Pilar Alda

Parasites and epibionts of grapsid crabs in Bahía Blanca estuary, Argentina

Epibionts and parasites were recovered from the grapsid crabs Cyrtograpsus angulatus and Neohelice granulata in the Bahia Blanca estuary, Argentina. Among epibionts, we identified a filamentous bacterium, the protozoan Epistylis sp., and the copepod Neocancrincola platensis on the gills; and the barnacles Balanus amphitrite and Balanus glandula as well as the bryozoan Conopeum reticulum on the caparace. Among endoparasites, we identified the acanthocephalan Profilicollis chasmagnathi in the hindgut, nematodes of the subfamily Acuariinae and Ascarophis sp. in the haemocoel, and an encysted cyclophyllidean cestode in the gut wall. Among microphallid digeneans, we found four metacercariae: Maritrema bonaerensis in the gills, muscle, haemocoel, and gonads, Maritrema orensensis in the gills, Levinseniella cruzi in the gonads, and Odhneria sp. in the muscle. Except for P. chasmagnathi, N. platensis , and M. bonaerensis , all other epibionts and digeneans represent new host records. This paper also presents novel information regarding the possible sites of infection for M. bonaerensis . Our results add relevant data about possible life cycles of helminths in the study area. Se recuperaron epibiontes y parasitos de los cangrejos grapsidos Cyrtograpsus angulatus y Neohelice granulata en el estuario de Bahia Blanca, Argentina. Entre los epibiontes, se identificaron una bacteria filamentosa, el protozoo Epistylis sp. y el copepodo Neocancrincola platensis en las branquias, y los cirripedios Balanus amphitrite y Balanus glandula y el briozoo Conopeum reticulum en el caparazon. Entre los endoparasitos, se identificaron el acantocefalo Profilicollis chasmagnathi en el intestino posterior, los nematodes Acuariinae y Ascarophis sp. en el hemocele y un cestode cyclophyllideo en la pared intestinal. Entre los digeneos microphallidos, se encontraron cuatro metacercarias: Maritrema bonaerensis en las branquias, el musculo, el hemocele y las gonadas, Maritrema orensensis en las branquias, Levinseniella cruzi en las gonadas y Odhneria sp. en el musculo. Excepto por P. chasmagnathi, N. platensis y M. bonaerensis , todos los otros epibiontes y digeneos representan nuevos registros para los hospedadores. Ademas, este trabajo presenta nuevos sitios de infeccion para M. bonaerensis y revela nuevos datos sobre los posibles ciclos de vida de los helmintos en el sitio de estudio.

Some Digeneans from Olrog's Gull Larus atlanticus Olrog, 1958 (Aves: Laridae) from the Bahía Blanca Estuary, Argentina

Abstract Five species of digeneans (4 Microphallidae, 1 Echinostomatidae) were recovered from a total of 85 Olrogs gulls, Larus atlanticus (dead chicks). Birds were collected from a breeding colony in the Bahía Blanca estuary, Argentina, during breeding seasons 2003 (n = 6), 2005 (n = 66), and 2006 (n = 13). Digeneans were identified as Maritrema bonaerensis, Maritrema orensensis, Odhneria odhneri, Levinseniella cruzi, and Himasthla escamosa. Except for M. bonaerensis, all other helminth species represent new host records, and all the digeneans reported constitute new locality records. Likely intermediate hosts for digeneans, such as Neohelice granulata (Crustacea: Decapoda), Cyrtograpsus angulatus (Crustacea: Decapoda), and Heleobia australis (Mollusca: Gastropoda), were also studied. The metacercariae of M. bonaerensis were found in the crabs N. granulata and C. angulatus, and cercariae closely resembling those of M. bonaerensis, L. cruzi and H. escamosa were found in the mollusc H. australis.

Morphological and molecular identification of the fish-borne metacercaria of Ascocotyle (Phagicola) longa Ransom, 1920 in Mugil liza from Argentina

This is the first report of Ascocotyle (Phagicola) longa Ransom, 1920 (Digenea: Heterophyidae) in Argentina confirmed by morphological and molecular studies. The metacercaria was found encysted in myotomal musculature, heart and mesentery of the mullet Mugil liza (Pisces: Mugilidae) from Samborombon bay. We provide a morphological description of the metacercaria which we identified using species-specific primers for A. (Phagicola) longa and nucleotid sequence. This worldwide parasite has been reported as one of the causative agents of heterophyiosis, an emerging fish-borne disease of humans, contracted by the consumption of raw mullet. The discovery of A. (Phagicola) longa in Argentina represents a warning of the potentially great impact of this parasite on public health.

Larval Digeneans of the Siphonariid Pulmonates Siphonaria lessoni and Kerguelenella lateralis and the Flabelliferan Isopod Exosphaeroma sp. from the Intertidal Zone of the Argentinean Sea

Abstract We report sporocysts and cercariae from 2 species of limpets (Siphonaria lessoni [n  =  500] and Kerguelenella lateralis [n  =  100]) and a metacercaria from S. lessoni, as well as an isopod (Exosphaeroma sp. [n  =  100]), all collected from the intertidal zone of the Argentinean Sea near Comodoro Rivadavia, Rada Tilly, and Punta Maqueda, Argentina. We assigned the limpet digeneans to Microphallidae, Schistosomatidae, and Hemiuroidea and provide a description of the metacercaria. We experimentally infected isopods with the microphallid cercaria for correlating this cercaria with metacercariae found in naturally infected isopods. Information regarding seasonal variation in prevalence is also provided.

Maritrema orensense and Maritrema bonaerense (Digenea: Microphallidae): Descriptions, Life Cycles, and Comparative Morphometric Analyses

Abstract: We elucidate the life cycle of Maritrema orensense for the first time and experimentally confirm that of the sympatric Maritrema bonaerense. In Argentinean estuaries, both species parasitize the cochliopid snail Heleobia australis as first intermediate host, the grapsid crabs Neohelice granulata and Cyrtograpsus angulatus as second intermediate hosts, and gulls as definitive hosts. Here, we describe the daughter sporocysts and cercariae of M. orensense and redescribe these stages for M. bonaerense. Sporocysts of M. orensense are shorter, with fewer developed cercariae than M. bonaerense. The cercariae of M. orensense have longer, larger, and more undulating cephalic glands than M. bonaerense. We redescribe metacercariae and adults of both species and compare them with the previous descriptions. Intestinal ceca length, vitellaria shape and extension, and egg size are the most relevant characteristics in metacercariae and adults for differentiating the species. Hence, the detailed morphological description and comparative analyses of morphometrics obtained from natural and experimental infections permit clear differentiation of M. orensense and M. bonaerense at each life stage.

Larval trematodes infecting the South-American intertidal mud snail Heleobia australis (Rissooidea: Cochliopidae)

Larval trematodes infecting the snail Heleobia australis (Cochliopidae) from the Bahía Blanca estuary, Argentina were surveyed for two years. A total of 7,504 snail specimens was dissected and the larval stages of 15 different trematodes were recovered and examined morphologically. These larvae included four species that had previously been reported from H. australis in Brazil, Uruguay, and Argentina: the heterophyid Ascocotyle (Phagicola) longa and the microphallids, Maritrema bonaerense, Maritrema orensense, and Microphallus simillimus. Three other species, the echinostomatid Stephanoprora uruguayensis, the microphallid Levinseniella cruzi, and the psilostomid Psilochasmus oxyurus are reported here for the first time as parasites of H. australis. Eight other trematodes found in H. australis are described and placed in the appropriate superfamilies, families or genera (Cryptogonimidae, Apocreadiidae, Aporocotylidae, Notocotylidae, Haploporidae, Renicolidae, Himasthla, and Renicola). The prevalence of the trematode taxa infecting H. australis in the Bahía Blanca estuary was low (<3%) with a single exception (M. simillimus; >20%). Microphallidae were the richest and the most prevalent family, probably because of the high abundance of crabs — the second-intermediate hosts of certain microphallid species — and the considerable diversity of gulls. Here we compare the parasite assemblage found in the H. australis from Bahía Blanca estuary with other parasite assemblages infecting Heleobia spp. and other rissooids from the rest of the world.

First molecular identification of Ascocotyle (Phagicola) longa in its first intermediate host the mud snail Heleobia australis.

This is the first study that used species-specific DNA primers to confirm the presence of the heterophyid Ascocotyle (Phagicola) longa Ransom, 1920 in its first intermediate host. The larval stages (rediae and cercariae) of this parasite were morphologically and genetically identified in the gonad of the intertidal mud snail Heleobia australis (d’Orbigny, 1835) (Cochliopidae) in the Bahía Blanca estuary, Argentina. In addition, we asked whether the prevalence in H. australis varied between seasons. Mullets - the second intermediate host of this heterophyid - migrate in estuaries during the warmer seasons and it is expected that piscivorous birds and mammals - the definitive hosts - prey more intensively on this species at those times. Thus, the number of parasite eggs released into the tidal flat within their feces should be higher, thereby increasing the ingestion of the parasite by H. australis. We therefore expected a higher prevalence of A. (P.) longa in H. australis in the Bahía Blanca estuary during spring and summer than autumn and winter. We found that 16 out of 2,744 specimens of H. australis had been infected with A. (P.) longa (total prevalence of 0.58%). Nonetheless, the prevalence showed no significant variation between seasons. Hence, we discuss an alternative scenario where the lack of seasonal changes might be mostly related to the permanent residence of definitive hosts in the estuary and not to the seasonal recruitment of mullets. Finally, we highlight the need for more experimental and comparative approaches in order to understand the diagnosis and geographical distribution of this worldwide heterophyid.

Digenean Parasites in the White-Backed Stilt Himantopus melanurus Vieillot, 1817 (Recurvirostridae) from the Argentine Coast

Abstract Four species of digeneans were recovered from 1 specimen of Himantopus melanurus (Aves: Recurvirostridae) from Bahía Blanca estuary, Argentina. Digeneans were assigned to Psilochasmus oxyurus (Psilostomidae), Pygidiopsis crassus (Heterophyidae), Ascocotyle (Ascocotyle) felippei (Heterophyidae), and Levinseniella cruzi (Microphallidae). Psilochasmus oxyurus and A. (A.) felippei have been reported from other species of hosts, mostly from South America, but this is the southernmost report for these species. Levinseniella cruzi has been reported from H. melanurus from Mar Chiquita lagoon, to the north of Bahía Blanca estuary. This is the first report of P. crassus parasitizing a natural host.

Some Nematodes from Olrog's Gull, Larus atlanticus Olrog, 1958 (Aves: Laridae), and Prey Crabs from the Bahía Blanca Estuary, Argentina

Abstract Three species of nematodes (Acuariidae) were recovered from a total of 108 adult and chick Olrogs Gulls, Larus atlanticus. Birds were collected from a breeding colony in the Bahía Blanca estuary of Argentina, during the breeding seasons of 2005 (n  =  66 chicks, 3 adults), 2006 (n  =  37 chicks, 1 adult), and 2007 (n  =  1 chick). Nematodes were identified as Pectinospirura argentata, Skrjabinoclava andersoni, and Sciadiocara sp., and all represent new host and locality records. Prevalence of infection among chicks during the 2005 and 2006 breeding seasons was 80.3% and 89.2%, respectively, and 67% for adults in 2005. Also, third-stage acuarid nematodes were found in possible intermediate hosts, Neohelice granulata (Crustacea: Decapoda) and Cyrtograpsus angulatus (Crustacea: Decapoda).