Category: Research

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Comparative gonadal histology reveals complex reproductive traits in Cubozoa (Cnidaria: Medusozoa) – Frontiers –

New Lab Publication, Led by Dr. Jimena Garcia-Rodriguez

Cubozoa, a relatively small class within Medusozoa (Cnidaria), is distinguished by its complex sexual behaviors, setting it apart from other medusozoan classes. However, reproductive traits and seasonality remain poorly characterized for many species, largely due to difficulties in obtaining specimens. In this comparative histological study we describe the reproductive tissues (gonads) of males and females at multiple maturity stages across 15 cubozoan species, representing two orders, seven families, and eight genera. We document several reproductive traits: (1) variation in oocyte shape, including polygonal oocytes; (2) unidentified cytoplasmic inclusions within oocytes suggestive of undescribed component of vitellogenesis; (3) swollen gonadal structures in mature males, hinting at an uncharacterized spawning mechanism; and (4) a diverse repertoire of nematocysts within gonadal tissues, including putative nematoblasts in species of both cubozoan orders, indicating distinct developmental pathways for these organelles. Ancestral state reconstruction of three reproductive characters, viz. oocytes with unidentified cytoplasmic inclusions, the presence of nematocysts in gonads, and fertilization mode, suggests that all but the latter likely evolved independently within Cubozoa. By uncovering and characterizing these novel sexual traits in cubozoan jellyfishes, this study provides fundamental baseline data for comparative analyses aimed at elucidating the diversity and evolution of reproductive strategies across medusozoan taxa and their roles in spawning aggregations, also known as jellyfish blooms.

Access the full publication here

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Chironex box jellyfishes (Cnidaria: Cubozoa: Chirodropida) in Singapore: Chironex blakangmati, new species, and range extension of C. indrasaksajiae

New Discovery: A New Species of Deadly Box Jellyfish Uncovered!

Iffah Iesa, Cheryl Lewis Ames, Nicholas Wei Liang Yap & Danwei Huang

Abstract. Two venomous box jellyfish species of the genus Chironex Southcott, 1956 (Cnidaria: Cubozoa: Chirodropida) were collected from Singapore’s coastal waters: Chironex indrasaksajiae Sucharitakul, 2017 and a novel species described herein as Chironex blakangmati, new species.
Chironex indrasaksajiae was collected from both the Johor and Singapore Straits around mainland Singapore. Chironex blakangmati, new species, was collected from Sentosa Island along the Singapore Strait and is the fourth species described in the genus. While C. blakangmati’s volcano-shaped pedalial canal and tentacle number are similar to C. yamaguchii Lewis & Bentlage, 2009, its elongated, sharp-tipped velarial canals and DNA sequences distinguish it from other Chironex species. Comparisons of Chironex blakangmati, new species, with C. yamaguchii and C. fleckeri
reveal novel morphological differences at the terminal end of the perradial lappet along the velarium edge, where C. blakangmati, new species, lacks velarial canals extending from the perradial lappet terminus. Juvenile Chironex yamaguchii specimens were examined and ontogenetic variations of velarial canals are herein reported. Preliminary cnidome analysis reveals eight types of nematocysts observed in C. blakangmati, new species, five types in C. indrasaksajiae, and five types in C. yamaguchii. Molecular phylogenetic reconstruction places C. blakangmati, new species, in a clade distinct from its congeners, as sister group to C. yamaguchii based on 16S rRNA gene analysis but diverging earlier than the clade comprising C. yamaguchii and C. indrasaksajiae based on cytochrome c oxidase subunit I gene analysis for which sequence data are comparatively limited. Understanding the biodiversity and seasonality of venomous cubomedusae will help mitigate the risk they pose to human health and safety during maritime activities.

Read the full article here: Raffles Bulletin of Zoology

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New Research: A comparative molecular study of rhizostome jellyfishes from Japan reveals variability in Symbiodiniaceae taxon associations and cassiosome production.

Led by Kei Chloe Tan , this study dives deep into the complex world of Rhizostomeae that play massive roles in Asian ecology and industry.

What makes these jellies unique?

Rhizostome jellyfishes are unlike your average medusa. They don’t have long, trailing tentacles neither other structures at the eadg of theyr bell; they have eight highly branched oral arms, along which there are suctorial minimouth orifices.

Our study focused on three main goals:

  • Identity: Using DNA barcoding to accurately identify species in Japanese waters.
  • Partnership: Mapping which types of algae live inside which jellyfish.
  • The Sting: Identifying which species produce cassiosomes—the “mucus grenades” responsible for the mysterious “stinging water” syndrome.

Key Discoveries

  • A New Neighbor: We discovered that Cassiopea (Upside-down jellyfish) found in Kagoshima likely represents a new, undescribed species.
  • Symbiotic Flexibility: We found that these jellyfishes are “plastic” in their partnerships, meaning the same species of jellyfish can host different types of algae (Symbiodinium, Cladocopium, or Durusdinium) depending on the individual.
  • The “Grenade” Evolution: We confirmed that cassiosome production is a unique trait of the suborder Kolpophorae. Interestingly, we found that young jellies might not produce them until they reach a certain developmental stage.

“This research provides a baseline for understanding how jellyfish and algae co-evolve, helping us manage coastal ecosystems and the jellyfish fisheries that are so vital to the region.” — Chloe Tan, Lead Author

Lab Work in Action

This paper wasn’t just about sequences; it combined advanced molecular techniques with classic microscopy.

  • Tandem DNA Amplification: Chloe developed a new method to simultaneously sequence the DNA of both the jellyfish host and its tiny algal residents.
  • Microscopy: We captured high-resolution images of the cassiosomes—clusters of stinging cells (nematocysts) with algae at their core—proving exactly how these “contactless stings” work.

Read the Full Paper

Interested in the molecular data or the high-resolution phylogenetic trees? You can find the full study here:

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Physalia mikazuki sp. nov. (Phylum Cnidaria; class Hydrozoa) blown into Japan’s northeast (Tohoku) at the whim of marine ecosystem change

Researchers in Japan Discover New Jellyfish Species Deserving of a Samurai Warrior Name

A groundbreaking study co-authored by Cheryl Lewis Ames, Chanikarn Yongstar, Kei Chloe Tan, Ayane Totsu, and colleagues, has led to the identification of a new species of Portuguese Man-of-War (Physalia mikazuki sp. nov.) found in the waters of northeastern Japan (Tohoku).

The research, which also contou com Yoshiki Ochiai, Muhammad Izzat Nugraha, e Waka Sato-Okoshi, attributes the sudden presence of this new species in the temperate region to significant marine ecosystem changes. This discovery is vital for understanding how environmental shifts—such as changes in currents and climate—are forcing the global redistribution of marine organisms.

The findings emphasize the urgent need to monitor these shifts to protect marine biodiversity.

  • Authors: Chanikarn Yongstar, Yoshiki Ochiai, Muhammad Izzat Nugraha, Kei Chloe Tan, Ayane Totsu, Waka Sato-Okoshi, Cheryl Lewis Ames

Find the original scientific paper here:

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Dr. Ames’s research

As an experienced research scientist, teacher and mentor, Dr. Ames employs a combination of molecular and morphological tools to address major scientific questions in the fields of behavior, ecology, evolution and systematics. Her research focuses on venomous box jellyfish and seeks to further understanding of this cosmopolitan aquatic organism.

Cheryl has extensive field research experience having worked around the world including in the United States, Canada, Japan, and numerous tropical and subtropical regions. She has a demonstrated ability to collaborate with top-level government and academic researchers and obtain funding for multidisciplinary research projects. While designing experiments and conceiving ideas for publications, she strives to develop projects that strike an even balance between fundamental and applied marine biology.

A selected list of major research works appears below. For a full list of all of her work and more information about her research please visit her Research Gate profile.

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Pathways to an integrated understanding of marine environments and ecosystems in the Asia-Pacific Region

Figure 1. Trends of (A) sea surface height from 1993 to 2022 and (B) sea surface temperature from 1982 to 2023. (C) Average scores of Ocean Health Index (OHI) components in the APR. The error bars indicate one standard deviation of the annual mean. (D) Trends of OHI components in the APR from 2012 to 2023. (E) Average scores of the biodiversity component of the OHI. (F) Trend of the biodiversity component from 2012 to 2023. The trends are calculated by using linear regression. The black box (93°E-120°W, 60°S-45°N) indicates the APR

The Asia-Pacific Region (APR) is a global hub of marine biodiversity, essential for global ecological stability and climate regulation. However, its ecosystems from extensive commercial fisheries to vital coral reefs face growing threats due to intense resource extraction and extreme climate events, such as marine heatwaves.

This Perspective article, led by an international collaboration (including Dr. Cheryl Ames), is the result of a seminar and workshop held at Tohoku University (Japan) in 2023. The goal was to address substantial barriers—including the vast diversity of cultures, languages, and management practices—that impede cross-national research efforts in the region.

The article concludes that these efforts are urgent and essential for supporting science-based policies and decisions, capable of confronting the escalating effects of climate change on the Pacific Asian marine systems.

“Without shared, high-quality data, our ability to detect patterns, predict outcomes, and guide effective action remains severely constrained.”

“A productive way forward is to build on regional initiatives that are already redefining how marine science is approached in the Asia-Pacific. This effort aligns with the goals of the World Premier International Research Centre Initiative-Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), recently established at Tohoku University and Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and a satellite campus at the University of Hawai’i, Manoa. WPI-AIMEC brings together researchers across disciplines to better understand and forecast marine ecosystem responses to environmental change, with a global scope but a particular focus on the Northwest Pacific.”

Find the Full Paper at Frontiers in Marine Science

Find more articles related to WPI-AIMEC

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Raising Awareness of the Severity of “Contactless Stings” by Cassiopea Jellyfish and Kin

Current doctrine on jellyfish stings largely focuses on physical contact with a jellyfish. In rhizostome medusae capable of extruding agglomerations of nematocysts within mucus, physical contact is not necessary for skin irritation and pain. Here we highlight pain and symptoms reported by researchers and aquarists working with water around Cassiopea and several other jellyfish. We conclude that Cassiopea, long thought to be harmless, can lead to multi-day pain and rashes experienced largely as burning and itching sensations along entire limbs. We suggest that recommendations on sting avoidance expand to include consideration of these contactless stings so as to limit a previously under-publicized vector of envenomation.

Click here to access the full article.

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The role of taxonomic expertise in interpretation of metabarcoding studies

The performance of DNA metabarcoding approaches for characterizing biodiversity can be influenced by multiple factors. Here, we used morphological assessment of taxa in zooplankton samples to develop a large barcode database and to assess the congruence of taxonomic identification with metabarcoding under different conditions. We analysed taxonomic assignment of metabarcoded samples using two genetic markers (COI, 18S V1–2), two types of clustering into molecular operational taxonomic units (OTUs, ZOTUs), and three methods for taxonomic assignment (RDP Classifier, BLASTn to GenBank, BLASTn to a local barcode database). The local database includes 1042 COI and 1108 18S (SSU) barcode sequences, and we added new high-quality sequences to GenBank for both markers, including 109 contributions at the species level. The number of phyla detected and the number of taxa identified to phylum varied between a genetic marker and among the three methods used for taxonomic assignments. Blasting the metabarcodes to the local database generated multiple unique contributions to identify OTUs and ZOTUs. We argue that a multi-marker approach combined with taxonomic expertise to develop a curated, vouchered, local barcode database increases taxon detection with metabarcoding, and its potential as a tool for zooplankton biodiversity surveys.

Click here to access the full article.

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Cassiopea upside-down jellyfish in Key Largo mangrove forest waters (Florida Keys, USA)

Video showing footage of Cassiopea upside-down jellyfish in Key Largo mangrove forest waters (Florida Keys, USA). Water samples were taken from this collection site during a jellyfish environmental DNA (eDNA) metabarcoding study by Ames et al. 2021, published in Frontiers of Marine Science. Copyright A.C. Morandini (coauthor on the study) “Fieldable Environmental DNA Sequencing to Assess Jellyfish Biodiversity in Nearshore Waters of the Florida Keys, United States”

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Fieldable Environmental DNA Sequencing to Assess Jellyfish Biodiversity in Nearshore Waters of the Florida Keys, United States

Recent advances in molecular sequencing technology and the increased availability of fieldable laboratory equipment have provided researchers with the opportunity to conduct real-time or near real-time gene-based biodiversity assessments of aquatic ecosystems. In this study, we developed a workflow and portable kit for fieldable environmental DNA sequencing (FeDS) and tested its efficacy by characterizing the breadth of jellyfish (Medusozoa) taxa in the coastal waters of the Upper and Lower Florida Keys. Environmental DNA was isolated from seawater collection events at eight sites and samples were subjected to medusozoan 16S rRNA gene and metazoan mitochondrial cytochrome oxidase 1 gene profiling via metabarcoding onsite. In total, FeDS yielded 175,326 processed sequence reads providing evidence for 53 medusozoan taxa. Our most salient findings revealed eDNA from: (1) two venomous box jellyfish (Cubozoa) species, including taxa whose stings cause the notorious Irukandji envenomation syndrome; (2) two species of potentially introduced stalked jellyfish (Staurozoa); and (3) a likely cryptic species of upside-down jellyfish (Scyphozoa). Taken together, the results of this study highlight the merits of FeDS in conducting biodiversity surveys of endemic and introduced species, and as a potential tool for assessing envenomation and/or conservation-related threats.

Click here to access the full article