Pairs Of Pleopods Research Articles

A new freshwater crab species of the genus Vela Bahir & Yeo, 2007 (Decapoda: Brachyura: Gecarcinucidae) from the Western Ghats of Karnataka, India

Vela bandhavya sp. nov., a new species of gecarcinucid crab is described from the Central Western Ghats, Uttara Kannada district, Karnataka state, India. The new species can be immediately distinguished from three other species of Vela Bahir & Yeo, 2007, mainly by its short male sternopleonal cavity and a relatively shorter distal article of the male first gonopod. The diagnosis of Vela is revised to accommodate the new species, and an illustrated identification key is provided for all four species. An anomalous adult male crab, with a pair of pleopods on the pleonal somite 5 in addition to the male gonopods, is also reported.

Mantis Shrimp Locomotion: Coordination and Variation of Hybrid Metachronal Swimming.

Across countless marine invertebrates, coordination of closely spaced swimming appendages is key to producing diverse locomotory behaviors. Using a widespread mechanism termed hybrid metachronal propulsion, mantis shrimp swim by moving five paddle-like pleopods along their abdomen in a posterior to anterior sequence during the power stroke and a near-synchronous motion during the recovery stroke. Despite the ubiquity of this mechanism, it is not clear how hybrid metachronal swimmers coordinate and modify individual appendage movements to achieve a range of swimming capabilities. Using high-speed imaging, we measured pleopod kinematics of mantis shrimp (Neogonodactylus bredini), while they performed two swimming behaviors: burst swimming and taking off from the substrate. By tracking each of the five pleopods, we tested how stroke kinematics vary across swimming speeds and the two swimming behaviors. We found that mantis shrimp achieve faster swimming speeds through a combination of higher beat frequencies, smaller stroke durations, and partially via larger stroke angles. The five pleopods exhibit non-uniform kinematics that contribute to the coordination and forward propulsion of the whole system. Micro-hook structures (retinacula) connect each of the five pleopod pairs and differ in their attachment across pleopods-possibly contributing to passive kinematic control. We compare our findings in N. bredini to previous studies to identify commonalities across hybrid metachronal swimmers at high Reynolds numbers and centimeter scales. Through our large experimental dataset and by tracking each pleopod's movements, our study reveals key parameters by which mantis shrimp adjust and control their swimming, yielding diverse locomotor abilities.

Crustacean Female Sex Hormone (CFSH) Transcript and Protein Profiles and Its Functions in Gradually Developing Adult-Specific-Features during the Prepuberty Molt Cycle of the Blue Crab, Callinectes sapidus

Crustacean female sex hormone (CFSH) plays a pivotal role in developing adult-specific female characteristics, specifically the mating and parental care system of the female blue crab, Callinectes sapidus, manifested after the puberty-terminal molt. Therefore, this study aimed to determine if there is a relationship between CFSH and the development of phenotypes specific to the female C. sapidus during its life cycle and if the continued presence of CFSH is required for developing adult-specific features during the prepuberty molt cycle. First, CasCFSH transcripts in females steadily increase, starting from crab stages 3-4 to prepuberty, except for a decrease at crab stages 15-16. The prepuberty females have the highest CasCFSH transcripts, with ∼5.6-fold higher than adults. CFSH protein levels at prepuberty are the highest but similar to adults. The first and visible secondary female characteristics include a pair of gonopores or a triangular abdomen and four pairs of pleopods seen as early as crab stages at ∼3 (carapace width, CW, 5-7 mm) - 5 (CW 8-10 mm), respectively. The adult-specific female morphological features that are developed gradually throughout the prepuberty molt cycle are manifested only after the puberty-terminal molt. A CasCFSH knockdown study by injecting CasCFSH-dsRNA into prepuberty females at specific molt stages provides further evidence: the continued presence of CasCFSH is required for gradually developing adult-specific morphological features during the prepuberty molt cycle. Overall, the abdomen size is first determined at the intermolt stage. Then, the abdominal shape, gonopores, sternal tubercles, spermathecae, and ovigerous setae and hairs are formed at the intermolt and early premolt stages. Finally, the plumose hairs are developed during intermolt, early, and late premolt stages.

Pleopodal lung development in a terrestrial isopod, Porcellio scaber (Oniscidea)

During evolution, various lineages of arthropods colonized land and independently acquired air-breathing organs. Some taxa of oniscidean isopods (Crustacea, Isopoda, Oniscidea) are the most successful crustacean lineages on land and possess organs called “lungs” or “pseudotrachea” for air-breathing in their abdominal appendages, i.e., in pleopods. Although these lungs are important for adapting to the terrestrial environment, their developmental process has not yet been elucidated. In the present study, we investigated the process of lung development in Porcellio scaber, the common rough woodlouse with pleopodal lungs in the first two pairs of pleopods. The lungs in the second pleopods developed at the manca 1 stage (immediately after hatching) and became functional at the manca 2 stage. In the first pleopods, which appear at the manca 3 stage, the lungs were gradually developed during the manca 3 stage and became functional in post-manca juveniles. In the second pleopods, epithelial invaginations led to lung development. These results suggest that some novel developmental mechanisms with epithelial invaginations and cuticle formation were acquired during terrestrialization, resulting in the development of functional lungs in the terrestrial isopod lineages.

On the role of phase lag in multi-appendage metachronal swimming of euphausiids

Metachronal paddling is a common method of drag-based aquatic propulsion, in which a series of swimming appendages are oscillated, with the motion of each appendage phase-shifted relative to the neighboring appendages. Ecologically and economically important euphausiid species such as Antarctic krill (Euphausia superba) swim constantly by stroking their paddling appendages (pleopods), with locomotion accounting for the bulk of their metabolic expenditure. They tailor their swimming gaits for behavioral and energetic needs by changing pleopod kinematics. The functional importance of inter-pleopod phase lag (ϕ) to metachronal swimming performance and wake structure is unknown. To examine this relation, we developed a geometrically and dynamically scaled robot (‘krillbot’) capable of self-propulsion. Krillbot pleopods were prescribed to mimic published kinematics of fast-forward swimming (FFW) and hovering (HOV) gaits of E. superba, and the Reynolds number and Strouhal number of the krillbot matched well with those calculated for freely-swimming E. superba. In addition to examining published kinematics with uneven ϕ between pleopod pairs, we modified E. superba kinematics to uniformly vary ϕ from 0% to 50% of the cycle. Swimming speed and thrust were largest for FFW with ϕ between 15%–25%, coincident with ϕ range observed in FFW gait of E. superba. In contrast to synchronous rowing (ϕ = 0%) where distances between hinged joints of adjacent pleopods were nearly constant throughout the cycle, metachronal rowing (ϕ > 0%) brought adjacent pleopods closer together and moved them farther apart. This factor minimized body position fluctuation and augmented metachronal swimming speed. Though swimming speed was lowest for HOV, a ventrally angled downward jet was generated that can assist with weight support during feeding. In summary, our findings show that inter-appendage phase lag can drastically alter both metachronal swimming speed and the large-scale wake structure.

The different morphotypes in males of the freshwater prawn Macrobrachium tenellum (Smith, 1871) (Decapoda: Caridea: Palaemonidae) in Mexico

Abstract We analyzed the occurrence of morphotypes in the males of Macrobrachium tenellum (Smith, 1871), a species of potential use in farming, using biometric data and multivariate statistical analysis. Specimens were collected in the Ameca River, Mexico and grown for four months in two rectangular concrete ponds 50 m2 at an initial density of 10 individuals m–2. A biometric analysis was done on all male specimens, identified by the presence of the appendix masculina on the second pair of pleopods. We measured eight dimensions in each of the measured male specimens. Color and spination of the right second cheliped were also determined. We performed a statistical analysis of the data using multivariate analysis, which resulted in the identification of five morphotypes: dark-brown claw (DBrC), brown claw (BrC), cinnamon claw (CC), translucent claw (TC), and small male (SM). The mean of groups of almost all variables showed statistically significant differences except for the ratio Lcl:Lpo. There was no significant difference between groups BrC and DBrC, and spine angles were not significant between groups CC versus TC and BrC. A detailed description of the main macroscopic characteristics that differed between morphotypes is provided, which will allow their identification in future work. Our results will also help in studying social interactions between the male morphotypes.

Dual Phase-Shifted Ipsilateral Metachrony in Americamysis bahia.

Previously documented metachrony in euphausiids focused on one, five-paddle metachronal stroke, where contralateral pleopod pairs on the same abdominal segment beat in tandem with each other, propelling the animal forward. In contrast, the mysid shrimp Americamysis bahia's pleopods on the same abdominal segment beat independently of each other, resulting in two, five-paddle metachronal cycles running ipsilaterally along the length of the body, 180° out of phase. The morphology, kinematics, and nondimensional measurements of efficiency are compared primarily with the one-cycle Euphausia superba to determine how the two-cycle approach alters the design and kinematics of metachrony. Pleopodal swimming in A. bahia results in only fast-forward swimming, with speeds greater than 2 BL/s (body lengths per second), and can reach speeds up to 12 BL/s, through a combination of increasing stroke amplitude, increasing beat frequency, and changing their inter-limb phase lag. Trends with Strouhal number and advance ratio suggest that the kinematics of metachrony in A. bahia are favored to achieve large normalized swimming speeds.

Metachronal Swimming of Mantis Shrimp: Kinematics and Interpleopod Vortex Interactions.

Mantis shrimp swim via metachronal rowing, a pattern in which the pleopods (swimming limbs) stroke sequentially, starting with the last pair and followed by anterior neighbors. A similar swimming pattern is used at various sizes, Reynolds numbers, and advance ratios by diverse organisms including ciliates, ctenophores, copepods, krill, and lobsters. Understanding this type of locomotion is important because it is widespread and may inspire the design of underwater vehicles where efficiency, robustness, and maneuverability are desired. However, detailed measurements of the flow around free-swimming, metachronally rowing organisms are scarce, especially for organisms swimming in a high Reynolds number regime (Re ≥ 104). In this study, we present time-resolved, planar PIV measurements of a swimming peacock mantis shrimp (Odontodactylus scyllarus). Simultaneous kinematics measurements of the animal, which had body and pleopod lengths of 114 and 20 mm, respectively, reveal mean swimming speeds of 0.2-1.9 m s-1 and pleopod beat frequencies of 3.6-13 Hz, corresponding to advance ratios of 0.75-1.84 and body-based Reynolds numbers of 23,000-217,000. Further, the animal's stroke is not purely metachronal, with a long phase lag between initiation of the first and fifth pleopod power strokes. Flow measurements in the sagittal plane show that each stroking pleopod pair creates a posteriorly moving tip vortex which evades destruction by the recovery strokes of other pleopod pairs. The vortex created by the anteriormost pleopod pair is the strongest and, owing to the animal's high advance ratio, is intercepted by the power stroke of the posteriormost pleopod pair. The vortex strength increases as a result of this interaction, which may increase swimming speed or efficiency. A relationship for vortex interception by the posterior pleopod is proposed that relates the phase lag between the interacting pleopods to the beat frequency, distance between those pleopods, and speed of the vortex relative to the animal. We describe this interaction with a novel parameter called the interpleopod vortex phase matching Strouhal number StIVPM which is equal to the phase lag between interacting pleopods. This new nondimensional parameter may be useful in predicting the conditions where a constructive interaction may occur in other species or in physical models. Finally, we relate the advance ratio to the Reynolds number ratio, the ratio between the body-based Reynolds number and the pleopod-based Reynolds number. The importance of these parameters in promoting the interpleopod vortex interactions identified here, in dynamically scaled experiments, and in wake signatures behind schooling metachronal swimmers is discussed.

Morphometry, size at maturity, and fecundity of marbled crayfish (Procambarus virginalis)

Morphometric ratios, relationships and condition factors provide information regarding growth patterns, population dynamics and well-being of individuals in particular environments. Ecology of any species is then better understandable through life history traits and reproductive potential. The present study is aimed at exploring the morphometric and reproductive patterns of the parthenogenetic marbled crayfish, Procambarus virginalis. Marbled crayfish exhibited positive allometric growth and statistically significant common length–weight relationships. Abdomen width, claw length, width, and height increase significantly faster than the chosen most robust body size parameter, postorbital carapace length (POCL). Conversely, total length, carapace length, carapace width, and abdomen length grow proportionally slower than POCL. The condition factor was higher than the threshold value of ∼1 indicating the well-being of the crayfish used. Marbled crayfish, at their first reproduction, were recorded as long as 42.8 ± 10.8 (31.5–73.5) mm total length with a mean fecundity of 89.72 ± 56.9 (22–349) eggs. The relative fecundity (per 1 mm of POCL) of females reproducing for the first time was significantly lower compared to those reproducing repeatedly. Fecundity and relative fecundity exhibited a significant linear relationship with the carapace length and weight of mothers. As a tool for total fecundity estimation, the number of eggs on the third pair of pleopods was counted and plotted against size of mothers, and total fecundity. The number of eggs attached to the third pair of pleopods very closely correlates with the carapace length, weight and total fecundity. Based on our results, it can be concluded that abdomen width and claw growth is allometric compared to POCL which confirms the importance of these body parts. Fecundity parameters were confirmed to have a tight relationship to marbled crayfish size. Clutch size estimation can be used in future research based on the close correlation of egg counts on third pleopods and total fecundity.

Ontogenetic development of gonads and external sexual characters of the protandric simultaneous hermaphrodite peppermint shrimp, Lysmata vittata (Caridea: Hippolytidae).

The peppermint shrimp Lysmata vittata (Caridea: Hippolytidae) is a marine caridean shrimp popular in marine aquarium trade. The species is known to display the sexual system of protandric simultaneous hermaphrodite. In this study, based on captive bred specimens, the complete ontogenetic gonad development of L. vittata was studied both morphologically and histologically, from newly settled juveniles until they reached euhermaphrodite phase. It was found that in all specimens examined (carapace length: 1.8–8.5 mm), including the newly settled juveniles, possessed ovotestes, which comprised of an anterior ovarian and a posterior testicular part. Based on both morphological (e.g., size, color and shape) and histological features (e.g., oogenesis and spermatogenesis), four gonadal development stages were defined and described for L. vittata. From Stage I to III, the testicular part of the gonad became gradually mature but the ovarian part was still immature, which is defined as the male phase. At the male phase, cincinulli (5–8 hooks) presented at the tips of the appendix interna on the first pair of pleopods while appendices masculinae (AM), in a form of a stick structure with spines, presented at the inner edge of the appendix interna (AI) on the second pair of pleopods. At Stage IV, both the testicular part and the ovarian part were mature and hence is defined as euhermaphrodite phase. At the euhermaphrodite phase, most individuals lacked cincinulli and appendices masculinae on the first and second pair of pleopods respectively. This is the first time that complete ontogenetic gonadal and external sexual character development have been described and staged for a species from the genus Lysmata from newly settled juveniles to euhermaphrodite phase.

Embryonic Development of Macrobrachium idae (Heller, 1862)

The egg laying usually takes place between 6 and 20 hrs after mating. The laying of one whole batch of eggs is usually completed within 20 mins. The eggs are extruded through the female genital pores into the brood chamber, first on one side then the other. The chamber between the 4th pair of pleopods is filled first, then those between the 3rd, 2nd and 1st pairs, successively. The eggs are held in bundles like grapes by an extremely thin elastic membrane which is believed to be secreted by the ovigerous setae. During the development in prawns the colour of the eggs changed through greenish opaque, light green, brownish-yellow and dull whitish in colour. The embryonic stages are very much useful in recognizing the stages of development of the species. The process of embryonic development includes nuclear division, cleavage (blastomeres), segmentation, formation of optic vesicle, eye pigment development and larva formation. At third minute after mating the sperm fused with the egg membrane and subsequently the male pronucleus entered the egg’s cytoplasm. The first and second nuclear divisions were completed without any corresponding division of the cell. Third division begun at 8 h and eight nuclei were formed after 9 hrs. Subsequent divisions of sixteen and thirty two nuclei stage took place at about 1 to 1.30 hrs interval and segmentation was completed at 22-24 hrs. Embryonic development follows the normal blastula and gastrula stages, ending with the closing of the blastopore. When larva hatches out from the eggs, they undergo a series of development stages before metamorphosing to juvenile. During this period, they exhibit marked variations in morphological features. These variations are unique for each and every species according to the developmental stages.

Functional anatomy of the male reproductive system of the American lobster (Homarus americanus).

Despite supporting a valuable fishery, the reproductive system of the male American lobster (Homarus americanus) is poorly understood. The elongated H-shaped testis is responsible for spermatogenesis and is composed of follicles, a common collecting duct with interlaced scattered striated muscles, and a serosa as an external wall. Sertoli cells are associated with the spermatogenesis that produces spermatozoa, which are transferred to the collecting duct through a temporary passageway. Spermatogenesis is asynchronous between follicles and occurs on a continuous basis. The anterior and posterior lobes of the testes are independent and connect to the vasa deferentia through the Y-shaped collecting tubules that have a different cell anatomy and function than the two organs they connect. The vas deferens is divided into four regions. Spermatophores, produced in the proximal vas deferens, are packets of spermatozoa encapsulated in a single layer-the spermatophoric wall, which is composed of mucopolysaccharide acid. Large dense ovoid granules and the seminal fluid, composed of acidic sulfated mucosubstances, are secreted in the median vas deferens. Spermatophores within these secreted substances (i.e., semen) are stored in the distal vas deferens that, with the spermiduct (last region of the vas deferens), is responsible for the extrusion of the semen by striated muscle contractions. Smooth muscles suggest a peristaltic movement of the spermatophores within the vas deferens. Finally, the gonopores and the first pair of pleopods (i.e., gonopod) move the semen to the female seminal receptacle during copulation.

Male external genitalia tracts of Côte d’Ivoire Brackishwaters crabs, Callinectes amnicola, (De Rochebrune, 1883; Decapoda: Portunidae)

Objective: The crab Callinectes amnicola is Crustacean specie especially found in West Africa. Due to over fishing, the crab Callinectes amnicola that is the most exploited specie in Côte d’Ivoire, is facing extinction. In order to palliate this phenomenon, the management of the natural stock or breeding becomes indispensable. These aspects involve the mastering of structural organisation and physiology of the reproductive organs. The present study aims to clarify morphology and function of the external organs of the reproductive system.Methodology and Results: Investigations were made by histological technique. The external reproductive tract is composed of paired penes and two pairs of pleopods (G1 and G2). Macroscopic observations indicate 7 stages in male sexual maturity. Investigations with light microscope after histological treatment, allowedfollowing the evolution of these two organs. In the juvenile and mature males, the wall of penes is composed of a connective tissue layer, a muscular layer, an internal columnar and ciliated epithelium and relatively broad lumen. Callinectes amnicola possesses two types of gonopods, the tubular long first gonopods (G1) and the shorter second pleopods (G2). The first gonopod (G1) consists of coxopodite XIII, subterminal segment, and terminal segment or telopodite, which forms a tube. The tube or groove possesses basal and apical opening. A calcified wall surrounding bundles of striated muscle fibres and glandular areas bound Gonopods. The second gonopod (G2) consists of three segments, the coxopodite XIV, a medial portion and apical spine. It is inserted into the posterior foramen of the first pleopod and it forces semen and spermatophores through the first pleopod. Physiology of the external tract was carried out. Penis and first pleopods are mechanical organs of copulation.Keywords: Callinectes amnicola, penes and pleopods, Morphology, histology

The morphology of the reproductive system in the crab Percnon gibbesi (Decapoda: Brachyura: Grapsoidea) reveals a new combination of characters in Thoracotremata.

Recent studies revealed a high diversity of reproductive structures in heterotreme brachyurans, while those of Thoracotremata seem rather uniform. Yet, there still is a huge lack of data in this group as only few species have been studied with respect to their reproductive system. The phylogenetic position of Percnidae is ambiguous. Recent molecular studies place it within polyphyletic grapsoids. We herein study the reproductive morphology of Percnon gibbesi using histology, scanning electron microscopy, micro-computed tomography and 3D-reconstructions to test whether this species shows the characteristic thoracotreme pattern. Our results reveal that the male copulatory system conforms to other thoracotremes. It is composed of two pairs of pleopods (gonopods) and likewise paired penes. The first gonopod is relatively long. It possesses a bent terminal process with a distal opening of the ejaculatory canal, a character also present in other grapsoids. The second gonopod is short and terminates in an apical girdle. The female reproductive system reveals a combination of characters, so far unknown for thoracotremes. The paired oviducts do not lead into the seminal receptacles, but run into separate cuticular ducts joined with the vaginae. Accessory sperm storage organs, the bursae, are also connected to the vaginae. Bursae have previously only been described in heterotreme crabs. The data presented in this study reveals a higher diversity of thoracotreme reproductive systems than anticipated.

Appendages, functional morphology and possible sexual dimorphism in a new ceratiocaridid (Malacostraca, Phyllocarida) from the Early Devonian Hunsrück Slate (south‐western Germany)

AbstractWe describe a new archaeostracan phyllocarid from the famous Early Devonian Hunsrück Slate, Germany. Morphological features suggest a new ceratiocaridid species for which we propose the name Ceratiocaris harpago sp. nov. The exceptionally well‐preserved holotype specimen is the most completely known ceratiocaridid with an almost entire set of appendages including biflagellate antenniform antennules, robust uniramous antennae with hook‐like flagellum, thoracopods densely covered with setae and probably six pairs of pleopods. A nectobenthic lifestyle is considered the most probable and the clasper‐like morphology of the antennae suggests the presence of a sexual dimorphism in this taxon, with the holotype specimen being a male individual.

Functional morphology of the reproductive system and sperm transfer in Stenopus hispidus (Crustacea: Decapoda: Stenopodidea), and their relation to the mating system

AbstractThe morphology of the reproductive system of a stenopodidean decapod is described here for the first time, with an interpretation of the sperm transfer process. Pairs of adults of Stenopus hispidus were maintained under laboratory conditions to observe reproductive cycles. Mating behavior and sperm transfer were video‐recorded for analysis. After copulation, the shrimps were anesthetized and dissected to record the shape and location of the gonads, and pleopod morphology was described and illustrated. The reproductive systems (RS), thoracic sterna, and male and female genitalia were observed by scanning electron microscopy. The male reproductive system was restricted to the cephalothorax and was highly reduced compared with that of other decapods. Only the first pair of pleopods may be involved in the sperm transfer process; there was no appendix masculina on the second pair of pleopods as in many other decapods. The ovaries of prespawning females occupied much of the cephalothorax and reached to the 3rd abdominal segment. The oviducts were short and simple, without structures for sperm storage. We conclude that the male deposits a simple spermatophoric mass onto the posteroventral surface of the female and fertilization occurs externally as mature oocytes are subsequently spawned. This mode of sperm transfer and egg fertilization is ancestral within the decapod suborder Pleocyemata. As in some other animals, the relatively small size of the testes in S. hispidus may be related to the monogamous mating system, which may minimize selection for a large volume of sperm production.

Reproductive Biology of the Commercially Important Portunid Crab, Portunus sanguinolentus (Herbst)

The male reproductive system of P. sanguinolentus is bilaterally symmetrical creamy to whitish in colour, composed of a pair of testes, a pair of vas differentia, and a pair of ejaculatory ducts internally, and a pair of pleopods externally as accessory reproductive organs, present on the inner side of the abdominal flab. The vas differentia has been divided into three distinct regions, based on the morphological and functional criteria: Anterior (AVD), Median (MVD) and Posterior (PVD) vas deferens. The gonads of the male measuring below 8.5 cm carapace width (CW) has immature stage, above 10.5 cm CW has mature stage, whereas the CW in between 14.5-10.5 cm was maturing stage. The female reproductive system composed of a pair of ovaries, a pair of seminal receptacles (or) spermatheca, and a pair of oviducts open to the exterior through the female genital opening situated on the left and right sternites of sixth thoracic segment. The ovaries of P. sanguinolentus are categorized into five stages, according to the size, colour and external morphology of the ovaries. They are immature, early maturing, late maturing, ripe and spent. Fifty percent of the female crabs attained sexual maturity when they reached the size of 9.1- 9.5 cm CW. Fifty percent of the male crabs attained sexual maturity when they reached the size of 9.5-10.0 cm CW. However, the smallest berried female attained sexual maturity in the present study was measured at 8.6 cm CW. Based on the change in colour, increase in the size and change in the shape of the berry eggs, three different stages of egg development was observed. Stage-I has pale yellow to deep yellow coloured egg mass was 260.16 ± 0.24 μm. Stage-II has yellow to gray coloured egg mass was 290.2 ± 0.31 μm. Stage-III has deep gray to black coloured egg mass was 340.32 ± 0.34 μm.

Uropods of Eumalacostraca (Crustacea s.l.: Malacostraca) and their phylogenetic significance

The uropods are the specialised sixth pair of pleopods of eumalacostracan Crustacea. Their quite variable morphology is suggestive of a good potential as a phylogenetic signal. Because uropods have hitherto been neglected in analyses of malacostracan phylogeny, we examined them in 11 representative species of Eumalacostraca and the sixth pleopods of a phyllocarid malacostracan for outgroup comparison. Uropods have apparently evolved in the stem species of Eumalacostraca, possibly being leaf-shaped in the ground-pattern state but already with stabilising carinae along their surface and marginal setae enlarging the effective surface of the rami. Functionally, uropods aid in locomotion and, within the taxon Caridoida, also add to the special tail-flip mechanism. From an original leaf-shaped design in adaptation to different functions and lifestyles uropods may have become rod-shaped, as in Bathynellacea, Cumacea and Amphipoda, but independently so in the first taxon, while this shape might have developed in a common stem species of the latter two, inter alia. Among the taxa that have retained the leaf shape, mysidacean uropods possess a basipod that is drawn out medio-proximally into an outgrowth; Lophogastrida have a triangular median keel there. The uropods of both Euphausiacea and Decapoda also have a laterodistal prolongation, while those of Decapoda are special in bearing a longitudinal median keel on their basipod. All these differences appear to be exclusive to the respective higher taxa, demonstrating the value of uropods, and pleonal structures in general, for phylogenetic considerations.

Notes on two species of Processa (Decapoda: Processidae) from the Mexican Pacific

Material belonging to the genus Processa, held in the Regional Marine Invertebrates Collection in Mazatlán, Mexico, is revised including specimens of the widely distributed P. peruviana, and the scarcely collected P. hawaiensis. For comparative purposes with the specimens from Hawaii and other localities, a detailed description of a male of P. hawaiensis collected in continental Mexico is provided, including illustrations of all appendages. Small differences are noted with previous description and partial redescriptions of this species, including proportion between propodus and dactylus of the fourth pereopod, and between merus and carpus of the right cheliped. In addition, the shape and setation of the first pair of pleopods in the Mexican material differs from the description of P. hawaiensis based on African material.

Protandric simultaneous hermaphroditism in Parhippolyte misticia (Clark, 1989) (Caridea: Hippolytidae): implications for the evolution of mixed sexual systems in shrimp

The sexual system of the shrimp Parhippolyte misticia (Clark, 1989), inhabiting the rocky subtidal at Okinawa, Japan and Kimbe Bay, Papua New Guinea, was examined. Dissections suggested that the population consisted of male phase (MP) and functional simultaneous euhermaphrodite (EH) individuals. MPs 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 containing sperm, but an undeveloped female portion. EHs lacked appendices masculinae and cincinulli. However, they have male gonopores and ovotestes with well-developed ovaries containing mature oocytes and testes with sperm. When EHs were maintained in pairs, both shrimp molted and spawned eggs which attached below the pleon and developed as embryos, demonstrating that EHs can reproduce as males and inseminate other EHs acting as females. These results demonstrate that P. misticia is a protandric simultaneous hermaphrodite, as reported before for other shrimp of the genera Lysmata and Exhippolysmata. Also, these results suggest that protandric simultaneous hermaphroditism might have evolved more than once independently in shrimp from the diverse and species-rich Infraorder Caridea. Future research aimed at disentangling the phylogenetic relationship of Parhippolyte, Lysmata, Exhippolysmata and other closely related genera (Calliasmata, Lysmatella, Barbouria) and describing the sociobiology of additional representatives from the genera above is needed to understand the evolutionary history of sexual systems in caridean shrimp.