Does pregnancy affect swimming performance of female Mosquitofish, Gambusia affinis?

Abstract

Summary 1.The cost of reproduction due to limiting of the reproductive female's locomotion capability has been suggested many times, but has rarely been directly examined, especially in fishes. Here, the effect of pregnancy on swimming performance in the viviparous Mosquitofish, Gambusia affinis, was studied. 2. Eight females of G. affinis were isolated, each in a separate aquarium, and critical swimming speed (U crit ), body mass (BM) and cross-section area were measured every 5 days from the beginning of the pregnancy until 2-4 days after parturition. 3. Swimming kinematics (tail beat frequency and amplitude) was measured in nonpregnant and pregnant females at different swimming speeds. 4. BM increased during pregnancy from 0·47 ± 0·13 g to 0·72 ± 0·19 g, and the crosssection area also increased during pregnancy from 0·21 ± 0·06 cm 2 to 0·32 ± 0·07 cm 2 . U crit decreased from 25·0 ± 1·3 cm s −1 before pregnancy to 20·1 ± 1·5 cm s −1 just before parturition, and returned to 24·7 ± 1·4 cm s −1 2-4 days after parturition. Interindividual variation was repeatable and reflects real differences among individuals. 5. Swimming kinematics was not affected by pregnancy. 6. The results suggest that reductions in U crit are probably because of aerobic constraints and not necessarily due to hydrodynamic changes resulting from changing in body form or plasticity. Moreover, the reduction in U crit is, potentially, a 'cost of reproduction' owing to decrease in the ability to gain food during pregnancy in G. affinis females.

Repeatability of locomotor performance and of morphology – locomotor performance relationships

“…We anticipated that female performance might decline as a result of increased breeding activity. Locomotor speed is typically lower in reproductively active (pregnant or gravid) females (Plaut, 2002;Ghalambor et al, 2004;Iraeta et al, 2010) and in zebrafish, body shape associated with gravidity is negatively correlated with U crit (Conradsen and McGuigan, 2015). However, males and females declined in performance to the same (statistically indistinguishable) extent, an observation at odds with reproductive investment in females as the sole cause.…”

“…The effect of sex on repeatability of U crit Although several studies have considered the effects of intra-sex variation on fish locomotion, for example, investigating the effects of sexual signalling in males (Basolo and Alcaraz, 2003;Karino et al, 2006;Baumgartner et al, 2011;Trappett et al, 2013;Oufiero et al, 2014) or reproduction (pregnancy or gravidity) in females (Plaut, 2002;Ghalambor et al, 2004;Svendsen et al, 2009;Belk and Tuckfield, 2010), surprisingly little attention has been paid to intersex differences of locomotor performance (Conradsen and McGuigan, 2015). Sexual dimorphism could have an impact on conclusions about repeatability in two ways.…”

Pregnancy is a drag: hydrodynamics, kinematics and performance in pre- and post-parturition bottlenose dolphins (Tursiops truncatus)

“…It was hypothesized that the decreased maternal locomotor ability was due to carrying an extra load associated with gravidity or pregnancy for crustaceans (Winfield and Townsend, 1983;Berglund and Rosenquist, 1986), fish (Plaut, 2002;Svendsen et al, 2009), scorpions (Shaffer and Formanowicz, 1996), insects (Isaacs and Byrne, 1998;Gu and Danthanarayana, 2000), reptiles (Shine, 1980;Seigel et al, 1987;Cooper et al, 1990), birds (Lee et al, 1996;Veasey et al, 2001) and mammals (McLean and Speakman, 2000). Prelaying common eiders (Somateria mollissima) are even rendered flightless (Guillemette and Ouellet, 2005).…”

Bathymetric segregation of spawning stages in the Atlantic sardine Sardina pilchardus

“…Although constraints on locomotion have been suggested in gravid females of many animal species (for review see Magnhagen 1991), the effect of pregnancy on locomotion has rarely been measured in fish (James & Johnston 1998, Plaut 2002. In these 2 studies, gravid fish displayed decreased swimming performance, which was mainly attributed to the added mass of eggs; the latter might either cause hydrodynamic or biomechanical constraints or decrease the amount of oxygen that can be allocated to swimming (Plaut 2002).…”

“…Although constraints on locomotion have been suggested in gravid females of many animal species (for review see Magnhagen 1991), the effect of pregnancy on locomotion has rarely been measured in fish (James & Johnston 1998, Plaut 2002. In these 2 studies, gravid fish displayed decreased swimming performance, which was mainly attributed to the added mass of eggs; the latter might either cause hydrodynamic or biomechanical constraints or decrease the amount of oxygen that can be allocated to swimming (Plaut 2002). Indeed, as mentioned in the previous paragraph (see also Somarakis et al 2004), the process of hydration adds a significant amount of mass in imminent spawners, since the gonadosomatic index increases within a few hours from 5% at the completion of yolk deposition to > 20% at the final stages of hydration (Somarakis et al 2004).…”