Advancing the knowledge of the nematode Echinocephalus pseudouncinatus (Gnathostomatidae, Spirurida): Morphological and molecular identification, new host, and host specificity in two coexisting pen shells (Bivalvia: Pinnidae).

The life cycle of Echinocephalus pseudouncinatus has not been described in detail to date, as is also the case of other species in the genus. This study contributes to the information available about the life history of the genus, particularly E. pseudouncinatus, by (1) using molecular techniques (small subunit rRNA gene [SSU rRNA] sequences) to identify larvae of this species; (2) describing the most conspicuous morphological characteristics that distinguish the species by scanning electron microscopy; (3) describing histological characteristics of the internal anatomy of larvae and the lesions caused by them in the gonads of hosts; (4) reporting new host and reporting evidence of host specificity of E. pseudouncinatus between two species of edible pen shells coexisting in the northern Pacific of Mexico; and (5) analyzing the frequency of infested gonads by host sex, size, and gonadal development stage. The molecular analysis confirmed the morphological and histological diagnosis of E. pseudouncinatus larvae infesting gonads of Atrina maura and Pinna rugosa in Ojo de Liebre and San Ignacio lagoons. The morphological characterization of larvae provides internal details of the cephalic bulb (including rows of hooks and ballonets), neural chord, and cell types of the body wall. Histopathological findings such as degenerated and atretic gametes and the displacement of gonadal tissue in hosts infested with E. pseudouncinatus larvae are discussed in terms of temperature anomalies caused by the "Godzilla El Niño". The frequency of infestation increased with shell length and gonadal development in A. maura, with a higher infestation frequency in females versus males observed at both study sites. Our findings expand the list of hosts of E. pseudouncinatus, which was previously unknown as a parasite of P. rugosa. In P. rugosa, infestation frequencies are noticeably lower (<1 %) compared with those observed in A. maura (>30 %) at both study sites, suggesting host-specific requirements or preferences in E. pseudouncinatus larvae.

Is There a Risk to Humans from Consuming Octopus Species from Sites with High Environmental Levels of Metals?

Although octopuses are in high-demand globally and can bioaccumulate high concentrations of metals, the risk associated to its consumption is poorly understood. We compiled literature data from eight locations in Europe, North America and Northern Africa with different environmental levels of metals to evaluate: (1) the risk to human health through consumption of muscle tissues and digestive glands of Octopus hubbsorum, O. vulgaris and Eledone cirrhosa, and (2) the maximum allowable consumption rates (CRlim). The assessments were done according the United States Environmental Protection Agency. The results indicate the absence of health risk through consumption of muscle tissues, and high health risk through consumption of digestive glands (attributed to its high Cd levels), reflected in its 1ow CRlim values. In conclusion, even in contaminated sites the consumption of octopus muscle tissues is not an issue of concern, while the consumption of digestive glands should be more carefully monitored to avoid health problems.