Major Cheliped Research Articles

Growth, Sexual Maturity and Dimorphism in Six Species of Snapping Shrimps of the Genus Alpheus (Decapoda: Alpheidae)

This study investigated the sexual dimorphism, allometric growth, and morphological maturity of six sympatric species of Alpheus. The samplings occurred in August 2015, February and August 2016, and February 2017, in the intertidal, during low spring tides, in two localities in the northeastern Brazilian coast. In total, 3038 individuals were captured: 302 A. angulosus, 400 A. bouvieri, 516 A. buckupi, 410 A. carlae, 1002 A. estuariensis, and 408 A. nuttingi. According to our data, the six species lack sexual dimorphism regarding the carapace length. However, the major chelipeds were more robust in males of five species, whereas abdominal structures (pleurae and sternites) were larger in females, both indicatives of sexual dimorphism. The analyses of the relative growth of cheliped dimensions versus body size demonstrate that males of six species invest more energy in the chelipeds during the adult and juvenile phases. On the other hand, in the females the cheliped growth is higher during the juvenile phase. The analysis of energy allocation (calculated using body and chelipeds mass) also confirmed a high energetic investment in this appendage in males (minimum 32% of the body mass). Our results also show that females can also invest a lot of energy in the chelipeds (minimum 22% of the body mass). However, the intraspecific sex differences may be consequences of a trade-off between embryo production and cheliped development. The growth rate of pleura and sternites were higher in the adult females of all species except for A. bouvieri. In the males of the six species the appendix masculina grows faster during the juvenile phase. Lastly, in the six species of Alpheus studied, males and females reach the morphological maturity at very similar sizes, indicating a synchrony of reproduction and growth.

An updated checklist and key to the Zambian species of freshwater crabs, with the description of a new species of Potamonautes MacLeay, 1838 (Brachyura: Potamoidea: Potamonautidae)

AbstractA new species of the freshwater crab genus PotamonautesMacLeay, 1838 from Mporokoso, northern Zambia, southern Africa is described. Potamonautes caputanatisn. sp. is morphologically distinct from other species of this genus found in Zambia and its neighboring countries. The new species is recognised by a unique combination of morphological characters of the carapace, thoracic sternum, major cheliped, and adult male first gonopod. Illustrations of P. caputanatisn. sp. are provided and differences with congeners found elsewhere in Zambia and southern Africa are discussed. The addition of P. caputanatis n. sp. raises the number of species of freshwater crabs known to occur in Zambia to eleven. An updated checklist and key are provided to the Zambian species of freshwater crabs.

Description of a new alpheid shrimp, Automate isabelae sp. nov. (Decapoda, Caridea, Alpheidae) found in fish stomach contents of the lane snapper Lutjanus synagris (Linnaeus, 1758), from the west coast of Florida, Gulf of Mexico.

A new species of caridean shrimp of the family Alpheidae, Automate isabelae sp. nov., found in stomach analysis contents of the lane snapper Lutjanus synagris (Linnaeus, 1758), from the Keys and SW coast of Florida, Gulf of Mexico, is described. The abdomen and portions of the cephalic appendages were damaged in holotype, but remainder of the body and the chelipeds, whith the most important diagnostic characters are in decent or perfect condition, the description was further supplemented based on intact morphological parts of the paratypes. The presence of tubercles on the dorsal and ventral margins of the major chela palm, shows this new species to be related to the eastern Pacific Automate rugosa Coutière, 1902. Both congeners can be easily discriminated by the proportions and shape of the third maxilliped, the proportions and ornamentation of the carpus, merus, and chela of the major cheliped, the ventral seta of the carpus of the minor cheliped, the presence of a distoventral spine on the propodi of third and fourth pereopods, the armature of dorsal surface of telson, and their geographical distribution. The description of this new species increases the number of worldwide valid species known of the genus Automate to 12.

Alpheus luiszapatai, a new species of rare and colorful deep water alpheid shrimp (Crustacea: Decapoda: Alpheidae) from Arusí, Chocó Department, Pacific Coast of Colombia.

A new species of deep water alpheid shrimp, Alpheus luiszapatai sp. nov., from Arusí, Chocó, Pacific coast of Colombia is described. The single female known was collected between the discarded bycatch of deep water shrimp trawls dedicated to the commercial fisheries of the "coliflor" shrimp Solenocera spp. This new species is placed putatively in the Alpheus brevirostris (Olivier, 1811) species group, and share some external morphological characters with Alpheus hephaestus Bracken-Grissom Felder, 2014. It can be differentiated by the shape and ornamentation of major and minor chelipeds, the propodi and dactyli of third to fifth pereopods, the diaresis of uropodal exopod, the length of the rostral carina, color in life and bathymetric distribution. Additional comparison with another congeners pertaining to this species group complex from the eastern Pacific, western Atlantic and other oceanographic regions is discussed. A key for Alpheus brevirostris species group from the eastern Pacific is presented.

A review of the brachyuran deep-sea vent community of the western Pacific, with two new species of Austinograea Hessler & Martin, 1989 (Crustacea, Decapoda, Brachyura, Bythograeidae) from the Lau and North Fiji Back-Arc Basins

ABSTRACT Two new species of the genus Austinograea Hessler & Martin, 1989 (Bythograeidae Williams, 1980), distinct from A. williamsi Hessler & Martin, 1989 and A. alayseae Guinot, 1990, are here reported from hydrothermal vent fields of the southwestern Pacific: A. hourdezi n. sp. and A. jolliveti n. sp., both in the Lau and North Fiji Back-Arc Basins. Austinograea hourdezi n. sp. is characterised by two depressions appearing as dark spots on the palm of both chelipeds in males and differs from the more northern A. williamsi and the Indian A. rodriguezensis Tsuchida & Hashimoto, 2002, which show only one spot on the male chelae, near the base of the dactylus. Some individuals exhibiting all morphological characters of A. hourdezi n. sp. bear only one spot on the chelae, near the base of dactylus; the fact that most are left-handed corresponds to the presence of a regenerated cheliped, with handedness reversal after the accidental loss of the major cheliped: these atypical individuals are here treated as A...

Potamonautes nheenae, a new species of freshwater crab from Gabon, Central Africa, with a description of the first known male of Erimetopus brazzae (A. Milne-Edwards, 1886) from the Democratic Republic of the Congo, Central Africa (Brachyura: Potamoidea: Potamonautidae)

A new species of the freshwater crab genus Potamonautes MacLeay, 1838, is described from Ivindo National Park in Sofala Province, Gabon, Central Africa. Potamonautes nheenae n. sp. is morphologically distinct from the other species of this genus found in Gabon and nearby countries in Central Africa, and is most closely related to P. paecilei (A. Milne-Edwards, 1886) from the Lower Congo River basin in the Democratic Republic of the Congo. The new species is recognised by a unique combination of morphological characters of the adult male first gonopod, anterior sternum, mouthparts, and major cheliped. Illustrations of P. nheenae n. sp. are provided and differences with congeners found in Central Africa are discussed. In addition, the male gonopods, pleon, and sternum of the unusual freshwater crab Erimetopus brazzae (A. Milne-Edwards, 1886), are illustrated for the first time since its description in 1886, following the discovery of the first known male specimen of this species in the collection of the Museum of Comparative Zoology at Harvard University.

New records and description of two new species of carideans shrimps from Bahía Santa María-La Reforma lagoon, Gulf of California, Mexico (Crustacea, Caridea, Alpheidae and Processidae).

Two new species of the family Alpheidae: Alpheus margaritae sp. n. and Leptalpheus melendezensis sp. n. are described from Santa María-La Reforma, coastal lagoon, SE Gulf of California. Alpheus margaritae sp. n. is closely related to A. antepaenultimus and A. mazatlanicus from the Eastern Pacific and to A. chacei from the Western Atlantic, but can be differentiated from these by a combination of characters, especially the morphology of the scaphocerite and the first pereopods. Leptalpheus melendezensis sp. n. resembles L. mexicanus but can be easily differentiated because L. melendezensis sp. n. has the anterior margin of the carapace broadly rounded and has only one spine on the mesial margin of ischium in the major cheliped, versus an acute rostrum and an unarmed major cheliped. Additionally, a phylogenetic analysis was used to explore the relationships of these two new taxa. These results show that Alpheus margaritae sp. n. and Leptalpheus melendezensis sp. n. are indeed related to the species against which we are comparing them, and demonstrate that they can be considered as different species. Additional specimens of Leptalpheus cf. mexicanus, Ambidexter panamensis and A. swifti are recorded for the first time in the Santa María-La Reforma coastal lagoon.

Seasonal change in sexual size dimorphism of the major cheliped in the hermit crab Pagurus minutus

AbstractSexual size dimorphism is a common phenomenon in the animal kingdom, and its seasonal change has been reported in some species that possess traits dimorphic only in males and specialized for male mating success. However, few studies have examined seasonal change in sexual dimorphism of traits possessed by both sexes. Here, we examined the reproductive biology of the hermit crab Pagurus minutus, at a sandflat in the Waka River estuary, Japan, with special reference to seasonal changes in sexual dimorphism of the large claw (major cheliped) size by conducting population and precopulatory guarding‐pair sampling. Previous investigation demonstrated that the major cheliped is used as a weapon, and its size, more than body size, determines the winner in male–male contests of this species. We found ovigerous females from November to April, peaking in January, when 80% of females were ovigerous. Sexual size dimorphism of the major cheliped was observed; the degree of dimorphism increased in the reproductive season, when only males possessed an enlarged major cheliped. In addition, in the reproductive season, precopulatory guarding males had a larger body and larger relative size of the major cheliped than did solitary males, although the major cheliped size in guarding males seemed to reach an upper limit. These results suggest that seasonal change in sexual dimorphism of the major cheliped size in P. minutus strongly reflects sexual selection favoring the development of this natural weaponry, and that the degree of the dimorphism might be limited through natural selection.

Importance of weapon size in all stages of male–male contests in the hermit crab Pagurus minutus

Physical traits such as body size and weapon size typically reflect an individual’s resource holding potential (RHP). During male–male contests, contestants use these traits to assess their own and their opponent’s RHP. However, the advertisement of RHP does not always predict contest outcome. Here, we examined whether assessment index (body size or weapon size [major cheliped size]) and assessment tactics (self or mutual) are predictors of outcome in male–male contests of the hermit crab Pagurus minutus. In experimental contests over guarded females, intruders did not escalate the contest when their major cheliped was smaller than their opponent’s, implying that intruders use mutual assessment based on weapon size when deciding whether to escalate a contest. After escalation, intruders succeeded in taking over females within a shorter period of time with increasing major cheliped size relative to their opponent’s. Overall, males with a major cheliped that was larger than their opponent’s were more likely to win the contest, although some intruders later stopped guarding the female they had taken over. The importance of relative weapon size after escalation indicates that mutual assessment was also used in this phase of male–male contests. Together, these results suggest that males of P. minutus use mutual assessment based on weapon size throughout male–male contests, and that weapon size is an honest index of RHP. We examined whether assessment index (body or weapon size) and tactics (self or mutual) are predictors of outcome in male–male contests of the hermit crab Pagurus minutus. Intruders did not escalate contests when their major cheliped was smaller than their opponent’s, implying that mutual assessment based on weapon size was used to decide whether to escalate contests. After escalation, intruders succeeded in taking over females within a shorter period of time and were more likely to win with increasing weapon size relative to their opponent’s. The importance of relative weapon size after escalation indicated that mutual assessment was also used in this phase of contests. Together, these results suggest that males of P. minutus use mutual assessment based on weapon size throughout male–male contests, and that weapon size is an honest index of actual strength.

Population biology and morphometric sexual maturity of the fiddler crab Uca (Uca) maracoani (Latreille, 1802) (Crustacea: Decapoda: Ocypodidae) in a semiarid tropical estuary of northeastern Brazil

The population biology and size at sexual maturity of Uca (Uca) maracoani were studied for the first time in a semi-arid tropical estuary of northeastern Brazil. A catch-per-unit-effort (CPUE) technique was used to sample the crabs, on the surface and inside burrows, for 60-min sampling periods by one person on a monthly basis during spring low tide periods from June 2013 to June 2014 in an estuary area of Baixa Grande Beach. A total of 406 crabs were obtained, of which 317 were males, 87 non-ovigerous females, and two ovigerous females. Males were larger than non-ovigerous females. The U. (U.) maracoani population presented unimodal size frequency distribution, which may reflect a continuous recruitment, with no disruption of classes and constant mortality rates, indicating a stable population. The overall sex ratio (3.5 males: 1 female) differed significantly from the expected 1:1 proportion. The major cheliped was on the right side in 45.1% of the males, as reported for other fiddler crabs populations. A total of 294 males and 89 females were used in the allometric study. The specimens were measured at carapace width (CW), the major propodus length (MPL) of males, and abdomen width (AW) of females. In males, the relationship between CW and MPL was 22.3 mm CW, which is considered the functional value at maturity. In females, the size at sexual maturity was 19.3 mm CW based on the relationship between CW and AW. The CPUE method is discussed as one of the reasons of the high sex ratio skewed towards males. This is the first account regarding population structure of U. (U.) maracoani in semi-arid tropical areas.

Do weaponless males of the hermit crab Pagurus minutus give up contests without escalation? Behavior of intruders that lack their major cheliped in male-male contests.

In dyadic contests, theoretical studies have predicted that weaker contestants are less likely to engage in fights to minimize the cost of aggression. Since the major cheliped of decapod crustaceans is critically important as a weapon, contestants without a major cheliped should be more likely to give up the contests. We therefore examined whether loss of the major cheliped by the hermit crab Pagurus minutus would affect their decision to escalate male–male contests over guarded females. Intruders without a major cheliped showed no difference in the frequency of escalation compared with intact intruders, and the decision to give up was affected by the body size difference between the contestants. After escalation, compared with intact intruders, intruders without a major cheliped had significantly decreased success of takeover of a female from opponents, suggesting a strong disadvantage of losing their major cheliped. Although the decision of weaponless intruders to escalate seems irrational, several factors, such as poor accuracy of resource holding potential assessment, the influence of body size, and a high benefit to cost ratio of male–male contests, may have affected their behavior.

Potamonautes gorongosa, a new species of potamonautid freshwater crab (Decapoda, Brachyura) from Mozambique, southeastern Africa

A new species of the freshwater crab genus Potamonautes MacLeay, 1838, is described from Gorongosa National Park in Sofala Province, Mozambique, southern Africa. Potamonautes gorongosa, new species, is morphologically and phylogenetically distinct from the other species of Potamonautes found in Mozambique and nearby countries, and is most closely related to Potamonautes mutareensis Phiri and Daniels, 2013, from eastern Zimbabwe. The new species differs from this species and its other congeners by a unique combination of morphological characters of the first gonopod, the anterior sternum, third maxilliped, and the major cheliped. Illustrations of P. gorongosa new species are provided, and differences with other species found in Mozambique and southeastern Africa are discussed.

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

The present study tests hypotheses about sexual dimorphism in body size and morphology versus differential mating behaviours of three male ontogenetic stages (typus, intermedius and robustus morphotypes) of the hingebeak shrimp Rhynchocinetes durbanensis Gordon using canonical discriminant analysis. There is strong sexual dimorphism in this species, in that robustus morphotypes are greater in size and with larger appendages (extended third maxillipeds and major [first] chelipeds) than females. As typus males grow bigger in size, their third maxillipeds and major chelipeds become proportionately larger than those of females, and the numbers of corneous spines on the terminal segment of the maxillipeds are reduced. Although there is no sexual dimorphism in body size between typus and intermedius males and females, the robustus males are often substantially larger than females. During mating and spermatophore transfer, all male morphotypes performed similar behaviours (touching, overlapping and holding), but only intermedius and robustus morphotypes appeared to fertilize the broods of the females successfully. Robustus males were faster in approaching as well as mating with receptive females than subordinate males. When mating with robustus males, females spawned more quickly than after mating with typus and intermedius males. Additionally, the time taken for spermatophore transfer by typus males was longer. Rejection by females during the initial approach by typus males often resulted in unsuccessful spermatophore attachment. Results of this study suggest a dominance hierarchy in R. durbanensis similar to certain other rhynchocinetid species in which females appear to prefer mating with the larger robustus males.

Uca (Xeruca), a new subgenus for the Taiwanese fiddler crab Uca formosensis Rathbun, 1921 (Crustacea: Decapoda: Ocypodidae), based on morphological and molecular evidence.

The fiddler crab Uca formosensis Rathbun, 1921 (Crustacea: Decapoda: Ocypodidae), restricted to the western part of Taiwan and the offshore Penghu (Pescadores) Islands in the Taiwan Strait, has been placed under the subgenus Uca (Gelasimus) Latreille, 1817 (= Uca (Thalassuca) Crane, 1975) based on only less than a dozen specimens, but later suggested under the subgenus Tubuca Bott, 1973 because the similarity of external morphology. A suite of characters of carapace, major cheliped, gastric mill, male first gonopod, and chela handedness, as well as the phylogenic relationships (mitochondrial 16S rDNA and cytochrome oxidase subunit I, and nuclear 28S rDNA), nevertheless support this species belongs to its own subgenus. A new subgenus Uca (Xeruca) subgen. nov. is herein established for U. formosensis.

Population biology of the ‘uçá'-crab, Ucides cordatus(Linnaeus, 1763) (Brachyura: Ucididae), in mangroves of the Joanes River, Bahia State, Brazil

This study evaluated the population structure, relative growth and morphological maturity size in Ucides cordatus in the Joanes River, Bahia State (Brazil). Crabs were sampled in a fragmented and human-altered mangrove ecosystem in a Brazilian Environmental Protected Area (EPA). A total of 431 crabs were sampled (265 males and 166 females) between September 2011 and August 2012. The following measurements were taken using precision callipers: carapace width (CW) and length (CL), the length of the propodus of the major cheliped (PL, males only), and the width of the 5th somite of the abdomen (AW, females only). Specimens were also weighed to a precision of 0.5 g on a scale to obtain the total wet weight (WW). The relative growth of this species was studied by using biometric relationships to estimate the morphological maturity size in both sexes (PLxCW in males and AWxCW in females). The overall sex ratio was 1.6:1, with a predominance of males (p & 0.05). The population structure of ‘uca'-crabs was composed of two normal curves (juveniles and adults) in both sexes. A relative growth analysis using the CLxCW relationship revealed a negative allometric growth in adult males whereas adult females exhibited an isometric growth, with an inverse pattern occurring in juveniles. In males, the PLxCW relationship indicated a change in allometric growth at 39.4 mm CW (isometric growth in juveniles changing to positive allometry growth in adults). In females, the AWxCW relationship indicates that morphological maturity occurs at a delay (44.5 mm CW) and that growth changes between phases (positive allometry to isometry). Isometric growth was found using the WWxCW relationship, also regardless of sex. A literature review combined with results previously published about this species in northeast Brazilian region suggests that U. cordatus had a seasonal reproduction during six months (from December to May), with a fattening season in the following six months (June to November). Joanes River is an environmental protected area, but had a high anthropic pressure by closed condos and marinas. Despite the high anthropic pressure on this EPA, the population structure and reproduction of U. cordatus did not appear to be affected.

Constraints imposed by the major cheliped on burrow construction in the male fiddler crab, Uca annulipes (H. Milne Edwards, 1837)

The burrows excavated by male Uca annulipes at a lagoonal shore on Pulau Hantu Besar, an offshore island of Singapore, are generally less acutely bent, i.e., have significantly smaller mid-angles, than the burrows of females. In an ex situ study, burrows dug by males with the major cheliped removed, and by males with intact major cheliped, were cast with wax. Seven non-angular burrow morphological parameters (burrow diameter, total burrow depth, burrow neck height, curved burrow length, horizontal length, chamber diameter and burrow volume) and two angular variables (mid-angle and ground-angle) were compared to determine if sexual dimorphism in burrow curvature was due to the effect of the major cheliped on burrow excavation. A similar experiment using females with two intact chelipeds and one cheliped removed was conducted to determine if male crabs without the major cheliped dug burrows with dimensions similar to those of females with one cheliped removed. Mean mid-angle of burrows (± SE) was 24.9 ± 1.3° and 16.0 ± 1.0° for males whose major chelipeds were removed and with major intact chelipeds, respectively. Of all the burrow morphological parameters, only the mean mid-angle differed significantly between the two groups of crabs. Female crabs (with and without cheliped removal) did not excavate significantly different-shaped burrows (mid-angles: 20.7 ± 2.1° and 18.2 ± 1.5°, respectively) suggesting that removal of cheliped did not affect burrow architecture. The curvature of the burrows of males that had the major cheliped removed was not significantly different from those of females with one cheliped removed (mid-angles: 24.9 ± 1.3° and 20.7 ± 2.1°, respectively). Results of the study showed that the major cheliped in a male U. annulipes is most likely to be responsible for the sexual dimorphism in curvature of the burrows.

Reproductive biology and population structure ofAxianassa australis(Crustacea, Axianassidae) on a sand-mud flat in north-eastern Brazil

The life history of the mud shrimpAxianassa australis, a common and widespread burrower inhabiting coastal mangroves and mud flats, is poorly known. This contribution presents the first information about the population structure, reproductive biology and fecundity ofA. australis, based on individuals collected from September 2011 to December 2012 on Casa Caiada Beach, located in a densely urbanized area in north-eastern Brazil, using a yabby pump. The sex ratio did not depart significantly from the expected 1:1 proportion. A significant trend of left-handedness of the major cheliped was observed in the population. Females reached a larger maximum cephalothorax length (CL) than males. The differential growth between CL and the propodus of the major cheliped showed negative allometric growth for females and positive allometric growth for males, suggesting a trade-off between somatic growth and reproductive effort. Females bearing uneyed orange embryos predominated during all months in which ovigerous females were collected. Mean fecundity was 2379 eggs, ranging from 5 (7.55 mm CL) to 8300 (14.19 mm CL) eggs per female. About 71% of the variation in the number of eggs carried per female was explained by CL. The mean egg size correlated negatively with fecundity, indicating that large females ofA. australisproduce more and larger eggs than smaller females.

First record of bilateral hypertrophy in chelas of Uca rapax male specimen (Crustacea, Decapoda, Ocypodidae) on the Brazilian coastline

An adult male specimen ofUca rapax(Crustacea, Decapoda, Ocypodidae), containing bilaterally hypertrophied chelipeds, was found in the mangrove area of the Rio Grande do Norte state, north-eastern Brazil. The chelipeds are subequal in size and similar to the major cheliped of normal male specimens ofUca rapax. This paper is the first record of the aforementioned anomaly for the species from the Brazilian coastline.

Sex‐related differences in size, function and regeneration of the major cheliped in the hermit crab Pagurus filholi

AbstractPagurus hermit crabs have a well‐developed right cheliped (major cheliped) and in some species the major cheliped of males is longer than that of females. This paper describes sex‐related differences in major cheliped length and regeneration pattern of the major cheliped in the hermit crab Pagurus filholi. We also examined the function of the major cheliped in male–male competition. Major cheliped length of males was longer than that of females in P. filholi. Males regenerated larger chelipeds than females at the first molt after experimentally induced autotomy. Body size growth in males of the regeneration group was less than that in intact males of the control group while there was no significant difference in body size growth of females between regeneration and control groups. Major cheliped length was included in the best model to explain the outcome of male–male competition and thus sexual selection appears to be a causative factor in the sex‐related difference of the major cheliped length. Sex‐related differences in the regeneration pattern may reflect differences in evolutionary pressures on males for large major chelipeds and females for large body size.

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

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.