Crepipatella Dilatata Research Articles

Introduction of the South American slipper limpet Crepipatella dilatata in Europe: Secondary spread in the Northeast Atlantic and first records for the Mediterranean Sea

The slipper limpet Crepipatella dilatata, native to Chile and Argentina, was introduced in north-western Spain in 2005 and since then has spread to the Galician and Cantabrian coasts. In this work, we provide the first molecularly validated record of an established population of C. dilatata in central Portugal (Aveiro), and of reproductive individuals (i.e. brooding females) of C. dilatata in the Mediterranean Sea, from three Italian mussel farms (in eastern Sardinia and northern Adriatic). DNA barcoding and phylogenetic analyses based on mitochondrial markers indicate that limpets from Italian farms belong to the C. dilatata ‘clade1’, whereas limpets collected in Aveiro cluster within the C. dilatata ‘clade2’. All these limpets share the same COI haplotypes with introduced populations from Galicia. The arrival of C. dilatata to Europe is undoubtedly due to transoceanic live mussel trade from southern Chile to Galicia. Mussel trade and farming are also the most likely drivers for the post-border dispersal of C. dilatata from Spain to Portugal and to Italy. Several countries have a potential role as a hub for the primary and secondary dispersal of slipper limpets towards and within Europe. This calls the attention for future research focused on assessing the current occurrence and ecological impact of established populations of slipper limpets within and nearby mussel farms along the eastern Atlantic and Mediterranean coasts.

Abundance and distribution of the alien Crepipatella dilatata in NW Atlantic Iberian Peninsula two decades after its first record

Crepipatella dilatata was first reported out of its native range in south Galicia (NW Spain) in 2005. After that, there are no quantitative data about its abundance and the dynamics of its invasion. In this study, the abundance and distribution of C. dilatata were assessed in the area of the original invasion. The species was found in the intertidal of nearly all visited shores, preferring sheltered conditions and avoiding river mouths and wave exposed oceanic areas. Total abundance and biomass were significantly lower in southern internal area however, no significant differences were detected between areas (external, median and internal) and orientation (North and South) for the relative abundances of egg masses and sexual categories. Size-class frequencies also showed significant differences between areas and orientations suggesting a continuous recruitment. Therefore, overall results indicated that C. dilatata is well-established in the area.

Abundance and distribution of non-indigenous Calyptraeidae gastropods along north and central Atlantic shores of Portugal

Two non-indigenous species of slipper limpets (Gastropoda: Calyptraeidae) have been recorded in NW Europe: Crepidula fornicata and Crepipatella dilatata. Although the former is widespread distributed in European Atlantic, records on Portuguese coasts are scarce. Regarding C. dilatata, it has been only reported in the southern Galician Rías (NW Spain). In this study, C. dilatata is reported for first time on Portugal and the distribution of these two species were studied in the North and Centre of Portugal. Moreover, abundance, distribution and structure of C. dilatata populations were compared between two intertidal habitats. Abundance and structure of C. dilatata populations showed no significant differences between habitats, suggesting that the species is well established in both. Regarding size-frequencies, bigger individuals were more frequent in soft bottoms. The recent development of oyster aquaculture in Portugal and the variety of substrates in which these NIS have been found could facilitate future introductions in nearby locations.

SELECTION OF TARGET SPECIES FOR MARINE PROTECTED AREAS: A MULTI CRITERIA APPROACH USING BENTHIC ORGANISMS

The selection of optimal target species to define and manage protected marine areas (MPAs) has generated a great scientific discussion during the past decades. Benthic invertebrates are commonly less considered as important target species, despite their pivotal role in marine ecosystems. To address this issue, we determined target species among benthic marine organisms using a multi-criteria approach. For this purpose, we used a data base from the Katalalixar National Reserve (RNK) in central Patagonia, Chile. The data were obtained through underwater photography and quantitative sampling by means of scuba diving during three expeditions between 2017 and 2019. Based on the total taxonomical inventory from both methods, a SIMPER analysis was used to determine 10 candidate species, and the Landscape Selection Species program was used for the selection of target species. Finally, eight target species were selected. The black snail Tegula atra, the hermit crab Pagurus comptus, the gastropod Crepipatella dilatata, and the polychaete Platynereis australis were selected among errant species. Among sessile species, the encrusting coralline algae Lithothamnium sp., the sea anemone Actinostola chilensis, the parchment worm Chaetopterus variopedatus, and the encrusting ascidia Didemnum sp. were the selected species. Based on our results we expect that these species will be included as target species in future management plans to improve protection of the marine environment of the Katalalixar National Reserve, one of the most pristine areas of the Chilean fjord region.
 Keywords: macroinvertebrates, macroalgae, biodiversity, Patagonia.

Ancestral form and function of larval feeding structures are retained during the development of non-planktotrophic gastropods.

Mode of development (MOD) is a key feature that influences the rate and direction of evolution of marine invertebrates. Although many groups include species with different MODs, the evolutionary loss of feeding larvae is thought to be irreversible, as the complex structures used for larval feeding and swimming are lost, reduced, or modified in many species lacking feeding larvae. This view is largely based on observations of echinoderms. Phylogenetic analysis suggests that feeding larvae have been re-gained in at least one species of calyptraeid gastropod. Further, its sister species has retained the velum, the structure used for larval feeding and swimming. Here, we document velar morphology and function in calyptraeids with 4 different MODs. Embryos of Crepidula navicella, Crepidula atrasolea, Bostrycapulus aculeatus, Bostrycapulus odites, Bostrycapulus urraca, Crepipatella dilatata, Crepipatella occulta, Crucibulum quiriquinae and Crepidula coquimbensis all hatch as crawling juveniles, yet only Crepidula coquimbensis does not make a well-formed velum during intracapsular development. The velar dimensions of 6 species with non-planktotrophic development were similar to those of planktotrophic species, while the body sizes were significantly larger. All of the species studied were able to capture and ingest particles from suspension, but several non-planktotrophic species may ingest captured particles only occasionally. Video footage suggests that some species with adelphophagic direct development capture but frequently fail to ingest particles compared to species with the other MODs. Together these lines of evidence show that, among calyptraeids at least, species that lack planktotrophic larvae often retain the structures and functions necessary to successfully capture and ingest particles, reducing the barriers to the re-evolution of planktotrophy.

Reproductive biology of the encapsulating, brooding gastropod Crepipatella dilatata Lamarck (Gastropoda, Calyptraeidae).

Among calyptraeid gastropods, males become females as they get older, and egg capsules containing developing embryos are maintained beneath the mother’s shell until the encapsulated embryos hatch. Crepipatella dilatata is an interesting biological model considering that is an estuarine species and thus periodically exposed to elevated environment-physiological pressures. Presently, there is not much information about the reproductive biology and brooding parameters of this gastropod. This paper describes field and laboratory observations monitoring sex changes, brooding frequencies, sizes of brooding females, egg mass characteristics, and embryonic hatching conditions. Our findings indicate that C. dilatata is a direct-developing protandric hermaphrodite, changing from male to female when individuals were between 18 and 20 mm in shell length. At our study site in Quempillén estuary, females were found to be brooding almost continuously throughout the year, having an average maximum of 85% of simultaneous brooding, with a short rest from April through June. No relationship was found between the number of capsules per egg mass and the size of the brooding female. However, capsule size and the number of embryos and nurse eggs were strongly related to female size. The offspring hatched with an average shell length > 1 mm. About 25% of the hatched capsules were found to contain both metamorphosed (juveniles) and non-metamorphosed (veliger) individuals. The sizes of the latter were < 1000 μm. The length of hatching juveniles was inversely related to the number of individuals per capsule, which seems related to differences in the availability of nurse eggs per embryo. Although fecundity per reproductive event of this species is relatively low (maximum approx. 800 offspring per egg mass) compared with those of calyptraeid species showing mixed development, the overall reproductive potential of C. dilatata seems to be high considering that females can reproduce up to 5 times per year, protecting their encapsulated embryos from physical stresses until well-developed juveniles are released into the population, avoiding a dangerous pelagic period prior to metamorphosis.

The alien slipper limpet Crepipatella dilatata (Lamarck, 1819) in northern Spain: A multidisciplinary approach to its taxonomic identification and invasive biology.

The slipper limpet Crepipatella dilatata, native to Chile and Argentina, was introduced in Spain in 2005. The species was thought to inhabit the region of Rias Bajas, yet recently, putative C. dilatata populations have been documented on the coast of north-central Spain and in the Ebro Delta of the Spanish Mediterranean. Here we undertook a multidisciplinary approach to study the invasion biology of this species. Specifically, two geographically distant populations, one being a successfully established population from O Grove and the other a declining population from Gijon, were studied over the course of four years. Analyses of morphological and developmental traits as well as genetic information confirmed the presence of C. dilatata in these sites. The results revealed polymorphism in anatomical traits and shell shape. Shell shape polymorphism was unevenly distributed among sites and among sexes. Males were monomorphic, while females were polymorphic. Of the female morphotypes encountered, one was absent in the declining population from Gijón. Size at first female maturation and female size were greater in the declining population than in the established population. Reproductive success varied seasonally but not spatially among populations. In the established population, gregariousness was significantly greater; the size when sex changes was found to be plastic and socially controlled. The sex ratio of the declining population was female biased while in the established population the sex ratio changed during the study period from being balanced to being female biased. This change in sex ratio was probably due to higher male mortality. Molecular analyses pointed to the localities of Corral Bay in southern Chile and Puerto Madryn in southern Argentina as potential population sources. The intercontinental import of fresh mussels cultivated in Chilean farms is a likely source of this mussel in Spain. Comparison with available data of native populations of C. dilatata strongly indicate that ecophenotypic plasticity, socially controlled sex change, high gregariousness, increased nurse egg supply to viable larvae during the encapsulated developmental period, later maturation and larger female sizes altogether enhance establishment success of this non-indigenous species. Human-mediated factors like the intraregional mussel trade and transplantation are also likely secondary dispersal mechanisms favouring the spread of this organism.

Survey of trematodes in intertidal snails from Patagonia, Argentina: new larval forms and diversity assessment.

Larval trematodes are the main parasites of snails, and they play a crucial role because they usually castrate their snail hosts and can thus alter their population and community dynamics. This study involved a survey of seven gastropod species (Crepipatella dilatata, Fissurella radiosa, Nacella magellanica, Pareuthria fuscata, Siphonaria lessonii, S. lateralis and Trophon geversianus) parasitized by 12 trematode species (one hemiurid, one gymnophallid, two lepocreadiids, two microphallids, one notocotylid, two renicolids, one philophtalmid, one schistosomatid and one zoogonid) from southern Patagonia (47°S, 65°W), Argentina. Only F. radiosa was free of parasites. The study included the description of five new larvae, based on morphological and molecular information, and a comparison of the parasite diversity with that of a northern locality (42°S, 64°W), characterized by a lower mollusc diversity. Species richness and diversity of parasites were higher in the southern site. This suggests a correlation between the level of parasitism and the diversity of molluscs (first intermediate hosts), which is higher at the high-latitude site and seems to attract shorebirds, which disperse the digenean eggs and facilitate the completion of their life cycles. These results support the notion that parasitism is influenced by large-scale factors such as biogeographical patterns, and small-scale factors such as diversity or abundance of intermediate and definitive hosts.

Possible Mechanisms of Hatching from Egg Capsules in the Gastropods Crepipatella dilatata and Crepipatella peruviana, Species with Different Modes of Early Development.

Many invertebrates enclose their embryos within egg capsules, from which the offspring hatch. In marine gastropods that brood their egg capsules, hatching could involve radular activity by the mother or by unhatched stages, increased osmotic concentration of the intracapsular fluid, or production of hatching enzymes. The present research sought to determine whether mechanical action by the brooding female or by the encapsulated embryos was involved in the hatching for two sympatric and closely related species of calyptraeid: Crepipatella dilatata, which exhibits direct development without free-living larvae, and Crepipatella peruviana, which releases free-living veliger larvae. We also considered the role that enzymatic action or osmotic changes in the intracapsular fluid might play in hatching. Using scanning electron micrograph analyses, we found no evidence that the well-developed, pre-hatching juvenile radula of C. dilatata played any role in the hatching process and that the radula of C. peruviana did not even develop until long after hatching; so there was no evidence of radular activity involved in the hatching of either species. For C. peruviana, the intracapsular fluid osmolality was always higher than that of the surrounding seawater, suggesting that there is a strong natural water inflow during development. Moreover, when egg capsules of C. peruviana were exposed to lower ambient salinities, the substantial entry of water correlated well with high percentages of hatching, particularly for egg capsules containing advanced veligers, suggesting that an osmotic mechanism may be involved in the hatching process of this species. In contrast, hatching in C. dilatata appeared to be enzymatically mediated.

The influence of season and the tidal cycle on division of labour by the radula during feeding in the estuarine brooding gastropod Crepipatella dilatata (Calyptraeidae)

The brooding gastropod Crepipatella dilatata can feed by scraping the substrate with the radula and by suspension-feeding, which also requires use of the radula. There is a “division of labour” for the radula among three discrete tasks associated with feeding: (1) removing mucous balls from the food pouch; (2) transferring the mucous cord from the neck channel to the mouth (both components of suspension-feeding); (3) scraping the substrate. We hypothesised that the proportion of time used for each feeding activity varies according to environmental conditions. Total radular activity in females was greatest at high tide and in summer. The rate of radular extrusion for ingesting the mucous cord varied seasonally and between brooding and non-brooding females. Non-brooding females exhibited higher rates of radular extrusion for ingesting the mucous cord and for scraping the substrate than did brooders. In females, radular activity in removing the mucous ball from the food pouch was strongly influenced by the tidal cycle during winter, reaching minimum values at low tide. Differences were recorded in substrate scraping among seasons and within tidal cycles, and among males, brooding females and non-brooding females. Brooding females displayed less rasping than non-brooders, since the area available for grazing was restricted by the egg mass. Throughout the year, including low salinity periods, males allocated a greater proportion of total radular activity to rasping than to removing the mucous ball or ingesting the mucous cord. The feeding behaviour of both males and females is modulated by salinity, but the principal determinants of radular activity are the mode of reproduction (brooding in females) and, in males, motility.

The influence of encapsulated embryos on the timing of hatching in the brooding gastropod Crepipatella dilatata

Encapsulated embryos are generally thought to play an active role in escaping from egg capsules or egg masses. However, for species that brood their egg capsules, the factors controlling the timing of hatching are largely unclear, particularly the degree to which hatching is controlled by the embryos rather than by the mother, and the degree to which the hatching of one egg capsule influences the hatching of sister egg capsules within the same egg mass. We studied aspects of hatching using the direct-developing gastropod Crepipatella dilatata, which includes nurse eggs in its egg capsules and broods clusters of egg capsules for at least several weeks before metamorphosed juveniles are released. Isolated egg capsules were able to hatch successfully, in the absence of the mother. Moreover, the hatching of one capsule did not cause adjacent sister capsules to hatch. Hatched and un-hatched sister egg capsules from the same egg mass differed significantly in the number of metamorphosed juveniles, average shell size, offspring biomass (juveniles+veliger larvae), and the number of nurse eggs remaining per egg capsule. Differences in when egg capsules hatched within a single egg mass were not explained by differences in egg capsule age. Hatching occurred only after most nurse eggs had been ingested, most offspring had metamorphosed into juveniles, and juveniles had reached a mean shell length>1.36mm. Whether the mother has any role to play in coordinating the hatching process or juvenile release remains to be determined.

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.

Fouling community dominated by &lt;em&gt;Metridium senile&lt;/em&gt; (Cnidaria: Anthozoa: Actiniaria) in Bahía San Julián (southern Patagonia, Argentina)

The objective of this study is to provide information about a harbour-fouling community dominated by Metridium senile in southern Patagonia. Several steel tubes from the wharf of Puerto San Julian were extracted to perform repair tasks, allowing the attached benthic community to be studied. Sampling was conducted at three levels: lower intertidal, 3-4 m depth and 6-7 m depth. In the lower intertidal, M. senile had a relative abundance of 43%, the most abundant accompanying species being Perumytilus purpuratus, Mytilus edulis platensis and Aulacomya atra atra . At subtidal level, the anemone showed relative abundances of 64% and 65%, and was accompanied by Monocorophium insidiosum at 3-4 m depth and by polychaetes of families Sabellidae and Syllidae at 6-7 m at depth. In the lower intertidal, epibiosis was more frequent on P. purpuratus, A. atra atra and M. edulis platensis , while in the subtidal, the richness of substrate-organisms increased significantly and the anemone was fixed to A. atra atra, M. edulis platensis, Paramolgula gregaria, Crepipatella dilatata, Austromegabalanus psittacus, Hiatella arctica, Polyzoa opuntia, Pyura sp. and Sabellidae tubes. The ability of M. senile to settle on many different organisms, along with other strategies, makes it a colonizer able to displace other species that could compete with it for substratum. Given the cosmopolitan nature of M. senile , the fact that this species has not been previously reported in the coastal zone of the region, and the results of our study, we discuss the possibility that this sea anemone is an invasive alien species in southern Patagonia, or at least a cryptogenic species.

Consequences of maternal isolation from salinity stress for brooded embryos and future juveniles in the estuarine direct-developing gastropod Crepipatella dilatata

At reduced salinities, brooding females of some gastropods and bivalves may isolate their mantle cavities from the environment for several days, maintaining internal osmotic concentration but causing severe declines in dissolved oxygen and pH, and increases in ammonia and other toxic substances in the mantle fluid. This study in November–December examined the immediate consequences of such stresses for brooded embryos of Quempillen estuary gastropod Crepipatella dilatata, in terms of time to juvenile emergence and rates of embryonic growth [measured as shell length (SL)]. Juveniles were also monitored for latent effects on feeding rates, oxygen consumption, and growth for the first 4 weeks after emergence into normal salinity seawater. An acute salinity stress lasting 3 days applied to females that were brooding pre-shelled or intermediate-shelled stages increased embryonic incubation periods, but without affecting SL at emergence. Growth rates were reduced for encapsulated embryos regardless of the stage at which the salinity stress was applied. Latent effects on juvenile development included slower shell growth and reduced rates of oxygen consumption and feeding. These effects were sustained for the first month after release from the female. The results suggest that marked reductions in salinity lasting for several days indirectly but negatively affect the development of brooded embryos of C. dilatata and also affect the juveniles for at least several weeks following their release, even after salinity has returned to normal.

A new species of Crepipatella (Gastropoda: Calyptraeidae) from northern Chile

Crepipatella occulta n. sp. is described from the intertidal zone in northern Chile. This species is morphologically cryptic with two other Crepipatella species from Chile, Crepipatella dilatata (Lamarck, 1822) and Crepipatella peruviana (Lamarck, 1822) (a senior synonym of C. fecunda), with respect to adult shell morphology and anatomy. However, Crepipatella occulta is clearly distinguishable from both of them on the basis of embryonic development. It can be distinguished from Crepipatella peruviana, a planktotroph, and Crepipatella dilatata, a direct developer with uncleaved nurse eggs, because it has direct devel-opment with developing nurse embryos that are consumed before the juveniles hatch. Genetic data from DNA sequences also support the distinct status of this species, and show that the South African species C. capensis (Quoy Gaimard, 1832–33) is more closely related to C. dilatata and C. peruviana than is C. occulta. In addition Crepipatella occulta displays diagnostic alleles in 14 allozyme loci when compared with the other two co-occuring Chilean species in northern Chile. Morphologically, Crepipatella occulta n. sp. does not attain the large size often observed in C. peruviana, and it typically has a shiny dark chest-nut or chocolate shell interior.

Crepipatella dilatata (Lamarck, 1822) (Calyptraeidae): an example of reproductive variability among gastropods

Reproductive characteristics of a species are often defined from a small number of individuals collected from a single location at one particular time. However, this study reveals that the South American gastropod Crepipatella dilatata (Lamarck, 1822) shows an unusually high level of intraspecific variability in some key reproductive characteristics: the number of egg capsules brooded per female, the size of the egg capsules, the number of eggs per capsule and the sizes and size distributions of the uncleaved eggs. Larger females were more fecund than smaller ones, not because they produced more egg capsules, but because they produced capsules of significantly larger size. Such variability was evident not only when considering different populations, but also within a single population sampled in different years, as well as among specimens collected during a single sampling event. Thus our data emphasize the importance of obtaining information from numerous specimens per locality as well as from specimens from different localities and in different years when describing the reproductive characteristics of any particular taxon.

Castrating effects of trematode larvae on the reproductive success of a highly parasitized population of Crepipatella dilatata (Caenogastropoda) in Argentina

Crepipatella dilatata (Calyptraeidae) is a common intertidal or shallow subtidal protandric hermaphroditic gastropod. Intertidal snails from Puerto Madryn, Chubut, Argentina (42°46′37″S, 64°54′51″ W), showed a high prevalence, up to 46 %, of a castrating larval microphallid trematode. Reproductive success was studied during a 2-year period from September 2007 to August 2009, and the results were compared to those from an unparasitized subtidal sample. Brooding females and males were never found infected. The proportion of brooding females was higher in months with a higher prevalence of infection. The number of brooding females in the intertidal sample was higher than in the subtidal sample. Generalized linear models were utilized to determine the effects of parasitism on the reproductive success of the host population. Anticipated reproduction in smaller females in the intertidal sample, increased reproductive success in months with higher prevalence, and unparasitized males are interpreted as fitness responses to ensure host population survival when the prevalence of trematode infection is high.

Phylogeography and Biogeography Concordance in the Marine Gastropod Crepipatelladilatata (Calyptraeidae) along the Southeastern Pacific Coast

The biogeography and phylogeography concordance hypothesis suggests that the same factors, for instance physical barriers or environmental gradients, shape both species assemblages and intraspecific genetic structure. In the marine realm, previous studies have however suggested that phylogeographic patterns are also explained by the life-history strategy of the species. However, evidence is contradictory and comes mainly from the northern hemisphere, which is characterized by specific environmental conditions and evolutionary histories of species. In this work, we evaluated the concordance hypothesis in the southern Pacific using the marine gastropod Crepipatella dilatata as a case study. This intertidal species with direct development exhibited a restricted dispersal potential, a feature that contrasts with previous species studied in the same area. Using the gene cytochrome oxidase I, we analyzed 253 individuals sampled at 10 locations covering 543 km of the coast of Chile. The study sites also incorporated 2 biogeographic regions separated by a well-studied biogeographic break (at 30°S). Populations of C. dilatata displayed a high degree of genetic structure and a perfect match between phylogeographic and biogeographic breaks at 30°S. When comparing our data with previous research over the same geographic range, life history traits related to dispersal ability seem to be a good proxy for explaining the concordance between biogeography and phylogeography along the southeastern pacific coast. In addition, in this and other marine invertebrate species, gene flow limitations across both sides of the 30°S break may act as a driver of the speciation process.

Ammonia accumulation in the brood chamber of the estuarine gastropod Crepipatella dilatata: How big a problem for mothers and brooded embryos?

Crepipatella dilatata is an estuarine gastropod that broods its encapsulated embryos in the pallial cavity for several weeks before releasing juveniles. When environmental quality declines (e.g., in response to decreased salinity), females seal themselves against the substrate and isolate the pallial cavity from surrounding seawater, altering the chemistry of the pallial fluid surrounding the embryos. We documented rates at which total ammonia concentrations (NH 4 +–N + NH 3) increased in the pallial cavity during these extended periods of isolation, as well as excretion rates for both adult females and developing embryos (veligers). Also, we quantified the effects of elevated ammonia concentrations on both adults (mortality, egg capsule abandonment, and neck-radular activity) and veligers (mortality, and activity of the velum and velar cilia). In the pallial fluid, ammonia concentration increased about 150% during the first 16 h of female isolation from about 7–17 μg ammonia l −1, while excretion rates decreased nearly 85%, from an average of 5.5 to about 0.85 μg ammonia h −1 g −1 after 12 h of isolation. Brooded veligers also decreased their individual excretion rates over time, from 0.0035 to 0.0007 μg ammonia h −1 veliger −1 over 12 h. Ammonia accumulation eventually caused females to abandon their egg capsules and to detach from the substrate; in the field, this would probably lead to the death of both the encapsulated embryos and the detached females, but this happened only at concentrations of ≥ 0.1 mg ammonia l −1. In contrast, veligers withstood concentrations up to 34 mg ammonia l −1 for 72 h without dying, although ciliary activity and velar lobe activity decreased at concentrations of ≥ 0.1 mg ammonia l −1. Ammonia tolerance did not seem to change with continued development. Although previous studies have shown that prolonged isolation causes dangerous declines in oxygen and pH in pallial fluid for this species, the accumulation of ammonia in itself seems too low to cause direct harm to adults or developing embryos.

A survey of larval digeneans in the commonest intertidal snails from Northern Patagonian coast, Argentina

AbstractOver a two-years period, a survey was carried out in order to increase the knowledge of digeneans parasitising the commonest intertidal gastropods on the Patagonian coast, Southwestern Atlantic Ocean. A total of 4,725 gastropods were examined. Six species of digenean parasitising four snail species were found; four of them were registered for first time: Maritrema sp. 1 (Microphallidae) in Crepidula dilatata (Calyptraeidae), Parorchis sp. (Philophtalmidae) and sporocyst of Renicolidae in Trophon geversianus (Muricidae), and Diphterostomum sp. (Zoogonidae) in Buccinanops globulosus (Nassariidae). Two other species were found in Siphonaria lessoni (Siphonariidae): Maritrema sp. 2 and Hemiuridae. One snail species, Tegula patagonica (Trochidae) was not parasitised. These gastropods act as first intermediate host, and C. dilatata, S. lessoni and B. globulosus also frequently host metacercariae within the sporocyst. Overall prevalences varied from 0.16% of Diphterostomum in the intertidal population of B. globulosus to 33.45% of Maritrema sp. 1 in C. dilatata.