TAXONOMY, MORPHOLOGY, AND RNA-SEQ TRANSCRIPTOMICS OF THE CUBOZOAN ALATINA ALATA, AN EMERGING MODEL CNIDARIAN

Cnidarians are often considered simple animals, but the more than 13,000 estimated species (e.g., corals, hydroids and jellyfish) of the early diverging phylum exhibit a broad diversity of forms, functions and behaviors, some of which are demonstrably complex. In particular, cubozoans (box jellyfish) are cnidarians that have evolved a number of distinguishing features. Some cubozoan species possess complex mating behaviors or particularly potent stings, and all possess well-developed light sensation involving image-forming eyes. Like all cnidarians, cubozoans have specialized subcellular structures called nematocysts that are used in prey capture and defense. The objective of this study is to contribute to the development of the box jellyfish Alatina alata as a model cnidarian. This cubozoan species offers numerous advantages for investigating morphological and molecular traits underlying complex processes and coordinated behavior in free-living medusozoans (i.e., jellyfish), and more broadly throughout Metazoa. First, I provide an overview of Cnidaria with an emphasis on the current understanding of genes and proteins implicated in complex biological processes in a few select cnidarians. Second, to further develop resources for A. alata, I provide a formal redescription of this cubozoan and establish a neotype specimen voucher, which serve to stabilize the taxonomy of the species. Third, I generate the first functionally annotated transcriptome of adult and larval A. alata tissue and apply preliminary differential expression analyses to identify candidate genes implicated broadly in biological processes related to prey capture and defense, vision and the phototransduction pathway and sexual reproduction and gametogenesis. Fourth, to better understand venom diversity and mechanisms controlling venom synthesis in A. alata, I use bioinformatics to investigate gene candidates with dual roles in venom and digestion, and review the biology of prey capture and digestion in cubozoans. The morphological and molecular resources presented herein contribute to understanding the evolution of cubozoan characteristics and serve to facilitate further research on this emerging cubozoan model

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

Discussion around avoidance and mitigation of jellyfish stings has traditionally focused on swimmers and divers being mindful of their behavior relative to swimming medusae (pelagic jellyfish). This framework must be restructured with the inclusion of the oblique risk posed by novel autonomous stinging structures like cassiosomes from Cassiopea (a jellyfish genus of the taxonomic order Rhizostomeae). Cassiosomes are released by Cassiopea sp. into subtropical waters that can consequently sting human skin, causing varying degrees of pain and irritation; this trait extends to other rhizostome jellyfish species. Swimmers and waders may put themselves at risk simply by coming into contact with agitated water in the vicinity of Cassiopea medusae, even without touching any part of the jellyfish (medusa, tentacles, or otherwise). Herein, we highlight details provided by 46 researchers and professional aquarists reporting incidents in which they experienced “stinging water” sensations, which we also refer to as “contactless stings’’. We report these findings in order to increase the awareness of a public safety hazard the community may be unaware of in their own labs, aquariums, and sampling locations

Sustainable seafood using octopus as a model

The global catch of octopus and squid shows annual variability and demand is likely to increase for both locally-supplied and imported products. However, the vulnerability of seafood resources is now well known, the reliability of fisheries catch data is still unclear, management of cephalopod stocks is mostly rudimentary, and there is uncertainty and concern about their sustainability among fisheries managers, the fishing industry, retailers, researchers and consumers. Here, a new project is presented which aims to address and resolve ways to enhance the effectiveness of seafood sustainability in general, with the aid of a freely accessible identification and traceability tool linked to sophisticated databases, and using artificial intelligence, machine learning and blockchain technology, to provide an easy and reliable way to trace seafood using octopus as a model. The project is a contribution to UN Sustainable Development Goals 2, 9, 14, and 17

The role of taxonomic expertise in interpretation of metabarcoding studies

Abstract 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

Cassiosomes are stinging-cell structures in the mucus of the upside-down jellyfish Cassiopea xamachana

This work is licensed under a Creative Commons Attribution 4.0 International License.Snorkelers in mangrove forest waters inhabited by the upside-down jellyfish Cassiopea xamachana report discomfort due to a sensation known as stinging water, the cause of which is unknown. Using a combination of histology, microscopy, microfluidics, videography, molecular biology, and mass spectrometry-based proteomics, we describe C. xamachana stinging-cell structures that we term cassiosomes. These structures are released within C. xamachana mucus and are capable of killing prey. Cassiosomes consist of an outer epithelial layer mainly composed of nematocytes surrounding a core filled by endosymbiotic dinoflagellates hosted within amoebocytes and presumptive mesoglea. Furthermore, we report cassiosome structures in four additional jellyfish species in the same taxonomic group as C. xamachana (Class Scyphozoa; Order Rhizostomeae), categorized as either motile (ciliated) or nonmotile types. This inaugural study provides a qualitative assessment of the stinging contents of C. xamachana mucus and implicates mucus containing cassiosomes and free intact nematocytes as the cause of stinging water

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Calcium-dependent membrane association of a flagellar calcium sensor does not require calcium binding

Flagellar calcium-binding protein (FCaBP) is a dually acylated Ca(2+) sensor in the Trypanosoma cruzi flagellar membrane that undergoes a massive conformational change upon Ca(2+) binding. It is similar to neuronal Ca(2+) sensors, like recoverin, which regulate their binding partners through a calcium acyl switch mechanism. FCaBP is washed out of permeabilized cells with buffers containing EDTA, indicating Ca(2+)-dependent flagellar membrane association. We hypothesized that, like recoverin, FCaBP projects its acyl groups in the presence of Ca(2+), permitting flagellar membrane and binding partner association and that it sequesters the acyl groups in low Ca(2+), disassociating from the membrane and releasing its binding partner to perform a presumed enzymatic function. The X-ray crystal structure of FCaBP suggests that the acyl groups are always exposed, so we set out to test our hypothesis directly. We generated T. cruzi transfectants expressing FCaBP or Ca(2+)-binding mutant FCaBP(E151Q/E188Q) and recombinant wildtype and mutant proteins as well. Both FCaBP and FCaBP(E151Q/E188Q) were found to associate with lipid rafts, indicating the Ca(2+)-independence of this association. To our initial surprise, FCaBP(E151Q/E188Q), like wildtype FCaBP, exhibited Ca(2+)-dependent flagellar membrane association, even though this protein does not bind Ca(2+) itself [16]. One possible explanation for this is that FCaBP(E151Q/E188Q), like some other Ca(2+) sensors, may form dimers and that dimerization of FCaBP(E151Q/E188Q) with endogenous wildtype FCaBP might explain its Ca(2+)-dependent localization. Indeed both proteins are able to form dimers in the presence and absence of Ca(2+). These results suggest that FCaBP possesses two distinct Ca(2+)-dependent interactions-one involving a Ca(2+)-induced change in conformation and another perhaps involving binding partner association

Upside-down but headed in the right direction:Review of the highly versatile Cassiopea xamachana system

The upside-down jellyfish Cassiopea xamachana (Scyphozoa: Rhizostomeae) has been predominantly studied to understand its interaction with the endosymbiotic dinoflagellate algae Symbiodinium. As an easily culturable and tractable cnidarian model, it is an attractive alternative to stony corals to understanding the mechanisms driving establishment and maintenance of symbiosis. Cassiopea is also unique in requiring the symbiont in order to complete its transition to the adult stage, thereby providing an excellent model to understand symbiosis-driven development and evolution. Recently, the Cassiopea research system has gained interest beyond symbiosis in fields related to embryology, climate ecology, behavior, and more. With these developments, resources including genomes, transcriptomes, and laboratory protocols are steadily increasing. This review provides an overview of the broad range of interdisciplinary research that has utilized the Cassiopea model and highlights the advantages of using the model for future research