Understanding the morphology and ultrastructure of spermatophores from the copepod Notodiaptomus spinuliferus (Dussart & Matsumura-Tundisi, 1986)

• Grant number: 24/08354-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): September 01, 2024
• Effective date (End): August 31, 2025
• Field of knowledge: Biological Sciences - Zoology - Applied Zoology
• Principal Investigator: Gilmar Perbiche Neves
• Grantee: Paulo Henrique Cardilli Hor
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Throughout evolutionary history, a lot of reproductive strategies have been developed, one of which is the spermatophore. This structure is present in many groups, primarily invertebrates, allowing the female to store sperm for post-copulatory fertilization, often carrying more than one spermatophore from different individuals. This strategy is also present in copepods, being common to find females carrying spermatophores during plankton sampling, especially calanoid copepods from the Diaptomidae family. While studies on this structure are more common for brackish water copepods, they are scarce for their freshwater representatives. The target of this research is the spermatophores of the species Notodiaptomus spinuliferus, commonly found in freshwater waters in the state of São Paulo, aiming to understand its functional morphology, anatomy, and ultrastructure.Initially, plankton samples will be made in 6 large and small freshwater reservoirs within the state, using a conical plankton net of 68 µm and 70% ethanol to fix the samples on site. In each sampling, 700 liters of water will be filtered.In the laboratory, individuals will be sorted and identified using a stereoscope and common optical microscopes, aided by specialized literature. With this, the spermatophores attached to the females of the target species will be removed and processed later in normal optical microscopy and transmission electron microscopy. In addition to the separated spermatophores, whole individuals containing the structure will also be processed.In traditional histological studies, fixation and preparation for paraffin embedding will be performed, followed by processing in a microtome to obtain the sections for study. The sections will be used to prepare histological slides, stained with hematoxylin-eosin and methylene blue. The results will be photographed with specialized equipment.The functional morphology and ultrastructural study will be performed using transmission electron microscopy, following established practices at the Center for Electron Microscopy at IBB - UNESP. The spermatophores separated and attached to the female bodies will be investigated to understand the fixation mechanism.The images obtained in the microscopes will be processed to integrate them, through image editing, overlaying them, but also with schematic illustrations. Articles published on marine copepod spermatophores and specialized literature will be used to aid in identifying the structures. By the end of this stage, it will be possible to understand the internal and external morphology of the structure, as well as its functional anatomy, filling this knowledge gap. This will provide a better understanding of the life cycle of these animals, especially their reproductive character.Upon completing the research, the results will be presented at specialized scientific events. The article prepared will be submitted for publication in journals in the field.