Small Mediterranean coastal Lagoons Under Threat: Hydro-ecological Disturbances and Local Anthropogenic Pressures (Size Matters).

Mediterranean coastal lagoons are affected by multiple threats (demographic pressures, eutrophication, climate change) expected to increase in the future and impact the ecosystem services provided. Conservation norms and scientific studies usually focus on large lagoons (> 0.5 km2) due to their economic importance, while they ignore smaller lagoons. These are poorly understood and often unprotected, despite their prevalence within the Mediterranean region and their importance. Qualitative and quantitative characterisation of small lagoons, in terms of functioning and sensitivity to global and local changes, are needed to develop appropriate management strategies. For this purpose, this work provides the first inventory of all Corsican lagoons and has investigated three of them of small size (Arasu, Santa Giulia, Balistra), characterised by contrasting anthropogenic contexts (highly modified/disturbed, medium disturbance, quasi-pristine). At the regional level, 91 of the 95 lagoons identified are < 0.5 km2, making Corsica a good example for the study of small Mediterranean lagoons. The three case studies showed differences in their seasonal biogeochemical cycles and phytoplankton communities (biomass, diversity, photosynthetic efficiency). Arasu and Santa Giulia lagoons showed an increase in watershed urbanisation (+ 12% and + 6% in 30 years), high phytoplankton biomass, low diversity and blooms of potentially harmful dinoflagellates. Conversely, Balistra lagoon showed a good status overall, but some anthropogenic pollution sources within its watershed. This study demonstrates the importance of small lagoons at regional and Mediterranean scale, and provides knowledge on studied local sites but also potential applications elsewhere. The importance of an integrated approach considering lagoons within their adjacent connected systems (watershed and sea) and anthropogenic contexts is highlighted. Supplementary Information: The online version contains supplementary material available at 10.1007/s12237-023-01182-1.

Microcystins and Cyanobacterial Contaminants in the French Small-Scale Productions of Spirulina (Limnospira sp.).

Spirulina is consumed worldwide, in the form of food or dietary supplements, for its nutritional value and health potential. However, these products may contain cyanotoxins, including hepatotoxic microcystins (MCs), produced by cyanobacterial contaminants. The French spirulina market has the particularity of being supplied half-locally by approximately 180 small-scale spirulina production farms. Data about this particular production and possible contaminations with other cyanobacteria and MCs are scarce. Thus, we collected the results of MC analyses and total cyanobacteria counts, carried out between 2013 and 2021, from 95 French spirulina producers who agreed to share their data. These data consisted of MC concentrations determined with an enzyme-linked immunosorbent assay (ELISA) using 623 dry spirulina samples and 105 samples of spirulina cultures. In addition, potentially unsafe samples of dry spirulina were further investigated through mass spectrometry, as duplicate analysis. We confirmed that the situation of the French spirulina production stayed within the safe regulatory level in terms of MC levels. On the other hand, the inventory of cyanobacterial contaminants, based on 539 count results, included 14 taxa. We present their prevalence, interannual evolution and geographical distribution. We also suggested improvements in cultivation practices to limit their propagation.

Detection of Pathogens and Ticks on Sedentary and Migratory Birds in Two Corsican Wetlands (France, Mediterranean Area).

Birds are one of the most species-diverse vertebrate groups and are susceptible to numerous hematophagous ectoparasites. Migratory birds likely contribute to the circulation of these ectoparasites and their associated pathogens. One of the many migration paths crosses the Mediterranean islands including Corsica and its wetlands, which are migration stopovers. In our study, we collected blood samples and hematophagous ectoparasites in migratory and sedentary bird populations in two coastal lagoons: Biguglia and Gradugine. A total of 1377 birds were captured from which 762 blood samples, 37 louse flies, and 44 ticks were collected. All the louse flies were identified as Ornithomya biloba and all the ticks were from the Ixodes genus: Ixodes sp. (8.5%), I. accuminatus/ventalloi (2.9%), I. arboricola/lividus (14.3%), I. frontalis (5.7%) and I. ricinus (68.6%). Five pathogens were detected: Anaplasma phagocytophilum, Erhlichia chaffeensis, and Rickettsia helvetica in ticks, and Trypanosoma sp. in louse flies. Ehrlichia chaffeensis and the West Nile virus were both detected in bird blood samples in Corsica. This is the first report of these tick, louse fly and pathogen species isolated on the bird population in Corsica. Our finding highlights the importance of bird populations in the presence of arthropod-borne pathogens in Corsican wetlands.

Harmful algae and pathogens on plastics in three mediterranean coastal lagoons.

Plastic is now a pervasive pollutant in all marine ecosystems. The microplastics and macroplastic debris were studied in three French Mediterranean coastal lagoons (Prevost, Biguglia and Diana lagoons), displaying different environmental characteristics. In addition, biofilm samples were analyzed over the seasons to quantify and identify microalgae communities colonizing macroplastics, and determine potentially harmful microorganisms. Results indicate low but highly variable concentrations of microplastics, in relation to the period and location of sampling. Micro-Raman spectroscopy analyses revealed that the majority of macroplastic debris corresponded to polyethylene (PE) and low-density polyethylene (LDPE), and to a far lesser extent to polypropylene (PP). The observations by Scanning Electron Microscopy of microalgae communities colonizing macroplastic debris demonstrated differences depending on the seasons, with higher amounts in spring and summer, but without any variation between lagoons and polymers. Among the Diatomophyceae, the most dominant genera were Amphora spp., Cocconeis spp., and Navicula spp.. Cyanobacteria and Dinophyceae such as Prorocentrum cordatum, a potentially toxic species, were also found sporadically. The use of Primer specific DNA amplification tools enabled us to detect potentially harmful microorganisms colonizing plastics, such as Alexandrium minutum or Vibrio spp. An additional in situ experiment performed over one year revealed an increase in the diversity of colonizing microalgae in relation to the duration of immersion for the three tested polymers PE, LDPE and polyethylene terephthalates (PET). Vibrio settled durably after two weeks of immersion, whatever the polymer. This study confirms that Mediterranean coastal lagoons are vulnerable to the presence of macroplastic debris that may passively host and transport various species, including some potentially harmful algal and bacterial microorganisms.

Detecting zoonotic and non-zoonotic pathogens in livestock and their ticks in Corsican wetlands.

BACKGROUND: Corsica is a large French island in the Mediterranean Sea with high human and animal migration rates, especially near wetlands where these migrations are particularly frequent. Among the livestock populations, cattle and sheep are widely present all across the entire Mediterranean region. Trade can be responsible for the circulation of numerous pathogens and their vectors, thereby representing a health and economic threat for the livestock industry. OBJECTIVES: The objective of our study was to investigate the presence of pathogens in cattle and sheep farms in the wetlands of Corsica using a high-throughput screening technique. METHODS: In our study, blood samples and ticks were collected from cattle and sheep in 20 municipalities near Corsican wetlands to screen for the presence of various types of pathogens. The samples were processed using a high-throughput screening technique based on real-time microfluidic PCR: 45 pathogens were screened in 47 samples simultaneously. RESULTS: A total of 372 cattle and 74 sheep were sampled, and 444 ticks were collected from cattle. Out of the eight tick species detected, the main one was Rhipicephalus bursa (38.7% of the ticks collected). From cattle blood samples, one species and two genera were found: Anaplasma marginale, Trypanosoma sp. and Babesia sp. in respectively 61.5%, 58.3% and 12.2% of the cattle blood samples. From sheep blood samples, 74.3% were positive for Anaplasma sp, 2.7% for Anaplasma ovis and 1.4% for Anaplasma capra. This is the first report of A. ovis DNA in blood samples from sheep in Corsica. Out of 444 the tick samples, 114 were positive: 77.2% for Rickettsia aeschlimannii, 20.2% for Rickettsia sp., 3.5% for Babesia sp. and 1.8% for Anaplasma sp. Among them, 2.7% were co-infected with R. aeschlimannii and Babesia sp. CONCLUSIONS: Our results confirm the extent of possible circulation of different pathogens near Corsican wetlands, not only in ticks collected from livestock but also directly in cattle and sheep, with two (Trypanosoma sp. and Babesia sp.) being detected for the first time in cattle, one for the first time in sheep (A. ovis) and one for the first time in Corsica (A. capra).

A Systematic Review of the Distribution of Tick-Borne Pathogens in Wild Animals and Their Ticks in the Mediterranean Rim between 2000 and 2021.

Tick-borne pathogens (TBPs) can be divided into three groups: bacteria, parasites, and viruses. They are transmitted by a wide range of tick species and cause a variety of human, animal, and zoonotic diseases. A total of 148 publications were found on tick-borne pathogens in wild animals, reporting on 85 species of pathogens from 35 tick species and 17 wild animal hosts between 2000 and February 2021. The main TBPs reported were of bacterial origin, including Anaplasma spp. and Rickettsia spp. A total of 72.2% of the TBPs came from infected ticks collected from wild animals. The main tick genus positive for TBPs was Ixodes. This genus was mainly reported in Western Europe, which was the focus of most of the publications (66.9%). It was followed by the Hyalomma genus, which was mainly reported in other areas of the Mediterranean Rim. These TBPs and TBP-positive tick genera were reported to have come from a total of 17 wild animal hosts. The main hosts reported were game mammals such as red deer and wild boars, but small vertebrates such as birds and rodents were also found to be infected. Of the 148 publications, 12.8% investigated publications on Mediterranean islands, and 36.8% of all the TBPs were reported in seven tick genera and 11 wild animal hosts there. The main TBP-positive wild animals and tick genera reported on these islands were birds and Hyalomma spp. Despite the small percentage of publications focusing on ticks, they reveal the importance of islands when monitoring TBPs in wild animals. This is especially true for wild birds, which may disseminate their ticks and TBPs along their migration path.

Distribution of Tick-Borne Pathogens in Domestic Animals and Their Ticks in the Countries of the Mediterranean Basin between 2000 and 2021: A Systematic Review.

Tick-borne pathogens (TBPs) include a wide range of bacteria, parasites and viruses that cause a large spectrum of animal, human and zoonotic tick-borne diseases (TBDs). The object of this review was to establish an inventory and an analysis of TBPs found in domestic animals in the countries of the Mediterranean Basin. This geographic area occupies a central position between several continents and is an area of movement for animals, humans and pathogens of interest and their vectors, which is important in terms of animal and human health. In this systematic review, we included a total of 271 publications produced between 2000-2021 concerning TBPs in domestic animals. Among this literature, we found a total of 90 pathogen species (known as TBPs) reported in the 20 countries of the area; these were detected in tick species from domestic animals and were also directly detected in domestic animals. In all, 31 tick species were recorded and 12 domestic animal species, the latter comprising nine livestock and three pet species. More than 50% of the publications were from Western Europe. Island data were extracted and assessed, as islands of the Mediterranean Basin were represented in 16% of the publications and 77.8% of the TBPs reported. Our results show the importance of islands in the monitoring of TBPs, despite the low percentage of publications.

Molecular Detection of Zoonotic and Non-Zoonotic Pathogens from Wild Boars and Their Ticks in the Corsican Wetlands.

Corsica is the main French island in the Mediterranean Sea and has high levels of human and animal population movement. Among the local animal species, the wild boar is highly prevalent in the Corsican landscape and in the island's traditions. Wild boars are the most commonly hunted animals on this island, and can be responsible for the transmission and circulation of pathogens and their vectors. In this study, wild boar samples and ticks were collected in 17 municipalities near wetlands on the Corsican coast. A total of 158 hunted wild boars were sampled (523 samples). Of these samples, 113 were ticks: 96.4% were Dermacentor marginatus, and the remainder were Hyalomma marginatum, Hyalomma scupense and Rhipicephalus sanguineus s.l. Of the wild boar samples, only three blood samples were found to be positive for Babesia spp. Of the tick samples, 90 were found to be positive for tick-borne pathogens (rickettsial species). These results confirm the importance of the wild boar as a host for ticks carrying diseases such as rickettsiosis near wetlands and recreational sites. Our findings also show that the wild boar is a potential carrier of babesiosis in Corsica, a pathogen detected for the first time in wild boars on the island.

Evaluation of FluoroProbe® performance for the phytoplankton-based assessment of the ecological status of Mediterranean coastal lagoons.

The European Water Framework Directive and several other legislations worldwide have selected phytoplankton for monitoring the ecological status of surface waters. This assessment is a complicated task in coastal lagoons due to their intrinsic variability, prompting moves to use real-time measurements. Here, we tested the ability of the submersible spectrofluorometer FluoroProbe® to accurately estimate the phytoplankton biomass and to efficiently discriminate spectral groups in Mediterranean coastal lagoons, by using sub-surface water samples (n = 107) collected at Biguglia lagoon (Corsica) in different environmental situations (salinity and trophic state) from March 2012 to December 2014. We compared the estimates of biomass and phytoplankton group composition obtained with the FluoroProbe® (in situ and lab measurements) with the spectrofluorimetrically measured biomass and HPLC-derived quantifications of pigment concentrations. FluoroProbe® provided good estimates of the total phytoplankton biomass (particularly, the lab measurements). The FluoroProbe® data were significantly correlated with the HPLC results, except for the in situ measurements of very weak concentrations of blue-green and red algae. Our findings indicate that factory-calibrated FluoroProbe® is an efficient and easy-to-use real-time phytoplankton monitoring tool in coastal lagoons, especially as an early warning system for the detection of potentially harmful algal blooms. Practical instructions dedicated to non-specialist field operators are provided. A simple and efficient method for discarding in situ measurement outliers is also proposed.

Relationship between swimming capacities and morphological traits of fish larvae at settlement stage: a study of several coastal Mediterranean species.

Experimental measurements were made in the laboratory to determine the swimming capacities of settlement-stage fish larvae of several Mediterranean coastal species collected from the nearshore waters of Corsica, France. Critical swimming speed (Ucrit , cm s-1 ) was measured to provide a realistic laboratory estimate of in situ swimming speed. Morphometric traits were measured to assess potential predictors of a species' swimming ability and, when possible, daily otolith increments were used to estimate age. Observed swimming speeds were consistent with other temperate species and demonstrated that the tested species are competent swimmers and not passive components of their environment. Morphological traits varied in their correlation with Ucrit across groups and species. Direct measurements of morphological traits were better predictors than calculated ratios. Pelagic larval duration had little relationship with swimming speed among species for which daily otolith increments were counted. In addition to expanding the database on swimming capacities of settlement-stage fish larvae in the Mediterranean Sea, this study also developed methods that simplify the assessment of larval fish swimming ability. Swimming speed data are essential for improving larval dispersal models and for predicting recruitment rates in coastal fish populations.

Comparison of elemental composition in two wild and cultured marine fish and potential risks to human health.

Among all available species, fish are a powerful model for risk-benefit assessments to study the effects of contaminants on human health. Gilthead seabream (Sparus aurata, Linnaeus 1758) and european seabass (Dicentrarchus labrax, Linnaeus 1758) are two species of great economic importance, representing very large production volumes in the Mediterranean. The objective of this study is (1) to analyze the concentrations of Trace Elements (TE) between wild and cultured seabream and seabass specimens, (2) to compare the determined concentrations with other studies, and (3) to increase the data about the potential risks to human health. Our results point to significant intra- and interspecies-specific differences between wild and cultured fish for several trace elements. Several strong and moderate inter-elemental correlations in fish muscle were observed through correlation analysis. In our study, the mean levels of trace elements were still below the standard safety values for fish intended for human consumption. The same results were reached for all the parameters analyzed (international legal limits, estimated weekly intake, provisional tolerable weekly intake, target hazard quotient, target cancer risk), with trace element levels in fish below those that could pose a risk to human health. Consequently, these fish can be considered safe for human consumption. A better understanding of the levels of trace elements in fish would also better inform consumers about the potential risks of exposure to contaminants.

A GIS-based multicriteria evaluation for aiding risk management Pinus pinaster Ait. forests: a case study in Corsican Island, western Mediterranean Region.

Forest management can benefit from decision support tools, including GIS-based multicriteria decision-aiding approach. In the Mediterranean region, Pinus pinaster forests play a very important role in biodiversity conservation and offer many socioeconomic benefits. However, the conservation of this species is affected by the increase in forest fires and the expansion of Matsucoccus feytaudi. This paper proposes a methodology based on commonly available data for assessing the values and risks of P. pinaster forests and to generating maps to aid in decisions pertaining to fire and phytosanitary risk management. The criteria for assessing the values (land cover type, legislative tools for biodiversity conservation, environmental tourist sites and access routes, and timber yield) and the risks (fire and phytosanitation) of P. pinaster forests were obtained directly or by considering specific indicators, and they were subsequently aggregated by means of GIS-based multicriteria analysis. This approach was tested on the island of Corsica (France), and maps to aid in decisions pertaining to fire risk and phytosanitary risk (M. feytaudi) were obtained for P. pinaster forest management. Study results are used by the technical offices of the local administration-Corsican Agricultural and Rural Development Agency (ODARC)-for planning the conservation of P. pinaster forests with regard to fire prevention and safety and phytosanitary risks. The decision maker took part in the evaluation criteria study (weight, normalization, and classification of the values). Most suitable locations are given to target the public intervention. The methodology presented in this paper could be applied to other species and in other Mediterranean regions.

Variations in allelochemical composition of leachates of different organs and maturity stages of Pinus halepensis.

We investigated changes in the occurrence of allelochemicals from leachates of different Pinus halepensis organs taking into account the stages of pine stand age (i.e., young < 15-years-old, middle age +/- 30-years, and old > 60-years-old). GC-MS analysis of aqueous extracts revealed approx. 59 components from needles and roots. The major constituents were divided into different phytochemical groups-phenolics (50%), fatty acids (44%), and terpenoids. Further analyses were carried out to characterize the distribution of allelochemicals in different organs and P. halepensis successional stages. Roots and needles had two distinct chemical profiles, while needle leachates were composed mainly of oxygenated terpenoids (e.g., alpha-eudesmol, alpha-cadinol, and alpha-terpineol). Roots mainly contained fatty acids. Needles from young pine stands had the highest content of monoterpenes, suggesting their role as potential allelochemicals that could help young pine stands to establish. Pooling the different functional chemical groups showed that needles and, to a lesser extent, old roots, had higher chemical diversity than the roots of young and medium-aged pines. The highest diversity in phenolic constituents and fatty acids was in young needles (D(chem) = 2.38). Finally, caffeic acid, a compound that has allelopathic properties was found in aqueous extracts at high concentrations in both young needles and old roots. The role of this compound in mediation of biological interactions in P. halepensis ecosystem functioning is discussed.

Phenolic compounds of Pinus laricio needles: a bioindicator of the effects of prescribed burning in function of season.

Fire is a dominant ecological factor in Mediterranean-type ecosystems. Forest management includes many preventive tools, in particular for fire prevention, such as mechanical treatments and prescribed burning. Prescribed burning is a commonly used method for treating fuel loads, but fuel reduction targets for reducing wildfire hazards must be balanced against fuel retention targets in order to maintain habitat and other forest functions. This approach was used on Pinus nigra ssp laricio var. Corsicana, a pine endemic to Corsica of great ecological and economic importance. Many studies of plant phenolic compounds have been carried out concerning responses to various stresses. The aim of this study was to understand i) the effects of prescribed burning 1 to 16 months later and ii) the effects of the seasonality of burning, spring or fall, on the production of phenolic compounds in Pinus laricio. After prescribed burning conducted in spring, Pinus laricio increases the synthesis of total phenolic compounds for a period of 7 months. The increase is greater after spring-burning than fall-burning. With regard to simple phenols, only dihydroferulic acid responds about 1 year after both types of prescribed burning. The causes of these increases are discussed in this paper. Total phenolic compounds could be used as a bioindicator for the short-term response of Pinus laricio needles to prescribed burning. Simple phenols may be useful for revealing the medium-term effects of prescribed burning. The results of this study include recommending forest managers to use prescribed burning in the fall rather than spring to reduce fuel loads and have less impact on the trees.

Characterization of phenolic compounds in Pinus laricio needles and their responses to prescribed burnings.

Fire is a dominant ecological factor in Mediterranean-type ecosystems. Management strategies include prescribed (controlled) burning, which has been used in the management of several species, such as Pinus nigra ssp laricio var. Corsicana, a pine endemic to Corsica of great ecological and economic importance. The effects of prescribed burning on Pinus laricio have been little studied. The first aim of this study was to characterize total and simple phenolic compounds in Pinus laricio. The second aim was to understand: i) the short term (one to three months) and medium term (three years) effects of prescribed burning, and ii) the effects of periodic prescribed burning on the production of phenolic compounds in Pinus laricio. The first result of this study is the presence of total and simple phenolic compounds in the needles of Pinus laricio. 3-Vanillyl propanol is the major compound. After a prescribed burning, the synthesis of total phenolic compounds increases in Pinus laricio for a period of three months. Total phenolic compounds could be used as bioindicators for the short-term response of Pinus laricio needles to prescribed burning. Simple phenolic compounds do not seem to be good indicators of the impact of prescribed burning because prescribed burnings are low in intensity.

The influence of tissue handling on the flavonoid content of the aquatic plant Posidonia oceanica.

In recent times, more and more studies have focused on flavonoids as biomarkers of environmental quality in aquatic plants, in particular, Posidonia oceanica (Linnaeus) Delile. It is therefore of interest to determine how different prehandling methods can affect flavonoid concentrations. The methods tested were (1) immediate extraction of fresh samples, (2) extraction after 48 hr chilling, (3) freeze-drying, and (4) oven drying. Chilling and freeze-drying considerably altered the quantity of flavonoids measured, but not their profile. The effect of oven drying was not significant. Chilling led to a loss of 57% of total (pro)anthocyanidins, 39% of total flavonols, and 48% of all simple flavonols (myricetin, quercetin, isorhamnetin, and kaempferol). Freeze-drying caused a loss of 71% of total (pro)anthocyanidins, 87% of total flavonols, and 95% of all simple flavonols.

Ecological data in Integrated Coastal Zone Management: case study of Posidonia oceanica meadows along the Corsican coastline (Mediterranean Sea).

Integrated Coastal Zone Management (ICZM) contributes towards maximizing the benefits provided by the coastal zone and minimizing conflicts and the harmful effects of activities upon each other. The coastal zone includes highly productive and biologically diverse ecosystems, but ecological data (including structure and processes) seem to be neglected. The purpose of this article is to present a case study of Posidonia oceanica meadows (seagrass beds) along the Corsican coastline (Mediterranean Sea) in order to exemplify the usefulness of ecological data to Integrated Costal Management programs. We will try to determine how the use of organisms could be enhanced. These investigations show the undoubted success of the Corsican Posidonia oceanica protection program, with a detailed description of the ICZM that precisely presents each component (e.g., mapping, assessment of water quality, implementation of a system to aid decision-making concerning the installation of new aquaculture units). This experience on the Corsican coasts could be used as an example in order to transfer to other locations in the Mediterranean Sea and/or to other target species.

Effects of fish farming on flavonoids in Posidonia oceanica.

This work is a first approach to flavonoid responses (total proanthocyanidins and total and simple flavonols) in Posidonia oceanica in function of nutrient enrichment (aquaculture activities - fish farming), in the western Mediterranean Sea (Calvi-Corsica-France). The first result is the presence of total and simple flavonoids in P. oceanica. The second result shows an increase in total proanthocyanidin and total flavonol concentrations near cages, which would be linked to the high grazing pressure induced by meadow enrichment. Concerning simple flavonols, only quercetin shows a response to fish farming, which could be due to its strong antioxidant capacity. The presence of fish farming, which causes variations in environmental parameters, could affect the functioning of P. oceanica meadows. Flavonoid concentrations in P. oceanica seem to be a possible bioindicator of nutrient enrichment for the management of the littoral environment.

Phenols and flavonoids in Aleppo pine needles as bioindicators of air pollution.

The aim of the present study is to assess whether certain ecophysiological responses (contents of total phenols, total proanthocyanidins, and total and simple flavonols), in the needles of Aleppo pines (Pinus halepensis Mill.) may be valid bioindicators for the assessment of the air quality. Samples were taken at five natural sites polluted by various pollutants (NO, NO2, other NOx, SO2, and O3). The results show a decrease in total phenol concentrations with levels of nitrogen oxide pollutions (significant negative correlations between the total phenol concentrations and concentrations of NO, NO2, and other NOx). Total flavonoids (total flavonols and proanthocyanidins) are useful bioindicators for ozone pollution (significant negative correlations between total proanthocyanidins and the concentrations of ozone and significant positive correlations between total flavonols and the ozone pollution). Sulfur dioxide pollution is distinguished by low concentrations in quercetin, isorhamnetin, and kaempferol (significant negative correlations between these simple flavonols and the concentrations of SO2). This work confirms the strong interest of using the phenolic compounds of Pinus halepensis as biological indicators of air quality.

Morphology and ultrastructure of the gut in Spadella cephaloptera (chaetognatha).

Structural and ultrastructural studies on the gut of the chaetognath Spadella cephaloptera, as well as observations on the feeding behavior of specimens bred in the laboratory, were conducted. The gut displays four distinct zones: pharynx, esophagus, and intestine, to which are connected a pair of diverticula, and the rectum, differing in length, shape, and cellular composition. The intestine alone represents ∼90% of the gut length. Upon ingestion, food in the intestine is submitted to successive backward and forward peristaltic movements until digestion has ended. Ultrastructural observations have identified five distinct cell types from granule morphology and the presence or absence of cilia at the apex of the cells. Three of the types undoubtedly correspond to secretory cells. They are the (1) pharyngeal, (2) esophageal, and (3) light intestinal ciliated cells, which could be, respectively, implicated in (1) mucous, (2) enzyme, and (3) both mucous and enzyme secretions. The fourth type, which corresponds to dense intestinal ciliated cells, displays all the characteristics of cells specialized in the absorption of macromolecules and intracellular digestion. The products of this digestion could be temporarily stored inside dense granules before being utilized during vitellogenesis. Except for the presence of cilia, the fifth type, which is localized in the short rectum, represents a common polyhedral epithelial cell type. © 1996 Wiley-Liss, Inc.