Metazoan parasites of California sea lions (Zalophus californianus): A new data and review

Abstract

The population of California sea lion Zalophus californianus (CSL) has steadily increased during the last several decades. Despite extensive research addressing CSL biology and ecology performed during the last decades, there has been a minimal number of published papers documenting their parasite fauna. Our objective was to analyze the actual list of the metazoan parasites reported from CSLs and add new data on the age-related differences in the prevalence and biodiversity of the parasite community. There have been 33 species recorded but this study considers only 24 of them valid. Among them, 11 species are specific parasites of CSLs and 13 species are not specific. Additional species represent accidental infections or misidentifications. In total, 6653 helminths and 847 mites were collected and identified from 34 CSLs for this study. Six species of nematodes, Anisakis simplex sensu lato s. l. (prevalence 41%; intensity 7.6), Contracaecum ogmorhini s. l. (38%; 269.6), Pseudoterranova decipiens s. l. (29%; 33), P. azarazi (9%; 2.7), Acanthocheilonema odendhali (15%; 3.5) and Parafilaroides decorus were found. Two species of cestodes, Diphyllobothrium sp. (38%; 8.5) and Anophryocephalus sp. (15%; 14.6) represent novel undescribed species. Two species of trematodes, Apophallus zalophi (18%; 19.7) and Zalophotrema hepaticum (12%; 39.2), and five species of acanthocephalans, Corynosoma obtuscens (68%; 100.8), C. strumosum (53%; 4.6), Andracantha phalacrocoracis (3%; 1), Andracantha sp. (9%; 4.3) and Profilicollis altmani (6%; 8.5) were found. Mites Orthohalarchne attenuata (prevalence 85%) were found in the nasal cavity, while O. diminuata (21%) parasitized in the trachea and bronchi. The highest levels of infection with nematodes and trematodes were found in adult CSLs (3–16 years old), whereas the highest level of infection with acanthocephalans was found in young CSLs (pups and yearlings).

Broad tapeworms (Diphyllobothriidae), parasites of wildlife and humans: Recent progress and future challenges

“…Infection rate in seals can be extraordinarily high, with prevalence reaching up to 100% (Kuzmina et al, 2015, 2018) and with extremely high intensity of infections, especially in Antarctic seals. For example, the Weddell seal ( Leptonychotes weddellii ) is a host of 7 diphyllobothriid species and the mean intensity reported by Yurakhno and Maltsev (1997) reaching an estimated 1,300,000 tapeworms per host (based on examination of 28 individuals).…”

Diphyllobothrium sprakeri n. sp. (Cestoda: Diphyllobothriidae): a hidden broad tapeworm from sea lions off North and South America

“…Synonyms : Diphyllobothrium sp. 1 of Waeschenbach et al [ 4 ], Hermosilla et al [ 24 ] and Kuzmina et al [ 18 ]…”

“…A total of 39 CSLs, 9–10 months to 16 years old, were collected stranded on the Pacific coast of central California (36°57′–38°32′N, 121°95–123°00′W), USA, between 2012 and 2018 (see [ 18 ] for details). CSLs died in the Marine Mammal Center (Sausalito, California, USA) from different causes and were necropsied using a standard procedure [ 26 ].…”

“…Later, several authors reported diphyllobothriids from CSL as Adenocephalus pacificus Nybelin, 1931 (under the names D. glaciale [Cholodkovsky, 1915] or D. pacificum [Nybelin, 1931]) [ 12 – 17 ]. The recent revision of metazoan parasites of CSL considered 24 valid species, including two undescribed tapeworm species [ 18 ].…”

“…The main goal of this article is the description of a new species previously reported as ‘ Diphyllobothrium ’ sp. 1 by Waeschenbach et al [ 4 ], Hermosilla et al [ 24 ] and Kuzmina et al [ 18 ] on the basis of detailed morphological and molecular data.…”