In vertebrates, gonadotropin-releasing hormone (GnRH), which is synthesized in the brain, is a key peptide involved in gonadal maturation regulated by the brain-pituitary-gonadal axis. GnRH isoforms and their primary structures have recently been determined in two species of non-chordates, the octopus (Octopus vulgaris) and sea hare (Aplysia californica), which are mollusks. Octopus and sea hare GnRHs are dodecapeptides that contain the structural core of chordate GnRH; however, chordate GnRHs, including tunicate GnRH, are decapeptides. in this study, we examined a GnRH-like peptide in the swordtip squid, Loligo edulis, to provide information on the structural evolution of GnRH in non-chordates. We isolated the full-length cDNA of a GnRH-like molecule from the central nervous system (CNS) of the squid. The open reading frame of this cDNA encodes a protein of 90 amino acids, which consists of a putative signal peptide, a GnRH dodecapeptide, a processing site, and a GnRH-associated peptide. This architecture is generally conserved in chordates. Compared to octopus GnRH, Squid GnRH is identical in the deduced amino acid sequence of the peptide, and 80.5% similar in base sequence. in a phylogenetic analysis, prepro-GnRHs of octopus, sea hare, and squid were segregated from all chordate prepro-GnRHs, in a group designated GnRHS. The squid prepro-GnRH mRNA was expressed mainly in the CNS. This study is the first report of GnRH cDNA cloning in squid and the third in non-chordates.

Anisakis is a parasite that is found in many marine products and can cause anisakiasis when present in fish consumed raw. The most common way to prevent anisakiasis is to freeze the fish, but this causes a noticeable decrease in the quality of the fish when eaten as sashimi. Although no practical method of killing anisakis other than freezing has been found, we have now succeeded in inactivating anisakis inside the fish meat by repeatedly and instantaneously applying electric current to the fish meat using pulsed power technology. The fish meat was placed in buffer saltwater, and pulsed power was applied multiple times. The immobilization rate was highest when the buffer saltwater was 5 mS/cm. The immobility ratio increased as the number of shots increased. Sensory evaluation of the fish meat after the pulse treatment confirmed that it retained its quality as sashimi. Breaking tests and color measurements were also conducted. We believe that this pulsed power treatment is a useful alternative to freezing as a method for killing anisakis.

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