CASA in invertebrates

Abstract

Sperm movement has been described in several phyla of invertebrates. Yet, sperm motility has only been quantified using computer-aided sperm analysis (CASA-Mot) in externally fertilising species (broadcast spawners) of two phyla, molluscs and echinoderms. In the present study we quantified in detail the nature of the sperm tracks, percentage motility groupings and detailed kinematics of rapid-, medium- and slow-swimming spermatozoa in the oyster Crassostrea gigas and four species never previously studied by CASA-Mot, namely the molluscs Choromytilus meridionalis, Donax serra and Haliotis midae and the echinoderm Parechinus angulosus. A feature common to all these species are the helical tracks, the diameter of which seems to be species specific. Using CASA-Mot, the behaviour of spermatozoa was also studied over time and in the presence of egg water and Ca2+ modulators such as caffeine and procaine hydrochloride. For the first time, we show that hyperactivation can be induced in all species in the presence of egg water (sea water that was mixed with mature eggs and then centrifuged) and/or caffeine, and these hyperactivated sperm tracks were characterised using CASA-Mot. We relate the different patterns of sperm motility and behaviour to reproductive strategies such as broadcast spawning and spermcasting, and briefly review studies using CASA-Mot on other invertebrates.

Optimizing cryopreservation of sea cucumber (Apostichopus japonicus) sperm using a programmable freezer and computer-assisted sperm analysis

“…The acquisition parameters were set as follows: frame rate = 60/s; total captured images = 60; microscope 100x magnification. We analyzed the following semen characteristics using the CASA system: a) sperm density (SD): the number of spermatozoid(spz) per unit volume in semen (spz/mL); b) sperm motility rate (SMR): motile sperm count as a percentage of total sperm count; c) sperm curvilinear velocity (VCL-tm, µm/sec): the ratio of the distance traveled by the sperm along the two-dimensional movement curve seen in the microscope to time; d) straight line velocity (VSL-tm, µm/sec): the average of the straight-line distance traveled by the sperm in the tested time range versus the time value; and e) beat cross frequency (BCF): whips per second) (Fabbrocini et al, 2016;Van Der Horst et al, 2018).…”

Polystyrene Nanoplastics in Aquatic Microenvironments Affect Sperm Metabolism and Fertilization of Mytilus galloprovincialis (Lamark, 1819)

“…The sperm cell of bivalves is activated, following spawning, upon contact with seawater through the action of various chemical signals, including pH, ions, and cyclic nucleotides [53,54]. Once activated, the generation of an asymmetric oscillation of flagellum creates a curvilinear trajectory, interspersed with small linear segments [55,56]. The disturbance of the microenvironment, mainly caused by pollutants, could result in a change in swimming behavior [57].…”

Comparative toxicity of ionic and nanoparticulate zinc in the species Cymodoce truncata, Gammarus aequicauda and Paracentrotus lividus

“…Due to the rapid and wide solubilization of ZnO NPs at the concentrations used in this study, the sea urchin sperms and embryos have been exposed to solubilized Zn 2+ throughout the entire assay, and, consequently, the toxicity of ZnO NPs may be largely attributed to the dissolution of Zn ions into seawater. Motile sperm tests did not show a clear concentration–response when exposed to ZnO NP suspensions, only VCL (curvilinear velocity) being slightly affected by the exposure, while the other endpoints as lateral head displacement (ALH, depending on active sperm motility) and beat-cross frequency (BCF, depending on the flagellar beating) (Gallego et al 2014 ; van der Horst et al 2018 ) seemed not affected, indicating no clear alteration of both the structural integrity of the sperm cell and to the physiology of sperm movement.…”