Raquel Xavier

First record of Halidrys siliquosa on the Portuguese coast: counter-intuitive range expansion?

The occurrence of the pod weed, Halidrys siliquosa , is recorded for the first time on the Portuguese coast. Several specimens of this brown algae were observed attached to the rocky surface in tide pools at 41o44′10″N 8o52′34″W, extending southward its previously known geographical distribution. The observed shift is inconsistent with general predictions of species migrations under warming climate conditions, which anticipate poleward shifts rather than southern expansions. Although more data will be required to undoubtedly uncover its cause, the recently observed range expansion raises important questions about the generalization of the previously stated biogeographic rules.

tcsBU: a tool to extend TCS network layout and visualization

MOTIVATION TCS is a widely used haplotype network reconstruction software, but lacks the capability of overlapping genetic with geographic structure, which is often a first step in phylogeographic analysis. RESULTS tcsBU is a web-based program that extends the capabilities of TCS, by implementing haplotype classification into an arbitrary user-defined scheme, which is displayed as pie-chart like graphs embedded into the network. Taking advantage of modern graphic libraries, tcsBU also improves the speed at which the final network layout is reached. Networks can be saved as a Scalable Vector Graphics format. AVAILABILITY AND IMPLEMENTATION tcsBU is available on-line at http://cibio.up.pt/software/tcsBU/. The source code is freely available from https://github.com/sairum/tcsbu/ under a standard MIT license.

Invasion or invisibility: using genetic and distributional data to investigate the alien or indigenous status of the Atlantic populations of the peracarid isopod, Stenosoma nadejda (Rezig 1989).

The peracarid isopod, Stenosoma nadejda (Rezig 1989), until recently considered to be endemic of the Mediterranean region, was first reported in the Atlantic coast of southern Spain in 2001, and in 2006 abundant populations were discovered throughout the southwestern Portuguese coast. This fast expansion was intriguing because, as a direct brooder, this species has limited mechanisms for dispersal, such as rafting on seaweeds. Did S. nadejda recently extend its range into the Atlantic or was it overlooked in the past? We examined the patterns of genetic diversity and population differentiation accordingly by sequencing the cytochrome c oxidase subunit I mitochondrial gene from 75 individuals collected in five locations in Atlantic Iberia and one in the Mediterranean. Our results indicate that the newly discovered Atlantic populations of S. nadejda appear to be old and have long persisted on Atlantic shores rather than being a recent introduction. High levels of genetic diversity and geographic structure were uncovered in what was initially suspected to be an ‘invasive’ species. Recent changes in population dynamics may have made S. nadejda more conspicuous in the Atlantic shores, or a more comprehensive survey led to the recognition of this species where it was not expected.

Reproductive cycles of four species of Patella (Mollusca: Gastropoda) on the northern and central Portuguese coast

The reproductive cycles of four limpet species, Patella depressa, Patella ulyssiponensis, Patella vulgata and Patella rustica are described for several locations in northern and central Portugal. Patella depressa and P. ulyssiponensis displayed almost continual gonad activity, with two main spawning periods, September–January and March–June, and minor spawning events dispersed throughout the year. Patella vulgata and P. rustica exhibited highly synchronized reproductive cycles, with well-defined breeding and resting periods. Gonad development in P. vulgata started in September and spawning took place from November–December to March. In P. rustica development started in June and spawning occurred from September–October to December–January. Compared to the 1980s these results suggest that breeding periods are becoming longer in southern species and shorter in northern species.

DNA barcoding identifies a cosmopolitan diet in the ocean sunfish.

The ocean sunfish (Mola mola) is the world’s heaviest bony fish reaching a body mass of up to 2.3 tonnes. However, the prey M. mola consumes to fuel this prodigious growth remains poorly known. Sunfish were thought to be obligate gelatinous plankton feeders, but recent studies suggest a more generalist diet. In this study, through molecular barcoding and for the first time, the diet of sunfish in the north-east Atlantic Ocean was characterised. Overall, DNA from the diet content of 57 individuals was successfully amplified, identifying 41 different prey items. Sunfish fed mainly on crustaceans and teleosts, with cnidarians comprising only 16% of the consumed prey. Although no adult fishes were sampled, we found evidence for an ontogenetic shift in the diet, with smaller individuals feeding mainly on small crustaceans and teleost fish, whereas the diet of larger fish included more cnidarian species. Our results confirm that smaller sunfish feed predominantly on benthic and on coastal pelagic species, whereas larger fish depend on pelagic prey. Therefore, sunfish is a generalist predator with a greater diversity of links in coastal food webs than previously realised. Its removal as fisheries’ bycatch may have wider reaching ecological consequences, potentially disrupting coastal trophic interactions.

Invasion history of Caprella scaura Templeton, 1836 (Amphipoda: Caprellidae) in the Iberian Peninsula: multiple introductions revealed by mitochondrial sequence data

The caprellid Caprella scaura, native to the western Indian Ocean, is one striking example of a successful invader. It was first recorded in the Iberian Peninsula in Gerona (north-eastern coast of Spain), in 2005, and has recently been reported throughout the Mediterranean and Atlantic coasts of this region. The most likely vector of introduction and distribution is within the hull-fouling community on recreational craft. However, beyond the dates of detection, the introduction history of C. scaura remains unclear. Direct sequencing of mitochondrial DNA (cytochrome c oxidase subunit I) was used to compare genetic composition in native and introduced populations in order to infer the invasion history of this species. In addition, 18S rDNA sequences were used to resolve phylogenetic relationships within this species and with the morphologically closest species Caprella californica and Caprella scauroides. The high genetic divergence and population subdivision found between non-native Iberian populations together with a high level of genetic diversity in some populations indicate multiple geographical sources and introduction points for this caprellid. Our data suggest that Iberian populations may derive from at least two sources: (1) Pacific Australian, and (2) Indian Ocean, either directly, or, more likely, through stepping-stone events from central Mediterranean population(s). Atlantic Iberian populations seem to be the most recently established populations. On the other hand, this is the first study providing molecular evidence confirming C. scaura, C. californica and C. scauroides as distinct species. It also provides strong molecular evidence that C. scaura typica and C. scaura scaura correspond to the same subspecies, and the Japanese C. scaura diceros and the Chilean C. scaura spinirostris could merit specific rank.

Evidence for Cryptic Speciation in Directly Transmitted Gyrodactylid Parasites of Trinidadian Guppies

Cryptic species complexes are common among parasites, which tend to have large populations and are subject to rapid evolution. Such complexes may arise through host-parasite co-evolution and/or host switching. For parasites that reproduce directly on their host, there might be increased opportunities for sympatric speciation, either by exploiting different hosts or different micro-habitats within the same host. The genus Gyrodactylus is a specious group of viviparous monogeneans. These ectoparasites transfer between teleosts during social contact and cause significant host mortality. Their impact on the guppy (Poecilia reticulata), an iconic evolutionary and ecological model species, is well established and yet the population genetics and phylogenetics of these parasites remains understudied. Using mtDNA sequencing of the host and its parasites, we provide evidence of cryptic speciation in Gyrodactylus bullatarudis, G. poeciliae and G. turnbulli. For the COII gene, genetic divergence of lineages within each parasite species ranged between 5.7 and 17.2%, which is typical of the divergence observed between described species in this genus. Different lineages of G. turnbulli and G. poeciliae appear geographically isolated, which could imply allopatric speciation. In addition, for G. poeciliae, co-evolution with a different host species cannot be discarded due to its host range. This parasite was originally described on P. caucana, but for the first time here it is also recorded on the guppy. The two cryptic lineages of G. bullatarudis showed considerable geographic overlap. G. bullatarudis has a known wide host range and it can also utilize a killifish (Anablepsoides hartii) as a temporary host. This killifish is capable of migrating overland and it could act as a transmission vector between otherwise isolated populations. Additional genetic markers are needed to confirm the presence of these cryptic Gyrodactylus species complexes, potentially leading to more in-depth genetic, ecological and evolutionary analyses on this multi-host-parasite system.

Phylogenetic analysis of the north-east Atlantic and Mediterranean species of the genus Stenosoma (Isopoda, Valvifera, Idoteidae)

Xavier, R., Santos, A. M., Harris, D. J., Sezgin, M., Machado, M., Branco, M. (2012). Phylogenetic analysis of the north‐east Atlantic and Mediterranean species of the genus Stenosoma (Isopoda, Valvifera, Idoteidae). —Zoologica Scripta, 41, 386–399.

Stenosoma stephenseni sp. n. (Isopoda, Idoteidae), from the southwestern Mediterranean, with a note on the nomenclatural status of Synisoma Collinge, 1917

Abstract Recent collections of isopods in Alboran Island and Algeria included several specimens of the species Stenosoma stephenseni sp. n. This is the fourteenth species described in the genus Stenosoma Leach, 1814. Examination of two specimens collected during the Danish oceanographic cruises of the Thor (1908–10) close to the Galite Islands, and identified as Stenosoma acuminatum Leach, 1814, revealed that both belong to Stenosoma stephenseni sp. n. In light of these findings, the Mediterranean records of Stenosoma acuminatum are revised, and it is proposed that Stenosoma acuminatum is a strictly Atlantic species. An updated diagnosis for the genus Stenosoma is given, together with a key for the identification of its species. The nomenclatural status of the name Synisoma Collinge, 1917 is addressed, and although it is in prevailing usage, it is shown that Stenosoma Leach, 1814 is the valid name of the genus.

Phylogenetic analysis of apicomplexan parasites infecting commercially valuable species from the North-East Atlantic reveals high levels of diversity and insights into the evolution of the group

BackgroundThe Apicomplexa from aquatic environments are understudied relative to their terrestrial counterparts, and the seminal work assessing the phylogenetic relations of fish-infecting lineages is mostly based on freshwater hosts. The taxonomic uncertainty of some apicomplexan groups, such as the coccidia, is high and many genera were recently shown to be paraphyletic, questioning the value of strict morphological and ecological traits for parasite classification. Here, we surveyed the genetic diversity of the Apicomplexa in several commercially valuable vertebrates from the North-East Atlantic, including farmed fish.ResultsMost of the sequences retrieved were closely related to common fish coccidia of Eimeria, Goussia and Calyptospora. However, some lineages from the shark Scyliorhinus canicula were placed as sister taxa to the Isospora, Caryospora and Schellakia group. Additionally, others from Pagrus caeruleostictus and Solea senegalensis belonged to an unknown apicomplexan group previously found in the Caribbean Sea, where it was sequenced from the water column, corals, and fish. Four distinct parasite lineages were found infecting farmed Dicentrarchus labrax or Sparus aurata. One of the lineages from farmed D. labrax was also found infecting wild counterparts, and another was also recovered from farmed S. aurata and farm-associated Diplodus sargus.ConclusionsOur results show that marine fish apicomplexans are diverse, and we highlight the need for a more extensive assessment of parasite diversity in this phylum. Additionally, parasites recovered from S. canicula were recovered as basal to their piscine counterparts reflecting hosts phylogeny.