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Disseminated neoplasia is reported for the first time in Ameghinomya antiqua (Veneridae) from Chile on the southeastern Pacific coast. A total of 710 clams were collected in winter 2019 and summer 2021 from five sites in three regions: Coquimbo. Biobio. and Los Lagos: all clams were processed by histology. The disease was only detected in clams from the Biobio region. It was characterized by the presence of numerous neoplastic cells with enlarged nuclei and high nuclear to cytoplasmic volume ratios and the almost absence of normal hemocytes. The prevalence did not vary between seasons (7% in winter and 9% in summer). KEY WORDS: neoplasia, venerid clam. Chile, Southeastern Pacific Ocean, INTRODUCTION Cancers normally arise from mutations in an organism's own cells, and they either regress or continue to grow until they kill the host organism. Cancer cells can grow and [...]

Oysters are farmed worldwide and one of the main problems is infestation by polydorin polychaetes. The native Crassostrea gasar and the exotic Pacific Crassostrea gigas oysters support aquaculture production along the subtropical southern Brazilian coast. Worm infestation rates in the two oyster species were evaluated, hypothesizing that infestation is related to stocking densities and hydrodynamic intensity. The main oyster production areas in Brazil were sampled: Parana state, Medeiros (25[degrees] 22' S, 48[degrees] 27' W), Ponta Oeste da Ilha do Mel (25[degrees] 29' S, 48[degrees] 22' W), and Cabaraquara (25[degrees] 49' S, 48[degrees] 34' W) and the Santa Catarina state, Riberao da Ilha (27[degrees] 43' S, 48[degrees] 33' W). Generalized linear models were performed to analyze the effects of sites characterized by different stocking density, hydrodynamic intensity and mean sea surface temperature (SST), the condition index, and the oyster species (native or exotic). Polydorin infestation was higher (mean of 6.02 polydorins/oyster) under higher oyster stocking densities and intermediate hydrodynamic intensity sites (Riberao da Ilha, in the Santa Catarina state). In Parana State, the two sites with similar stocking densities, Ponto Oeste (7,638 oysters/[m.sup.2]) and Cabaraquara (7,550 oyster/[m.sup.2]) presented a higher polydorin infestation in the site with low hydrodynamic intensity and higher mean SST (5.34 vs. 2.64 polydorins/oyster, respectively). The condition index was not impacted by the polydorin infestation. Native C. gasar showed a higher polydorin infestation than the exotic C. gigas (6.02 vs. 1.36, respectively), indicating a higher vulnerability to worm infestation. These results may lead to a better understanding of the infestation patterns of locally grown oysters and to the implementation of better farming management. KEY WORDS: spionids, shell-boring, aquaculture, oysters, Brazil, INTRODUCTION Oysters are farmed globally and their commercial production has increased rapidly in recent decades (Wijsman et al. 2019, FAO 2020). Many direct and indirect factors can affect the functioning [...]

Transmissible cancers, in which cancer cells themselves act as an infectious agent, have been identified in Tasmanian devils, dogs, and four bivalves. We investigated a disseminated neoplasia affecting geographically distant populations of two species of mussels (Mytilus chilensis in South America and M. edulis in Europe). Sequencing alleles from four loci (two nuclear and two mitochondrial) provided evidence of transmissible cancer in both species. Phylogenetic analysis of cancer-associated alleles and analysis of diagnostic SNPs showed that cancers in both species likely arose in a third species of mussel (M. trossulus), but these cancer cells are independent from the previously identified transmissible cancer in M. trossulus from Canada. Unexpectedly, cancers from M. chilensis and M. edulis are nearly identical, showing that the same cancer lineage affects both. Thus, a single transmissible cancer lineage has crossed into two new host species and has been transferred across the Atlantic and Pacific Oceans and between the Northern and Southern hemispheres.

ABSTRACT The yellow clam Amarilladesma mactroides (Deshayes, 1854) is considered a vulnerable species since the mid-1990s. Populations have experienced mass mortalities throughout their entire range of distribution (23-41°S) along exposed [...]

Diphterostomum brusinae (Zoogonidae) is a digenean species that has been recorded worldwide parasitizing marine fishes. Several species have been synonymized with D. brusinae because they lack conspicuous morphological differences. However, due to the breadth of its geographic distribution and the variety of hosts involved in the life cycles, it is likely to be an assemblage of cryptic species. Diphterostomum flavum n. sp. is described here as a morphologically cryptic relative of D. brusinae, in the fish Pinguipes brasilianus (Pinguipedidae) off the Patagonian coast, Southwestern Atlantic Ocean, and its life cycle is elucidated through morphology and molecular analysis. This species uses the gastropod Buccinanops deformis (Nassariidae) as first and second intermediate host with metacercariae encysting within sporocysts. They also, however, use the polychaete Kinbergonuphis dorsalis (Onuphidae) as second intermediate host. No morphological differences were found between adults of D. flavum n. sp. and D. brusinae; however, the number of penetration glands of the cercariae, a diagnostic feature, differed (9 vs. 3 pairs), as well as the ITS2 sequences for the two species. This work provides morphological and molecular evidence of cryptic diversification among species described as D. brusinae, in which the only clear differences are in larval morphology and host spectrum. The strict specificity to the snail acting as the first intermediate host and the variety of fishes with different feeding habits acting as definitive hosts support the likely existence of multiple cryptic species around the world.

ABSTRACT Disseminated neoplasia in cultured Mytilus chilensis (Mytilidae) from the Beagle Channel (Tierra del Fuego Province) in southern Argentina has been detected for the first time. The disease is characterized [...]