Abstract
BackgroundLittle is known about the life history of oarfish of the genus Regalecus, although it is a famous deep-sea fish and an apparent origin of sea serpent legends. We successfully performed artificial insemination using a recently dead pair of sexually mature individuals. We report for the first time development from fertilized eggs to early larvae in the Lampridiformes.ResultsEggs required 18 days of development from fertilization to hatching under 20.5–22.5 °C conditions. Oarfish larvae had similar morphological features as other lampridiform larvae hatched in the ocean. Larvae typically faced downward and swam using pectoral fins; they frequently opened their mouths. This mouth-opening behavior and swimming ability were both consistent with osteological development. The larvae did not eat and died four days after hatching.ConclusionsThis is the first successful instance of artificial insemination and hatching in the oarfish, as well as the first reliable morphological and behavioral description of lampridiform larvae.
Highlights
Little is known about the life history of oarfish of the genus Regalecus, it is a famous deepsea fish and an apparent origin of sea serpent legends
The tip of the tail was released from the yolk at 9 day after fertilization (DAF), and the heart beats were confirmed with the body development at 11 DAF, when 270 eggs remained (Fig. 2d)
We cannot exclude the possibility that the captive environmental conditions caused this feeding dysfunction. This is the first report of successful artificial insemination in oarfish and provides the first reliable record of development from fertilized eggs to early larval stages in Lampridiformes
Summary
Little is known about the life history of oarfish of the genus Regalecus, it is a famous deepsea fish and an apparent origin of sea serpent legends. We report for the first time development from fertilized eggs to early larvae in the Lampridiformes. Regalecus russelii has a unique morphology and a large body; much of the information about it comes from findings of dead bodies on beaches [2,3,4]. Beyond this basic information, we know little else about oarfish, despite the species being cited frequently as a possible origin of sea serpent and mermaid legends [1, 5]. The only reliable record of the early stages of Regalecus is a report of eggs from the western Pacific, identified using DNA barcoding techniques [8], and a juvenile (13.7 mm in standard length) identified from developed morphological features [9]
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