Seasonal variation of male-type antennular setation in female Calanus finmarchicus

Miller, Charles B.; Crain, Jennifer A.; Marcus, Nancy H.

doi:10.3354/meps301217

Cited by 9 publications

(10 citation statements)

References 31 publications

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“…Miller et al (2005) demonstrated that sex deter mination in C. finmarchicus was labile, that sex change was an important factor controlling adult sex ratios in situ, and that adult sex ratios can be biased even if copepodite sex ratios are close to unity. Further, Miller et al (2005) found evidence that intersexes may be rare, even if sex change is frequent in the population. The fact that no intersexes were reported in Crain & Miller (2000) suggests that sexchanged animals were counted as females in that study.…”

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

“…For example, Miller et al (2005) studied the occurrence of quadrithek antennules (a male characteristic) in female Calanus. They concluded intersex characters in Calanus are most likely evidence of switching after first initiation of male development in C5 and that many sex-changed individuals may mature as females and not show any intersex characteristics.…”

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

“…Since only male copepods can change sex, sex ratios of populations undergoing sex change will tend to be skewed towards females. To demonstrate this, we use studies by Crain & Miller (2000) and Miller et al (2005) on Calanus finmarchicus and Liang & Uye (1996) on Paracalanus as examples. Studies of Crain & Miller (2000) and Liang & Uye (1996) were used in Hirst et al (2010) to support the MSP theory.…”

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

“…The analysis by Hirst et al (2010) of Crain & Miller (2000) data showed that sex ratios of C5 C. finmarchicus were not significantly different from unity, but adult sex ratios were significantly biased towards females. Although intersexes are not reported in Crain & Miller (2000), the same authors later published one of the most comprehensive studies of intersexuality on the same population of C. finmarchicus (Miller et al 2005). Miller et al (2005) demonstrated that sex deter mination in C. finmarchicus was labile, that sex change was an important factor controlling adult sex ratios in situ, and that adult sex ratios can be biased even if copepodite sex ratios are close to unity.…”

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

“…Although intersexes are not reported in Crain & Miller (2000), the same authors later published one of the most comprehensive studies of intersexuality on the same population of C. finmarchicus (Miller et al 2005). Miller et al (2005) demonstrated that sex deter mination in C. finmarchicus was labile, that sex change was an important factor controlling adult sex ratios in situ, and that adult sex ratios can be biased even if copepodite sex ratios are close to unity. Further, Miller et al (2005) found evidence that intersexes may be rare, even if sex change is frequent in the population.…”

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

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No evidence of predation causing female-biased sex ratios in marine pelagic copepods

Gusmão¹,

McKinnon²,

Richardson³

2013

Mar. Ecol. Prog. Ser.

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Although sex ratios close to unity are expected in dioecious species, biased sex ratios are common in nature. It is essential to understand causes of skewed sex ratios in situ, as they can lead to mate limitation and have implications for the success of natural populations. Femaleskewed sex ratios are commonly observed in copepods in situ. Here we discuss the challenges of copepod sex ratio research and provide a critical review of factors determining copepod sex ratios, focusing on 2 main objectives. The first is a critique of the male predation theory, which is currently the main process thought to be responsible for female-skewed sex ratios. It assumes that males have higher mortality because of increased vulnerability to predation during their search for mates. We show that there is little support for the male predation theory, that sex ratios skewed toward females occur in the absence of predation, that sex ratios are not related to predation pressure, and that where sex-skewed predation does occur, it is biased toward females. Our second objective is to suggest alternative hypotheses regarding the determination of sex ratios. We demonstrate that environmental factors, environmental sex determination and sex change have strong effects on copepod sex ratios, and suggest that differential physiological longevity of males and females may be more important in determining sex ratios than previously thought. We suggest that copepod sex ratios are the result of a mixture of factors.

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Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

Section: Environmental Sex Determination and Sex Change Can Skew Copementioning

confidence: 99%

See 3 more Smart Citations

No evidence of predation causing female-biased sex ratios in marine pelagic copepods

Gusmão¹,

McKinnon²,

Richardson³

2013

Mar. Ecol. Prog. Ser.

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First evidence of biased sex ratio at birth in a calanoid copepod

Burris

Dam

2015

Limnol. Oceanogr.

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To test the hypothesis that the sex ratio of the copepod Acartia tonsa is biased at birth, adult sex ratios of the offspring of families (21 families in 2011 and 72 in 2013) produced by field-caught females were determined in the laboratory under controlled conditions. Sex ratios at birth were estimated from the adult sex ratio, and after applying a correction in which all dead/missing individuals were counted as the rarer sex (males). Before correction the overall population sex ratio was female biased during both years, with over 42% of mothers producing clutches that were significantly different from unity. After correction, 25% (2013) to 33% (2011) of mothers still produced significantly biased sex ratios. The ratio of deaths of males to females had to be 1.75 to 1 (2011) and 7.25 to 1 (2013) for sex ratios not to be biased at birth. There was no evidence of sex reversal in any individual from juvenile (C4 stage) to adult, implying that juvenile sex ratios were also significantly biased. Hence, neither sex reversal nor differential mortality of the sexes is a likely explanation for the observed skewed sex ratios. The sex ratios at birth varied widely from the expectation from Mendelian inheritance of sex chromosomes, suggesting that another mechanism is responsible for skewed sex ratios at birth. Since the majority of families with biased sex ratios at birth were female dominated as adults, biased sex ratio at birth may contribute to the skewed sex ratio of adults observed in the field.

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Sex, sex-ratios, and the dynamics of pelagic copepod populations

Kiørboe

2006

Oecologia

144

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I examine how the population biology of pelagic copepods depends on their mating biology using field data and a simple demographic model. Among calanoid copepods, two distinct patterns emerge. First, copepods that lack seminal receptacle and require repeated mating to stay fertilized have near equal adult sex ratios in field populations. Winter population densities are orders of magnitude less than the critical population density required for population persistence, but populations survive winter seasons as resting eggs in the sediment. Population growth in these species is potentially high because they have on average a factor of 2 higher egg production rates than other pelagic copepods. Second, other copepods require only one mating to stay fertile, and populations of these species have strongly female-skewed adult sex-ratios in field populations. Resting eggs have not been described within this group. Winter population sizes are well predicted by the critical density required for population persistence which, in turn, is closely related to the body-size-dependent mate-search capacity. Thus, the different requirements for mating lead in the first case to a more opportunistic reproductive strategy that implies rapid colonization of the pelagic during productive seasons, and in the second case to a strategy that allows maintenance of a pelagic populations during unproductive seasons. Positive density dependent population growth during periods of low population density ('Allee effect') amplifies population density variation during winter into the subsequent summer, thus explaining why summer densities appear to depend more on winter densities than on current growth opportunities in pelagic copepods.

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Seasonal variation of male-type antennular setation in female Calanus finmarchicus

Cited by 9 publications

References 31 publications

No evidence of predation causing female-biased sex ratios in marine pelagic copepods

No evidence of predation causing female-biased sex ratios in marine pelagic copepods

First evidence of biased sex ratio at birth in a calanoid copepod

Sex, sex-ratios, and the dynamics of pelagic copepod populations

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