Extended Abstract The freshwater red cherry davidi (incorrectly identified as N. denticulata) has been proposed as a new model organism for biology due to its ease of culture, high reproductive capacity, abbreviated intermolt periods, and tractability for transgenic studies. Prior work on this species is sparse and rife with taxonomic confusion, particularly regarding its molting ecology. To form a basis for studies on crustacean molt regulation, a simple and rapid staging method in live N. davidi was developed. Observing setagenesis through the transparent cuticle proved to be the simplest way to directly monitor molt cycle stages. The outer uropods of adult males were imaged daily through a complete molt cycle. Progressive changes in the structure of the developing cuticle and setae delineated intermolt (C4), premolt (D0, D1, D2, & D3,4), and postmolt (A, B) stages. The most informative of these changes include the development of setal cones during postmolt and the progressive evagination of the new cuticle as it separates from the epidermis (Figure 1). The approximate interval between consecutive molts was 10 days at 23 ˚C. Rapid growth was associated with a short intermolt stage of ~5 days; the durations of the postmolt and premolt stages were ~1 day and 4 days, respectively. Future studies will quantify hemolymph molting hormone (ecdysteroid) titers to confirm the molt stages and correlate the Neocaridina davidi molt cycle with that of more established study species including Gecarcinus lateralis and Cancer maenas. Immunohistochemistry will be used to identify the N. davidi Y-organ, which synthesizes and secretes ecdysteroids and must be isolated for more precise measures of hormonal activity and gene expression. Precise staging is essential for applying transcriptomic and transgenic tools to N. davidi for the study of the genetic mechanisms that regulate molting in decapod and to compare results across crustacean species. Supported by NSF (IOS-1257732).

Figure 1: Images of uropods throughout Neocaridina davidi molt cycle. Note the retraction of the setal matrix and development of cones in the setae between A/B and C, and the separation of cuticle from epidermis between C and D.

Cover Letter (DCPB) Neocaridina davidi is a small freshwater shrimp native to Taiwan. In recent years it has become a species of significant interest in both the aquaria trade and in the scientific literature. Due to a number of factors including low cost, ease of culturing in captivity, and accelerated life cycle the cherry shrimp is an excellent candidate model organism for research in several fields including crustacean biology and ecotoxicology. The Mykles lab at Colorado State University, which studies crustacean molt cycle signaling, is largely interested in the potential for N. davidi to be used in future transgenic studies. Current model species like Gecarcinus lateralis and Cancer maenas are nonviable as they cannot be easily bred in captivity. N. davidi’s reproductive characteristics including direct developmental pathway, relatively brief intergenerational time, and large easily accessible eggs make it a far more tractable subject for transgenic work involving the manipulation of key genes involved in the molting process. Despite increasing interest in this species over the past few years, the historic literature is sparse and there are significant concerns regarding species identity in some older papers due to taxonomic confusion amongst other East Asian shrimp of the genus Neocaridina. No description exists of certain aspects of N. davidi’s life history, including its molt cycle. A comprehensive understanding of the molt cycle and of its constitutive stage, as well as a method to identify these stages, is an essential prerequisite for any future work examining specific biochemical pathways involved in molting. We describe a methodology for staging live using a modified protocol involving observation of the developing cuticle through the ’s transparent . Additionally, we will show relative ecdysone levels of the animal at each observable stage. These two studies anchor the N. davidi molt cycle in the larger context of crustacean molting and permit comparison with other key study species including Gecarcinus lateralis and Cancer maenas. This work is the basis for my undergraduate honors thesis at Colorado State University. As our lab primarily works with Gecarcinus lateralis and Cancer maenas, the bulk of the research on Neocaridina davidi within the lab including this project has been associated with my independent research. I will be graduating with B.S. degrees in Biological Science and in Fish, Wildlife, and Conservation Biology in May 2019. Following my graduation, I intend to enter a doctoral program in Ecology & Evolutionary Biology in Fall 2019 focusing on the application of integrative methods in biology to the conservation of rare and threatened species.