Ultrastructure of the external sensory apparatus ofGyrodactylus gasterosteiGläser, 1974

Abstract

The aim of this study, therefore, was to investigate the ultrastructure of gyrodactylid sensilla and to ascertain how these may be employed in the colonisation of new hosts using the Gyrodactylus gasterostei Gläser, 1974--Gasterosteus aculeatus L. model. As Gyrodactylus has no specific transmission stage in its life-cycle, movement between hosts must be achieved by strategies employed by the adult. This study suggests that certain sensilla, presented for the first time in Gyrodactylus gasterostei, may serve as chemoreceptors and mechanoreceptors and possible photoreceptors. The results of this study provide photographic data using scanning electron microscope (SEM) and transmission electron microscopy (TEM) concerning the sensory structures that are found on the tegument and in the sub-tegumental zone of G. gasterostei that infect 3-spine sticklebacks (Gasterosteus aculeatus L.). For this reason, it is vital to understand the factors underlying transmission to a new host, and a detailed, ultrastructural examination of the sensory structures that are used may improve current understanding of the receptors that Gyrodactylus species employ to interpret both their host and ambient environments. Such information may assist in the interpretation of transmission behaviors, particularly their responses to chemical or physical cues which gyrodactylids employ in host location during the transmission process.

Transmission Strategies Used by Gyrodactylus gasterostei (Monogenea) on Its Host, the Three-Spined Stickleback Gasterosteus aculeatus

“…No free parasites were observed in the absence of nearby fish, indicating that parasite detachment was due solely attributable to the water turbulence created by the fish. It is possible that parasites may initially detect water movements associated with an approaching host using mechano-chemical and photosensitive receptors [15]. We observed that complex water flows, e.g., the pectoral-fin wake, may improve parasite transmission (see, for example, supplementary video S3).…”

Gyrodactylus gasterosteia difficult meal to swallow for the three-spined sticklebacks,Gasterosteus aculeatusL.

“…Recent studies have demonstrated a detailed ultrastructural examination of the sensory structures that Gyrodactylus species employ to interpret both their host and ambient environments, i.e. water turbulence, particularly their responses to chemical or physical cues which gyrodactylids employ in host location during the transmission process (Grano‐Maldonado, ). Rarely, although not the case for G. gasterostei, Gyrodactylus species may infect a host by swimming in the water column, e.g.…”

“…presence of a daughter in utero or the presence of male copulate organ (MCO) and any behavior in enhancing transmission to new hosts. Recent ultrastructural studies have shown a detailed examination of the sensory structures that Gyrodactylus species employ to interpret both their host and ambient environments (Grano‐Maldonado, ). This study utilizes a novel approach to visualizing transmission via the pharynx and gills, employed the Gyrodactylus gasterostei Gläser, 1974/ Gasterosteus aculeatus L. infection model to examine these questions.…”

Ultrastructure study of the stored lipid reserves in Gyrodactylus gasterostei (Monogenea) using confocal and transmission electron microscopy

“…This experiment follows a previous experiment's methods to evaluate the influence of the maturity of monogenean on host transfer using a parasite–host model. [ 8 9 10 11 12 ] Twenty individual sticklebacks were terminally euthanized with 0.01 M 2-phenoxyethanol (MERCK, Darmstadt, Germany) and placed in individual Petri dishes containing clean water at 10°C. Dead hosts were observed under an Olympus SZ30 stereomicroscope (Tokio, Japan) at different magnifications, with the time at which each gyrodactylid looped off the fish during 60 min being recorded.…”

“…An experimental model with Gyrodactylus gasterostei and the host fish Gasterosteus aculeatus was used for the purposes of this study. This is a simple and successful system to examine the aspects of transmission of parasites from live to dead fish, since Harris[ 7 ] and recently Grano-Maldonado[ 8 9 10 11 12 ] employed this model on the biological and behavioral bases of host selection, gyrodactylid transfer during multiple fish transportation, influence of maturity in transmission routes; this information about parasite migration from the dead host has upgraded knowledge on the management of parasitic diseases.…”