In this study, we developed a simple and rapid restriction fragment length polymorphism (RFLP) method to distinguish the sibling species Hemigrapsus penicillatus and H. takanoi based on interspecific base substitutions within the 16S rRNA region of mitochondrial DNA. Sequencing and alignment of partial sequences revealed two haplotypes for H. penicillatus and one for H. takanoi, and five species-specific base substitutions. Digestion of the PCR products using the restriction endonuclease Dde I produced a banding pattern that was consistent with species identification based on morphological and pigmentation patterns. The sequence for H. takanoi collected in Japan showed high homology with that reported for specimens collected in Europe. This method could be useful for identification of these two species by researchers without specific taxonomic knowledge.

The estuarine crab Hemigrapsus crenulatus (H. Milne Edwards, 1837) is a native of New Zealand, but it is also known from the coast of Chile some 8900 km eastwards across the Pacific. Mary Rathbun (1898) was the first person to call crabs from the Chilean coast, H. crenulatus, saying that they were conspecific with crabs described by Milne Edwards (1837). However, Bennett (1964) took the advice of H. Balss that the Chilean species should be known as Hemigrapsus granarius (Nicolet, 1849). No type specimens are available for either of these species. We have used mitochondrial 16S rRNA and COI sequences derived from fresh specimens to find out who was correct. There are few if any consistent morphological differences between populations from either side of the South Pacific and very few molecular differences (only 3 fixed nucleotide differences out of 1190 bp total sequenced – 0.25%). None of these differences exceed variation within either population, so we must declare Miss Rathbun the winner! The molecular data suggest that there is only one species, Hemigrapsus crenulatus, and that the two populations have been separated only recently in the last few thousand years, perhaps during the last glacial epoch. How this species colonized the coast of South America remains an open question. It does not even occur on off-shore islands near the New Zealand mainland so it probably needed assistance to cross the Pacific.

External colour differences in crustaceans were examined using a non-invasive study of morphology and colour in epidermal chromatosomes. Three different phenotypes of the shrimp, Neocaridina denticulata (< 2 cm total length), differ in the quantity and dispersal of chromatosomes in the epidermis, with resulting differences in body colour. Also, pigmentation pattern is most pronounced in the anterior body parts. The exopod of uropod was the most suitable body area to monitor colour changes in this shrimp. This non-invasive method allows for the study of external pigmentation in crustaceans at different stages and may help to understand how these animals manipulate their chromatosomes under physiological and environmental variability in order to acquire the final external colour.

The setae involved in the gill-cleaning mechanism of six species of Japanese sentinel crabs are described. The setae are classified as belonging to five types: anchor, serrate, simple, digitate-scale-setule, and normal setule setae. The anchor setae are further divided into ten sub types based on the combinations of digitate-scale setule, normal setule, anchor type, and the shape of their tip. Setae on out-growths and tips were compared with those identified in previous studies. As a result, the single row half anchor setae were found only in the subgenus Macrophthalmus and might be used as a special characteristic in the subgenus.

Growth and morphometric characteristics of the caridean Palaemon longirostris Milne Edwards, 1837, were studied in the Gironde estuary population. Their first comparison with earlier studies in this estuary and in the Mira River provided the first step towards developing environmental indicators using a species represented at the European scale. Mean individual growth was modelled for each sex using the classical von Bertalanffy growth model and the seasonal model that integrates periods of lower growth. Morphometric relationships, in particular the spatio-temporal variability in the relative weight of individuals, were explored according to sex and physical parameters of the environment. Females grew to larger size than males. Growth estimates showed the importance of accounting for the seasonal variations to evaluate non-biased growth. Sex and the presence of eggs for females showed significant interaction within the carapace length – total length relation as well as for the carapace length – weight relation. Body condition was significantly greater in spring and summer for both sexes and was significantly correlated with salinity, but only for males. Comparison with the Mira River was limited to the range of data available. However, the population of the Gironde estuary, being similar in both recent and historical studies, showed morphometric differences when compared to that of the Mira River. Indeed, the growth performance index was higher in the Gironde estuary and likely linked to temperature constraints. Conversely, differences between males and females were much higher in the Mira River than in the Gironde estuary.

Two amphipod species, Niphargus ictus and N. frasassianus, which are endemic to Frasassi Caves, Italy, possess morphological features typical of most troglobitic species. Most notably they lack eyes. Although cave waters flow directly into the adjoining Sentino River and N. frasassianus is found within two meters of the resurgence, neither species is present at or further outside the mouth of the cave, which raises the question of how they avoid leaving the cave. It was hypothesized that these animals might be able to detect light, and could use light cues to remain inside the cave. Individuals of both species exhibited greater activity levels in the presence of bright vs. low light levels. Neither species exhibited the dorsal light reflex, but both showed weak negative phototaxis when exposed to bright light directed at them from above and below. N. frasassianus, tested in an apparatus that permitted them to travel freely between bright or low lighted areas, demonstrated negative phototaxis. The results show that both species can detect light, and suggest light cues may be utilized to remain in the caves.

The grooming behaviors of the Hawaiian river shrimp, Macrobrachium grandimanus (Caridea: Palaemonidae), are examined in this study. This species has a dense aggregation of setae (termed the “setal patch”) located on the major second cheliped. The function of this setal patch is unknown but hypothesized to be utilized in grooming activities. The grooming behaviors were documented in terms of appendages used to groom, groomed body areas, type of grooming behavior (pick, brush, or scrape) and a time budget for grooming. The most frequently used grooming appendages are the third maxillipeds and first pereiopods, while the most frequently groomed body region is the antennules. The most frequently used grooming behavior is a scraping action; the body region groomed for the longest amount of time is the branchiostegite (gill cover) region where the gill chamber is located. The time budget for grooming was 24.7%, which suggests approximately six hours per day are dedicated to grooming. Multiple statistical analyses of the grooming behaviors of M. grandimanus indicate the setal patch is not associated with grooming either as a grooming appendage, or a groomed body region. Ideas for possible functions of the setal patch are presented.

Life table characteristics of three species of fairy shrimps from Thailand, Streptocephalus sirindhornae, S. siamensis, and Branchinella thailandensis are reported, based on laboratory cultures at 24-26°C. Comparative data on their growth and fecundity revealed that B. thailandensis had the largest size (male 26.2, female 27.8 mm) and the highest hatchability 87.67%. The shortest hatching time was found in B. thailandensis, it hatched within 3 days, while the other two species hatched within four days. Branchinella thailandensis showed more rapid growth than the other two species, and it reached maturity within 6.5 days. In contrast, S. sirindhornae had the highest fecundity, producing a mean of 35.3 broods and 17,865 eggs per individual female over its life time, whereas the other two species produced less than 8000 eggs. Life span was equal for both males and females in all three fairy shrimp species (P > 0.05). In this study, the fecundity data indicated that the number of eggs per brood recorded in the three species showed a positive correlation with the body length and age of females. The result indicated that the Thai fairy shrimps show several biological attributes making them suitable for aquaculture and other commercial purposes; B. thailandensis shows rapid growth and high hatching percentage which is suitable for mass production, while S. sirindhornae has high fecundity which is appropriate for the commercial production of eggs.

Gut evacuation time is a very useful parameter that allows us to understand the daily trophic cycle of a predator. Macrobrachium borellii is an inhabitant of the littoral-benthic community of the Paraná River system that preys on various organisms. In this work, three types of prey (cladocerans, dipteran larvae, and oligochaetes), which are different in shape and mobility, were offered to M. borellii to investigate the gut evacuation time of each one. All prey represent the natural diet of this prawn based on previous work. Results showed a faster digestion of cladocerans than mosquito larvae and oligochaete. These last two types of prey are cylindrical and may interfere with the maceration process in a stomach that lacks a gastric mill. In addition, the high mobility of cladocerans and mosquito larvae implies greater energy expenditure in their capture. However, cladocerans are the prey with the lowest caloric value per individual and therefore offers the lowest net energy to the prawn. This implies that a cladoceran diet would require higher daily consumption and more time foraging, and thus potentially exposing the prawn to greater predation risk. All of these factors direct selection toward the more profitable prey (oligochaetes and dipteran larvae), in agreement with the natural diet observation, suggesting that the time of digestion may have little importance in prey selection.

Spatial and temporal variations in the diet of Crangon uritai were examined using stable isotope and stomach content analyses. The sand shrimp and its potential prey were collected from Yura Estuary (3–5 m), shallow coast (5–10 m), and deep coast (30–60 m) stations of Tango Sea from April 2006 to February 2007. The measurements of the length (carapace and total lengths) and feeding habit (stomach content and stable isotope ratios) of C. uritai showed that this shrimp changed its diet during migrations between the estuary and marine environments. This species consumes a variety of food at the lower estuary: mysid Orientomysis japonica, small crustaceans particularly amphipod Melita hoshinoi, and bivalve Veremolpa micra. The abundant mysid O. japonica at the shallow coast and juveniles of unidentified bivalve species at the deep coast were the favored food throughout the year. The δ¹³C and δ¹⁵N variations in C. uritai confirmed the spatial and temporal diet shift in gut content composition as the sand shrimp grow and migrate along the estuary-marine gradient.

Cambarus elkensis (Elk River crayfish) was seined and dip-netted monthly during June through August and October through November 2003, and March through May 2004 from Left Fork Holly River in the Elk River drainage, West Virginia, U.S.A. Crayfish reproductive form was classified, and then individuals measured and returned to the stream. Carapace-length (CL) frequency analysis identified five overlapping year classes with growth progressing over a 5-year life span. Ovigerous females were collected in summer (June) and an individual with attached young in October, but young-of-the-year (Y-O-Y) crayfish did not appear in the collections until late winter (March). Juveniles and Y-O-Y dominated the collections and grew rapidly, reaching sexual maturity (≥ 29 mm CL) in 30-36 months. Growth continued but slowed in the older mature crayfish with the largest individuals (> 50 mm CL) disappearing from the collections sometime between fall and spring in the fifth year of life. Fastest growing individuals could have reproduced three times during their life. The overall sex ratio of 1265 crayfish favored females 0.87∶1. Females identified as form I individuals based on annulus ventralis architecture and presence of glair gland and ova had significantly wider pleons, longer chelae, and heavier bodies than similar CL form II female crayfish lacking these features. Form I males also weighed significantly more and had longer chelae than form II males of similar CL. This is the first evidence of the existence of reproductive form alternation in females in the genus Cambarus.

Size composition and growth pattern of the Japanese mitten crab Eriocheir japonica (de Haan, 1835), Varunidae, in their natural habitat was investigated. Crabs were collected using hand-held nets in the Saigo River and the adjacent seacoast in Fukuoka Prefecture, Japan. The dynamics of carapace width (CW) frequency distribution were analyzed and cohorts were identified from polymodal size distribution using Bhattacharya's method. In the lower tidal river and seacoast (Area I, reproductive area of the crabs), adult crabs comprising at least four cohorts were collected. From monthly data for 29 months (January 1997-May 1999) collected from the upper tidal to the lower freshwater area (Area II, growth area of the crabs), two cohorts that had settled in different seasons (fall and early summer) were confirmed for each year. Both cohorts reached minimum adult size (ca. 35 mm < CW and 45 mm < CW, average) in fall 2 years after settlement. This suggests that adult crabs in the tidal area (Area I) mostly comprise two cohorts of 2-year-olds (ca. 24 and 29 months) and two cohorts of 3-year-olds (ca. 36 and 41 months) after settlement.

Few studies have compared oyster habitat use with adjacent vegetated and non-vegetated habitats. We investigated habitat use by six common, estuarine, invertebrate species. In order to better understand the species-specific use of oyster and adjacent habitats within the salt marshes of Grand Bay NERR, MS, we examined the abundance patterns and size distributions among oyster, vegetated marsh edge (VME), and non-vegetated bottom (NVB) for three seasons (Fall 2003, Spring 2004, Summer 2004) for the following species: blue crab Callinectes sapidus, brown shrimp Farfantopenaeus aztecus, white shrimp Litopenaeus setiferus, daggerblade grass shrimp Palaemonetes pugio, flatback mud crab Eurypanopeus depressus, and oystershell mud crab Panopeus simpsoni. Three main trends emerged concerning habitat use: 1) the three crab species (juvenile C. sapidus, E. depressus, P. simpsoni) occupied oyster and VME habitats in higher abundances relative to NVB with minor to moderate fluctuations in seasonal abundance. Smaller crabs tended to use oyster habitat (although differences were not significant for all three species) and this may be related to the higher abundance of smaller refuges in oysters; 2) for one species, P. pugio, abundance in VME was significantly higher than in the other habitats, which may be related to P. pugio reliance on VME stems, and associated flora and fauna for refuge and food; and 3) the estuarine-dependent species F. aztecus and L. setiferus had relatively equal use of VME and oysters, which both species selected for structured habitat over NVB and both species were significantly larger in oyster habitat. Additional investigation is needed to determine the mechanisms responsible for the species-habitat relationships documented in our study.

A re-description of the post-embryonic development of Derocheilocaris remanei Delamare-Deboutteville and Chappuis, 1951 (Mystacocarida) is presented. It includes nine stages, not ten as originally described. The first stage already has a maxillula (though not fully developed) and is, therefore, not an ortho-nauplius as previously reported. Particular focus is on the development of the post-mandibular appendages (maxillula, maxilla, maxilliped) that undergo significant changes during ontogeny, and the development of the so-called ‘toothed furrows’, all of which are good indicators of changes between the stages. The maxilla and maxilliped are quite different from each other in the adult stage, but they develop in a very similar manner, showing very similar morphologies at certain stages. None of the post-mandibular appendages has a fully formed coxa, but only a proximal endite, which is in contrast to some previous interpretations. The development of D. remanei was originally considered very different from that of its transatlantic ‘sister species’, D. typicus, but our observations indicate that this is not the case. Rather, the development of D. typicus and D. remanei is very similar. This implies that not only the adult morphology of Mystacocarida is remarkably conservative, but also the larval sequence. With regard to the feeding system, mystacocaridans have a cephalo-thoracic feeding apparatus including the first pair of trunk limbs modified as maxillipeds, which collaborate with the maxillulae and maxillae in the feeding process. All three limbs are very similar to each other (the main difference is that the maxilliped possesses a vestigial exopod). The feeding system is in both general aspects and in particular details very similar to that of Copepoda and the representatives of the Cambrian taxon Skara. This suggests a close relationship between these three taxa, for which we propose the name Copepodoida. The name refers to specific features found exclusively in copepodans and, in our view, mystacocaridans and the three species of Skara.

The American lobster (Homarus americanus Milne Edwards, 1837) is the focus of the most important commercial fishery in New England, which relies on a variety of biological monitoring programs and surveys to guide the development of appropriate management plans. One key piece of information provided by these surveys is the number of females that are carrying eggs (ovigerous) that will subsequently contribute new recruits to the fishery. A major assumption is that all eggs carried by ovigerous females are fertilized and will thus result in viable recruits. However, because some lobsters extrude, and briefly carry, unfertilized eggs, this assumption needs to be re-evaluated. In particular, it is important to determine the approximate proportion of newly extruded eggs that are either fertilized, or not. The major goal of this project was to develop reliable methods for determining if early-stage lobster eggs (live and preserved) were in fact fertilized. One method involved using a nucleic acid stain to visualize egg DNA, after pretreatment of eggs with a proteolytic and collagenolytic enzyme solution to facilitate stain penetration through the egg membrane. With this method multi-nucleated (fertilized) eggs could be clearly distinguished from unfertilized eggs. A total of 20 egg clutches were tested to determine their fertility status using this method. Of these, 16 clutches (80%) were fertilized while 4 were not fertilized (20%). Of the 16 clutches with fertilized eggs, two had a mix of both fertilized and unfertilized eggs. A second method, using fluorometry to obtain measurements of total egg DNA, was also developed. There was a significant difference between the total DNA concentration in unfertilized control oöcytes and early-stage fertilized eggs (P < 0.001), and the total amount of DNA gradually increased as eggs developed (r  =  0.961, P < 0.0001). Both of these methods will make it possible to make a more accurate assessment of the proportion of female lobsters that will actually contribute new recruits to the fishery.

The present study investigates morphologically similar species in the amphipod genus Niphargus, with special emphasis on three presumably closely-related species: N. fontanus, N. aquilex, and N. schellenbergi. The distribution ranges of these species overlap in Central Europe, and ambiguity of the current diagnostic characters has likely resulted in misidentifications. To address this issue, we carried out molecular-phylogenetic analyses of Cytochrome Oxidase Subunit 1 gene (COI) and 28S rDNA sequences for 34 individuals of the three species from 27 sites in Central Europe and Great Britain. We also included 14 GenBank sequences for two additional species, N. virei and N. rhenorhodanensis, to increase the resolution potential among our in-group taxa. In addition, about 100 specimens of the three species were examined for a reappraisal of diagnostic characters. Representative specimens taken from various subterranean habitat types were examined for each of the three species. A new morphological key, utilizing improved characters, is presented to clearly distinguish between N. fontanus, N. aquilex, and N. schellenbergi. Molecular-phylogenetic analysis using COI sequence data indicates geographically well-delimited clades for N. aquilex and N. fontanus. Our data suggest that some previously recorded niphargids from the Harz Mountains of Germany, initially identified as N. fontanus or N. aquilex, were all N. schellenbergi.

Leucothoid amphipods were investigated using nuclear 18S ribosomal DNA sequences. Analysis of sequences from eight species in two genera supported the current morphological species designations and the separation of the family into two clades. Additionally, an anamorph-leucomorph connection has been confirmed with molecular sequence data that demonstrated both morphologies conclusively belonged to the same species, Anamixis vanga Thomas, 1997. Analyses suggest that morphology is reflecting the genetic evolutionary history of the family. Levels of sequence divergence are compared for 18S rDNA and COI mitochondrial DNA in Leucothoidae.

Branchinecta pollicifera is redescribed from type material and additional material collected from Bolivian bofedal wetlands. Specific unique gonopod and genital segment features demonstrate that B. pollicifera constitutes a new genus, Archaebranchinecta, morphologically distinct from Branchinecta sensu stricto. Additionally, in B. pollicifera, the gonopod proximal projection is bifurcated as opposed to a spiniform Branchinecta, and the first abdominal segment bears a pair of ventrolateral spinule covered plates. These plates are unique amongst Anostraca. The form of the male second antennae in this species and in the related fossil species B. barstowensis demonstrates a potential close relationship, and this species is also referred to Archaebranchinecta. We also report melanisation in Andean anostracans.

Two new calanoid copepods, Pseudocyclops juanibali n. sp. and Pseudocyclops saenzi n. sp. are described from anchialine pools in the Galapagos Islands. Pseudocyclops juanibali n. sp. is similar to P. australis, P. mathewsoni, P. simplex, P. pacificus, and P. latisetosus. A deep cleft on the distal margin of the endopod of the left leg five of males separates these six species from all other Pseudocyclops likely forming a species group. Pseudocyclops juanibali differs from other members of this group in the shape and number of elements on the distal exopodal segment of the left leg five of males. Pseudocyclops saenzi n. sp. is most similar to P. rubrocinctus and P. steinitzi but differs in the presence of a posterior seta on the basis of the leg five of females, a sclerotized seta on the exopod of the maxillule, and several differences in the shape and ornamentation of the leg five of males. A 569-base-pair region of the internal transcribed spacer 1 ribosomal DNA region (ITS-1) was amplified from specimens of P. juanibali and P. saenzi, and from specimens of Pseudocyclops that were morphologically identical to P. juanibali but from two different anchialine pools. The phylogenetic analysis of the ITS-1 region shows that P. juanibali and P. saenzi are genetically different from each other and, furthermore, that the specimens from the two other anchialine pools are genetically isolated from the former species, a finding that suggests cryptic speciation. The morphological and genetic evidence presented here, including confirmation of a close sibling species of P. juanibali from the Ryukyu Islands of Japan, demonstrate that vicariance and active migration are responsible for the observed distribution of species, with faunal exchange occurring between the Galapagos and the Caribbean and Western Pacific Oceans. However, although these copepods are able to cross the entire Pacific, such long-range migration is not the norm. They tend to have restricted distributions with minimal migration and gene exchange, even between habitats that are very close to each other such as the anchialine pools in the Galapagos.