Laboratory culture of the California Sea Firefly Vargula tsujii (Ostracoda: Cypridinidae): Developing a model system for the evolution of marine bioluminescence

Abstract

27Bioluminescence, or the production of light by living organisms via chemical reaction, is 28 widespread across Metazoa. Culturing bioluminescent organisms from diverse taxonomic 29 groups is important for determining the biosynthetic pathways of bioluminescent substrates, 30 which may lead to new tools for biotechnology and biomedicine. Although some previously 31 cultured luminescent groups represent independent origins of bioluminescence, cnidarians, 32 ctenophores, and brittle stars use luminescent substrates (luciferins) obtained from their diets, 33 and therefore are not informative for determination of the biosynthethic pathways of the 34 luciferins. Terrestrial fireflies do synthesize their own luciferin, but the biosynthetic pathway for 35 firefly luciferin remains unclear. An additional independent origin of endogenous 36 bioluminescence is found within ostracods from the family Cypridinidae, which use their 37 luminescence for defense and, in Caribbean species, for courtship displays. Here, we report the 38 first complete life cycle of a luminous ostracod (Vargula tsujii, the California Sea Firefly) in the 39 laboratory. We also describe the embryonic development of Vargula tsujii and discuss the size 40 classes of instar development. We find embryogenesis in V. tsujii ranges between 25-38 days, 41 and this species appears to have five instar stages, consistent with ontogeny in other cypridinid 42 lineages. We estimate a complete life cycle at 3-4 months. We present the first complete 43 mitochondrial genome for Vargula tsujii. Finally, we find no evidence of significant population 44 genetic structure or cryptic species throughout the southern California range of V. tsujii. Bringing 45 a luminous ostracod into laboratory culture sets the stage for many potential avenues of study, 46including the biosynthetic pathway of cypridinid luciferin and genomic manipulation of an 47 autogenic bioluminescent system. 48 49

Sexual signals persist over deep time: ancient co-option of bioluminescence for courtship displays in cypridinid ostracods

“…To gain a broader understanding of cypridinid relationships, we included single-gene mitochondrial data (12S, 16S, CO1), summarized in Table S5. Some of these sequences are reported previously in conference proceedings (Torres and Gonzalez 2007) and other studies (Ogoh and Ohmiya 2004;Wakayama and Abe 2006;Wang et al 2019;Goodheart et al 2020;Pham et al 2020). We then identified these three mitochondrial genes from our transcriptomes by identifying the longest contigs with high similarity to published complete mitochondrial genomes of V. hilgendorfii and V. tsujii (Ogoh and Ohmiya 2004;Goodheart et al 2020).…”

“…Some of these sequences are reported previously in conference proceedings (Torres and Gonzalez 2007) and other studies (Ogoh and Ohmiya 2004;Wakayama and Abe 2006;Wang et al 2019;Goodheart et al 2020;Pham et al 2020). We then identified these three mitochondrial genes from our transcriptomes by identifying the longest contigs with high similarity to published complete mitochondrial genomes of V. hilgendorfii and V. tsujii (Ogoh and Ohmiya 2004;Goodheart et al 2020). We annotated mitochondrial data from transcriptomes using MITOS (Bernt et al 2013).…”

“…The rDNA analyses also suggested a single origin of luminous courtship in cypridinids, although with ambiguity from a low bootstrap support value of 56% for the node (Torres and Gonzalez 2007). Both morphology and rDNA found Vargula tsujii -a bioluminescent cypridinid from the Eastern Pacific -to nest phylogenetically within the courtship-signaling clade, even though luminous courtship is not known and probably absent in V. tsujii (Goodheart et al 2020). Beyond the topology itself, we have very little information about divergence times for these evolutionary transitions.…”

Infestation of Ostracoda Vargula tsujii (Myodocopa: Cypridinidae) in Lethrinus ornatus and Carangoides gymnostethus from Pamban, Southeast Coast India and Its Variation in Prevalence and Abundance with Respect to Seasonality

“…The infestation of metazoan and protozoan animals play an important role in the ecology of aquatic ecosystems. They can cause harm to the host by tissue damage and can also make the host more susceptible to secondary infection, by weakening host immunity and subsequent economic losses resulting from fish mortality [1]. Endoparasitic diseases affect the normal health conditions and cause reduction of growth, abnormal metabolic activities, and even death of affected fish.…”

“…Ostracods are a nexus for interdisciplinary studies in evolution, ecology, limnology, geology, paleontology and luminescent in nature [4][5][6]. Recently, Goodheart et al have cultured California Sea Firefly Vargula tsujii (Ostracoda: Cypridinidae) on a laboratory scale and attempted to develop a model system for the evolution of marine bioluminescence [7].…”