First in situ observations of the free-floating gelatinous matrix of blackbelly rosefish Helicolenus dactylopterus (Delaroche, 1809)

Abstract

<p>Reproductive mode in blackbelly rosefish, <em>Helicolenus dactylopterus</em>, has been debated since around 1900, and to our knowledge, there is no previous report on free-floating egg masses of <em>H. dactylopterus</em>. Some authors claim a viviparous strategy, others oviparous, or that the species displays a zygoparous or embryoparous form of oviparity. The most recent publications (ovarian studies) consider <em>H</em>. <em>dactylopterus</em> as zygoparous due to release of developing zygotes in the early phases of development. We report on the first free-floating, gelatinous egg mass matrices of <em>H. dactylopterus</em>, observed <em>in situ.</em> The first egg matrix was observed from Haganes, Bergen, Norway on 10 April 2020, at 20 cm depth. Live eggs were mostly of the same size (∼1 mm), and at late blastula stage. Ethanol-preserved eggs were obtained for DNA barcoding, employing sequences from the <em>cytochrome c oxidase subunit I gene</em> (COI). COI showed 100% similarity with sequences of adult <em>H. dactylopterus</em>. The second egg matrix was observed from Drengevika, Sveio on 12 April 2021, while diving at 15 m depth. <em>Helicolenus dactylopterus</em> is previously known for internal fertilization, and the <em>in situ</em> observations of these free-floating matrices, including embryos at late blastula stage, confirms theories of a zygoparous strategy.<br></p>