The evolutionary history of Whale Lice: from species adaptations to family phylogeny

• Grant number: 22/13979-4
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: January 01, 2023
• End date: July 10, 2026
• Field of knowledge: Biological Sciences - Zoology - Taxonomy of Recent Groups
• Principal Investigator: Sónia Cristina da Silva Andrade
• Grantee: Tammy Iwasa Arai
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/06738-8 - Seascape genetics and comparative genomics: an integrative evolutionary approach in marine invertebrates, AP.BTA.JP2
• Associated scholarship(s): 24/06934-0 - Advancing Phylogenomics of Whale Lice (Crustacea: Amphipoda: Cyamidae) through Ultraconserved Elements (UCEs), BE.EP.PD

Abstract

Parasites of marine vertebrates are essential to understand the interaction between history, ecology and geography, as the determinants of organismal evolution and distribution. Whale lice are obligate ectoparasites of cetaceans that undergo direct development and are dependent on direct physical contact to colonize a new host whale. Currently, the family Cyamidae is composed of 32 species divided into seven genera and two subfamilies. Whale lice are the sister clade of skeleton shrimps of the family Caprellidae, often found in shallow waters, in association with marine biological substrates, or occurring free on the bottom. Comparative studies between cyamids and caprellids are very scarce, and further genomic studies may elucidate adaptations related to the strict association between cyamids and their hosts. Recent studies on whale lice are minimal due to the difficulty of collecting samples and much of these works were written from specimens collected during the whaling expeditions, deposited in natural history collections, and nowadays samplings are resumed to few freshly stranded carcasses, which are more abundant from coastal and abundant cetacean species. Ultraconserved elements (UCEs) are highly conserved regions within the genome that are shared among evolutionarily distant taxa, while DNA adjacent to each 'core' UCE region, known as flanking DNA, increases in variability with distance from the region. UCEs and flanking regions can be selectively captured, and used to reconstruct the evolutionary history of taxa at various time scales, from deep to shallow phylogenetic divergences. The advantage of using UCEs for phylogenies is the high success rate with degraded or low-quantity samples. Therefore, coupling new genetic techniques with live and museum preserved specimens, we aim to identify functional regions potentially related to the ectoparasitism between whale lice and their hosts, with the comparison of Cyamidae genome with the free living Caprellidae may ellucidate adaptations to the parasitic lifestyle; and reconstruct the phylogeny of the family Cyamidae based on molecular markers, its divergence times, and the historical association with Cetacea to better understand the unique evolutionary history of this enigmatic taxon and its association with whales and dolphins. (AU)