This study reports an effective and simple method for culturing the comb jellyfish, Beroe cucumis. The method for breeding another comb jelly, Bolinopsis mikado, was published by Ikeda et al. (2022), in which Bolinopsis mikado was bred stably and in large numbers, and then provided as food to developing Beroe cucumis. Fertilized eggs were found in a 235-L tank two days after five parental Beroe cucumis were housed in the tank, and the parental individuals were isolated from the tank the next day. The day after the eggs were found, Beroe cucumis larvae (0.54 ± 0.04 mm long (n = 9)) were observed in the tank daily and were fed Bolinopsis mikado. The Beroe cucumis larvae were only fed Bolinopsis mikado during the early stages of development. They reached a total length of approximately 10 mm in 17 days, and by day 20, when most had grown large (approximately 12 mm and over) enough to not pass through the 3-mm perforated plates, they were moved to a 145-L display tank. Thereafter, they were reared in the same manner and were successfully propagated cumulatively for more than five generations. The greatest advantage of this culture method is that the larvae need only be fed and observed until they reach the size required for display. Therefore, stable breeding of Beroe cucumis can be achieved by feeding its larvae with Bolinopsis mikado, reducing labor and stress on the organisms from frequent water changes.

In this work, staurozoans of two distinct morphotypes are reported in Kitsunezaki (Ishinomaki City, Miyagi, Japan) in the years following the Great East Japan Earthquake and Tsunami. Staurozoa specimens were collected from Eisenia and Gelidium macroalgal beds at the Kitsunezaki survey site (October 2019–July 2021). Morphological observations indicated that the Kitsunezaki staurozoans represented two species, Haliclystus inabai and Calvadosia nagatensis, but molecular analyses of the genetic markers 16S rRNA and COI suggested that the former actually encompasses two distinct lineages, H. inabai and a cryptic as yet unnamed species. Phylogenetic analysis reveals the two H. inabai lineages are separated by significant divergences for both gene markers. H. inabai lineage 1 includes specimens sampled with molecular sequences from Hokkaido (Japan) and Kitsunezaki (Japan), whereas H. inabai lineage 2 includes sequences from Victoria (Australia), Kitsunezaki, as well as populations that appeared in a lab in Germany and aquariums in Tsuruoka and Kagoshima (Japan) and Québec (Canada). Conversely, C. nagatensis from Kitsunezaki appears to be a species distributed only in the temperate NW Pacific. Observations on early life stages of H. inabai lineage 2 within aquarium tanks permitted confirmation of the presence of “microhydrula” settled larva, frustules, and elongated settled larvae. C. nagatensis was collected from the Kitsunezaki survey site in warm months only, and always exhibited gonads, while H. inabai stauromedusae were collected in most months throughout the year, with gonads usually present irrespective of season. An extensive literature review covering more than 100 years and observations in this study revealed seaweed and seagrass as the primary substrates for these two Staurozoa species. Our findings show C. nagatensis is associated with just two types of algal substrates and seagrass, while H. inabai has a much broader substrate preference, consistent with its wider geographic distribution. These findings have contributed to our understanding of Staurozoa epibiotic associations in exposed bays during the recovery period following a major natural disaster.

This paper reports an effective and easy method to culture the ctenophore Bolinopsis mikado. Fifteen adult B. mikado individuals were maintained in a kreisel tank, and fertilized eggs, which were detected in the following days, were all raised together in the same tank. From the early development stage to day 13, the B. mikado cydippid larvae were only fed Artemia nauplii. The cydippid larvae were able to easily catch the Artemia nauplii excreted by adult B. mikado; therefore, they were considered capable of growing on excrement. Adult B. mikado individuals were removed from the tank when the cydippid larvae reached approximately 5 mm in length (day 14). The cydippid larvae were then transferred to a circular tank with a water spray chamber. Approximately 21 days after the early development stage, cydippid larvae had grown to lengths of approximately 20 mm and were then bred in the same manner up to the 5th generation. The greatest advantages of this culture method are that it is less cumbersome and only requires feeding and observation until the cydippid larvae attain a size that enables them to pursue live Artemia nauplii. Thus, damage to the living body due to water exchange and the labor involved are reduced, thereby allowing stable breeding of B. mikado.

Mastigias jellyfish (“tako kurage”) have been reported throughout littoral Japan for over a century, historically identified by morphology alone as Mastigias papua. Molecular resolution of the genus in 2018 revealed three geographically structured clades and suggested Japanese populations instead belong to M. albipunctata, but subsequent morphology-only studies of Japanese specimens have continued to apply the M. papua designation, leaving species identity unresolved across much of the species’ Japanese range. Here, we use cytochrome c oxidase subunit I (COI), combining published GenBank sequences with two newly collected specimens from Okinawa, the southernmost extent reported in Japan. Maximum-likelihood and Bayesian phylogenetic reconstruction recovered three reciprocally monophyletic clades consistent with previous molecular work, with all Japanese sequences, from Sukumo Bay (Shikoku Island) to Okinawa Island, falling within the M. albipunctata clade. Morphological comparison against published diagnostic characters showed consistency with this identification. These results indicate that Mastigias populations in Japan are consistently identified as M. albipunctata, while highlighting the value of molecular analysis in tandem with morphology-based identification approaches.