Littérature scientifique sur le sujet « Lessepsian »

Viruses are among the most abundant and diverse biological components in the marine environment. In finfish, viruses are key drivers of host diversity and population dynamics, and therefore, their effect on the marine environment is far-reaching. Viral encephalopathy and retinopathy (VER) is a disease caused by the marine nervous necrosis virus (NNV), which is recognized as one of the main infectious threats for marine aquaculture worldwide. For over 140 years, the Suez Canal has acted as a conduit for the invasion of Red Sea marine species into the Mediterranean Sea. In 2016–2017, we evaluated the prevalence of NNV in two indigenous Mediterranean species, the round sardinella (Sardinella aurita) and the white steenbras (Lithognathus mormyrus) versus two Lessepsian species, the Randall’s threadfin bream (Nemipterus randalli) and the Lessepsian lizardfish (Saurida lessepsianus). A molecular method was used to detect NNV in all four fish species tested. In N. randalli, a relatively newly established invasive species in the Mediterranean Sea, the prevalence was significantly higher than in both indigenous species. In S. lessepsianus, prevalence varied considerably between years. While the factors that influence the effective establishment of invasive species are poorly understood, we suggest that the susceptibility of a given invasive fish species to locally acquired viral pathogens such as NVV may be important, in terms of both its successful establishment in its newly adopted environment and its role as a reservoir ‘host’ in the new area.

A review of the non-indigenous ichthyofauna occurring in the Hellenic marine and estuarine waters is presented, including Atlantic origin colonizers, aquaculture introduced and Lessepsian alien species. 34 non-native species have been registered. The majority of allochthonous fish are Lessepsian immigrants, which represent approximately 80% of the ascertained non-native ichthyofauna in Hellenic waters; their establishment, spread, habitat, abundance and interaction with indigenous fish are discussed.

Background Parasites can play various roles in the invasion of non-native species, but these are still understudied in marine ecosystems. This also applies to invasions from the Red Sea to the Mediterranean Sea via the Suez Canal, the so-called Lessepsian migration. In this study, we investigated the role of parasites in the invasion of the Lessepsian migrant Sphyraena chrysotaenia in the Tunisian Mediterranean Sea. Methods We compared metazoan parasite richness, prevalence and intensity of S. chrysotaenia (Perciformes: Sphyraenidae) with infections in its native congener Sphyraena sphyraena by sampling these fish species at seven locations along the Tunisian coast. Additionally, we reviewed the literature to identify native and invasive parasite species recorded in these two hosts. Results Our results suggest the loss of at least two parasite species of the invasive fish. At the same time, the Lessepsian migrant has co-introduced three parasite species during the initial migration to the Mediterranean Sea, that are assumed to originate from the Red Sea of which only one parasite species has been reported during the spread to Tunisian waters. In addition, we found that the invasive fish has acquired six parasite species that are native in the Mediterranean Sea. However, parasite richness, prevalence and intensity were overall much lower in the invasive compared to the native fish host in the Mediterranean Sea. Discussion These results suggest that the Lessepsian migrant may affect native fish hosts by potentially altering the dynamics of native and invasive parasite-host interactions via parasite release, parasite co-introduction and parasite acquisition. They further suggest that the lower infection levels in the invasive fish may result in a competitive advantage over native fish hosts (enemy release hypothesis). This study demonstrates that cross-species comparisons of parasite infection levels are a valuable tool to identify the different roles of parasites in the course of Lessepsian migrations.

First record of a Lessepsian migrant: the sea cucumber Holothuria (Theelothuria) hamata Pearson, 1913. A single specimen of the Indo-West Pacific sea cucumber Holothuria (Theelothuria) hamata Pearson, 1913 has been captured in 2017 in the Mediterranean Sea, Turkey, Iskenderun Bay, at 30 m depth. This specimen is here described, and the taxonomy of the species is briefly discussed. Despite the lack of timed biogeographic evidence, we here argue that H. hamata is a Lessepsian migrant; the first in its genus and only the second holothuroid.

Data on Serpulidae collected in the Suez Canal were assembled and analyzed. Five serpulid taxa are reported from the canal for the first time bringing the number of serpulids to at least 16. The Systematic Section compiles revised literature records, confirmed synonymies of the taxa, redescriptions where necessary, photographic studies of taxa and remarks on the populations studied. The possible Indo-West-Pacific or Mediterranean origins of the taxa in the Suez Canal are considered and their chronological records and distributions tracked within the Red Sea, the Gulfs of Aqaba and Suez, the Suez Canal and the Levant Basin based on the compiled literature and our extensive databases. Two Lessepsian migrants, Hydroides heterocerus and H. homoceros, show evidence of morphological variability along their migration route; the last also provides an example of a founder effect. Problems of identifying Protula and Salmacina taxa are addressed, along with remarks on the “cosmopolitan” designations of some taxa. Various hypotheses concerning Lessepsian migration are discussed, and attributes making Lessepsian migrant serpulid tubeworms successful invasive species are evaluated.

A case study of the Lessepsian invasion of the Mediterranean Sea was carried out during the 1970s by a Hebrew University of Jerusalem team that included Uzi Ritte and his research students. The study zoomed on two mollusk “trios” of mytilid bivalves and cerithiid gastropods, each including an invader, a closely related and ecologically similar indigenous Red Sea species and a Mediterranean indigenous competitor. This paper revisits the results, conclusions and projections made by the 1970s study in the context of a recent unified invasion biology framework, and in the view of the dynamic development of the Lessepsian invasion and research into it throughout the more than 30 years since the case study took place. The approach of studying “trios” to detect potential invaders and project the course of invasions has not been repeated in the Lessepsian system since the 1970s case study. But the findings that opportunistic life history traits linked with a match of habitat in the invaded range to a species’ ecological niche make this species a potential invader and enable it to coexist with an encountered competitor remain robust. Recent human-induced and other environmental changes in the Mediterranean have however highlighted a potential significance of propagule pressure in intensifying competitive exclusion and resource monopolization by the invader, to the point of potentially impacting the invaded ecosystem.

Loliginid squids of the Sepioteuthis lessoniana complex are widely spread in the Indo-Pacific Ocean, where they constitute a commercially important resource for neritic fisheries. Sepioteuthis lessoniana is the only Lessepsian squid migrant till now, recorded for the first time in the Mediterranean in 2002 along the Turkish Levantine coasts. Two maturing males, with mantle lengths 193 mm and 244 mm, have been recently caught near the coasts of Rhodes Island (SE Aegean), extending the species distribution northward, into Hellenic waters. Their identity was confirmed by comparison of the main body, beak characteristics and morphometric measurements with those available in the literature for this species. Suspected expansion of the Lessepsian loliginid into the Aegean Sea, due to the gradual warming of the sea, is discussed.

After the opening of the Suez Canal in 1869 and after the further changes of the water regime of the canal and the near area of the Eastern Mediterranean Sea, the biogeographical barrier existing until that moment, between the Red Sea and the Mediterranean Sea, has been, as time goes by, weakened, allowing the contact between two different biota that was separated for 12 Million years. This work is focused on the mechanisms that set the spread and the colonization of Mediterranean Sea from Glyphidohaptor plectocirra, monogenoidean parasite of rabbit fish Siganus rivulatus (Siganidae), checking also the relationship between the spread of the host species, known to bibliography, and of the parasite, experimentally analysed. Based on available literature, several genetic studies of Lessepsian species often demonstrate the absence of a genetic bottleneck in a wide plethora of taxa, from plants to fish, but information regarding the genetic responses of their parasites in the newly colonized ecosystems is still lacking. In detail, in this work, the genetic flow relationships between five populations was estimated, three from the Red Sea (Nabq and Ismalia, Egypt, and Eilat, Israel) and two from Mediterranean Sea (Rhodes Island, Greece and Tel Aviv, Israel) by sequencing a portion of the mitochondrial CoxI gene. G. plectocirra specimens were extracted from gill arches of S. rivulatus and morphologically identified by analysing haptor sclerotized structures. After the morphological identification of specimens, two DNA regions were amplified, one mitochondrial, about 688 bps long, coding for the Cytochrome Oxidase I (COI) and one nuclear, 681 bps long, coding for the terminal region of the 18S gene, that include the entire ITS1 and a portion of the 5.8S gene, was then amplified using primers S1. The 681 bp alignment of 60 rDNA sequences found in all populations showed only two polymorphic sites, which distinguished only three haplotypes (data not shown). Thus, the low variability of this marker at the species level in the monogenoidean parasites was confirmed, and any downstream analysis was performed only on the CoxI gene. For CoxI marker about 197 sequences were obtained for a total of 58 haplotypes, showing 65 polymorphic sites (27 parsimony informative), and no gaps were observed. In the original populations were identified more than 30 haplotypes, half of which was private; while in the Mediterranean population were identified about 20 haplotypes, just under half of which was private. In general the values of haplotype and nucleotide diversity were higher within the origin population. The maximum parsimony network obtained showed absence of geographic structure, and is characterized by a star shape: by an ancestral haplotype are derived a large number of derived haplotypes, which are very similar to each other. Indeed, despite the large number of variants, derived haplotypes differ from the central one by a low number of mutations and, with very few exceptions, are equally low represented; in most of the cases derived haplotypes were identified in just one individual. The analysis of molecular variance showed that the Mediterranean populations may be considered a subgroup with reduced variability but that the genetic variance is attributable mostly to differences within individual populations. The maximum parsimony network, with star shape, is characterized by one central haplotype from which all the others derive. The analysis of molecular variance confirm that the genetic variance is attributable for 97% to differences within the populations, supporting that the Mediterranean populations are a subgroup of Red Sea, even if they show some private haplotypes. An analysis of Bayesian inference showed a significant unidirectional genetic flow, from Red Sea to Mediterranean Sea. While it even showed a large genetic dimension of Mediterranean populations that confirms the presence of different colonization source, not sampled, in Red Sea. Despite evidence of a slight decrease in the genetic diversity of Mediterranean populations, a simulation analysis based on coalescent theory demonstrated the absence of significant bottlenecks, but there was directional selection along a cline moving further from the Suez Canal. The absence of bottlenecks was congruent with that described for G. plectocirra hosts Siganus rivulatus and Siganus luridus, and reflected a common history of high propagule pressure during initial colonization, and constant or repeated gene flow from the Red Sea to the Mediterranean area. However, directional selection was peculiar to the parasites and likely originated from parasite genotype  environment interactions. Finally, an anisotropic contribution of Red Sea populations to the Lessepsian invasion was demonstrated.

L’objectif de cette étude était de contribuer à une meilleure connaissance des espèces démersales dans les eaux côtières libanaises en Méditerranée orientale. Différents aspects relatifs à la distribution, la diversité, et la biologie de ces espèces ont été étudiés. Les données ont été collectées à partir de captures expérimentales dans le cadre du projet ‘CIHEAM-PESCA Libano’. Un mélange hautement diversifié d'espèces de poissons (téléostéens et sélaciens), de céphalopodes et de crustacés, ainsi que de organismes macro-benthiques ont été échantillonnés. La distribution spatio-temporelle et la diversité ont été évaluées respectivement à l'aide de la ‘capture par unité d'effort’ qui a été assimilée à un indice d’abondance et du nombre total d'espèces capturées dans les relevés.Des relations longueur-poids ont été établies pour plusieurs espèces présentant un nombre d’individus suffisant. Finalement, l'accent a été porté sur la biologie et l'écologie d'une espèce lesseptienne et exploitée, l’holocentre rouge, Sargocentron rubrum. Cette étude constitue une première étape dans la gestion des pêches et la conservation dans cette région
The aim of this study was to contribute to a better knowledge of demersal species in the Lebanese coastal waters, Eastern Mediterranean. Various aspect related to the distribution, diversity and biology of these species were studied. The data were collected from a three-year experimental survey in the framework of the ‘CIHEAM-PESCA Libano project’. A highly diversified mix of fish species (teleosteans and selaceans), cephalopods and crustaceans were sampled. Spatio-temporal distribution and diversity was evaluated respectively using the ‘Catch Per Unit Effort’ which was considered as an approximation of an abundance index and the total number of species caught in the surveys