Parturition process in an amphibian mammal species: new evidences in South American fur seal (Arctocephalus australis)

Abstract

In mammals, the transition from a terrestrial to an aquatic environment has implied a great number of adaptations. While in terrestrial mammals the presentation of the foetus at birth is typically cephalic, in strictly aquatic mammals as cetaceans and sirenians the presentation of the foetus is mainly breech. The order Pinnipedia is the most recently evolved group of marine mammals and has an amphibian lifestyle. We document, for the first time, the parturition process in the largest breeding colony of the South American fur seal Arctocephalus australis in Uruguay and compare our results with the scarce information available for other species. The analysis of the parturition processes shows that the cephalic/breech birth ratio was 1. In this species, the presentation of the foetus did not affect the total duration of the parturition process, but the cephalic presentation implied a significantly lower duration of the stage 1 of birth, a trend that is also observed in other Otariid species. Phylogenetic reconstructions suggest that O. flavescens and E. jubatus are older than the Arctocephalus genus, having their most recent common ancestor dated between 5-5.8 mybp. Within the Arctocephalus genus, A. australis would be the most recent species (0.7 mybp). In this light, the skewed ratios of breech presentation in older otariids species may suggest a convergent adaptation toward the aquatic life. We hope this finding will promote an increase of studies aiming for a more detailed examination on the adaptive processes involved in the selection of both types of fetal presentations, and their potential effect on the survival of the pup.

The contrasting hidden consequences of parasitism: Effects of a hematophagous nematode (Uncinaria sp.) in the development of a marine mammal swimming behavior

“…The development of these skills results from interactions between animal behavior and physiology, which change with age, body size, reproductive status, and other life‐history traits (Gastebois, Viviant, & Guinet, ; Lea, Johnson, Melin, Ream, & Gelatt, ; Verrier et al, ; Weise & Costa, ). Among marine mammals, pinnipeds mix foraging in ocean with reproduction on shore, and they may exhibit different strategies and adaptations to guarantee their survival in these environments (Franco‐Trecu, García‐Olazábal, Tassino, & Acevedo, ; Verrier et al, ). In this context, otariids (fur seals and sea lions) and odobenids (walruses) display long periods of maternal dependency (income breeders) when pups must learn to swim and forage before weaning (Schulz & Bowen, ), while phocids (true seals) show strategies that allow pups to swim soon after birth (capital breeders) (Carter et al, ).…”

“…Among marine mammals, pinnipeds mix foraging in ocean with reproduction on shore, and they may exhibit different strategies and adaptations to guarantee their survival in these environments (Franco-Trecu, García-Olazábal, Tassino, & Acevedo, 2016;Verrier et al, 2011). In this context, otariids (fur seals and sea lions) and odobenids (walruses) display long periods of maternal dependency (income breeders) when pups must learn to swim and forage before weaning (Schulz & Bowen, 2004), while phocids (true seals) show strategies that allow pups to swim soon after birth (capital breeders) (Carter et al, 2017).…”

Heads or tails first? Evolution of fetal orientation in ichthyosaurs, with a scrutiny of the prevailing hypothesis

“…In Sirenia, both head-first and tail-first births have been recorded [ 65 – 67 ]. Such is also the case for hippopotami [ 27 , 68 , 69 ] (Appendix 1) (which can give birth in water or on land), as well as semi-aquatic mammals that give birth on land, such as sea otters [ 70 ] and pinnipeds [ 71 – 73 ]. Further, tail-first births clearly are not simply an adaptation to the aquatic habitat, given their presence in such large terrestrial mammals as elephants [ 69 , 74 , 75 ] (Appendix 1), as well as domestic pigs [ 76 ] and smaller mammals such as members of Chiroptera [ 77 ] and Sciuridae (Appendix 1).…”