Morphology and microchemistry of abnormal otoliths in the ayu, Plecoglossus altivelis

Abstract

The sagittal otolith morphology and microchemistry of reared juvenile ayu, Plecoglossus altivelis, were examined to describe the occurrence and microchemical characteristics of the abnormal otoliths in this species. Juvenile ayu (N=31) were collected in June 2004 at three different locations, Wakayama, Kumamoto, and Biwa Lake in Japan, where they were being reared in freshwater aquaculture ponds after having been collected in the wild as larvae. Otolith abnormality was found in the sagittae of 26% (N=8) of the individuals examined, of which five fish had abnormal otoliths only on one side, while the otolith on the other side was normal. Abnormal otoliths were more transparent and crystalline in appearance with irregular shapes compared to normal ones that were more opaque and less irregular. Abnormal otoliths were divided into two types, semi-abnormal (Type 1) with a normal part in the center, and fully-abnormal (Type 2) that were completely crystalline in appearance. The line transects and whole otolith concentration maps showed that the contents of Sr, Na and K were lower in the abnormal otolith regions compared to the normal ones, while those of Ca and S were almost constant in both. The appearance and microchemical properties of the abnormal ayu otoliths were similar to the abnormal otoliths in other species in which vaterite replaces the aragonite. Abnormal formation of otoliths occurred in ayu from Biwa Lake (30%) and Kumamoto (45%), while the Wakayama samples had no abnormality. The microchemical analyses of the normal and abnormal otoliths indicated that some abnormal otoliths had formed before the fish were captured and transferred to the hatchery, so the possible causes of otolith abnormality in ayu are discussed.

Morphological and biochemical analyses of otoliths of the ice‐fish Chionodraco hamatus confirm a common origin with red‐blooded species

“…A vateritic asteriscus is frequent in several teleosts (Lowenstam & Weiner, 1989;Campana, 1999;Falini et al 2005;Lenaz et al 2006), whereas a vateritic sagitta is characteristic of ancient species such as Ciclostomata, Polypterus and sturgeons (Carlstrom, 1963). It is, however, occasionally present as an abnormality (Gauldie, 1986;Ma et al 2007) or in juvenile (Tomàs et al 2004;Sweeting et al 2004) samples. Its constitutive presence in adults of a modern Notothenioid cannot be related to external factors such as stress or infections (Iguchi et al, 2003).…”

“…Its constitutive presence in adults of a modern Notothenioid cannot be related to external factors such as stress or infections (Iguchi et al, 2003). Rather, local changes in Sr, Na and K concentrations (Gauldie, 1986(Gauldie, , 1996Tomàs & Geffen 2003;Ma et al 2007) or the occurrence of a genetic mutation provide a better explanation. In the Chinook salmon, for example, it has been demonstrated that vaterite replacement is under single-locus genetic control and that this may be overridden by temperatures above or below an optimum range (Gauldie, 1986;Gauldie & Nelson, 1988).…”

Fantastically plastic: fish larvae equipped for a new world

“…; Tomas & Geffen ; Ma et al . ). The shift from aragonite to vaterite formation is linked to changes in the protein matrix.…”

“…Vaterite otoliths have also been observed occasionally in individuals instead of aragonite, and this substitution of morph may be linked to fish condition and especially welfare in the aquaculture environment (David et al 1994;Tomas & Geffen 2003;Sweeting et al 2004;Oxman et al 2007). Vaterite otoliths are more prevalent in aquaculture fish, occurring with a frequency of 50-80% of hatchery fish in some cases, compared with 3-20% in samples of wild fish (David et al 1994;Bowen et al 1999;Tomas & Geffen 2003;Ma et al 2008). The shift from aragonite to vaterite formation is linked to changes in the protein matrix.…”

Asteriscus v. lapillus: comparing the chemistry of two otolith types and their ability to delineate riverine populations of common carp Cyprinus carpio

“…The structure of vaterite differs markedly from aragonite, with the former typified by decreased density (Tomás & Geffen, 2003), increased translucency (Tomás et al , 2004; Ma et al , 2008) and less defined growth increments (Melancon et al , 2005; Tzeng et al , 2007). Biomineralization of these polymorphs may be physiologically (Gauldie, 1993; Bowen et al , 1999) or genetically (Gauldie, 1993; Brown & Severin, 1999; Söllner et al , 2003) controlled and related to spatially non‐uniform protein and chemical gradients in the surrounding endolymph (Payan et al , 1999).…”