Trematode metacercariae parasitic in the estuarine crustacean Cyathura muromiensis Nunomura, 1974 (Peracarida: Isopoda: Anthuroidea).

This is the first report of trematodes parasitic in the estuarine isopod crustacean Cyathura muromiensis, and the fourth report from anthuroid isopods worldwide. From 52 of 54 host individuals collected qualitatively on the tidal flat of the Muromi River estuary, Fukuoka, Japan, 389 cysts of metacercariae were extracted (sample prevalence = 96.3 %). Host individuals contained from one to 71 metacercarial cysts. The range in cyst diameter was 172.3-252.1 µm, and the distribution of cyst sizes contained only one component. Cysts occurred in pereonites 2-7 and the pleon of the host, but not in the head, pereonite 1, or telson. There was no correlation between the number of cysts and host sex or size. Sequences of the nuclear "ITS1 region," from the 3´ region of 18S rRNA to the 5´ region of internal transcribed spacer I gene (ITS1), from five cysts ranging in size from nearly the lowest diameter to the greatest diameter in our sample showed p-distances of 0.0-0.2 %, suggesting that all cysts obtained were conspecific. A phylogenetic reconstruction based on nuclear 28S rRNA gene sequences showed that the trematode belongs in the genus Microphallus. The definitive host of our trematode species is likely a bird, since the definitive hosts of microphallids are chiefly birds, and birds are known to prey on Cyathura isopods.

Molecular characterization of Microphallus sp. (Digenea: Microphallidae) parasitic in freshwater crabs of Manipur, India.

Freshwater crabs (Potamiscus manipuriensis), commonly consumed as local delicacies by the native people in the state of Manipur, were found to harbour metacercariae of Microphallus sp. (Family Microphyllidae), which were morphologically different from metacercariae of Microphallus spp reported earlier from different regions. So, PCR-based molecular characterization of this metacercaria was done utilizing rDNA marker regions: larger subunit (LSU) or 28S (D1-D3 region) and inter-transcribed spacer 2 (ITS2). Sequence and phylogenetic analyses confirmed that the taxon under study belonged to family Microphyllidae of genus Microphallus.

Long-term change in the parasite burden of shore crabs (Hemigrapsus oregonensis and Hemigrapsus nudus) on the northwestern Pacific coast of North America.

The abundances of free-living species have changed dramatically in recent decades, but little is known about change in the abundance of parasitic species. We investigated whether populations of several parasites have shifted over time in two shore crab hosts, Hemigrapsus oregonensis and Hemigrapsus nudus, by comparing the prevalence and abundance of three parasite taxa in a historical dataset (1969-1970) to contemporary parasite abundance (2018-2020) for hosts collected from 11 intertidal sites located from Oregon, USA, to British Columbia, Canada. Our data suggest that the abundance of the parasitic isopod Portunion conformis has varied around a stable mean for the past 50 years. No change over time was observed for larval acanthocephalans. However, larval microphallid trematodes increased in prevalence over time among H. oregonensis hosts, from a mean of 8.4-61.8% between the historical and contemporary time points. The substantial increase in the prevalence of larval microphallid trematodes could be owing to increased abundances of their bird final hosts, increased production of parasite infective stages by snail intermediate hosts or both. Our study highlights the variability among parasite species in their temporal trajectories of change.

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.

Microphallus ochotensis sp. nov. (Digenea, Microphallidae) and relative merits of two-host microphallid life cycles.

A new digenean species, Microphallus ochotensis sp. nov., was described from the intestine of Pacific eiders (Somateria mollissima v-nigrum) from the north of the Sea of Okhotsk. It differs from other microphallids in the structure of the metraterm, which consists of two distinct parts: a sac with spicule-like structures and a short muscular duct opening into the genital atrium. Mi. ochotensis forms a monophyletic clade together with other congeneric species in phylograms derived from the 28S and ITS2 rRNA gene. Its dixenous life cycle was elucidated with the use of the same molecular markers. Encysted metacercariae infective for birds develop inside sporocysts in the first intermediate host, an intertidal mollusc Falsicingula kurilensis. The morphology of metacercariae and adults was described with an emphasis on the structure of terminal genitalia. Considering that Falsicingula occurs at the Pacific coast of North America and that the Pacific eider is capable of trans-continental flights, the distribution of Mi. ochotensis might span the Pacific coast of Alaska and Canada. The range of its final hosts may presumably include other benthos-feeding marine ducks as well as shorebirds. We suggest that a broad occurrence of two-host life cycles in microphallids is associated with parasitism in birds migrating along sea coasts. The chances that migrating birds would stop at a site where both first and second intermediate hosts occur are relatively low. The presence of a single molluscan host in the life cycle increases the probability of transmission.

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.

Metacercarias de la familia Microphallidae (Trematoda: Digenea) en el anfípodo Hyale grandicornis en la costa de Maule, Chile Central / Metacercariae of the family microphallidae (Trematoda: Digenea) in the amphipod Hyale grandicornis from the coast of Maule, Central Chile

Los digeneos presentan ciclos biológicos complejos con 2 fases reproductivas y varios hospedadores, como moluscos y crustáceos (hospedadores intermediarios) y vertebrados (hospedadores definitivos). A pesar de los numerosos registros de digeneos en fases adultas en distintas especies hospedadoras, hay muy pocos registros en invertebrados y ninguno en crustáceos. Con el fin de aportar información sobre alguna de la fases juveniles de digeneos, se revisaron 98 anfípodos Hyale grandicornis (Krõyer, 1845) recolectados desde pozas intermareales en la costa de Maule, Chile Central. De estos el 64,3 por ciento albergaban entre 1 y 25 metacercarias por amfípodo. Se reconocieron 3 tipos de metacercarias de acuerdo a su forma (ovalada y esféricas) y tamaño (entre 200 y 375 µm). Para identificarlas, las metacercarias fueron incubadas y eclosionadas artificialmente. La morfología de los digeneos juveniles corresponde a Microphallidae: un tipo correspondería a Maritrematinae, y los otros dos podrían corresponder a Microphallinae. Estos digeneos principalmente son parásitos de aves y algunos son de peces, anfibios o mamíferos, sin embargo no hay registros de estos parásitos en ningun vertebrado en Chile. Varias especies de aves como Larus, Fulica y Phalacrocorax que habitan comúnmente en las costas de Maule, podrían ser las hospedadoras definitivas de estos digeneos.

Digeneans have complex life cycles with 2 reproductive phases and 2-3 hosts such as molluscs, crustaceans and vertebrates. Despite numerous records of adult digeneans from many host species of Chile, there are few records in invertebrates. The aim of this study is to provide information about juvenile phases of digeneans in the amphipod Hyale grandicornis (Kröyer, 1845). Ninety-eight amphipods were collected from intertidal pools at Maule, central coast of Chile. Sixty-four percent of the amphipods were parasitized with 1-25 metacercariae/host individual. Three types metacercariae were distinguished according their shape (spherical or ovalated) and size (between 200 to 375 µm legth). To identify them, the metacercariae were incubated and artificially opened. The morphology of juvenile digeneans of the 3 types of metacercariae corresponded to the family Microphallidae. One type of metacercaria may belong to Maritrematinae; the other two may belong to Microphallinae. The definitive hosts for Microphallidae are principally birds, although some species can be found in fishes, amphibians or mammals. In Chile, there are no records of these digeneans in any group of hosts. In the Coast of Maule usually inhabit many bird species such as Larus, Fulica, and Phalacrocorax genera, so that some of them could be definitive hosts of these digeneans.