We present a comparison of the development of trunk limbs in Nebalia sp. (Leptostraca) and Limnadopsis parvispinus (Branchiopoda). The overall correspondence in specific developmental steps and morphology, e.g., size and orientation of limb anlagen, plus the resulting interpretation of adult limb part homologies lead to the suggestion that phyllopodous limbs in Leptostraca and Branchiopoda are homologous. In addition, our data allow the conclusion that the branchiopod limb forms a three-lobed rather than an undivided endopod. During early development of Nebalia sp. the pleopods form a transitory, putative, and vestigial epipod. The presence of this epipod on the pleopod lends support to the idea that the tagmatisation of the malacostracan trunk into thorax and pleon is the result of a secondary subdivision of an ancestral crustacean thoracic region.

This paper is part of a comparative survey on the evolutionary morphology of the circulatory system in Malacostraca. Tethysbaena agentarii is a representative of Thermosbaenacea, a group which exhibits a relict distribution in cave or groundwater habitats. The study presents the first three dimensional data concerning the circulatory organs and their spatial relationships to other major organ systems. T. argentarii has a short dumbbell-shaped heart which lies in the posterior cephalothorax and the first free thoracic segment. It is equipped with one pair of incurrent ostia. The only vessel to emanate from the heart is the anterior aorta, which runs into the anterior cephalothorax and supplies the central nervous system and both pairs of antennae. Comparative and functional aspects of the circulatory system are discussed. The features of this highly reduced vascular system point to a closer phylogenetic relationship between Thermosbaenacea, and Spelaeogriphacea and Mictocarididae (Mictacea).

This study provides morphological descriptions of three distinct types of hemocytes and one type of oenocyte newly observed in the body cavity of several freshwater ostracode species (Candona candida, C. neglecta, Herpetocypris reptans, H. incongruens, Eucypris virens, Psychrodromus olivaceus, Notodromas monacha, N. persica and Scottia birigida, all Podocopida, Cypridoidea). These cells were found in both males and females and in both juveniles and adults predominantly in inter-lamellar space, along the dorsal margin of the body cavity and in the anteroventral part of the body cavity. In TEM, large granulocytes with a number of pseudopodia and remarkable rounded granula were observed. Their affinity to muscle syncytia and a role in phagocytosis of exogenous particles is distinct. Oenocytoid-like cells with homogenous cytoplasm, rich in polyribosomes and with few membrane-delimited vesicles, were caught in the peripheral parts of body cavity accumulating in special multicellular formations. The oenocytoid-like cells were observed in two cases also by light microscopy. Two types of plasmatocytes (agranular and granular) with numerous pseudopodia were observed in TEM to be involved in phagocytosis of cell debris. Moreover, the plasmatocytes are located in close vicinity with the multicellular formations of oenocytoid-like cells and envelope them or form a sheath. Oenocytes were shown by light microscopy using histological staining to occur in huge amounts in juveniles. In adults their frequency becomes considerably lower. Possible functions of these cells are discussed in the context of invertebrate haematology, physiology and immunology.

The ability to distinguish sex using secondary rather than primary sexual characteristics allows the reduction or elimination of handling organisms, an advantage with rare and/or fragile species. Based on observations of differences in the morphology of gnathopods 1 and 2 of male and female cave amphipods, Gammarus acherondytes and Gammarus troglophilus, we tested the hypothesis that gnathopod morphology could be used to identify sex. To examine the size at which gnathopod metrics allowed reliable identification of sex and to establish predictive relationships, we recorded sex, total body length, and the length and width of propodi from museum collections. In an attempt to test these predictive relationships with an independent data set, we discovered that relationships were species and population specific, even after accounting for shrinkage in the preserved samples. Sex could be most successfully distinguished for G. acherondytes from Reverse Stream Cave using propodus 1 length, while for G. troglophilus it was propodus 2 length. Because regression lines of relationships diverged for G. troglophilus from Fogelpole Cave, all metrics except propodus 1 length were predictive. Although gnathopod dimorphism was limited to large individuals, it was much faster than examining individuals for the presence of penal papillae or oöstegites. Thus, using gnathopod morphology to determine sex may be adequate for some studies.

This study analyzed and described the sexual system of Exhippolysmata oplophoroides through the study of primary and secondary sexual characters at macroscopic and microscopic levels, to address the question of the existence of gonochorism or hermaphroditism in this species. The shrimps were collected in the Ubatuba region, São Paulo, Brazil. A total of 487 individuals were examined, sexed, and measured. They were dissected and their gonads were fixed, sectioned, and stained. All individuals had ovotestes, oviducts, ejaculatory ducts, appendices masculinae, and gonopores on the coxae of the fifth pereiopods. Female gonopores were found only in shrimp above 6.0 mm carapace length (CL). According to the characters studied, E. oplophoroides is a protandric simultaneous hermaphrodite with a male phase and a simultaneous hermaphrodite phase and these findings confirm some recent experimental evidence from mating pairs. The gonad of the male phase consisted of paired ovotestes with an undeveloped ovarian portion. In the hermaphroditic stage, most individuals had small appendices masculinae, both male and female gonopores, and ovotestes with vitellogenic oöcytes and spermatozoa. The present study is the first detailed morphological description of the sexual system of Exhippolysmata oplophoroides. Our results are discussed in the light of new findings.

We studied the morphology of the male reproductive system and spermatophore formation in Astacus leptodactylus. The testis has two anterior lobules and only one posterior lobule, which lie dorsal to the gut on the large hepatopancreas. Collecting tubule cells comprise a simple cuboidal epithelium with synthetic activity. Vasa deferentia are laterally connected with the testis and have three parts: proximal vas deferens (PVD), middle vas deferens (MVD) and distal vas deferens (DVD). While the PVD is off-white in color similar to the testis and has no convolutions, the MVD is intensely white in color and convoluted. On the other hand, the DVD is the widest of all and an intensely white structure. The spermatophore, which is non-pedunculate and tubular, extrudes an uninterrupted column and consists of a sperm mass covered with primary and secondary layers. The primary layer is stained with bromephenol blue, while secondary layer gives positive reaction with Alcian blue and aldehyde fuchsin. The histochemical results indicate that the functions of layers are different.

Although movement of individuals has important consequences on population dynamics and various ecological interactions, it is often difficult to quantify fully. We investigated the temporal variation in the number of the amphipod Corophium volutator swimming in the water column during periods of immersion over an intertidal mudflat in the Bay of Fundy, Canada, in spring-summer 2006. Swimming is an important mode of dispersal, since the number of swimming amphipods can peak at over 30,000 individuals within a 20-cm-diameter, stationary plankton net over a period of immersion of ∼4 h. Amphipods swim throughout spring-summer, but abundance in the water column is less in May than in the other months. As well, amphipods swim during the day and night, but the number swimming shows periodicity in relation to diel time of high tide, with peaks when high tides occur around 1:45 am. Finally, the number of amphipods swimming shows periodicity in relation to lunar cycles, with peaks around the time of new moon and full moon. We developed a statistical model describing the swimming activity of C. volutator based on month, diel time of high tide, and day of the lunar calendar. The model accurately predicts the timing of peaks, but does not predict well the amplitude of the highest peaks. Overall, the model gives a very good approximation of the number of swimmers (61% of the variation is explained) and provides a strong basis for future modeling of spatial population dynamics of C. volutator.

The population structure of the land crab Johngarthia lagostoma was studied on Ascension Island from 2005-2007, predominantly during the period of the seaward breeding migrations; approximately 4000 crabs were examined. Sex ratio varied according to location of sampling. Males predominated in permanent residential areas on high ground. Sexes were equal along migration routes to the sea. Females predominated in the breeding sites on the shore. Very few immature crabs (< 60 mm CW) were found. Males had modal and maximum sizes of 100-109 mm and 120 mm CW, females of 90-99 mm and 110 mm, respectively. An aging population is indicated. Crabs < 40 mm CW were all dark coloured, and colour variation into yellow, purple and intermediate morphs developed between 40-50 mm CW. Overall colour distribution of the population was 85% yellow, 5% intermediate, and 10% purple. Yellow morphs were more abundant in females (89%) than males (81%). The predominance of yellow morphs may be an adaptation to reduce heat stress.

Halicarcinus cookii is a small intertidal New Zealand crab that has high levels of ovigerous females in all months. Continuous breeding requires continuous mating. Mating is not linked to moulting because the pubertal moult is terminal. Spermathecal fullness is modelled in terms of the difference between the rates of copulation and rates of brood production. It is estimated that females can fill their spermathecae with sperm after 3-4 copulations (depending on male size) and that approximately 15% of an ejaculate is used to fertilize each brood. Given the fact that females have multiple partners we asked the question: is it worthwhile for males to spend any time mate guarding? Using sterile males we showed that the majority of each brood is sired by the last male to mate. In females prevented from mating again, more of each successive brood is likely to be sired by earlier males who had mated with the female. This suggests that over periods exceeding one brood cycle (i.e., months) sperm slowly becomes mixed. Therefore, it is worthwhile for male H. cookii to invest time in guarding female partners.

The six naupliar stages of Acartia (Acanthacartia) steueri Smirnov, a calanoid copepod of the family Acartiidae, are described by both light microscopy and scanning electron microscopy. Each stage is discriminated by the number of setae on the distal segment of the antennule. The nauplii of A. steueri can be distinguished from those of two con-subgeneric species, Acartia (A.) californiensis Trinast and A. (A.) bifilosa Giesbrecht, by both the combination and the constancy in all naupliar stages of the exopodal setal counts of the antenna and mandible.

This work presents a comparative study of the electrophysiological properties of the peptidergic neurons in crayfish Procambarus clarkii and Cherax quadricarinatus. Recordings were made in order to determine the linear and non-linear properties of electrical activity in these neurons. Charge curves were obtained in order to carry out measurements of the input resistance and the determination of the electrotonic length as part of the linear properties of these cells. Different recordings of the action potentials and the ionic currents are presented as part of their non-linear properties. The electrotonic length in P. clarkii was 0.8253 ± 0.1311 and 1.7616 ± 0.4726 in C. quadricarinatus. The input resistance in P. clarkii was 92.4 ± 23.2 MΩ and 56.46 ± 17.2 MΩ in C. quadricarinatus. Silent neurons were recorded (53% in P. clarkii and 60 % in C. quadricarinatus) as well as tonic neurons (35% and 28% in each species respectively) and neurons responding with action potential bursts (12% for both species). We found potassium currents in both species that differ mostly in magnitude. Finally, we discuss the differences that were found in the electrical properties of the neurosecretory cells in crustaceans.

Delivery of live crustaceans to markets has the potential to increase profits for Alaskan fishermen, but the practice has been limited in part by mortality occurring during shipment to distant markets. Protocols that select crabs more likely to survive shipment would likely further develop this niche market and evaluating the physiological stress response in crustaceans provides a logical entry point to explore this area. This study measures oxygen consumption rates (MO₂; mgO₂ g⁻¹ hr⁻¹) of male Tanner crabs, Chionoecetes bairdi, following 15, 30 or 45 min of emersion at 8°C or −15°C followed 12 h later by a uniform handling stressor (emersion at −15°C for 10 min). MO₂ increased immediately following 15, 30 and 45 min emersion at 8°C (on average 1.5 times pre-treatment levels). All crabs survived emersion at 8°C and MO₂ returned to pre-treatment levels within 12 hours. These animals also responded similarly to a uniform second stress test by increasing MO₂. Crabs previously exposed to air at −15°C for 15 min had an increased MO₂ following a standardized handling stress in a pattern similar to the 8°C groups. However, MO₂ in crabs exposed to air at −15°C for 30 min did not respond to a uniform secondary stress treatment with an increase in MO₂. Thus, a robust increase in MO₂ to a uniform stress treatment indicates animals with a less severe stress history and likely an indicator of overall vigor.

The cytochrome c oxidase subunit I (COI) gene plays a pivotal role in a global effort to document biodiversity and continues to be a gene of choice in phylogenetic and phylogeographic studies. Due to increased attention on this gene as a species' barcode, quality control and sequence homology issues are re-emerging. Taylor and Knouft (2006) attempted to examine gonopod morphology in light of the subgeneric classification scheme within the freshwater crayfish genus Orconectes using COI sequences. However, their erroneous analyses were not only based on supposed mitochondrial sequences but also incorporated many questionable sequences due to the possible presence of numts and manual editing or sequencing errors. In fact, 22 of the 86 sequences were flagged as “COI-like” by GenBank due to the presence of stop codons and indels in what should be the open reading frame of a conservative protein-coding gene. A subsequent search of “COI-like” accessions in GenBank turned up a multitude of taxa across Crustacea from published and unpublished studies thereby warranting this illustrated discussion about quality control, pseudogenes, and sequence composition.

Phylogenetic relationships among 13 species of Clausocalanus (Copepoda: Calanoida) were examined based on morphological, quantitative (morphometrical), and molecular characters. This study builds upon monographic analysis by Frost and Fleminger (1968) and seeks to determine whether three described species groups are monophyletic evolutionary lineages. DNA sequences were determined for portions of three genes: mitochondrial cytochrome oxidase I (mtCOI; 639 base-pairs), nuclear internal transcribed spacer region (ITS-2; 203 base-pairs), and nuclear ribosomal gene (5.8S rRNA; 73 base-pairs). Phylogenetic analysis was carried out based on morphological, molecular, and combined morphological and molecular data using maximum parsimony, maximum likelihood, and Bayesian algorithms, with evaluation of best-fit models of nucleotide evolution. Phylogenetic reconstructions based on morphological characters provided strong support for species groups I and II; group III was not well-resolved. Analysis of the concatenated sequences of the three genes resulted in a tree resolving three of five group II species, with weak support for two pairs of group I species; the remaining species were not clearly resolved into groups. Although ITS-2 was statistically incongruent with the other data sets, the combined analysis of morphological, quantitative, and molecular data by maximum parsimony resolved all four group I species and four of five group II species; group III was not well resolved. All molecular and combined analyses consistently paired C. arcuicornis (group II) with C. parapergens (group III). This study provides independent evidence that some elements of Clausocalanus species groupings reflect evolutionary lineages. Additional genes and longer sequences may help resolve remaining questions about the evolutionary relationships among species of Clausocalanus.

As historically recognized, three stygobitic species of the subgenus Aviticambarus, genus Cambarus inhabit Mississippian limestone caves along the southern edge of the Southern Appalachians and Highland Rim in southeastern Tennessee and Northern Alabama, U.S.A. These include Cambarus hamulatus, C. jonesi, and C. veitchorum. All stygobitic members of the genus Procambarus inhabit caves in Florida, Cuba, and Mexico with exception of P. pecki (in the monotypic subgenus Remoticambarus), which exists in only three caves with C. jonesi in Northwestern Alabama. It was hypothesized that Procambarus pecki was derived from a primitive Procambarus stock that gave rise to the genera Cambarus and Orconectes based on the morphological shapes of the gonopods. Excluding the unsampled rare C. veitchorum, here we present 16S rDNA phylogenetic evidence, contrary to former morphological-based inferences, for the recognition of five distinct Aviticambarus lineages including P. pecki. Cambarus laconensis is a new species restricted to one locality in Northern Alabama along the southern border of the Highland Rim. Cambarus speleocoopi is also a new species of subterranean crayfish restricted to Marshall County, Alabama. These two cryptic species, with distributions that do not overlap any other stygobitic species, were discovered during a previous phylogeographic survey of cave crayfishes in the Southern Appalachians. For cave crayfishes in particular, similar morphology owing to convergent evolution in replicate subterranean environments, obscures phylogenetic relationships and cryptic stygobitic lineages.

During the late fall and early winter of 2007, we collected intertidal barnacles and observed reproductive activity. Among these, we found an otherwise normal barnacle that had two penises. At least one of these penises is inferred to have retained normal function and to have fertilized the egg brood of the barnacle's neighbor.