Morphological structures for potential sperm storage in poeciliid fishes. Does superfetation matter?

Abstract

Sperm storage within the female reproductive tract has been reported as a reproductive strategy in several species of vertebrates and invertebrates. However, the morphological structures that allow for sperm to be stored and kept viable for long periods are relatively unknown in osteichthyes. We use histological and stereological tools to identify and quantify sperm storage structures (spermathecae) in 12 species of viviparous Poeciliidae. We found spermathecae in nine species, six of which exhibit superfetation (the ability of females to simultaneously carry within the ovary two or more broods of embryos at different stages of development). These spermathecae are folds of ovarian tissue that close around spermatozoa. We compared the number and size (volume) of spermathecae between species with and without superfetation. Species that exhibit superfetation had a significantly higher number of spermathecae than species that do not exhibit this reproductive strategy. In addition, we found that the mean volume of spermathecae and total volume of spermathecae present in the ovary are marginally higher in species with superfetation. Our results contribute to the understanding of the morphological structures that allow for sperm storage in viviparous osteichthyes and suggest a positive relationship between superfetation and the capacity of females to store sperm.

Superfetation in the viviparous fish Heterandria formosa (Poeciliidae)

“…The intrafollicular gestation implies the presence of spermatozoa in the ovary is indispensable for the continuation of fertilization of mature oocytes and production of embryos throughout the annual reproductive cycle (Uribe & Grier, ; Uribe, Grier, De La Rosa‐Cruz, & García‐Alarcón, ). The spermatozoa were seen in the ovarian lumen, adjacent to the germinal epithelium in folds of the ovarian tissue, similar to that reported in other members of the Poeciliidae family (Campuzano‐Caballero & Uribe, ; Olivera‐Tlahuel, Villagrán‐Santa Cruz, Moreno‐Mendoza, & Zúñiga‐Vega, ; Uribe et al, ).…”

Sex, size and habitat complexity effects on emergence latency and latency to locate food of the invasive porthole livebearer (Poeciliopsis gracilis)

“…However, further research should be made, as if this were the case, guppy females would be expected to be bolder too. The fact that porthole livebearer females are more prompt to abandon a refuge could represent a key characteristic in their invasive process, especially at the beginning, as in many Poeciliid species adult females could store sperm from multiple males [ 64 – 66 ], and for guppies this is a characteristic that has enabled even a single female to form a viable population [ 35 ]. We thus hypothesise that the invasion of porthole livebearers could be female-biased.…”

Multiple paternity in superfetatious live‐bearing fishes

“…Figure S3) we deem it highly unlikely that these females re‐mated with only these same males. A more plausible explanation is that the overlap in sires between broods stems from sperm storage, which seems to be not only omnipresent, but also long‐term (up to 10 months) in live‐bearing poeciliids (Evans & Pilastro, 2011; Olivera‐Tlahuel et al, 2017; Potter & Kramer, 2000). That sperm storage can lead to the same males fertilizing successive broods was shown in a study by Lopez‐Sepulcre et al (2013) investigating reproductive success in wild guppy ( Poecilia reticulata ) populations (Lopez‐Sepulcre et al, 2013).…”