomenon has been demonstrated as a major cause of biodiversity alterations, which has prompted scientists to provide explanations for the success or failure of biological invasions. Crepidula fornicata is a gastropod native from the East coast of North America which has successfully invaded many European bays and estuaries since the 19th century, with some noticeable exceptions. Its spread over Europe has been explained by a combination of human-mediated transport and natural dispersal through its long-lived planktonic larva. We here investigated whether larval supply may explain the failure in the proliferation of this species within a particular bay, the Bay of Morlaix (France). Patterns of larval distribution and larval size structure were analysed over ten sites sampled three times (20 July, 4 August and 21 August 2006), regarding characteristics of the adult population and environmental features. Our results evidenced a strong spatial structure in both larval abundance and size at the bay scale, even if larval abundances were low. In this scheme, the location of spawning adults played a critical role, with high numbers of early larvae above the main spawning location. The larval size structure further showed that settlement-stage larvae were rare, which suggested that released larvae might have been exported out of the bay. The use of an analytical model aimed to study the effect of tidal currents on the potential for larval exportation confirmed that larval retention within the bay might be low. The limitation in larval supply resulting from the interactions between spawning location and local hydrodynamics may thus impede the proliferation of this species which is well established for more than 50 years. This study provided an example of factors which may explain the failure of the transition between two major steps of biological invasions, i.e. sustainable establishment and proliferation.

Problems facing maerl conservation in Brittany

1. Brittany has the majority of French maerl beds and some of the most extensive maerl grounds in Europe. 2. Breton maerl forms ancient (>5500 yr) but threatened habitats; several beds have been destroyed in the past 30 years. 3. Maerl extraction, eutrophication, mariculture and fishing are all major threats to Breton maerl beds, as is a continuing uncontrolled spread of the invasive gastropod Crepidula fornicata. 4. Maerl beds occur in 14 of the 28 Natura 2000 sites proposed along the Breton coast. 5. Maerl habitats are currently impacted by human activities in nearly all of the Breton proposed Natura 2000 sites which were mainly selected for terrestrial nature conservation features. Copyright © 2003 John Wiley & Sons, Ltd.