title: Malacobdella arrokeana: Parasite or Commensal of the Giant Clam Panopea abbreviata?
abstract: We examined trophic relationship between the nemertean Malacobdella arrokeana and its host, the edible geoduck Panopea abbreviata by studying the diets of both species by direct (stomach contents) and indirect methods (stable-isotope analysis of C and N). In addition to these methods, the feeding behavior of M. arrokeana within the host and the morphology of its feeding organs were examined. The feeding behavior of M. arrokeana did not exhibit parasitic characteristics, and the proboscis morphology indicates it is unable to injure host tissues. Analysis of stomach contents revealed a diet consisting mainly of microalgae and diatoms. Panopea abbreviata and M. arrokeana shared similar trophic levels, presenting no differences in the spread of the isotopic niches and high overlap (SEAB overlapped 63%). Consistent with this, our results showed no differences in δ(15)N or δ(13)C values between the two species. The combination of direct and indirect approaches revealed that M. arrokeana has a diet similar to that of its host, confirming a commensal relationship.
authors.affiliation: 1 LARBIM-IBIOMAR, Centro Nacional Patagónico (CENPAT-CONICET). Bvd. Brown 2915, U9120ACV Puerto Madryn, Chubut, Argentina.|2 Facultad de Ciencias Naturales, Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), Bvd. Brown 3100; U9120ACV Puerto Madryn, Chubut, Argentina.
authors.forename: José E F
authors.initials: JE
authors.lastname: Alfaya
authors.affiliation: CESIMAR, Centro Nacional Patagónico (CENPAT-CONICET). Bvd. Brown 2915, U9120ACV Puerto Madryn, Chubut, Argentina.
authors.forename: David E
authors.initials: DE
authors.lastname: Galván
authors.affiliation: 4 Museo Nacional de Ciencias Naturales (MNCN-CSIC). José Gutiérrez Abascal, 2. 28006 Madrid, Spain.
authors.forename: Annie
authors.initials: A
authors.lastname: Machordom
authors.affiliation: 5 Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-CONICET), Av. A. Gallardo 470 (C1405DJR), Buenos Aires, Argentina.
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Penchaszadeh
authors.affiliation: 1 LARBIM-IBIOMAR, Centro Nacional Patagónico (CENPAT-CONICET). Bvd. Brown 2915, U9120ACV Puerto Madryn, Chubut, Argentina.|2 Facultad de Ciencias Naturales, Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), Bvd. Brown 3100; U9120ACV Puerto Madryn, Chubut, Argentina.
authors.forename: Gregorio
authors.initials: G
authors.lastname: Bigatti
mesh_terms: D000818:Animals; D005247:Feeding Behavior; D007448:Invertebrates / Q000145:classification* / Q000502:physiology* / Q000648:ultrastructure; D013045:Species Specificity; D013559:Symbiosis
keywords: Hoplonemertea; bivalves; commensal nemertean; diet; feeding behavior; proboscis morphology; stable isotopes