Corynosoma magdaleni in Gray Seals from the Gulf of Bothnia, with Emended Descriptions of Corynosoma strumosum and Corynosoma magdaleni

Abstract

Because of the likelihood that Corynosoma magdaleni Montreuil, 1958. has been confused with C. strumosum (Rudolphi, 1802) in reports of parasites from seals and to clarify its distribution in the Baltic Sea, acanthocephalans from 26 young gray seals from the southwestern Finnish archipelago (western Baltic Sea) were examined. All harbored C. semerme (Forssell. 1904). In addition to C. semerme, 12 had both C. strumosum and C. magdaleni, 3 had only C. strumosum, and 9 had only C. magdaleni. Most anatomical structures of C. strumosum are similar to, but larger than, those of C. magdaleni. The most conspicuous differences are the longer and more robust trunk of C. strumosum, the routinely longer proboscis (mean, 653 vs. 476 microm) and larger proboscis hook (mean, 69 vs. 58 microm) of C. strumosum, and the greater extent of ventral trunk spines (mean, 61 vs. 47%) in C. magdaleni. In addition, C. strumosum consistently possesses 18 longitudinal rows of proboscis hooks, whereas C. magdaleni has 17-23, with 20 being the usual number by far. In seals aged 3.6 mo, on average, C. strumosum was more prevalent and abundant than was C. magdaleni, whereas in seals of age 2.0-3.0 mo the reverse was true, with C. strumosum being nearly absent. These differences might reveal the age-dependent food habits of the very young seals. No site segregation was found between C. strumosum and C. magdaleni in the small intestine, but they clearly segregated from C. semerme, which occurred mainly in the cecum, large intestine, and rectum. All species matured equally well in gray seals, with 62, 67, and 53% of the C. magdaleni, C. strumosum, and C. semerme, respectively, comprising gravid worms (possessing eggs with fully formed acanthors).

Habitat selection and populations ofCorynosoma(Acanthocephala) in the intestines of sea otters (Enhydra lutris) and seals

“…The genus is a wide-reaching group; C. strumosum and C. enhydri are the closest related members of Corynosoma and share a recent common ancestor, likely first evolving in seals as they predate otter evolution in the ocean (García-Varela et al ., 2005; Rybczynski et al ., 2009). In Europe, another member of the genus, C. semerme , also commonly infects seals (Nickol et al ., 2002). Although closely related, C. enhydri , C. strumosum and C. semerme vary significantly in size, body shape and proboscis morphology (Hennessey & Morejohn, 1977; Nickol et al ., 2002).…”

“…In Europe, another member of the genus, C. semerme , also commonly infects seals (Nickol et al ., 2002). Although closely related, C. enhydri , C. strumosum and C. semerme vary significantly in size, body shape and proboscis morphology (Hennessey & Morejohn, 1977; Nickol et al ., 2002). Corynosoma enhydri is the largest, with a maximum size of around 29 mm (Hennessey & Morejohn, 1977), while C. strumosum peaks at 9 mm and C. semerme at 2 mm (Nickol et al, 2002), and infect different portions of the intestine (Nickol et al ., 2002; fig.…”

“…Prevalence of infection with C. enhydri in southern sea otters has been seen at 90% (Hennessey & Morejohn, 1977) and 94.4% (Mayer et al ., 2003), while northern sea otters were observed to have a prevalence of 51% (Margolis et al ., 1977). Prevalence of Corynosoma infections in seals showed strong variability in geographic location and, over time, measured 56% in the Baltic ( n = 26) (Nickol et al ., 2002), 23% in the Wadden Sea ( n = 23) (Lehnert et al ., 2007), 87.5% in Japan ( n = 40) (Kaimoto et al ., 2018), 100% in Ireland ( n = 26) (O'Neill & Whelan, 2002) and 29.5% in Alaska ( n = 105) (Kuzmina et al ., 2012). This difference may be due to host species location, diet and availability of fish intermediate hosts (Nickol et al ., 2002).…”

“…Clustering of Corynosoma species within microhabitats of the intestine has been reported (Helle & Valtonen, 1981; Valtonen & Helle, 1988; Nickol et al ., 2002; Kaimoto et al ., 2018). The gastrointestinal (GI) tract offers a range of physiochemical gradients, microbiota, immune factors and intraspecific parasite competition for niche differentiation (Berrilli et al ., 2012).…”

“…Corynosoma strumosum in seals tend to congregate just past the midgut, and C. semerme has adapted to life in the nutrient-poor colon of seals (Helle & Valtonen, 1981; Nickol et al ., 2002; Kaimoto et al ., 2018). These two species differ in size and proportion, with C. semerme being smaller and stouter, with a shorter trunk than C. strumosum (Valtonen & Helle, 1988).…”