Larval morphology of carid shrimps: application of different microscopic tools for taxonomy and systematics

• Grant number: 24/13154-0
• Support Opportunities: Scholarships in Brazil - Support Program for Fixating Young Doctors
• Effective date (Start): September 01, 2024
• Effective date (End): August 31, 2025
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Acordo de Cooperação: CNPq
• Principal Investigator: Fernando Jose Zara
• Grantee: Rafael de Carvalho Santos
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated research grant: 24/01947-6 - Larval morphology in caridean shrimps: applied microscopical key tools for a new perspective in taxonomy and systematics, AP.R

Abstract

The morphological description of the larval stages of Decapoda crustaceans is significantly important for the classification and identification of new species, which have been described mainly based on adult and juvenile forms, integrated with other tools, such as molecular biology, contemplating the requirements of modern taxonomy. The identification of larval stages can be a complex task, given the deficiency regarding the morphology of different larval forms, with only a brief morphological description, few illustrations and a low number of parental individuals identified at the species level. Traditionally, studies related to the larval morphology of decapods use light microscopy (LM), following this pattern to this day. When it comes to describing caridean shrimps, some studies are found using specific microscopy techniques in an integrated manner. A scanning electron microscopy (SEM) application has already been used to describe the mandibles or details of just some appendages, setae or specific structures of the pleon and telson. The way in which samples are prepared for SEM can be decisive in the quality of the resulting material, as there is a wide variety of fixation methods applied to caridean larvae. When applied in the entire larval structures it is possible to observe a variation in the fixation methods, which may be in a graduated series of ethanol (30%, 50%, 70%); in 2.5% glutaraldehyde or 4% formaldehyde (both in seawater); or in 10% formaldehyde. Therefore, determining a specific standard for preparing caridean zoos for SEM is necessary to guarantee the quality of the data generated. In addition, the application of phase differential interference contrast (DIC) microscopy and confocal fluorescence, which allows observation of the morphology of the larvae in a three-dimensional way, with contrasts and marked by fluorescein, can complement the information obtained by the combination of LM and SEM. The integration of different microscopy techniques will be tested on the species of Lysmata Risso, 1816, caridean shrimps widely distributed in tropical and subtropical regions, which are among the most commercialized marine invertebrates, due to their high value for ornamental aquariums. Its species are grouped into different clades, with lineages defined considering molecular phylogeny, "Tropical American", "Cleaner", "Cosmopolitan" and "Morphovariable", or based on morphological characters of adults, following the active branch of the antennule, "long accessory branch" (LAB), "short accessory branch" (SAB) and "ungiform branch" (UB). Larval morphology is mentioned as an additional tool for understanding lineages in Lysmata, due to the presence or absence of the fifth pair of pereopods in the first zoea after hatching, in which species that zoea I hatch with the presence of the fifth pair of pereopods contain in adult phase, a long accessory branch in the antennule (LAB) and those that hatch without the presence of this appendage are part of distinct clades (SAB and UB), but there is still a need for a more robust assessment of how larval characters can contribute to the relationships within the genus. Currently, only 10 species, out of approximately 50 described, present information on larval morphology, at least up to Zoea III. Therefore, a morphological analysis will be applied using integrative microscopy techniques (LM, SEM, DIC and confocal) to describe the zoea projects for three species of Lysmata, and the morphological characteristics of their appendages will be compared and grouped to ascertain the contribution of larval morphology in separating the clades described for the genus. (AU)