Androdioecy (mixtures of males and hermaphrodites) is a rare mating system in both the plant and animal kingdoms. Androdioecy has been described in three branchiopod species, and is best known from the clam shrimp Eulimnadia texana Packard. Herein we describe sex ratio, genetic and histological evidence from the clam shrimp Eulimnadia agassizii Packard that suggest androdioecy is also found in this species. The E. agassizii population sampled had all-females, and when these females were isolated and allowed to produce eggs, those eggs yielded 100% female offspring in 15 out of 15 cases. Additionally, the originally isolated females proved to be completely homozygous at each of the six allozyme loci scored. The offspring from these isolated females also proved to be homozygous for the same alleles as their parent. Tissue sectioning of the gonad found that the “females” actually produced testicular tissue in the posterior portion of the gonad. Taken together, these data are entirely consistent with those of the androdioecious E. texana, and thus indicate that E. agassizii is also an androdioecious species, bringing the total number of branchiopod species with this form of reproduction to four.

Tetraclita japonica is a common barnacle in Hong Kong, occupying a wide vertical zonation on exposed to semi-exposed shores. The length of the exopodite of cirri IV–VI of T. japonica varied with different degrees of wave exposure and tidal levels. Barnacles on exposed shores had shorter cirri than those on semi-exposed ones. Barnacles at the low intertidal also had shorter cirri than those at the high intertidal zone. Differences in desiccation and heat stress, the length of the immersion period for feeding, and predation pressure along the tidal gradient may be additional factors affecting the cirral length of T. japonica. Compared with Balanus glandula in temperate waters, the proportional difference in the cirral length of T. japonica between wave-extreme locations is much smaller (4%) than that of B. glandula (80%). Differing from B. glandula, which actively beat their cirri to feed, T. japonica exhibits prolonged extension of the cirri for feeding, which may not favour long cirri even on semi-exposed shores. Barnacles with different cirral activities, therefore, appear to have different degrees of cirral responses to environmental stimulus.

Leg 5 development is described for 10 species from 10 genera in 6 families of centropagoidean calanoid copepods. Segment homologies are inferred from the order in which arthrodial membranes, setae, and attenuations are added to ramal segments during late copepodid development. Among centropagoidean males, the grasping chela on the side opposite the male genital pore develops in three different ways. The fixed part of the chela may be a ventral attenuation of the basis, or of the proximal exopodal segment, or of the middle exopodal segment, suggesting that a male leg 5 chela is not a synapomorphy of the Centropagoidea because nonhomologous segments make up the convergent morphology. In like manner, a grasping subchela on the side opposite the male genital pore is expressed in three different ways: basis plus proximal, middle and distal exopodal segments; basis plus proximal and distal exopodal segments; or basis plus distal exopodal segment; so nonhomologous segments also result in a convergent subchela morphology. On leg 5 of adult females, a ventral attenuation of the middle exopodal segment, initially formed at copepodid stage V, is present on species of Centropagidae and Diaptomidae. A ventral attenuation of the exopod initially expressed at copepodid stage V on females of Temoridae is considered a homologous structure, although failure to express the proximal arthrodial membrane of the exopod complicates the interpretation of its origin. A ventral attenuation first appears on the exopod of Pontellidae and Acartiidae at copepodid stage V, but its homologies with the above families are more difficult to determine because neither proximal or distal arthrodial membranes nor setae are present on the adult exopod. The species of Tortanidae studied here does not express a ventral attenuation on the exopod at copepodid stage V or at the adult stage, but adults of some other species of Tortanus do. The ventral attenuation of the exopod of adult female leg 5, initially present at copepodid stage V, is a more likely synapomorphy for the superfamily although evidence for this homologous structure may be difficult to identify due to the secondary loss of setae and arthrodial membranes on the exopod of some species. Presence at copepodid stage V of the presumptive genital somite complex of the adult female is expressed among all centropagoideans studied here and appears to be an unambiguous synapomorphy for species of the superfamily.

The copepodid phase of development of Euryte longicauda Philippi, 1843, is described from six stages associated with the bryozoan Flustra foliacea Linnaeus, 1758 Distinctive character states of the species include: distal teeth of mandibular gnathobase perpendicular to proximal teeth; distal seta of maxillular praecoxa with multiple cusps is perpendicular to proximal setae with one cusp; coxa of maxillule as a gnathobase perpendicular to praecoxa; maxillular palp comprised of two setae; fluted setae medially on the distal segment complex of both rami of swimming legs 1–4. The segmental homologies of the maxilla of E. longicauda are an unarmed syncoxa, a basis with two setiferous lobes, and a ramus of three segments. A re-examination of type specimens of E. bellatula Humes, 1991, and E. verecunda Humes, 1992, revealed a 2-segmented protopod for leg 5, confirming their inclusion in Euryte. Euryte longicauda retains the ancestral state for development of swimming legs 1–4. Development of the maxilliped suggests that E. longicaudata shares with Troglocyclops janstocki Rocha and Iliffe, 1994, and Neocyclops vicinus (Herbst, 1955) more states expressed during endopodal development of primitive cyclopoids, while endopodal development of the maxilliped of the remaining Cyclopidae is truncated. Euryte longicaudata, T. janstocki, and N. vicinus appear to belong to a monophyletic lineage at the base of the Cyclopidae; T. janstocki is most closely related to E. longicaudata.

Populations of the North American cryptic species complex of Acanthocylops vernalis (Fischer 1853) (Copepoda) possess unusually variable karyotypes and levels of reproductive isolation, but are difficult to discern morphologically. We established nine isofemale lines derived from four local and geographically isolated pond populations from Wisconsin and three isofemale lines from a lake in Ohio to explore the variability and relationships of chromosome numbers, genome sizes, and similarity of ribosomal DNA sequences. Five karyotypes (2n = 6, 7, 8, 9 and 10) were observed, although genome sizes were remarkably consistent. A 593 bp region of the 18S ribosomal gene was identical in four Wisconsin and three Ohio lines, but differed among five Wisconsin lines. This variability in 18S rDNA sequences among lines, which is uncharacteristic for well defined cyclopoid species, was used to construct a network of relationships among the isofemale lines. Mapping chromosome number onto this network revealed a cluster of lineages with variable chromosome numbers and a cluster with consistent chromosome number, although the overall pattern was more complex than this. Although 4–5 bivalents were observed in oocytes of the progeny from one isofemale line from Ohio, progeny of the latter had smaller genomes than any of the Wisconsin lines. All Wisconsin and Ohio lines lacked chromatin diminution, a trait previously attributed to some populations of A. vernalis by Standiford (1989, Genetika 79: 207–214) and Akifiev (1974, Priroda (USSR) 9: 49–54). Occurrence of chromosomal aberrations among disjunct populations may account for the unusual genetic variability of this species complex. Such differentiation also may be accelerated in fragmented habitats where genetic isolation seems to be recent and recurrent.

We present an inventory of the free-living freshwater copepod crustaceans recorded from the state of Florida, U.S.A. The list is based on previously published information and on new data collected during recent research on surface- and groundwater-dwelling copepods in Everglades National Park, and a few collections in temporary and permanent surface waterbodies elsewhere in the state. We provide information on the ecology and taxonomy of some of the species, and a key for the identification of all the taxa. A total of 65 taxa of free-living copepods: 9 calanoids, 41 cyclopoids, and 15 harpacticoids are now known from the peninsula. Forty-four of these are known from Everglades National Park and adjacent areas; we add four species to a previous checklist for this region. The historically more intensive sampling here has resulted in the discovery of five new named taxa and six that remain in open nomenclature, 10 of which have so far been found only in the Everglades. Of the species collected so far in central and northern Florida, two calanoids and one cyclopoid have been found only in the state so far, whereas all the others are widespread in North America and beyond. Among the predominant North American fauna is a small neotropical component consisting of one calanoid, six cyclopoids, and five harpacticoids. One cyclopoid species is considered to be introduced.

The four amphipod species Onisimus nanseni, O. glacialis (Lysianassidae), Gammarus wilkitzkii (Gammaridae), and Apherusa glacialis (Calliopiidae) have been identified earlier as autochthonous sympagic organisms that spend the whole life cycle in close association with the Arctic ice pack. Even one and a half centuries after the discovery of the ice-bound ecosystem, the ecology of these amphipod species, and in particular of Onisimus spp. and Apherusa glacialis, is only poorly known. In this study we evaluate and separate the trophic niches of the four amphipod species by analysing the morphology of mouthparts and accessory feeding appendages and compiling all information available on species distribution and feeding ecology. Morphological features and ecological observations imply that interspecific trophic niche overlap among these four amphipod species is reduced; each species has evolved a specific trophic strategy in selecting a different set of primary and supplemental food sources: O. nanseni is detritivorous (necrophageous), O. glacialis is detritivorous (herbivorous), G. wilkitzkii is carnivorous (detritivorous), and A. glacialis is herbivorous (detritivorous). Food choice plasticity in general, and facultative detritivory in particular, can be interpreted as an adaptation to the highly variable and dynamic character of the ice ecosystem. There is evidence that in both Onisimus species, as well as in A. glacialis, niche separation is furthermore provided by their temporary absence from the sympagic environment, which questions the affiliation of these species to the group of autochthonous sympagic organisms.

Entophilus mirabiledictu, new species, is described as a parasite of Callianassa aqabaensis Dworschak, 2003, in shallow water on the Jordanian coast of the Gulf of Aqaba. It is compared with the only species previously known from the genus or subfamily Entophilinae Richardson, 1903, Entophilus omnitectus Richardson, 1903, a parasite of several species of the galatheid anomuran genus Munida in water deeper than 300 m at widespread localities around the world. Information on the prevalence of the parasite and its effects on its hosts is provided.

Oniscidean isopods brood the eggs in a fluid-filled marsupium, and embryos undergo prolonged lecithotrophic development. After sloughing of the vitelline membrane (second embryonic molt), the mancas remain in the marsupium for several more days before emerging as free-living juveniles. Calcium is required for cuticle mineralization in crustaceans, and the time-course of net calcium uptake during these early developmental stages is thus of interest. We studied calcium uptake during embryogenesis and manca development in Armadillidium vulgare using Ca microelectrodes and atomic absorption spectrophotometry. Total Ca increased approximately 17-fold during egg development, from 0.33 ± 0.12 nmol in Early Stage 1 eggs to 5.58 ± 2.73 nmol in Late Stage 2 eggs. However, the major period of uptake occurred after the second embryonic molt, with total Ca increasing rapidly to 197 ± 19.5 nmol per animal in Day 4 mancas; this represents a 35-fold increase from Late Stage 2 eggs. Mancas take up amaranth when cultured in vitro, showing that they imbibe fluid and probably acquire Ca in this way. Eggs reared in vitro in isopod saline show greatly reduced Ca accumulation, indicating that marsupial development provides other sources of Ca and/or metabolic substrates essential for normal uptake. Periembryonic fluid Ca concentrations measured in Late Stage 2 eggs (following blastokinesis) were 22.1 ± 3.5 mmol L⁻¹, almost double the marsupial fluid levels. Stage 2 eggs reared in vitro in low-Ca (1 mmol L⁻¹) saline show a similar capacity to up-regulate periembryonic Ca concentrations, and the trans-vitelline membrane potential (TVMP) of these eggs lies far from the calcium equilibrium potential (E_Ca). Inward calcium transport may occur across the dorsal organ; the same eggs show prolonged loss of Ca when the dorsal organ degenerates following blastokinesis.

A new Miocene decapod fauna is described from the Navidad Formation of coastal Chile. The fauna includes five callianassoid taxa, none of which is preserved sufficiently to identify to species level. New species include Calappilia? chilensis, Hepatus spinimarginatus, Proterocarcinus navidad, Pilumnus cucaoensis, and Pinnixa navidadensis. A possible rhizopine member of the Pilumnidae Samouelle, 1819, is described. Trichopeltarion levis Casadío et al., 2004, previously known from the late Oligocene of western Argentina, was also recovered from these rocks. Calappa circularis Beurlen, from the lower Miocene Pirabas Formation in Brazil, is herein referred to Calappilia. This report greatly increases the known number of fossil decapods from Chile and sets the stage for paleobiogeographic comparison of the decapod faunas of Chile and Argentina.

Macrobrachium hainanense is a large palaemonid shrimp (total length up to 7 cm) present at high densities (>2 individuals m⁻²) in pools of low-order forested streams in Southern China. The present study investigated the reproductive biology and sexual dimorphism of this shrimp in Tai Po Kau Forest Stream (TPK) and Tai Shing Stream (TSS), Hong Kong. Recruitment occurred during the wet season (May to August). Macrobrachium hainanense, a truly freshwater species, has abbreviated larval development, and the study populations had smaller broods than euryhaline species of this genus. Most females probably produced only a single brood of 20–75 eggs each breeding season. They showed no size-specific fecundity. Egg development in the laboratory took over 53 days, and eggs grew larger during development. The reproductive output (RO) of females was 11% for each brood, lower than for most other species of Macrobrachium. Lifetime RO was 21%, assuming a single brood in each of two seasons. The population male-biased sex ratio was 1.7:1, although the size-specific sex ratio was 1:1. Females reached maturity at 15–17 mm carapace length (CL) while males matured later at 18–22 mm CL. Females bred at two and three years of age, while males bred three times at two, three, and four years. Interstream variation in size at onset of sexual maturity was found, with shrimps at TPK maturing later than at TSS. Discriminant Analysis revealed that mature males and females were distinct in their abdominal depths and carapace lengths with females having deeper abdomens (for egg brooding) and smaller carapaces. Juvenile males could be distinguished from females by the presence of the appendix masculina. The minimum lifespan for females of M. hainanense was approximately 29 months and for males, 48 months. Competition for females may be responsible for the longer lifespan and larger size at maturity of males.

The freshwater prawn Macrobrachium lar requires its chelipeds for defensive behaviors. When chelipeds are autotomized, it is beneficial for prawns to regenerate and then elongate the lost chelipeds as rapidly as possible. These prawns are hypothesized to distend their regenerating chelipeds by hydrostatic inflation immediately following ecdysis. The periods required for limb regeneration and subsequent elongation in adult M. lar were measured to be 18.8 ± 1.6 days for single cheliped replacement and 17.4 ± 1.3 for double cheliped replacement. Control prawns with both chelipeds intact were shown to molt every 19.1 ± 1.7 days. These measured periods for limb regeneration and subsequent elongation in M. lar are faster than those periods reported previously for all other adult decapod crustaceans measured from late intermolt (stage C_3–4). This rapid rate of cheliped replacement allows M. lar to minimize the amount of time they may be threatened with territory loss or predation.

Nine zoeal and one decapodid stages of the hippolytid shrimp Latreutes anoplonyx are described from laboratory-reared material. The shape and armature of the abdomen distinguish the larvae of L. anoplonyx from those of L. laminirostris, the other known species of Latreutes from East Asia. The larvae of L. anoplonyx show features not found in other Latreutinae, and Latreutes larvae show features not found in other Hippolytidae. Larval characters question the separation of the genera Latreutes and Tozeuma and the way in which the family Hippolytidae is divided into subfamilies.

Eyestalk length, internal eye structure, pigmented eye area, and pigments in eyes and exoskeleton were studied in two stygobiont crayfish, Procambarus cavernicola and Procambarus oaxacae reddelli. Results were compared with the epigeal crayfish Procambarus olmecorum, all three species inhabiting the karstic region of Acatlan, Oaxaca, Mexico. The stygobite species have shorter eyestalks and reduced pigmented areas compared with the epigeal species. For both eye and integument pigments, the stygobite species have a reduction in their total absorbance spectra compared to the epigeal species. Internal eye structure and organisation are reduced in both stygobite species, but to a greater extent in Procambarus cavernicola. These results are discussed in relation to the time of cave colonisation, the degree of adaptation, and the energy economy hypothesis.

Habituation to a novel environment (cross-shaped experimental chamber filled with water) was investigated in the crayfish Procambarus cubensis whose locomotor activity was recorded by a noninvasive “optical” technique. In the course of ten 30-min sessions, which were repeated twice a day for five days, the duration of an initial freezing reaction decreased, whereas there was no decrease in locomotor activity. The crayfish exhibited, however, a reduction of locomotor activity in the second session of the day, but this reduction did not carry over to the first session of the next day. In a second series of experiments, crayfish were placed in the same chamber for a single 5-hour session. As the session progressed, locomotor activity decreased to a level where animals were completely immobile. Tested the next day, these animals demonstrated less locomotor movements than in the beginning of the previous session. It is concluded that after short (30-min) exposures to a novel environment, crayfish can retained the information for at least four hours. Following a single 5-hour exposure, retention increases for at least 24 hours. Some similarities and differences in the behavior of the crayfish and rats in the “open field” are discussed.

This paper describes a population of Aegla longirostri from Ibicuí-Mirim River, Itaára, Rio Grande do Sul State, Brazil, evaluating the size at onset of sexual maturity, relative growth, mean size, size-frequency distribution, sex ratio, ovigerous-rate, and recruitment. Samples were collected monthly from September 1996 to August 1997. Sex, carapace length (CL), cheliped length (ChL), abdomen width (AW), and front width (FW) were recorded for each crab. A total of 586 specimens were collected (277 males, 244 females, and 65 unsexed juveniles). The smallest specimen was 1.5 mm CL and the largest male was 23.8 mm CL. The relative growth analysis and the Mature software showed that the size at onset of sexual maturity was 13.7 mm CL in males and 10.7 mm CL in females. Females were smaller than males and were more abundant in adult classes, whereas males were more representative in juvenile classes. The sex ratio did not differ from 1:1 throughout the collecting period. Recruitment was observed throughout the entire sampling period, but it was higher in the winter months (from June to August). However, ovigerous females were present in spring and summer (from January to April). This population seemed to be at equilibrium during the study period. Recently, this area has been changed because of the construction of a reservoir, and a new study is required to evaluate the present condition of this population of A. longirostri.

The pea crab Orthotheres barbatus is one of seven species of the family Pinnotheridae reported from Venezuelan marine waters. Larval life histories are not known for any species of the genus Orthotheres. Ten ovigerous females of O. barbatus were obtained from their host gastropod, Cittarium pica, at Los Roques Archipelago, Venezuela. Larvae of O. barbatus were reared in the laboratory from hatching to the first crab stage. This species exhibits abbreviated development in both the number of larval stages (two zoeal stages preceding a megalopa) and the duration of development (minimum of four days from hatching to first crab). The number of zoeal stages for pinnotherid species described to date ranges from 3 to 5, with only Tunicotheres moseri, Pinnotheres taylori, and Nepinnotheres pinnotheres known to also have only two zoeal stages. Morphology of the larval stages of O. barbatus is described, illustrated and compared to that previously described for larvae of the Pinnotherinae. Selected larval characters are proposed as typical larval features for this subfamily and are used to support separation of this group from the rest of Pinnotheridae.

Field and laboratory observations were carried out on the reproductive behaviour of Cyclograpsus lavauxi and Helice crassa, and the results were compared with other Grapsidae, with emphasis on New Zealand species. Mating in all species typically occurs during the intermoult and often coincides with the time of oviposition. Females of several species have been reported to mate multiple times, often in the few days prior to oviposition, leading to sperm competition within the female spermatheca. Females were found to be sexually receptive only in a short period before oviposition (e.g., C. lavauxi, Hemigrapsus crenulatus, H. sexdentatus), although some species were also receptive for about two weeks after oviposition (e.g., H. crassa). The exact duration of female receptivity is unknown for most grapsid species. Female grapsid crabs exhibit a wide range of gonopore structures which either restrict female receptivity to certain times or allow them to mate at any time. In species with restricted female receptivity (e.g., C. lavauxi, H. crassa, H. crenulatus, H. sexdentatus), the operational sex ratio is typically highly male-biased. Male-male competition was found to be intense in the four New Zealand grapsids, with frequent male-male interactions during which larger males were typically more successful in fights over females, resulting in a greater number of matings. Postcopulatory guarding, which is assumed to reduce the risk of sperm competition and to ensure paternity, has been observed in a few grapsid species (H. sexdentatus and H. crenulatus) but not in others (e.g., C. lavauxi and H. crassa). Overall, grapsid crabs employ a variety of reproductive strategies including direct competition between males for females, with postcopulatory guarding; males securing resources as sites for mating; and males having only brief interceptions with receptive females. These differences in reproductive behaviour are discussed in the context of sexual selection and the ecological and environmental differences of the habitats that grapsid crabs occupy. Mating strategies of grapsid species can be very different even if they occupy the same habitat and the females have similar duration of sexual receptivity.

“This is the last will and testament of me, William Harold Sharpe, professionally known as Leigh-Sharpe, of Hamilton House, 17 Clyde Street, Redcliffe Gardens, London” (22 June 1920).