Pairs Of Pleopods Research Articles

Occurrence of abnormal sexual dimorphic structures in the gonochoristic crustacean, Upogebia major (Thalassinidea: Decapoda), inhabiting mud tidal flats in Japan

Normal females of the mud shrimp, Upogebia major, have a pair of pleopods on the first abdominal segment, while normal males do not. We have investigated nine populations in the Seto-Inland Sea, Japan, and found morphological disorders on the first abdominal segments of both males and females. In males, the first pleopods occurred. Morphology and arrangement of these additional pleopods were classified into four types. The pleopods of Types M-1 and M-2 were similar in structure to those of normal females. These males could be considered as de-masculinized individuals, and the occurrence of males with these morphological disorders showed local variation: while their frequency was high in two specific sites in Kasaoka Inlet (11.5% in Site 6 and 5.5% in Site 7), it was less than 3.5% in other sites. Other types had abnormal additional appendages similar to the walking legs (pereiopods) (Type M-3) or biramous leaf-like pleopods (Type M-4), but their frequency was extremely low (only 3 out of 1558 males inspected). Morphological disorders in males (Types M-1 and M-2) occurred independently of gonadal development, and did not affect the sexual characteristics as revealed by analyses of allometric growth and gonadal index. In females, morphological disorders were classified into five types: incomplete first pleopods (Type F-1); lack of the first pleopods (Type F-2 and F-3); transformation into the pereiopod-like pleopods (Type F-4); and biramous leaf-like pleopods (Type F-5). The frequency of Types 1–3 was especially high in Site 6 in Kasaoka Inlet (24.4%), but was less than 9.4% in other sites. A feature was that cuticular lesions often co-occurred with the morphological disorders. Possible causal factors of these abnormalities are discussed.

Deep-sea Leuconidae (Cumacea, Peracarida) in the south-eastern Atlantic

The Leuconidae of the deep eastern Atlantic obtained during the German expedition Diva II and the French expeditions Zaiango and Biozaire 1 to 3 were analysed. Thirteen more or less frequently occuring leuconid species were found, including ten new deep-sea species from the Cape, Angola and Guinea Basin. The most speciose (ten species) genus is Leucon with three species in the subgenus Crymoleucon, four species in the subgenus Epileucon, one species in the subgenus Leucon and two species in the subgenus Makrauloleucon. A new genus—Afroleucon—is described, having penial lobes and only one pair of pleopods in males. One species each belongs to the genera Bytholeucon and Eudorella. Only three species, Leucon (Makrauloleucon) brigittehilbigae Muhlenhardt-Siegel 2005b, Leucon (Leucon) homorhynchus Bishop 1981a and Leucon (Epileucon) cf tenuirostris form A Bishop 1981b, were already known. The new species are: Afroleucon enigmatica n.g., Leucon (Crymoleucon) lufupa, L. (Crymoleucon) kafunta, L. (Crymoleucon) galeronae, L. (Epileucon) kapinga, Leucon (Epileucon) paraspiniventris, L. (Epileucon) paralongirostris, Leucon (Makrauloleucon) moritzi, Eudorella angolensis, and Bytholeucon kaingo.

Transferencia de espermatóforos en el camarón de roca Rhynchocinetes typus (Caridea: Rhynchocinetidae)

The manner in wich males of the rock shrimp Rhynchocinetes typus transfer spermatophores during mating was determined. Fecundation is external. The first and second pair of male pleopods play an active role in the transfer of sperm to the female's sternite. To he participation of these pleopods was determined by amputating the first, second, or both pairs of pleopods of sexually mature males of the type robustus. The number of fertilized eggs in the females was then counted. No fertilization was observed in he females that had mated with males lacking both the first and second pairs of pleopods. Females that had mated with males without either the first or second pair of pleopods presented (1.8% and 0.04%) fewer fertilized eggs than those females that had mated with intact males (100%). These results indicate that both pairs of pleopods participate in the transfer of sperm.

Sistema reproductivo de hembras y machos en Cancer setosus (Molina, 1782) (Decapoda, Brachyura)

Females of the genus Cancer have a spermathecae whose connection with the ovary can be dorsal or ventral, depending on the species. The spermathecae is a structure specialized in receiving the spermatophores released by the male during mating. This study aims to describe and measure the reproductive structures of both sexes in the crab C. setosus. Females have a pair of ovaries in an H-type conformation; the anterior lobes are 2.4 times longer than the posterior lobes. The spermathecae has walls that are not extensible and a ventral-type connection with the oviduct, which indicates internal fertilization for this species. Sixty-four percent (64%) of the studied females presented a couple of spermatic blockages. In males, the first pair of pleopods is tubular, with the distal tips pointed and/or open, forming a fold. The second pair of pleopods ends in a funnel structure with 12 side extensions. The two testes are whitish in color and converge in a vas deference (VD) that has three zones: proximal, middle, and posterior. Each of these plays a role in the elaboration of the spermatophores and seminal fluid production.

Morfología comparada de los pleópodos del macho de Rhynchocinetes typus (Caridea: Rhynchocinetidae)

The morphological adaptation that the first pair of pleopods has experienced in the Caridea group, permits to characterize them as gonopods which are used for transferring spermatophores to the female during the mating. In order to know the function of the pleopods in the transfer of spermatophores during the mating of the rock shrimp Rhynchocinetes typus, it was necessary to determine the morphology of the male pleopods. The analysis of the first pair of pleopods showed a different morphology compared to the subsequent pair of pleopods, and notable adaptative differences in comparison with the typical morphology of other Caridea. These results suggest that both pairs of pleopods are involved in the transfer of spermatophores to the female.

Paralamprops poorei, sp. nov. (Crustacea: Cumacea: Lampropidae), a new Australian cumacean

Gerken, S. 2009. Paralamprops poorei, sp. nov. (Crustacea: Cumacea: Lampropidae), a new Australian cumacean. Memoirs of Museum Victoria 66: 71–75. Paralamprops is a small genus in the cumacean family Lampropidae. A new species, Paralamprops poorei sp. nov. is described from the southern Australian continental slope. Paralamprops poorei can be distinguished from all other Paralamprops by the combination of a toothed marginal carina, subequal antennular fl agellae, maxillule without palp, pereopods 3 and 4 in the female with rudimentary exopods, pereopod 5 with article proportions as in pereopods 3 and 4, telson with 5 lateral setae and 3 equal terminal setae, and the male with three pairs of pleopods.

Phalloleucon abyssalis, a new cumacean genus and species (Crustacea: Peracarida: Leuconidae) from the Peru Basin

A new genus and species, Phalloleucon abyssalis, of the cumacean family Leuconidae from the Peru Basin is introduced. The new genus is characterised in having penial lobes and one pair of pleopods in males. It is suggested that the species Eudorella redacticruris Watling and McCann, 1997 is transfered into a new leuconid genus: Pseudeudorella.

Protandric simultaneous hermaphroditism in the shrimps Lysmata bahia and Lysmata intermedia

Abstract. The sexual system of two peppermint shrimps, Lysmata bahia and Lysmata intermedia, inhabiting intertidal fossil coral terraces at Bocas del Toro, on the Caribbean coast of Panama, was examined. Dissections suggested that the population of each species consisted of functional males and functional simultaneous hermaphrodites. Males have cincinulli and appendices masculinae on the first and second pair of pleopods, respectively, gonopores located at the coxae of the third pair of walking legs, and ovotestes with a well‐developed male portion full of sperm, but an undeveloped female portion. Hermaphrodites lacked appendices masculinae and cincinulli. However, they have male gonopores and ovotestes with well‐developed ovaries full of mature oocytes and testes with sperm. When hermaphrodites were maintained in pairs, both molted and spawned eggs (to beneath abdomen) that continued developing after 3 d, demonstrating that hermaphrodites can reproduce as males and inseminate other hermaphrodites acting as females. The possibility of self‐fertilization or parthenogenetic reproduction was tested and disregarded, because hermaphrodites reared in isolation spawned oocytes that failed to develop, disappearing from the abdomen after 2 d. Males reared in pairs mature as hermaphrodites in <50 d, showing the ability of males to mature as hermaphrodites. These results demonstrate that L. bahia and L. intermedia are protandric simultaneous hermaphrodites, as reported for all species of this genus whose sexual system has been examined. However, the studied species featured a lifestyle, termed “tropical‐low abundance,” here not recognized previously for the genus; they occur in low abundances in tropical environments, they do not develop symbiotic associations with sessile invertebrates, and they are not conspicuously colored. Information on the sexual systems and lifestyles of more species needs to be examined before these observations can be placed into a comparative context within the genus.

Reproductive Biology and Functional Maturity in Females of Aegla Franca (Decapoda: Anomura: Aeglidae)

Abstract We describe the reproductive period, fecundity, and average size at the onset of functional maturity of female Aegla franca, the northernmost distributed aeglid species. The reproductive period is markedly seasonal and takes place from May (austral mid-autumn) to August (late winter). Ovigerous females appear quite abruptly in the population by May, and this condition is observed in all adult females sampled regardless of their size. The average size at the onset of functional maturity in females, at which 50% of the females sampled during the reproductive period were considered adults, was 12.75 mm CL. The smallest post-ovigerous female measured 12.06 mm carapace length (CL). Mean fecundity (±S.D.) from 41 females bearing early and intermediate eggs was 129.1 ± 32.2 and corresponded to a mean female CL of 14.11 mm. The elliptical-shaped eggs exhibited significant increase in size along the development stages. The third pair of pleopods bore higher number of eggs than the others. Compiled informa...

Environmental sex determination, external sex differentiation and structure of the androgenic gland in the Pacific white shrimp Litopenaeus vannamei (Boone)

Environmental eiects on sex determination in Litopenaeus vannamei were studied by rearing day 1 postlarvae at three temperatures, under three photoperiods, at high density and by starving. None of the environmental conditions aiected sex determination or diierential development of gender in this species. From day 50, the development of the endopodite of the ¢rst pair of pleopods revealed the ¢rst external diierentiation, showing a triangular structure with three setae in females, whereas a tubular structure remained in males. Juvenile shrimp sex diierentiation took place from days 50^90, independent of size, only if postlarvae reached a development threshold of 150 mg of body weight and 20 mm of body length previously. Histology and scanning electron microscopy of the vas deferens revealed that the androgenic gland (AG) is a single 2-mm cord attached in the subterminal ejaculatory region, just before the distal vas deferens narrows. The AG is composed of large oval cells containing vacuolated cytoplasm, and each cell has a prominent rounded nucleus, similar to all descriptions of the AG in Malacostracans, so we assume that it should have the same function in sex diierentiation.

THE FECUNDITY, TIME OF EGG DEVELOPMENT AND JUVENILE PRODUCTION IN SPINY-CHEEK CRAYFISH (ORCONECTES LIMOSUS) UNDER CONTROLLED CONDITIONS

We comprehensively describe the fecundity and time of embryonic development of the spiny-cheek crayfish (Orconectes limosus). Linear relationships between female size and ovarian fecundity, pleopodal fecundity, and production of juveniles at the 3rd stage, were confirmed. The ovarian fecundity was evaluated for the smallest as well as largest females in the sampled population (43-93 mm of body length); the number of oocytes (eggs) ranged widely, between 46 and 505. No significant difference was found between the ovarian and pleopodal fecundity observed just after egg laying. The value of the female gonadosomatic index just before laying was 4.2 ± 1.8% (0.8-7.7%). The mean diameter of eggs on female pleopods was 1.8 ± 0.2 mm (1.45-2.15 mm). A statistically significant difference was found between the numbers of eggs carried on individual pairs of pleopods. Mean time from laying to hatching was 46 ± 3.8 days (37-56 days), i.e. 647 ± 39.9 CTU (Celsius Temperature Units = degrees Celsius × days). Mean production of juveniles at the 3rd stage was found to be 135.7 ± 67.24 (15-243) juveniles. The early sexual maturation and also high number of juveniles at the 3rd stage per female gives this species a good predisposition for quick establishment in new localities.

Sexual difference in modes of selection on the pleopods of crayfish (Decapoda: Astacoidea) revealed by the allometry of developmentally homologous traits

Crayfish have five pairs of abdominal limbs called pleopods. In males, the first and second pairs of pleopods are used for transferring spermatophores to the female during copulation. The remaining pleopods in males have no obvious function. Female crayfish use their pleopods to carry eggs. Accordingly, it is expected that the selection pressures that act on the pleopods differ between males and females. To test this hypothesis, we estimated modes of selection on pleopods in two species of crayfish (Procambarus clarkii and Pacifastacus trowbridgii) by comparing allometric relationships in functional and nonfunctional pleopods. Since pleopods are serially homologous traits, developmental constraints on these traits appear to be minimal. The lengths of the first male pleopods, used in copulation, showed lower allometric values and less dispersion around the regression line, suggesting that they have been under stabilizing selection. This likely occurs because the major selective force is the ability of males to copulate with females of various sizes. The pleopods of females showed higher allometric values than pleopods of males without an assigned function. This suggests that the pleopods of females have been under directional selection, most likely because they are longer and can therefore carry more eggs.

ARE PLEOPODS JUST “MORE LEGS”? THE FUNCTIONAL MORPHOLOGY OF SWIMMING LIMBS IN EURYTHENES GRYLLUS (AMPHIPODA)

Abstract Amphipods, like most swimming crustaceans, employ a drag-based mechanism to produce thrust. The propulsors are paddle-shaped pleopods that move parallel to the direction of motion. These paired abdominal limbs generate both the propulsive thrust and the respiratory currents that bathe the thoracic gills. This study addresses the basic kinematics of motion and the pleopodal skeletomusculature of the deep-sea scavenger Eurythenes gryllus. The limb beat cycle consists of a power stroke where the three pleopod pairs, with their setal fan outstretched, swing sequentially through an arc parallel to the body axis, and then return anteriorly in a collapsed and bent configuration. The joint connecting the body to the muscular peduncle is complex, allowing promotion and remotion along the main body axis. Several hard plates for extrinsic muscle attachment are surrounded by arthrodial membrane. The extrinsic musculature is proportioned accordingly, with a large mass of muscles controlling the power stroke a...

Amphi-Atlantic distribution of the Mancocumatinae (Cumacea: Bodotriidae), with description of a new genus dwelling in marine lava caves of Tenerife (Canary Islands)

A new cumacean genus and species, Speleocuma guanche gen et sp. nov., belonging to the subfamily Mancocumatinae Watling 1977, is described from marine lava caves of Tenerife, Canary Islands. This genus differs from others in the subfamily in having two pairs of pleopods in males and exopods on first to third pereopods, but not on fourth pereopod, in both sexes. Correlation between phylogenetic relationships of the new genus and the geological history of the Canarian archipelago points to a probable origin of this endemism: the subfamily Mancocumatinae show a disjunct distribution on both sides of the Atlantic Ocean, a pattern which has been associated with fauna of Tethyan origin. It is suggested that present day genera of the subfamily evolved from a common shallow water ancestor living in the late Mesozoic (c. 120 Myr BP), when the opening of the Atlantic Ocean had begun. It survived in shallow waters off the west African coast before the emergence of the Canary Islands from the sea floor. Later on, between the late Cretaceous and the Mio-Pliocene, it was able to colonize crevicular habitats of the eastern Canary Islands through continental or land bridges. Finally, their numbers increased to occupy more recent biotops like flooded lava tube caves as well as westward islands such as Tenerife.

Are Pleopods Just “More Legs”? The Functional Morphology of Swimming Limbs in Eurythenes Gryllus (Amphipoda)

Amphipods, like most swimming crustaceans, employ a drag-based mechanism to produce thrust. The propulsors are paddle-shaped pleopods that move parallel to the direction of motion. These paired abdominal limbs generate both the propulsive thrust and the respiratory currents that bathe the thoracic gills. This study addresses the basic kinematics of motion and the pleopodal skeletomusculature of the deep-sea scavenger Eurythenes gryllus. The limb beat cycle consists of a power stroke where the three pleopod pairs, with their setal fan outstretched, swing sequentially through an arc parallel to the body axis, and then return anteriorly in a collapsed and bent configuration. The joint connecting the body to the muscular peduncle is complex, allowing promotion and remotion along the main body axis. Several hard plates for extrinsic muscle attachment are surrounded by arthrodial membrane. The extrinsic musculature is proportioned accordingly, with a large mass of muscles controlling the power stroke and a few long muscles generating the recovery stroke forces. The intrinsic musculature within the peduncle and annular rami serves two functions: (1) many long, thin muscle fibers within the peduncle function as support muscles responsible for shape changes; (2) large, strap-like muscles control flexion for the recovery stroke and abduction-adduction of the exopod for the power stroke. Several ancillary skeletal structures enhance swimming efficiency: reinforcement in the pleonal wall for muscle attachment, coupling hooks between the pleopod pair to effectively create a single paddle, the complementary shapes of the exopod and endopod, and an exopodal hook that facilitates the complete collapse of the pleopods on the recovery stroke. The functional design of the pleopod maximizes efficient recovery stroke motion while still providing strong remotion during the recovery stroke.

LEPIDOPHTHALMUS MANNINGI, A NEW GHOST SHRIMP FROM THE SOUTHWESTERN GULF OF MEXICO (DECAPODA: THALASSINIDEA: CALLIANASSIDAE)

Lepidophthalmus manningi, new species, is described from intertidal and shallow subtidal margins of estuarine embayments, ephemeral tidal ponds, and river mouths in the states of Veracruz, Tabasco, and Campeche, eastern Mexico. This apparent endemic of the southwestern Gulf of Mexico is ornamented by conspicuous sclerotized plates on ventral surfaces of the abdomen, a feature it shares with several other tropically distributed species in the western Atlantic and eastern Pacific. Lepidophthalmus manningi is very close in morphology to the recently described L. richardi from Belize, its apparent sibling, but can be distinguished by unique features in sculpture and shape of not only the ventral abdominal plating, but also in structures such as the eye tubercles, major chelipeds, and the anterior two pleopod pairs, dorsal abdominal tergites, and the uropods. It is readily distinguishable from two other Gulf of Mexico species, both of which lack ventral sclerotized plates on the abdomen. The latter include the widely distributed warm-temperate species, L. louisianensis, which ranges throughout the northern Gulf of Mexico and into Tamaulipas, Mexico, and a second southwestern Gulf endemic form that remains undescribed and is currently under study. Disjuncture of appropriate habitats in the northern Yucatan Peninsula and limited dispersal ability in the genus appear to account for isolation of L. manningi from its Caribbean sibling.

Philosciids with pleopodal lungs from Brazil, with description of a new species (Crustacea, Isopoda)

Several species of “philosciid” Oniscidea are known from Brazil, most of them were found in the southern and eastern parts of this country. The genera Atlantoscia Ferrara & Taiti, 1981, Benthana Budde-Lund, 1908 and Balloniscus Budde-Lund, 1908, the latter considered to represent a separate family Balloniscidae Vandel, 1963, are considered the only neotropical philosciids bearing respiratory areas on their pleopods. Therefore, representatives of these genera are re-examined to shed new light on the question whether these species can be considered to be a monophylum with the autapomorphy “respiratory areas present”, The phylogeny of the above-mentioned genera is discussed under morphological and biogeographical aspects. Furthermore, a remarkable new species of Atlantoscia Ferrara & Taiti, 1981, which bears pleopodal lungs in all five pairs of pleopods, is described. In regard to this character, it differs from its sister species Atlantoscia floridana (Van Name, 1940). Additionally, the hitherto unknown male of Benthana convexa Lemos de Castro, 1958 will be described; it is evident that this species is different from its closest relative B. schubarti Lemos de Castro, 1958, which is also found in Brazil.

Burrow ventilation in the tube-dwelling shrimp Callianassa subterranea (Decapoda: thalassinidea). I. Morphology and motion of the pleopods, uropods and telson.

The morphology of the pleopods, uropods and telson of the tube-dwelling shrimp Callianassa subterranea have been studied using dissection microscopy and scanning electron microscopy. The kinematics of these appendages were examined by motion analysis of macro-video recordings of ventilating shrimps in transparent artificial burrows. The pleopods show the usual crustacean biramous anatomy, but all segments are rostro-caudally flattened. The protopodite bears a triangular medially oriented endopodite and a scoop-shaped exopodite. The contralateral endopodites are linked by the appendix interna, ensuring a perfect phase relationship between contralateral pleopods. The outer rims of the exopodites are fringed with long fern-leaf-like plumose setae bearing flattened setules. These setae have very mobile joints and can be turned caudally. The slits between contralateral endopodites have rims of leaf-like setae as well. Setae of the same leaf-like type fringe the uropods, but these are non-motile. The telson has a narrow fringe of leaf-like setae, locally interrupted by long mechanoreceptory setae. A shrimp, wandering through the burrow or resting, holds its pleopods against the abdomen with the exopodites and their setal fringes retracted medially. The uropods are folded medially as well, probably to reduce the shrimp's drag. During ventilation, the uropods are extended against the tube wall, leaving only a small opening for flow ventral from the telson, and the pleopods beat at a frequency of approximately 1 Hz (0.9+/-0.2 Hz). Fourier analysis of pleopod kinematics showed that the motion pattern of the first flow-generating pleopod pair (PP1) consisted mainly of the first harmonic (75 %) and to a lesser extent of the third harmonic (20 %), resulting in almost perfect sinusoidal motion. The motion patterns of PP2 and PP3 could be modelled by assigning pure sinusoids with a 120 degrees phase shift and a rostro-caudal ranking to the three pairs of pleopods.

Burrow ventilation in the tube-dwelling shimp Callianassa subterranea (Decapoda: thalassinidea). III. Hydrodynamic modelling and the energetics of pleopod pumping.

The process of flow generation with metachronally beating pleopods in a tubiform burrow was studied by designing a hydrodynamic model based on a thrust-drag force balance. The drag of the tube (including the shrimp) comprises components for accelerating the water into the tube entrance, for adjusting a parabolic velocity profile, for accelerating the flow into a constriction due to the shrimp's body and another constriction due to the extended tail-fan, for shear due to separation and for the viscous resistance of all tube parts. The thrust produced by the beating pleopods comprises components for the drag-based thrust and for the added-mass-based thrust. The beating pleopods are approximated by oscillating flat plates with a different area and camber during the power stroke and the recovery stroke and with a phase shift between adjacent pleopod pairs. The added mass is shed during the second half of the power stroke and is minimized during the recovery stroke. A force balance between the pleopod thrust and the tube drag is effected by calculating the mean thrust during one beat cycle at a certain flow velocity in the tube and comparing it with the drag of the tube at that flow velocity. The energetics of the tube and the pump are derived from the forces, and the mechanical efficiency of the system is the ratio of these two. Adjusted to standard Callianassa subterranea values, the model predicts a mean flow velocity in the tube of 1.8 mm s-1. The mean thrust force, equalling the drag, is 36. 8 microN, the work done by the pleopod pump per beat cycle is 0.91 microJ and the energy dissipated by the tube system is 0.066 microJ per cycle. The mechanical efficiency is therefore 7.3 %. Pump characteristics that may be varied by the shrimp are the beat frequency, the phase shift, the amplitude and the difference in pleopod area between the power and recovery strokes. These parameters are varied in the model to evaluate their effects. Furthermore, the moment of added mass shedding, the distance between adjacent pleopods, the number of pleopods and the total tube drag were also varied to evaluate their effects.

The Megalopa and Juvenile Development of Pachygrapsus Transversus (Gibbes, 1850) (Decapoda, Brachyura) Compared With Other Grapsid Crabs

Megalopae were reared in the laboratory to the 7th crab stage. The megalopa and 1st crab stage are described and juvenile development was studied with emphasis on pleopodal differentiation. The megalopal phase, is easily identified, and shares with those of other Grapsinae and Plagusiinae big size, the presence of many natatory setae, and a series of conspicuous teeth on the inner margin of the dactyli from the 2nd to 4th walking leg. These features are regarded as adaptive for settlement in a wave-swept environment, such as the rocky marine intertidal where most of those species live. Fast development of juvenile pleopods is another characteristic of these subfamilies. In Pachygrapsus transversus, the sexes can be distinguished from the 2nd crab stage. Gonopod differentiation in males and the basic segmentation of all four pleopod pairs in females are already concluded at the 5th instar. A review of the available information indicated that settlement of large megalopae and fast juvenile development, preceding a precocious sexual maturity, are trends in Grapsinae and Plagusiinae. On the other hand, the Sesarminae pass through a more extensive juvenile instar sequence and presumably a delayed maturity.