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

Bauer RT, Okuno J, Thiel M - Zookeys (2014)

Bottom Line: The major (pereopod 1) chelipeds of males are significantly larger and longer than those of females.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, University of Louisiana, Lafayette, Louisiana 70504-2451, USA.

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.

No MeSH data available.


Related in: MedlinePlus

Puncture wounds (unmarked arrows) on the propodi of the major chelipeds of three large Cinetorhynchus males. ACinetorhynchus sp. A B and CCinetorhynchus sp. B D Regenerating major cheliped of a male Cinetorhynchus sp. B; only two articles plus a rudimentary cheliped with underdeveloped propodus and dactyl have formed. d dactyl (movable finger); p propodus. Scale bars represent 3 mm.
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Figure 8: Puncture wounds (unmarked arrows) on the propodi of the major chelipeds of three large Cinetorhynchus males. ACinetorhynchus sp. A B and CCinetorhynchus sp. B D Regenerating major cheliped of a male Cinetorhynchus sp. B; only two articles plus a rudimentary cheliped with underdeveloped propodus and dactyl have formed. d dactyl (movable finger); p propodus. Scale bars represent 3 mm.

Mentions: The major chelipeds of a number of males showed injuries. These injuries took the form of puncture wounds (Fig. 8A–C) to the elongated propodal portion (“palm”) of the major chelipeds. Previous possible injury, i.e., complete loss, of the cheliped may be indicated by regeneration of the cheliped (Fig. 8D). Puncture wounds were recognized by roughly circular perforations in the cuticle surrounded by melanized exoskeleton, a sign of scabbing and healing. Regenerating chelipeds were recognized by a combination of characteristics: much smaller than the other member of the pair (if present), a poorly sclerotized (whitish in preservative) cuticle, and a reduced number of poorly formed articles (Figure 8D). Of 38 males (both species) with one or both chelipeds, 10 individuals (26%) showed signs of injury (5 with puncture wounds, 5 with regenerating cheliped). By species, Cinetorhynchus sp. B males (N = 27), 3 (11.1%) had puncture wounds, while 4 (14.8%) had a regenerating major cheliped. In Cinetorhynchus sp. A males (N = 11), 2 (18.2%) showed puncture wounds and 1 (9.1%) had a regenerating cheliped. None of the females (Cinetorhynchus sp. A, N = 6; Cinetorhynchus sp. B, N = 14) showed any obvious sign of injury to their major chelipeds.


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

Bauer RT, Okuno J, Thiel M - Zookeys (2014)

Puncture wounds (unmarked arrows) on the propodi of the major chelipeds of three large Cinetorhynchus males. ACinetorhynchus sp. A B and CCinetorhynchus sp. B D Regenerating major cheliped of a male Cinetorhynchus sp. B; only two articles plus a rudimentary cheliped with underdeveloped propodus and dactyl have formed. d dactyl (movable finger); p propodus. Scale bars represent 3 mm.
© Copyright Policy - creative-commons-attribution
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4283371&req=5

Figure 8: Puncture wounds (unmarked arrows) on the propodi of the major chelipeds of three large Cinetorhynchus males. ACinetorhynchus sp. A B and CCinetorhynchus sp. B D Regenerating major cheliped of a male Cinetorhynchus sp. B; only two articles plus a rudimentary cheliped with underdeveloped propodus and dactyl have formed. d dactyl (movable finger); p propodus. Scale bars represent 3 mm.
Mentions: The major chelipeds of a number of males showed injuries. These injuries took the form of puncture wounds (Fig. 8A–C) to the elongated propodal portion (“palm”) of the major chelipeds. Previous possible injury, i.e., complete loss, of the cheliped may be indicated by regeneration of the cheliped (Fig. 8D). Puncture wounds were recognized by roughly circular perforations in the cuticle surrounded by melanized exoskeleton, a sign of scabbing and healing. Regenerating chelipeds were recognized by a combination of characteristics: much smaller than the other member of the pair (if present), a poorly sclerotized (whitish in preservative) cuticle, and a reduced number of poorly formed articles (Figure 8D). Of 38 males (both species) with one or both chelipeds, 10 individuals (26%) showed signs of injury (5 with puncture wounds, 5 with regenerating cheliped). By species, Cinetorhynchus sp. B males (N = 27), 3 (11.1%) had puncture wounds, while 4 (14.8%) had a regenerating major cheliped. In Cinetorhynchus sp. A males (N = 11), 2 (18.2%) showed puncture wounds and 1 (9.1%) had a regenerating cheliped. None of the females (Cinetorhynchus sp. A, N = 6; Cinetorhynchus sp. B, N = 14) showed any obvious sign of injury to their major chelipeds.

Bottom Line: The major (pereopod 1) chelipeds of males are significantly larger and longer than those of females.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, University of Louisiana, Lafayette, Louisiana 70504-2451, USA.

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.

No MeSH data available.


Related in: MedlinePlus