Population dynamics, sex ratio and size at sex change in a protandric simultaneous hermaphrodite, the spiny shrimp Exhippolysmata oplophoroides

Abstract

One of the main goals of sex allocation theory is understanding sex ratio evolution. However, theoretical studies predicting sex ratios in species with unusual sexual systems, such as protandric simultaneous (PS) hermaphroditism, are rare. In PS hermaphrodites, juveniles Wrst develop into functional males that mature into simultaneous hermaphrodites later in life. Here, we report on the sex ratio (males/males + hermaphrodites) in the PS hermaphroditic shrimp Exhippolysmata oplophoroides. A 2-year study demonstrated that hermaphrodites dominated the population in two diVerent bays. This skewed sex ratio may be explained by limited encounter rates among conspeciWcs. In agreement with this idea, the density of shrimps was extremely low (•1 shrimp km ¡2 ) at the two study sites. Size at sex phase change and sex ratios remained relatively stable through time at the two bays. The stability of these parameters might be explained by the rather steady population structure of this species during the study period. A review of sex ratios in PS hermaphroditic shrimps (Lysmata and Exhippolysmata) revealed considerable variation; some species have male-and others hermaphroditeskewed sex ratios. The conditions explaining inter-and intra-speciWc sex ratio variation in protandric simultaneous hermaphroditic species remain to be addressed.Communicated by F. Bulleri.

Love the one you're with: proximity determines paternity success in the barnacle Tetraclita rubescens

“…This observation also agrees with data for other barnacles, where broods are 2-18 times the mass of seminal vesicles (Raimondi & Martin 1991). Other simultaneous hermaphrodites with low levels of sperm competition also show a strong bias towards female allocation (Fischer 1981;Petersen 1991;Baeza et al 2010), whereas hermaphrodites with linear male gain curves show equal allocation to male and female function (McCartney 1997).…”

A test of large-scale reproductive migration in females of the amphidromous shrimp Macrobrachium acanthurus (Caridea : Palaemonidae) from south-eastern Brazil

“…Logistic and time constraints did not permit measuring and sexing each collected individual in such a large sample. Thus, we followed the criterion of Wenner et al (1991) (also employed in Baeza et al 2010) to obtain a representative sample from each study site and sampling date. We measured and sexed all individuals in samples comprising 80 or fewer shrimps.…”

“…For each study site and for all study sites grouped together, the age and growth of M. acanthurus were determined using length-frequency distributions (LFDs) Pérez 2004, 2007;Baeza et al 2010). We reconstructed monthly LFDs using 3-mm-CL size intervals, as this scale proved useful for the detection of modes during preliminary data analyses.…”

Molecular phylogeny of hinge-beak shrimps (Decapoda: Caridea:RhynchocinetesandCinetorhynchus) and allies: a formal test of familiar and generic monophyly using a multilocus phylogeny

“…Although the majority of caridean species are gonochoric (separate sexes), some species have some sort of sequential (protandric) hermaphroditism in which individuals first develop as males and then later change sex to female (Bauer, ; Bauer & Conner, ). In a few hippolytid genera, particularly Lysmata Risso, 1816, the male‐phase individual changes into a simultaneous hermaphrodite although with an overall female phenotype (Bauer & Holt, ; Baeza et al ., , ; Onaga et al ., ). The distribution of hermaphroditic species in the Caridea is scattered and somewhat bewildering, with no apparent pattern (Bauer & Conner, ).…”