DOI: 10.5061/dryad.5dv41ns7j
title: Data from: Sperm longevity and salinity – the overlooked importance of spawning environment for alternative reproductive tactics

description: Studies on adaptive responses to sperm competition have focused on mating
 modes and mating roles. The main mating modes studied are external and
 internal fertilization and spermcasting. The focus of male mating roles
 assumes one advantageous ‘bourgeois’ role and another disadvantageous
 ‘parasitic’ role regarding the probability of fertilization. However,
 sperm longevity between teleost fishes spawning in hypoosmotic freshwater
 and species spawning in hyperosmotic saltwater differs markedly. We argue
 that this can have major impacts on sperm adaptations in relation to sperm
 competition, due to physiological constraints and different outcomes of
 trade-offs. To test this hypothesis, we extracted sperm longevity data
 from studies on species with alternative reproductive tactics. We show
 that spawning salinity affects sperm longevity by orders of magnitudes and
 that this affects the direction in which male tactics differ in sperm
 longevity: parasitic males’ sperm lived shorter than bourgeois males’
 sperm in freshwater spawners, but longer than bourgeois males’ sperm in
 saltwater spawners. These results highlight a need to take spawning
 salinity into account in intraspecific as well as interspecies comparisons
 of adaptations to sperm competition in external fertilizers.
description: To collect data on sperm
 longevity in teleost fish, we followed methods set by Kustra and Alonzo
 [11] which searched the bibliographic database Web
 of Science with the phrase: ‘(“Alternative Reproductive” OR “Alternative
 Mating”) AND (“Sperm”)’. They identified 46 studies comparing sperm traits
 of different ARTs in externally fertilising teleosts that we added to our
 list of records. Since Web of Science has recently updated its interface,
 we did a complementary search using the phrases “Alternative Reproductive”
 OR “Alternative Mating” (with quotation marks) in different rows and
 thereafter refined our results by searching for ‘sperm’ within the
 results, restricting our search to 2019 - 2021 (N=57). We also did a
 forward search by checking the studies citing Kustra and Alonzo
 [11] and Fitzpatrick [16], which yielded no additional record. In
 addition, we included two older studies that we came across during this
 work, as well as data from one unpublished study of ours. All identified
 records were filtered for externally fertilising teleost with ARTs and
 sperm longevity data. This resulted in 18 species across 19 studies with
 data showing direct statistical comparisons (or non-overlapping ranges in
 [19]) between ARTs in sperm longevity, velocity over
 time or motility over time. Following Kustra and Alonzo
 [11], we categorised the ARTs of these species into
 ‘dominant’ (i.e. bourgeois) or ‘sneaker’ (i.e. parasitic) tactics, such
 that dominant males experience lower sperm competition on average than
 sneaker males, and if more than two tactics were present, we compared the
 most dominant to the least dominant male tactic. From these studies, we
 extracted absolute values of longevity, spawning environment (categorised
 as saltwater or freshwater) and temperature. In some cases, values were
 extracted from figures. The most common (N=6) definition for sperm
 longevity was time until 95% of sperm had stopped swimming. We followed
 this guideline and collated data of the average time point (in seconds)
 until only 5% of sperm remained motile for each tactic, either by
 calculating it from the data provided by the studies, or by extracting
 this value from figures. For one record [20], we extracted the time point from when the
 average sperm <em>velocity </em>reached 5% of the starting
 value, since % motile sperm was not available for this study. See
 Supplementary Table S1 for details. The phylogenetic relationships among
 the surveyed species, based on published phylogenies [21-26], are shown in Supplement Figure
 S1.
description: Key of definitions of variable names, column headings and row
 labels: Species: The species of the study and for Salmo
 salar study location Salinity: The salinity in which
 sperm longevity was measured (same as male native salinity)
 Temperature: The temperature in which sperm longevity was
 measured ART_highest_longevity: which of the two
 alternative reprocuctive tactics which has significantly higher sperm
 longevity than the other. Sneaker = sneaker male and dominant = dominant
 male. NS = no significant difference
 Longevity_sneaker_s: Sperm longevity of sneaker males
 Longevity_dominant_s: Sperm longevity of dominant males
 Longevity_sneak_log10: Sperm longevity of sneaker males log10
 transformed Longevity_dominant_log10: Sperm longevity
 of dominant males log10 transformed
 Longevity_sneaker_s_Ss_pooled: Sperm longevity of sneaker males
 Salmo salar from same temeperature pooled (Salmo salar 1 and Salmo salar 2
 as well as Salmo salar 3 and Salmo salar 4)
 Longevity_dominant_s_Ss_pooled: Sperm longevity of dominant males
 Salmo salar from same temeperature pooled (Salmo salar 1 and Salmo salar 2
 as well as Salmo salar 3 and Salmo salar 4)
 Longevity_sneak_log10_Ss_pooled: Sperm longevity of sneaker males
 Salmo salar from same temeperature pooled (Salmo salar 1 and Salmo salar 2
 as well as Salmo salar 3 and Salmo salar 4) log10 transformed
 Longevity_dominant_log10_Ss_pooled: Sperm longevity of dominant
 males Salmo salar from same temeperature pooled (Salmo salar 1 and Salmo
 salar 2 as well as Salmo salar 3 and Salmo salar 4) log 10
 tranformed Reference: The study with the original
 data Dominant: The sperm longevity was significantly
 higher for dominant bourgeois males than for sneaker parasitic
 males Sneaker: The sperm longevity was significantly
 lower for dominant bourgeois males than for sneaker parasitic
 males NS: No significant difference in sperm longevity
 between dominant bourgeois males and sneaker parasitic males
 n/a: Not available. This is because Salmo salar tested in the
 same temperature intervall were pooled and that we also give the dta for
 all Salmo salar studies