Among animals, conflicts are resolved through agonistic behavior, an expression of which embraces a range of fleeing behaviors, displays, up to the extreme of physical combat. This study aims to establish an observation protocol and to describe the aggressive acts of Aegla longirostri. Aeglids were collected in the field and kept for one week of acclimation in individual fishbowls with no contact with other animals. A total of ten pairs of males were paired, the members of each pair differing by no more than 1 mm in cephalothorax length. The behavioral acts were described from the combats videotaped for 20 minutes with each pair, of which 16 were considered aggressive acts. The animals took an average of 198 seconds to start combat. A table of aggression intensity was established, ranging from −2 (fleeing) to 5 (intense combat). There was a significant difference between winners and losers in the time spent in the different levels of intensity and in the duration of the acts performed. Aegla longirostri showed very intense aggression with defined aggressive acts and continued to engage in agonistic behavior for the entire duration that was recorded. This is the first report of aggressive behavior in aeglids, it will be possible to carry out more profound studies on the behavior of these animals.

We describe growth, longevity, sex ratio, reproductive period, and recruitment of Aegla paulensis from Jaraguá State Park, São Paulo, Brazil (23°27′27.9″S; 46°45′32.3″W). The population was sampled monthly (September 2007 through August 2009) with the aid of traps. Over five thousand individuals were captured, sexed, measured (carapace length  =  CL) and inspected for reproductive traits (females only), and then released back to the sampling site. The pattern of the reproductive cycle was strongly seasonal (austral mid autumn through late winter), with a single recruitment pulse per year. The obtained von Bertalanffy growth equations were CL  =  21.25[1-e^{−0.041(t 1.250)}] and CL  =  16.52[1-e^{−0.049(t 1.823)}] for males and females, respectively. Males (mean CL ± SD  =  11.86 ± 2.79 mm) attain larger sizes than females (mean CL ± SD  =  10.84 ± 2.36 mm). Aegla paulensis reproduces twice during an estimated life span of 40.2 months for females and 33.9 months for males. Temporal variation of sex ratio showed a distinctive pattern characterized by a sequence of three distinct periods that repeated from one year to another, and which suggested that a behavioral component influence the proportion of sex in adult specimens sampled with traps during reproductive and non-reproductive periods.

Aegla alacalufi and A. neuquensis are exclusively found in freshwater systems of Patagonia. The geographic distribution range of A. alacalufi is vast and fragmented, covering continental and insular rivers. A new record of this species on Duque de York Island (50°34′S-75°20′W) defines the southernmost limit for the distribution of freshwater anomuran crustaceans. Aegla neuquensis is only found in Extra-Andean Patagonian rivers. The current geographic distribution patterns of these species can be explained by the existence of multiple island glacial refuges during the Last Glacial Maximum and by the hydrographic captures that occurred during the Late Glacial.

Wave action and density dependent effects can strongly affect the ability of sessile barnacles to feed and assimilate energy. Phenotypic plasticity in cirrus form has been demonstrated in several species of acorn barnacles in response to those factors. Field experiments were used to test whether cirrus morphology of the North Atlantic acorn barnacle, Semibalanus balanoides, varied in sites over a gradient of wave-exposure or in aggregations manipulated for population density and neighborhood size. Variation in morphology of the feeding cirri differed between sites, but was not directly related to estimates of wave exposure. This may have been a result of altered feeding behavior in different types of flow. Cirrus morphology did not vary with either aggregation size or density. This study identifies variation in cirrus form for S. balanoides, suggests its dependence on the hydrodynamic environment and lack of dependence on density.

Maxilliped-setation in two Australian fiddler crabs, Uca perplexa (n  =  104) and U. vomeris (n  =  128) was studied and related to the habitats in which these crabs live. Both species were collected from the banks of Myora Springs, North Stradbroke Island, Queensland, Australia. We counted the total number of setae (both plumose and spoon-tipped) on: 1) the inner and outer surfaces of the first and second maxillipeds, and 2) the inner surface of the third maxilliped. In general, there is no distinct sexual dimorphism for both types of setae in the two species. For any given size of crab, significantly more spoon-tipped setae were present in U. perplexa than in U. vomeris, providing further quantitative evidence that fiddler crabs from sandy habitats possess more spoon-tipped setae (an adaptation for processing sandy sediments) than those living in muddy habitats. No significant difference in plumose setation between the two species was generally detected; perhaps plumose setation is of less adaptive significance in terms of habitat adaptation than spoon-tipped setation in these two species. There is generally no sexual dimorphism in the size of the three maxillipeds for both species. Uca perplexa males had longer minor chelipeds than females while U. vomeris males had minor chelipeds that are deeper in the centre than females. These results provide evidence that male fiddler crabs could compensate for their foraging handicap by having longer or deeper minor chelipeds which enable them to scoop larger amounts of substrate.

Male fiddler crabs either produce lateral or vertical waves. The function of lateral waves is well documented, but vertical waves have been largely unexplored. Here we explore the function of vertical claw-waving by the Japanese fiddler crab Uca arcuata by examining the context in which males produced both directed waves (the waver is facing a nearby crab) and undirected waves (waving when no other crabs are present). There are two types of mating in this species: burrow mating (the male chases a female to his burrow and they mate underground); and surface mating (the male holds the female down and they mate on the surface). Attempted burrow matings were more likely to be preceded with directed waving at the female than were attempted surface matings (83% vs. 50%). All successful burrow matings were preceded by directed waving at the female, while only 50% of successful surface matings were preceded by directed waving. Undirected waving was given in the absence of a nearby crab. The frequency of undirected waving was not related to the number of males within a 60 cm radius around the male, but was negatively related to the number of females within that distance. This suggests that undirected waving acts as a long-range female attractant.

Performance related traits and habitat of the mantis shrimp Rissoides desmaresti are described for specimens collected from the Solent region on the south coast of England, close to the species northern border. Most animals were collected over sub tidal ‘mud’ and ‘sandy mud’ sediments, although new recruits and adults were also found on intertidal mudflats. Winter size-frequency distributions showed evidence of regular recruitment and growth to maturity. The reproductive condition of females was staged according to the colour of cement glands, which developed synchronously with ovaries. Females with ripe ovaries were observed between October and April and animals kept in aquaria deposited and brooded eggs in March and April. Results showed that regular recruitment and large breeding populations can occur close to range borders.

Amphipods play important roles in the cycling of nutrients and energy in many aquatic systems where they display a wide range of feeding modes ranging from detritivore to predator. Although the biology of many amphipod species has been examined, little is known of hypogean amphipods inhabiting cave streams. Gammarus troglophilus is a stygophilic amphipod that co-occurs with the federally endangered stygobiont G. acherondytes in cave streams of the Salem Plateau Karst Region of southwestern Illinois. With the goal to establish a self-sustaining laboratory population of cave amphipods to obtain amphipods for lethality experiments, we tested hypotheses relating the survival and growth rates of G. troglophilus collected from cave streams to different laboratory conditions of food and water velocity. We used a series of microcosm experiments to test the hypotheses that survival and growth are not affected by type of water (cave water vs. amended water), water velocity (static vs. dynamic/recirculating), or the type of available food (sediment vs. sediment, leaf discs, and TetraMin®). We also tested if different food treatments affected the survival and/or growth of juvenile amphipods and newly released neonates in static chambers. Our results indicate that cave water was important for survival because no amphipods survived past 30 days in experiments with water amended to resemble cave water. The addition of food (leaf discs and TetraMin®) and water velocity affected survival but not growth rates in microcosm experiments. Food treatment (leaf discs vs. TetraMin®) did not significantly affect survival or growth rates of juvenile amphipods. However, leaf discs increased the survival and growth of neonate amphipods. Overall, survival was low in all experiments and further research is needed to examine the effects of handling stress on survival during experiments because amphipods left in stock tanks survived and grew well.

The pandalid Heterocarpus vicarius is a deepwater shrimp, commercially exploited along the Pacific coast of Costa Rica and neighboring countries. The constant decrease of commercial landings in recent years has provoked an increasing concern about the sustainability of this deepwater resource. To facilitate an adequate management of H. vicarius, we examined 240 ovigerous females collected between 2004 and 2007. Females ranged in size between 29.4 and 45.4 mm carapace length and carried on average 15,008 newly-extruded eggs. To our best knowledge, the maximum of 33,549 eggs for H. vicarius is the highest number so far reported for any pandalid species. During embryogenesis, the average number of eggs decreased by 46.9%, while the average egg volume increased by 53.3%. Average egg volumes were statistically different between early (Stage I: 0.045 mm³) and late (Stage III: 0.069 mm³) development. The egg mass volume comprised on average 17.8% of the dry weight of ovigerous females (Stage I). Although fecundity increased significantly with female size, the relation between reproductive output (Stage I) and female size was not significant. We compare our results with those from other pandalids, especially with the closely-related H. reedi from Chilean waters.

The pandalid shrimp Plesionika izumiae is a relatively common shrimp in the coastal waters of Japan, except off northern Honshu and Hokkaido. This is one of the dominant species in the benthic community of Kagoshima Bay, southern Japan. The reproductive biology including, reproductive period, size at sexual maturity, embryo size and brood size of P. izumiae was studied in the bay. All females were examined for the presence of embryos attached to the pleopods and the developing embryos were classified into four stages. Ovarian development was also observed based on morphological observation. Ovigerous females occurred throughout the year with higher percentage during May to November, indicating this was the main reproductive period. Ovarian maturation was observed during the incubation process of embryos, suggesting that females were potentially capable of multiple spawning during a reproductive period. The size at sexual maturity was estimated to be 8.5 mm in carapace length based on the method using the size at which 50% of the females were ovigerous. Embryo size was independent of the body size (carapace length) of females but increased with development. There was a positive correlation between brood size and body size, while a significant reduction of embryos was observed during the course of development.

The population structure of the freshwater land crab Discoplax hirtipes (Gecarcinidae) was studied on Christmas Island, Indian Ocean, to which this species is endemic in its blue colour form. Despite previous overexploitation of this crab, this is the first such study to take place for this species on Christmas Island. Surveys were conducted in the dry (non-migration) season, at Ross Hill Gardens, which is one of several permanent ‘residential areas’ inhabited by D. hirtipes. The sex ratio was found to be skewed in favour of males 2∶1. Similarly to other gecarcinid species, male crabs were found to grow larger than females in terms of body weight, carapace width and chelae size (length and width). During the survey, few juveniles were found, which could suggest an ageing population. Despite being protected by law on Christmas Island, this is potentially worrying for a species that due to its restricted distribution continues to be especially vulnerable to outside threats, including that of aggressive invasive species and long term habitat destruction.

I reviewed the penaeid literature for characters ‘traditionally’ used to discriminate Litopenaeus setiferus, Farfantepenaeus aztecus, and F. duorarum and examined early life stages (ELS) with 3 0 to 8 2 rostral teeth based on these characters. The species identity of most of the specimens examined were verified ‘a priori’ with a multiplex PCR assay that targeted the 16S rRNA mitochondrial gene. My objectives were to re-evaluate ‘traditional’ characters by re-examining ELS for differences in morphology and timing of character development based on number of rostral teeth rather than body size, and, to identify a reliable suite(s) of characters to discriminate taxa in areas where distributions overlap. I found the absence of spinules along the dorsal carina of the sixth pleomere in young with < 4 dorsal teeth (DT), and the supposed difference in length of the third pereopod relative to the distal margin of the eye to be unreliable characters for generic discrimination. Differences in the thoracic sternal spine pattern, rostrum depth at the third DT, and relative lengths of segment one of the inner and outer antennular flagellum are ‘new’ characters for genus and/or species level discrimination discussed here. Differences in antennal scale shape and sixth pleomere length can help discriminate F. aztecus from F. duorarum, but these characters should be used cautiously in areas where distributions overlap, especially during summer and early fall when water temperatures and rates of growth and development are high. Young with ≤ 7 − 8 1 teeth and a sixth pleomere length > 2.5 mm can be assigned to F. aztecus, regardless of collection date, because all comparably developed F. duorarum and L. setiferus examined had a sixth pleomere length < 2.5 mm. Given temporal and species-specific differences in rates of growth and development that contribute to morphological variability, number of rostral teeth provides a more consistent criterion than body size to determine which characters reliably discriminate taxa.

Tadpole shrimp are known to be important animals in the ecology of ephemeral wetlands. In the northern Chihuahuan Desert of North America, the tadpole shrimp fauna is composed of possibly three species in the genus Triops, which have variously been referred to as species, subspecies, and intraspecific variation. Our results support the presence of three morphologically distinct forms, which will be referred to herein as T. newberryi, T. longicaudatus “short,” and T. longicaudatus “long.” We report analyses of Triops spp. sampled in summer 2008 from 14 natural playas and man-made flood retention ponds. Data were recorded on meristic counts and quantitative measurements of morphological features. We also sequenced portions of the mitochondrial COI and ND1 genes for 72 shrimp, including individuals from all three morphological forms and for multiple ponds for each form where possible. The three forms were morphologically distinct for multiple characters and molecular analyses showed large differences in DNA nucleotide sequence and the presence of multiple unique amino acid substitutions in each form. Finally, prior literature suggests the three forms exhibit different reproductive systems, with populations of T. longicaudatus “long” thought to be gonochoric (equal sex ratios and obligate outcrossing), T. longicaudatus “short” having only self-fertilizing hermaphrodites, and T. newberryi being androdioecious, having both self-fertilizing hermaphrodites and males. While these three forms may be sufficiently distinct in morphology, mitochondrial DNA, and reproductive life history to warrant elevation to species level, additional geographical sampling and an examination of the various type specimens are necessary for a formal taxonomic revision.

The genus Parvulobathynella Schminke, 1973a, presently contains six species: three each from South America and Africa. Two new species of this genus, viz. Parvulobathynella distincta n. sp. and Parvulobathynella projectura n. sp., collected in the interstitial banks of the Rivers Krishna and Godavari in the southeastern India, are described and illustrated and their taxonomic position in the genus Parvulobathynella is discussed. To accommodate the Indian species, the generic diagnosis of Parvulobathynella is amended based, among other things, on the mandibular features such as the size and arrangement of molar teeth. The salient morphologic characters and their various states in the species of Parvulobathynella are reviewed. A note on the ecology and biogeography of the species is added. The monophyletic status of the family Leptobathynellidae is also briefly discussed.

The juvenile stages of the isopod family Gnathiidae have a large impact on marine ecosystems through their parasitic interactions with marine fishes, as well as being a substantial food source for the cleaner fish guild. However, the taxonomy of Gnathiidae is based on non-feeding adult males. Adults are difficult to obtain owing to their cryptic lifestyle in the sea floor, while the juveniles can be collected in abundance either from their hosts or using emergence traps. Given the known diversity of the hosts, and assuming host partitioning among species, the diversity of gnathiids could be much greater than currently recognised. We argue that the systematics of this group should recognise this ecological role, and develop the taxonomy of the juvenile stages. We provide a detailed external anatomy of one species, Gnathia aureamaculosa, that has been used extensively in recent ecological studies. Images from scanning electron microscopy of two juvenile instars are compared with two other species, and the literature surveyed to illustrate a range of taxonomically useful traits. The expansion cuticle of the pereion shows how gnathiids are able to expand enormously during a blood meal and also lends caution on using total body length for comparative purposes. A range of morphometric and categorical features are available on the non-expandable sections of the body, such as the head, pleotelson and uropods. Of the three species illustrated, the shape of the eyes and head, and the shape and setation of the pleotelson uropods are diagnostically useful. Evidence from the literature shows that the free-living juveniles are not mancas; the manca instars are passed during the internal developmental period. Anatomical observations cast doubt on the classification of Gnathiidae as Cymothoida, in agreement with recent phylogenetic studies.

A phylogenetic analysis based upon 30 extinct and extant taxa of podotrematous brachyuran decapods using 74 characters shows that Podotremata sensu Guinot, 1977 is not monophyletic and results in a new classification for these crabs. Four new taxa are recognized at the section-level (Homoloida, Torynommoida, Etyoida, and Dakoticancroida) as well as two new families (Basinotopidae and Xandarocarcinidae). Dromiacea as historically defined is redefined herein to exclude Homoloidea. New generic names Noetlingocarcinus and Xandarocarcinus, and Seorsus millerae new combination also resulted from the work.

A new species of subterranean amphipod, Bogidiella veneris, from Venus Bay, South Australia is described. The species was found in a groundwater observation well drilled in an aeolianite limestone formation only 500 m from the seashore. The discovery of the new bogidiellid amphipod is one of the outcomes of a three year stygofauna survey in South Australia. Bogidiella veneris is the fourth species of Bogidiellidae from the Australian region.