Hermaphroditism and Gonochorism

Abstract

This chapter compares two sexual systems: hermaphroditism (each individual can produce gametes of either sex) and gonochorism (each individual produces gametes of only one of the two distinct sexes) in crustaceans. These two main sexual systems contain a variety of alternative modes of reproduction, which are of great interest from applied and theoretical perspectives. The chapter focuses on the description, prevalence, analysis, and interpretation of these sexual systems, centering on their evolutionary transitions. The ecological correlates of each reproductive system are also explored. In particular, the prevalence of “unusual” (non-gonochoristic) reproductive strategies has been identified under low population densities and in unpredictable/unstable environments, often linked to specific habitats or lifestyles (such as parasitism) and in colonizing species. Finally, population-level consequences of some sexual systems are considered, especially in terms of sex ratios. The chapter aims to provide a broad and extensive overview of the evolution, adaptation, ecological constraints, and implications of the various reproductive modes in this extraordinarily successful group of organisms.

Two Homogametic Genotypes – One Crayfish: On the Consequences of Intersexuality

“…Our phylogenetic analysis of available transcriptomes from different decapod species with respect to reproduction strategies indicates that C. quadricarinatus is found within the Astacidea clade, closely related to another Cherax species that also exhibits intersexual forms, C. destructor (Austin and Meewan, 1999) [C. destructor is missing from the phylogenetic analysis in the present study due to lack of transcriptional data in the National Center for Biotechnology Information (NCBI) server]. This clade is evolutionarily remote from the Caridea clade, which comprises a cluster of many decapod crustaceans exhibiting hermaphroditism (Baeza, 2007;Bauer and Holt, 1998;Benvenuto and Weeks, 2020;Subramoniam, 1981;Yaldwyn, 1966) but has a common ancestor with gonochoristic species. This finding is in agreement with a recent comprehensive phylogenomic analysis indicating that the Astacidea and Caridea infraorders diverged from a common ancestor 450 mya (Wolfe et al, 2019).…”

“…However, gynandromorphs are the outcome of random and rare events of abnormalities produced through several possible mechanisms, including improper migration of chromosomes or cytogenetic complications in early embryonic development (Gjershaug et al, 2016), while C. quadricarinatus intersexuals are not rare and their fraction in the population is not random but relatively constant Webster et al, 2004). While intersexuality in C. quadricarinatus could be attributed to a simply random phenomenon, it could also potentially represent ''evolution in the making'' in which intersexuality is the current form in an evolutionary process from a gonochoristic mode of reproduction toward hermaphroditism or vice versa, as has been suggested to have occurred repeatedly in crustaceans along evolution (Benvenuto and Weeks, 2020). However, discussions of ''evolution in the making'' with respect to intersexuality are fraught with controversial theories regarding the direction of the transition process, suggesting either that the first crustacean lineage, the ''ur-crustacean'' (Hessler and Newman, 1975;Richter and Wirkner, 2020), had a gonochoristic mode of reproduction that changed to hermaphroditism at low population densities (Cisne, 1982) or vice versa (Hessler and Newman, 1975;Juchault, 1999).…”

“…Unlike protandric hermaphrodite species, which episodically transform from one sex to the other (Bauer and Holt, 1998;Benvenuto and Weeks, 2020;Heath, 1977;Levy et al, 2020;Mutalipassi et al, 2018), the intersexual form in C. quadricarinatus uniquely represents a natural case of permanent co-occurrence of male and female characteristics within a gonochoristic scheme. The intersex animal is a functional male with a female genotype (WZ), bearing a combination of male and female gonopores and a mix of male and female reproductive systems (Khalaila et al, 1999;Parnes et al, 2003;.…”

“…Article of hermaphroditism (Bauer and Holt, 1998;Brook et al, 1994;de Almeida and Buckup, 2000;Levy et al, 2020) and even to parthenogenesis (Benvenuto and Weeks, 2020;Scholtz et al, 2003). Our phylogenetic analysis of available transcriptomes from different decapod species with respect to reproduction strategies indicates that C. quadricarinatus is found within the Astacidea clade, closely related to another Cherax species that also exhibits intersexual forms, C. destructor (Austin and Meewan, 1999) [C. destructor is missing from the phylogenetic analysis in the present study due to lack of transcriptional data in the National Center for Biotechnology Information (NCBI) server].…”

“…The sex manipulation was In the Australian redclaw crayfish, Cherax quadricarinatus, a gonochoristic species in which, according to progeny testing, sex is determined by the WZ/ZZ mode of inheritance (Parnes et al, 2003), a natural occurrence of 1-8% of intersexuals (i.e., bearing a combination of both male and female gonopores) within a given population has been reported . In contrast to protandric hermaphrodite species in which male and female phases are well defined (except during episodic transitional phases between sexes [Benvenuto and Weeks, 2020]), intersexuals of the redclaw crayfish, although bearing both male and female gonopores, do not shift between sexes but are actually males with a female genotype (WZ males) (Parnes et al, 2003;. Anatomically, they have a constantly arrested ovary in a pre-vitellogenic state (Sagi et al, , 2002.…”