Whale lice (Isocyamus deltobranchium & Isocyamus delphinii; Cyamidae) prevalence in odontocetes off the German and Dutch coasts – morphological and molecular characterization and health implications

Abstract

Whale lice (Cyamidae; Amphipoda) are ectoparasitic crustaceans adapted to the marine environment with cetaceans as their host. There are few reports of cyamids occurring in odontocetes from the North Sea, and long-term studies are lacking. Marine mammal health was monitored along the German and Dutch coasts in the past decades, with extensive post mortem investigations conducted. The aim of this study was to analyse archived ectoparasite samples from stranded cetaceans from the North Sea (2010–2019), to determine species, prevalence and impact of ectoparasite infection. Ectoparasites were found on two cetacean species – harbour porpoises ( Phocoena phocoena ), as the most abundant cetacean species in the North Sea, and on a pilot whale ( Globicephala melas ), as a rare species here. Prevalence of ectoparasitic crustaceans in cetaceans was low: 7.6% in porpoises stranded in the Netherlands (n = 608) and 1.6% in porpoises stranded in Germany (n = 122). All whale lice infections were found on hosts with skin lesions characterised by ulcerations. Morphological investigations revealed characteristic differences between the cyamid species Isocyamus (I.) delphinii and I. deltobranchium identified. Isocyamus deltobranchium was determined in all infected harbour porpoises. I. delphinii was identified on only the pilot whale. Molecular analyses showed 88% similarity of mDNA sequences of I. delphinii with I. deltobranchium supporting them as separate species. Phylogenetic analyses of additional gene loci are required to fully assess the diversity and exchange of whale lice species between geographical regions as well as host specificity. Differing whale lice prevalences in porpoises stranded in the Netherlands and Germany could indicate a difference in severity of skin lesions between these areas. It should be further investigated if more inter- or intraspecific contact, e.g., due to a higher density of porpoises or contact with other cetaceans, or a poorer health status of porpoises in the southern North Sea could explain these differences.

Defining a common language to assess external deformities in free‐ranging cetaceans

“…scars deriving from wounds), and some sub‐categories are often correlated (e.g. vesicular and starburst lesions are associated, Barlow et al 2019; skin lesions can be infested with cyamids, Lehnert et al 2021). In general, individuals in poor health are more susceptible to epibionts and more likely to contract additional diseases or get injured (Vecchione & Aznar 2014, Herr et al 2020, Olaya‐Ponzone et al 2020).…”

Epibiotic fauna of the Antarctic minke whale as a reliable indicator of seasonal movements

“…Firstly, B. balaenopterae , transmitted by contact, will be useful for phylogeographic studies, potentially shedding light on intra- and interspecific interactions between whale individuals or populations [see e.g. 23 , 126 , 127 ]. Moreover, the potential relationship of B. balaenopterae prevalence with the population density of balaenopterid whales in the Southern Ocean opens interesting venues to analyze historical whaling data.…”

Deciphering Eurasian otter (Lutra lutra L.) and seal (Phoca vitulina L.; Halichoerus grypus F.) diet: Metabarcoding tailored for fresh and saltwater fish species

“…Carcasses of seals and otters found dead in Schleswig Holstein, Germany, were collected in the frame of research and monitoring projects and submitted for post‐mortem investigations to the Institute for Terrestrial and Aquatic Wildlife Research (ITAW), Büsum (Siebert et al, 2001). They were assigned decomposition status (DCC) based on a five‐point scale with DCC1 being very fresh carcasses, DCC2 fresh, DCC3 good, DCC4 moderate and DCC5 the skeletal remains of animals (Lehnert et al, 2021) and underwent complete necropsy (Lakemeyer et al, 2020; Shanebeck et al, 2020; Siebert et al, 2007).…”