Inferences on mating and sexual systems of two Pacific Cinetorhynchus shrimps (Decapoda, Rhynchocinetidae) based on sexual dimorphism in body size and cheliped weaponry

Abstract

Sexual dimorphism in body size and weaponry was examined in two Cinetorhynchus shrimp species in order to formulate hypotheses on their sexual and mating systems. Collections of Cinetorhynchus sp. A and Cinetorhynchus sp. B were made in March, 2011 on Coconut Island, Hawaii, by hand dipnetting and minnow traps in coral rubble bottom in shallow water. Although there is overlap in male and female size, some males are much larger than females. The major (pereopod 1) chelipeds of males are significantly larger and longer than those of females. In these two Cinetorhynchus species, males and females have third maxillipeds of similar relative size, i.e., those of males are not hypertrophied and probably not used as spear-like weapons as in some other rhynchocinetid (Rhynchocinetes) species. Major chelae of males vary with size, changing from typical female-like chelae tipped with black corneous stout setae to subchelate or prehensile appendages in larger males. Puncture wounds or regenerating major chelipeds were observed in 26.1 % of males examined (N = 38 including both species). We interpret this evidence on sexual dimorphism as an indication of a temporary male mate guarding or “neighborhoods of dominance” mating system, in which larger dominant robustus males defend females and have greater mating success than smaller males. Fecundity of females increased with female size, as in most caridean species (500–800 in Cinetorhynchus sp. A; 300–3800 in Cinetorhynchus sp. B). Based on the sample examined, we conclude that these two species have a gonochoric sexual system (separate sexes) like most but not all other rhynchocinetid species in which the sexual system has been investigated.

Reproductive morphology and mating behaviour in the hingebeak shrimp Rhynchocinetes durbanensis Gordon, 1936 (Decapoda: Caridea: Rhynchocinetidae) in India

“…One-way ANOVA of total time duration (min) of reproductive behaviours performed by male morphotypes (TM, typus male; IM, intermedius male; RM, robustus male) of R. durbanensis. Rojas et al, 2012), rhynchocinetids (Correa et al, 2000;Thiel et al, 2010;Bauer et al, 2014; present study) and hippolytids (Tirmizi & Kazmi, 1971;Bauer, 1977;Jensen, 2014). In these shrimps, the changes during male ontogeny are striking and there are discrete differences among male morphotypes, which can be clearly distinguished based on the colour patterns of the major chelae, variation in cheliped morphology, and other morphometric characters.…”

“…Males also differ in important behavioural and physiological characters, indicating that the largest males dominate the mating process owing to their high resource holding potential (Correa et al, 2003). In the other rhynchocinetid genus, Cinetorhynchus, there is also a similar ontogeny of males in which the larger males have hypertrophied major chelipeds (but not third maxillipeds) and in which a similar mating system has been hypothesized (Bauer et al, 2014).…”

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

“…). Other species whose population structure and reproductive characters have been carefully examined are all gonochoric species with large males and hypertrophied chelipeds ( R. typus , Correa & Thiel, ; R. brucei , Thiel et al ., ; two Cinetorhynchus species from Hawaii, Bauer et al ., in press; Fig. ).…”

Is the Setal Patch on the Chelae of Hemigrapsus takanoi and Hemigrapsus sinensis (Crustacea, Brachyura, Varunidae) Advantageous in Fighting and Mating?

“…; Bauer et al. ), and injuries may affect an animal's fighting abilities and its general health (Berzins & Caldwell ; Claverie & Smith ; Thiel et al. ).…”

“…A setal patch on the chelae affected the outcome of intrasexual fighting in only males of the non-dimorphic species. Fights between crustaceans often result in damage to the chelae (Jones 1980;Barki et al 1997;Claverie & Smith 2007;Rypien & Palmer 2007;Thiel et al 2010;Rojas et al 2012;Bauer et al 2014), and injuries may affect an animal's fighting abilities and its general health (Berzins & Caldwell 1983;Claverie & Smith 2007;Thiel et al 2010). Crabs close their chela by contracting the closer muscle on the propodus (Warner 1977).…”