Molecular confirmation of twinning in the West Indian Manatee (Trichechus manatus)

Abstract

Few twinning events have been recorded in the West Indian manatee (Trichechus manatus, Sirenia: Trichechidae) and no previous published study has provided confirmation of this phenomenon based in molecular tools. Here we investigate a possible case of twinning in an endangered Brazilian population of T. manatus using molecular tools. We analyzed two male neonates found stranded in Ceará State, on the northeastern coast of Brazil. The DNA of both individuals was isolated, and 10 microsatellite loci were amplified and genotyped. Following the identification of the alleles, the probabilities of identity by descent (∆7 and ∆8) and relatedness (rxy) were calculated using estimators that evaluate inbreeding. The two individuals shared most of the alleles, with differences in the genotypes being identified in only two loci. All the estimators identified a level of relatedness compatible with that found between siblings (selfed or outbred), indicating they were dizygotic twins. This is the first confirmed case of fraternal twins in free-ranging West Indian manatees in South America. The recognition of this type of twinning provides elements to improve actions for the rehabilitation of stranded animals and their subsequent release to the environment.

Where there’s smoke, there’s fire: Hypotheses for the high incidence of West Indian manatee calf strandings on the Brazilian semi-arid coast

“…Nevertheless, populations that have undergone one of these processes are expected to present high intra-populational relatedness (Hunter et al, 2010). In fact, evidence of inbreeding in the manatee population inhabiting the study area was already reported (Moreira et al, 2022). Additionally, samples from 37 manatees stranded in the study area indicated that 34% of the pairs had some level of genetic kinship (Moreira, 2015).…”