Histological and histochemical characterisation of glands associated with the feeding appendages of Argulus foliaceus (Linnaeus, 1758)

Abstract

Argulus foliaceus (Linnaeus, 1758) is a member of the branchiuran family Argulidae, a group comprising parasitic "fish lice". A. foliaceus is distributed worldwide and causes major economic impacts for cultured freshwater fish globally. The work described in this study was undertaken with the objective of identifying, describing and characterising glands associated with feeding in A. foliaceus. From structural and ultrastructural microscopic studies of A. foliaceus, three types of gland were determined to be associated with the pre-oral spine and mouth tube and were suggested to be involved in feeding activities. Two of these glands, the labial glands and the proboscis glands, appeared to secrete their products via the mouth tube and a third, the spinal gland, was connected directly to the pre-oral spine. The current study confirmed that the pre-oral spine delivers active secretions from the spinal gland, which may aid in immunomodulation, while the tubular labial spines and proboscis glands openings within the mouth tube may serve to enhance the feeding process by delivering salivary components to aid pre-digestion and immune-modulate the host. The suggested functions are supported by histological and histochemical staining, coupled with fluorescent lectin-binding assays, which enabled characterisation of the carbohydrate moieties associated with these glandular tissues.

Stable isotopes reveal contrasting trophic dynamics between host–parasite relationships: A case study of Atlantic salmon (Salmo salar) and parasitic lice (Lepeophtheirus salmonis and Argulus foliaceus)

“…L. salmonis is the most widely investigated species of sea lice due to its substantial economic impact on the salmon industry and its ambiguous transmission potential to wild salmon populations (Boxaspen, 2006; Johnson & Albright, 1992; Wagner et al ., 2007). Similarly, A. foliaceus is a prevalent ectoparasitic crustacean that is a substantial hazard to wild S. salar , as well as a variety of other wild and cultured fish species (AmbuAli et al ., 2019; Sahoo et al ., 2013). To our knowledge, this research provides the first account of the isotopic signals of A. foliaceus .…”

Identification of proteins from the secretory/excretory products (SEPs) of the branchiuran ectoparasite Argulus foliaceus (Linnaeus, 1758) reveals unique secreted proteins amongst haematophagous ecdysozoa

“…may be one of the major components involved in evasion of the host defence mechanisms for ingestion of a successful blood meal. We recently used lectin-binding assays to characterise the A. foliaceus glands and have localised proteins with binding affinity to glycoaminoglycans (GAGs) to the spinal gland [7]. Serpins utilise GAGs for protease inhibition activity including modulation of coagulation [105] so it is likely that the spinal glands secretions are involved in A. foliaceus serpin activity.…”

“…It has been hypothesised that to enable long term host contact and feeding, Argulus spp., like other ectoparasitic arthropods such as ticks and salmon lice (Lepeophtheirus salmonis (Krøyer, 1837)), must secrete a range of pharmacologically active components. These components have been suggested to be produced in the parasite's spinal, proboscis and labial glands and to be delivered through the preoral spine and the mouth tube to facilitate blood-feeding [7,8]. Argulus spp.…”

Identification of Transcripts Relating to Host-parasite Interactions and Feeding-associated Activities Through De Novo Transcriptome Sequencing of Branchiuran Fish Lice, Argulus Foliaceus (Linnaeus, 1758) and Argulus Coregoni Thorell, 1865

“…For A. foliaceus four different sample types were extracted; a whole adult male, a whole adult female, a pool of mixed juvenile stages and a pool of six dissected pieces from adult parasites. The latter comprised tissue taken from the expected position of the pre-oral spine gland and proboscis glands as established from histological sections [18]. Equal amounts of RNA from the four sources were used.…”

“…This program was run using the parameters option "ILLUMINACLIP". Deconseq v0.4.3 program [18] was used to remove any sequence contamination. For this, reads were mapped against different databases.…”