Algunos helmintos parásitos de la gaviota peruana (Larus belcheri) / Some parasitic helminths of the Belcher's gull (Larus belcheri)

La información sobre helmintos parásitos de aves marinas es muy limitada en el Perú. En el presente trabajo, se identificaron helmintos colectados de la gaviota peruana (Larus belcheri) provenientes de algunas playas de Lima (Pucusana, Chorrillos, Ventanilla y Ancón) en Perú. Los helmintos fueron estudiados morfológicamente e identificados como Skrjabinoclava sp. (Nematoda), Contracaecum sp. (Nematoda), Maritrema sp. (Trematoda) y Profilicollis altmani (Acanthocephala). El presente trabajo corresponde a los primeros registros de estos parásitos en la gaviota peruana.

Information on parasitic helminths of seabirds is very limited in Peru. In the present work, helminths collected from the Belcher's gull (Larus belcheri) from some beaches of Lima (Pucusana, Chorrillos, Ventanilla and Ancón) in Peru were identified. The helminths were studied morphologically and identified as Skrjabinoclava sp. (Nematoda), Contracaecum sp. (Nematoda), Maritrema sp. (Trematoda) and Profilicollis altmani (Acanthocephala). The present work corresponds to the first records of these parasites in the Peruvian gull.

A new species of Maritrema (Trematoda: Microphallidae) parasitizing the Baird's sandpiper Calidris bairdii, and comments about diversity of Microphallidae in two Nearctic shorebirds at Patagonian sites in Argentina.

Birds are hosts of a wide diversity of trematodes. Between them, the Microphallidae is a common family with a cosmopolitan distribution. Nevertheless, only 10 Maritrema species have been recorded previously in South America. The aim of the present paper is to describe a new species of Maritrema parasitizing the Nearctic Baird's sandpiper, Calidris bairdii in its wintering areas in Patagonia, Argentina. We also analyze and compare the microphallid diversity in two host species. We collected 44 C. bairdii and 50 Calidris fuscicollis in search of helminths. Trematodes were found only in C. bairdii. A total of 694 trematodes belonging to 4 microphallid species were found parasitizing the intestine and caeca. Four microphallid species were found: Maritrema formicae, Odhneria odhneri, Levinseniella cruzi and Maritrema pichi n. sp. M. formicae showed the highest prevalence, while M. pichi n. sp. was the species with the highest mean intensity and mean abundance. The new species M. pichi n. sp. differs from congeners by the position of the acetabulum that is included within the vitellarium ring, the ovary is anterior to the acetabulum, and the testes are lateral to it. We discuss the parasitological results in relation with the biological and ecological characteristics of both different host species.

Caste ratio adjustments in response to perceived and realised competition in parasites with division of labour.

Colonial organisms with division of labour are assumed to achieve increased colony-level efficiency in task performance through functional specialisation of individuals into distinct castes. In social insects, ratios of individuals in different castes can adjust adaptively in response to external threats. However, whether flexibility in caste ratio also occurs in other social organisms with division of labour remains unclear. Some parasitic trematodes, in which clonal colonies within the snail intermediate host comprise a reproductive caste and a soldier caste, offer good systems to test the general nature of adaptive caste ratio adjustments. Using the trematode Philophthalmus sp. as model, we test whether trematode colonies shift their composition towards more soldiers when exposed to a sustained risk of invasion by a competitor parasite species, and/or when experiencing sustained, active competition. We also quantify the colony-level fitness impact of caste ratio adjustments, measured as the colony's output of larval infective stages. We conducted two long-term laboratory experiments on within-snail trematode colonies. First, snails harbouring Philophthalmus colonies were exposed to different levels of invasion risk by another trematode species, Maritrema novaezealandense. Second, the structure of Philophthalmus colonies was quantified after a year-long period of within-snail competition with the other trematode species. When facing the risk of invasion by a competitor, independently of the level of risk, Philophthalmus colonies showed a significant shift towards producing more soldiers, resulting in altered caste ratio. Similarly, when experiencing actual competition by another trematode established in the same snail, Philophthalmus colonies also adjusted by producing significantly more soldiers. Greater investments in defense via more soldiers had negative impacts on the establishment and size of the competitor's colonies. Nevertheless, the presence of the competitor reduced the fitness (output of infective stages) of Philophthalmus colonies, although the production of more soldiers mitigated that effect. Our findings demonstrate that trematode colonies with division of labour are capable of adaptive caste ratio adjustments in response to both the perceived threat of competition and actual competition, with trade-offs against reproductive success only apparent when soldier numbers are very high. Combined with results on social insects, our study suggests parallel adaptations of colonial organisms in phylogenetically disparate organisms.

Coastal ecosystems on a tipping point: Global warming and parasitism combine to alter community structure and function.

Mounting evidence suggests that the transmission of certain parasites is facilitated by increasing temperatures, causing their host population to decline. However, no study has yet addressed how temperature and parasitism may combine to shape the functional structure of a whole host community in the face of global warming. Here, we apply an outdoor mesocosm approach supported by field surveys to elucidate this question in a diverse intertidal community of amphipods infected by the pathogenic microphallid trematode, Maritrema novaezealandensis. Under present temperature (17°C) and level of parasitism, the parasite had little impact on the host community. However, elevating the temperature to 21°C in the presence of parasites induced massive structural changes: amphipod abundances decreased species-specifically, affecting epibenthic species but leaving infaunal species largely untouched. In effect, species diversity dropped significantly. In contrast, four degree higher temperatures in the absence of parasitism had limited influence on the amphipod community. Further elevating temperatures (19-25°C) and parasitism, simulating a prolonged heat-wave scenario, resulted in an almost complete parasite-induced extermination of the amphipod community at 25°C. In addition, at 19°C, just two degrees above the present average, a similar temperature-parasite synergistic impact on community structure emerged as seen at 21°C under lower parasite pressure. The heat-wave temperature of 25°C per se affected the amphipod community in a comparable way: species diversity declined and the infaunal species were favoured at the expense of epibenthic species. Our experimental findings are corroborated by field data demonstrating a strong negative relationship between current amphipod species richness and the level of Maritrema parasitism across 12 sites. Hence, owing to the synergistic impact of temperature and parasitism, our study predicts that coastal amphipod communities will deteriorate in terms of abundance and diversity in face of anticipated global warming, functionally changing them to be dominated by infaunal species.

M aritrema corai n. sp. (Digenea: Microphallidae) from the white ibis Eudocimus albus (Linnaeus) (Aves: Threskiornithidae) in Mexico.

M aritrema corai n. sp. is described based on material from the intestine of the white ibis Eudocimus albus (L.) (Threskiornithidae) in Mexico. The new species can be distinguished morphologically from all congeners by the unique combination of the following morphological features: a very long cirrus sac attenuated distally [cirrus sac to body length ratio 1:0.90-1.29 (mean 1:1.07)]; a large, elongate-oval seminal receptacle, located dorsally between the cirrus sac and ovary; and long, filiform, unarmed, evaginable cirrus. Phylogenetic analyses of 28S ribosomal DNA (rDNA) sequences for the new species and for Maritrema spp. and Microphallus spp. depicted strong support for the two genera (excluding Microphallus fusiformis) and revealed close relationships between Ma. corai n. sp. and the clade formed by Maritrema novaezealandense Martorelli, Fredensborg, Mouritsen & Poulin, 2004, Maritrema heardi (Kinsella & Deblock, 1994) and Maritrema cf. eroliae.

Variation among genotypes in responses to increasing temperature in a marine parasite: evolutionary potential in the face of global warming?

Climates are changing worldwide, and populations are under selection to adapt to these changes. Changing temperature, in particular, can directly impact ectotherms and their parasites, with potential consequences for whole ecosystems. The potential of parasite populations to adapt to climate change largely depends on the amount of genetic variation they possess in their responses to environmental fluctuations. This study is, to our knowledge, the first to look at differences among parasite genotypes in response to temperature, with the goal of quantifying the extent of variation among conspecifics in their responses to increasing temperature. Snails infected with single genotypes of the trematode Maritrema novaezealandensis were sequentially acclimatised to two different temperatures, 'current' (15°C) and 'elevated' (20°C), over long periods. These temperatures are based on current average field conditions in the natural habitat and those predicted to occur during the next few decades. The output and activity of cercariae (free-swimming infective stages emerging from snails) were assessed for each genotype at each temperature. The results indicate that, on average, both cercarial output and activity are higher at the elevated acclimation temperature. More importantly, the output and activity of cercariae are strongly influenced by a genotype-by-temperature interaction, such that different genotypes show different responses to increasing temperature. Both the magnitude and direction (increase or decrease) of responses to temperature varied widely among genotypes. Therefore, there is much potential for natural selection to act on this variation, and predicting how the trematode M. novaezealandensis will respond to the climate changes predicted for the next century will prove challenging.

Discovery of Maritrema obstipum (Digenea: Microphallidae) from migratory birds in Korea.

Adults of Maritrema obstipum (Digenea: Microphallidae) were found in the intestines of 4 species of migratory birds, including the sanderling (Crocethia alba), Kentish plover (Charadrius alexandrines), Mongolian plover (Charadrius mongolus), and red-necked stint (Calidris ruficollis), collected from Yubu Island, Chungcheongnam-do, Korea. The worms of were 451 × 265 µm in size, and were easily identifiable as Maritrema species by the presence of the cirrus sac, and the ring-like distribution of the vitellaria. More specifically, the ejaculatory duct curved posteromedially, and the 2 parts of vitelline follicles were found to be distinct at the posterior end. The eggs were brown-colored, and 19.8 × 12.3 µm in size. All these findings implicated M. obstipum as the pertinent species of the worms. Beside these, adult worms of Gynaecotyla squatarolae, Parvatrema duboisi, and Acanthoparyphium sp. were also discovered. This is the first report establishing migratory birds as the natural definitive hosts for M. obstipum.

Discovery of Maritrema obstipum (Digenea: Microphallidae) from Migratory Birds in Korea

Adults of Maritrema obstipum (Digenea: Microphallidae) were found in the intestines of 4 species of migratory birds, including the sanderling (Crocethia alba), Kentish plover (Charadrius alexandrines), Mongolian plover (Charadrius mongolus), and red-necked stint (Calidris ruficollis), collected from Yubu Island, Chungcheongnam-do, Korea. The worms of were 451x265 microm in size, and were easily identifiable as Maritrema species by the presence of the cirrus sac, and the ring-like distribution of the vitellaria. More specifically, the ejaculatory duct curved posteromedially, and the 2 parts of vitelline follicles were found to be distinct at the posterior end. The eggs were brown-colored, and 19.8x12.3 microm in size. All these findings implicated M. obstipum as the pertinent species of the worms. Beside these, adult worms of Gynaecotyla squatarolae, Parvatrema duboisi, and Acanthoparyphium sp. were also discovered. This is the first report establishing migratory birds as the natural definitive hosts for M. obstipum.

Discovery of Maritrema jebuensis n. sp. (Digenea: Microphallidae) from the Asian Shore Crab, Hemigrapsus sanguineus, in Korea.

Maritrema spp. (Digenea: Microphallidae) are parasites of birds, but have not been found in the Republic of Korea. In this study, metacercariae of Maritrema sp. were discovered in the Asian shore crab, Hemigrapsus sanguineus, caught in the mud-flats of Jebu-do, Hwasung-gun, Gyeonggi-do, and the adult flukes were confirmed by experimental infection into mice. Based on the symmetric ribbon-like vitellarium, adult flukes of Maritrema sp. were identified, but did not belong to previously described species in terms of the following morphologic characteristics: ceca reaching to the lateral wall at the anterior border of the ovary; ventral sucker larger than oral sucker; a prominent metraterm; and vitellarium forming a complete ring. Hence, we named this microphallid M. jebuensis n. sp. after the island where the second intermediate hosts were collected. From this study, it has been shown that Maritrema sp. is distributed in Korea and transmitted by the Asian shore crab, H. sanguineus.

Discovery of Maritrema jebuensis n. sp. (Digenea: Microphallidae) from the Asian Shore Crab, Hemigrapsus sanguineus, in Korea

Maritrema spp. (Digenea: Microphallidae) are parasites of birds, but have not been found in the Republic of Korea. In this study, metacercariae of Maritrema sp. were discovered in the Asian shore crab, Hemigrapsus sanguineus, caught in the mud-flats of Jebu-do, Hwasung-gun, Gyeonggi-do, and the adult flukes were confirmed by experimental infection into mice. Based on the symmetric ribbon-like vitellarium, adult flukes of Maritrema sp. were identified, but did not belong to previously described species in terms of the following morphologic characteristics: ceca reaching to the lateral wall at the anterior border of the ovary; ventral sucker larger than oral sucker; a prominent metraterm; and vitellarium forming a complete ring. Hence, we named this microphallid M. jebuensis n. sp. after the island where the second intermediate hosts were collected. From this study, it has been shown that Maritrema sp. is distributed in Korea and transmitted by the Asian shore crab, H. sanguineus.