Eggs of 20 females were sampled to analyze lipid, protein, and carbohydrate content during the embryonic development of Cherax quadricarinatus. Sampling was performed on recently spawned eggs to first juvenile stage. Ten eggs were sampled every 48 h during the first two weeks and every 72 h thereafter for biochemical analysis. Total proteins, lipids, and carbohydrates were measured. Proteins were the most abundant egg component (63.2%), followed by lipids (32.3%), and carbohydrates (4.4%). A steady decrease of lipid content was observed ( y = 895.38 − 9.93x, r² = 0.94; y = lipid concentration, x = days). For proteins, two different depletion rates were observed, with the initial rate maintained for 30 days ( y₁ = 1,443.0 − 4.46x₁, r² = 0.90) and an increased depletion rate after hatching ( y₂ = 1,936.60 − 21.10x₂, r² = 0.96). Carbohydrates were always present as a minor constituent, and its concentration did not change significantly. Water content increased from 52% in recently spawned egg to 85% in juveniles. Energy equivalents were calculated from each component, and the overall energy expenditure is represented by the equation y = 13.86 − 0.11x (r² = 0.95). Relevant morphological features for each sample day are indicated.

For many organisms, chemoreception plays a key role in numerous aspects of daily life. Crayfish use chemical signals to find mates, warn conspecifics of predators, and relay social status. While many of these situations have been studied in detail, behavior of conspecifics toward chemical signals from molted individuals has not been thoroughly examined. The physiology of crayfish changes dramatically during molting (ecdysis), which in turn may change both the chemical content and concentrations of the chemical cues released into the water. We hypothesized that conspecifics are sensitive to chemicals released during molting. A Y-maze experimental design was used to test for differential responses to various molt-related chemical stimuli presented to intermolt male crayfish (Orconectes rusticus). The sources of chemical stimuli were recently molted male crayfish, intermolt male crayfish, control (aged tank water), and food (fish). Behavioral indices of response included initial arm choice, time spent in each arm, time spent at each nozzle, number of arm changes, and meral spread at each nozzle. Experiments were also conducted where crayfish were presented the same chemical stimuli in each arm to obtain measures of locomotor activity in the different stimuli. In addition, orientation parameters such as walking speed, walking speed to source, and distance to source were analyzed. Intermolt individuals spent more time in the presence of molt signals, although the food stimulus was more attractive than any other stimuli tested. Crayfish showed a significant initial arm choice when molt stimulus was paired with control. During the identical presentation of chemical stimuli, crayfish showed an increase in locomotor activity in the molt and food chemical stimuli than in the intermolt and control chemical stimuli. There were no significant differences in orientation parameters between chemical stimuli. These results show that crayfish can discriminate molted male conspecifics from the other chemical stimuli tested.

Postlarvae of the blue crab, Callinectes sapidus, settle and metamorphose in beds of submerged vegetation in estuarine nursery areas. They remain there until crab stage IV or V, which disperses throughout estuaries. The study considered orientation of Stage IV–V crabs to chemical and visual cues in the presence of current flow. Crabs were tested in a horizontal rectangular chamber that had test waters entering the ends of the chamber and exiting at the center. An orientation response occurred if crabs moved from a center release site to the end of the chamber. Test waters were “Offshore” odor water and estuarine odors (estuarine water, habitat odor from salt marsh cord grass and oysters, predation odors from mud crabs, and predation event odors from crushed conspecifics). In apparent darkness (red light), crabs did not orient to flow (flow rates = 0–30 ml min^–1; current speeds = 0–6.2 cm s^–1) but moved away from all estuarine odors. When a visual target representing a predator was placed at one end of the chamber, the crabs failed to orient to the target in Offshore odor water. However, when Offshore odor water was paired with any estuarine odor, the crabs moved away from the visual target regardless of its location. These results indicate there is a hierarchy of responses to flow, odors, and visual cues. Subtle changes in behavior with odor type were not evident. Thus, crabs have different behavior in Offshore odor water and in estuarine odor waters.

The sperm structures of pandalid shrimps were previously undescribed. We determined the mature sperm morphology and ultrastructure of Pandalopsis japonica by means of light and electron microscopy and compared them with the known morphology and ultrastructure from other carideans. Spermatogenesis is initiated in the testicular tissue of the male-phased Pandalopsis japonica ranging from 14 to 23 mm in carapace length. The sperms are 52 to 55 μm in length and consist of a cup-shaped main body and a spike extending from the convex surface of the main body. The main body, of which the size is 24 to 26 μm in width and 5 to 7 μm in height, has a nucleus and a cup-shaped base. The spike, 40 to 44 μm long and approximately 3 μm thick, consists of the central core filled with electron-lucent materials and the electron-dense wall containing a number of tubular-like structures that are aligned along the longitudinal spike. The unique structure of Pandalopsis japonica sperm, particularly in the spike possessing tubular-like structures of approximately 24 nm in the outside diameter and 15 nm in the inside diameter, offers a good taxonomic tool among shrimp species in the carideans.

During ontogeny, male rock shrimp Rhynchocinetes typus develop from the typus morphotype through several intermedius stages to the robustus morphotype, the last molt stage, which features powerful third maxillipeds and chelae. In a competition-free environment, all male stages mate in a similar manner. They guard females for 23 min to 3 h and perform several behaviors before and after they transfer spermatophores. In the present study, we observed the mating behavior of three different ontogenetic stages of male rock shrimp in a competitive environment in which the three different male stages competed directly for access to receptive females. In the first set of experiments, two males of different ontogenetic stages were placed together with a receptive female. The results indicated the existence of a linear dominance hierarchy, being robustus > intermedius > typus. In the second experiment, we examined the behavior of subordinate males while two dominant-stage males competed for a receptive female. During agonistic displays of the two dominant-stage males, the female escaped from the embrace of her (dominant) mating partner. Some subordinate males used this opportunity to pair with the female and mate rapidly without courting, contrasting to their courting in a competition-free situation. In a competitive situation, subordinate males that gained access to a female deposited several spermatophores as soon as possible (within 1 min). At the beginning of both experiments, subordinates that interacted first with the receptive female rapidly transferred spermatophores. Thus, in a competitive environment, subordinate males may use an alternative mating tactic that is characterized by speed. The social environment may impose divergent selective pressures favoring the evolution of conditional alternative mating tactics.

This study compared trade-offs between brood size and brood interval, as well as feeding activity and ovarian development during brood incubation, among fiddler crabs of three subgenera: Uca (Celuca) perplexa, U. (Thalassuca) vocans, and U. (Deltuca) dussumieri. Female U. perplexa remained in their burrows throughout incubation, and egg mortality was low despite relatively large brood sizes. These females did not feed during incubation, and their ovaries remained small until the eggs hatched. Female U. vocans fed actively on the surface during incubation, and egg mortality was high, despite relatively small brood sizes. Female U. dussumieri also fed actively during incubation, but their broods were very small and egg mortality was low. In the latter two species, the ovaries grew rapidly during incubation, and many females produced consecutive broods. Incubation in burrows may be adaptive for females that are exposed to severe heat stress and desiccation in the upper tidal flats, and a simple model demonstrates that large broods may be advantageous for females incubating broods in burrows because of shorter interruptions during feeding.

Young Cardisoma carnifex were found living within burrows of conspecific adults, in diverticula starting from the main branch of the burrow. Their gill chamber structure is much less adapted for air-breathing than that of the adult. The young spend at least three years in this environment, probably feeding on leaves remaining from the adult meals. Nothing is known about when they start to dig their own burrows or how they avoid being cannibalised within the adult burrows.

Remains of Anostraca, such as exuvia and cysts, are preserved in the sediments of temporary pools. Sampling the bottom gravels of the pools in the draining system of the Oued Djerat in the Sahara desert (Tassili N'Ajjer, Algeria; Kairaouan, Tunisia), revealed anostracan fauna diversity which surpassed that in live plankton sampling. The deposits in the Oued Djerat contained exuvia and cysts of Chirocephalus, Branchipus, and Streptocephalus, with S. torvicornis and S. rubricaudatus living together. Cyst variability of Streptocephalus torvicornis was higher than expected; even a type similar to S. ovamboensis was found. Taxonomy was corroborated by the morphology of exuvial remains of the limbs (endite 1) recovered from the same deposits.

Ceratonotus pectinatus Sars, 1909, the type species of Ceratonotus Sars, 1909 (Copepoda: Harpacticoida: Ancorabolidae), is redescribed on the basis of females collected from southern Norway and by re-examination of extant material from the collections of Sars (Oslo, Norway), Lang (Stockholm, Sweden), and Drzycimski (Bergen, Norway). Some morphological characteristics of C. pectinatus males are provided from direct observations of the male copepodid V stage. Re-examination of Por's (1965) material from Raunefjord, Norway, did not provide any conclusive evidence to maintain C. pectinatus elaphus as a valid subspecies; it is considered here a junior subjective synonym of C. pectinatus. The validity of C. coineaui Soyer, 1964, is confirmed. Two new species of Ceratonotus are described, each based on a single sex, C. thistlei (♀) from the San Diego Trough (northeastern Pacific) and C. concavus (♂) from the eastern Mediterranean. An updated generic diagnosis for Ceratonotus is provided and intergeneric relationships discussed. Dendropsyllus thomasi, new genus, new species, is described from the San Diego Trough, northeastern Pacific. The new genus is characterised by the distinctive pattern of dendroid body processes (lacking on abdominal somites), lateroventral margins of cephalothorax with well-developed conical process, P1 exp-2 with 4 geniculate setae, P1 enp-2 with 1 apical seta, complete absence of P2 endopod, P3 exp-3 with 1 inner seta, and loss of the inner seta on P4 exp-3. Ceratonotus magellanicus and C. antarcticus, previously isolated as a distinct clade through parsimony analysis by Conroy-Dalton (2001), are both transferred to Dendropsyllus because they deviate significantly from the revised diagnosis for Ceratonotus. Ceratonotus and Dendropsyllus share a close sister-group relationship strongly supported by eight synapomorphies. The general phylogenetic relationships within the Ceratonotus-group are reinforced.

A number of harpacticoid copepods were collected during two series of sampling campaigns in a coastal lagoon and in a brackish system in northern and southern Sinaloa (northwestern Mexico), respectively. Four enhydrosomid species were recognized. Three of them are new to science. Enhydrosoma lacunae is reported for the sixth time. This record extends the distribution of the species from the Caribbean Sea to the Eastern Tropical Pacific, and it is suggested that it is an invasive species borne in water ballast of ships. Enhydrosoma parapropinquum sp. nov. bears a strong resemblance to E. propinquum, but these species are different in shape of the caudal rami and female fifth leg. Enhydrosoma casoae sp. nov. and E. solitarium sp. nov. showed to be closely related to E. vicinum. These three species seem to be related by the structure and armature formula of the female fifth swimming leg. Enhydrosoma casoae sp. nov. and Enhydrosoma solitarium sp. nov. can be separated from each other by the ventral spinular ornamentation of urosome and spinular ornamentation of female P5 baseoendopod.

Nucleotide sequences for the 18S rDNA of 28 cytherocopine ostracods that represent 16 families were determined and compared with those of bairdioidean and cytherelloidean ostracods. Resulting molecular phylogenetic trees consistently indicated that cytheroideans formed a monophyletic group and that bythocytheroideans are paraphyletic outside of the cytheroideans. This relationship suggests that the diagnostic morphological features of the Bythocytheroidea, such as the five adductor muscle scars and the first antenna with seven articulated podomeres, are plesiomorphic. The molecular phylogenetic relationships among cytheroideans indicated polyphyly of the amphidont basic type hingement, which is distributed in four lineages, i.e., the loxoconchids, leptocytherids, schizocytherids, and a group of hemicytherids, thaerocytherids, and trachyleberidids, suggesting that the hinge structure of the amphidont basic type has evolved at least four times independently in cytheroidean ostracods. The ostracod hinge structures may have evolved in concert with the extent of carapace calcification.

The taxonomic study on the Caprellidea collected from the shallow waters of north-west area of Mirs Bay, Hong Kong revealed the distribution of four species in this area. Of them, Tropicaprella minuta, new genus, new species, and Caprella hirayamai, new species, are described. Tropicaprella, new genus, is close to Heterocaprella Arimoto, 1976, but differs by the absence of the clavate projection on the pereonite 4, the elongate pereopods 3 and 4 and the five-articulate pereopod 5. The closest species to Caprella hirayamai, n. sp., are Caprella californica Stimpson, 1857, and Caprella scaura Templeton, 1836, but C. hirayamai can be easily distinguished by less elongated pereonite 1, short basis of gnathopod 2 and oval propodus with dorsal setae in gnathopod 2.

The evolutionary history and classification of the palaemonid shrimps has been the subject of constant speculation and debate. At present, all major systematic treatments have been based on morphological characteristics. To help resolve the phylogenetic relationships, and thus enable the creation of a classification system that reflects evolutionary history, a region of the 16S mitochondrial rRNA gene was sequenced for a number of Australian Palaemonidae. The resulting phylogenetic analyses indicated the presence of major anomalies in the current classification of Australian Palaemonidae. Significantly, three species belonging to three separate genera, Macrobrachium intermedium, Palaemon serenus, and Palaemonetes australis, are closely related, with genetic differences more characteristic with that of congeneric species. The results also demonstrate non-monophyly in Australian palaemonids with respect to both Palaemonetes and Macrobrachium.

Clawed lobster diversity through time [Lower Cretaceous (Valanginian)–Recent] is compiled and interpreted herein. Species diversity trends are evaluated using raw numbers of species per geologic time unit (period, age) and also by using a variety of species-numbers normalization factors that address sampling biases. Species numbers are normalized for: 1) duration of time intervals (periods), 2) sedimentary rock exposure area per time intervals (periods), and 3) area under the Vail et al. (1978) sea-level curve (ages). The Vail curve method, new herein, normalizes for marginal/epicontinental sea coverage per age. By any measure; i.e., raw or normalized data, and over any time interval considered, shallow-dwelling (shelf depth) lobsters were significantly more diverse in the Cretaceous than in the Tertiary (e.g., 53 Cretaceous species vs. 16 Tertiary species, raw count; 18 Tertiary species if normalized for duration). Reduction in Tertiary lobster diversity seems due, in part, to mass extinction at the K/T boundary. However, lobster diversity rebounds in the Eocene, and it seems apparent that lower diversity of Tertiary lobsters is due more to post-Paleocene events than to K/T boundary events. The reduction in Tertiary fossil diversity seems largely explained by the lobsters' general abandonment of shelf depths in the Tertiary (ca. late Eocene–early Oligocene). Deep-dwelling lobsters are seldom collected as fossils, and their diversity history will never be known, but it seems clear that shelf-dwelling lobsters were significantly more diverse in the Cretaceous.

Larval development of Macrocoeloma diplacanthum (Stimpson) consists of two zoeal stages, followed by the megalopa. Each larval stage is described in detail. The duration of the zoeal stages was 2–3 (2.4 ± 0.5) and 3–4 (3.5 ± 0.5) days for the first and second zoea, respectively, the megalopa phase appearing 6–8 (7.0 ± 0.5) days after hatching. Unlike for other majids, zoeal stages of M. diplacanthum can be readily distinguished by their distended forehead with strong underlying muscle bands, undercut dorsal carapace spine, and spine on the terminal endopod segment of the first maxilliped. No other known mithracine or majid zoeae exhibit this combination of features. Our zoeal account of M. diplacanthum from Mexico is remarkably consistent with Floridian specimens previously described. However, we have found some differences between descriptions, which could be attributed to natural variation or inadequate description. Previous attempts to evaluate the relationships within Mithacinae have been based on larval characters widely distributed throughout Majidae and therefore are considered inadequate to infer sister-group relationships. The phylogenetic analysis of majids suggested that the position of Mithracinae is still uncertain, as is its monophyletic status. We recommend that additional characters, particularly of the megalopa phase, be sought for a better resolution of majid evolutionary history.

Four species of portunid crabs from South Brazil were studied by allozyme electrophoresis. The morphological and genetic distinction of C. sapidus subspecies (C. s. sapidus and C. s. acutidens) was studied by multivariate analysis of 10 morphometric characters and by allozyme electrophoresis of eighteen enzymes. The genetic relationship among Arenaeus cribrarius, C. sapidus, C. danae, and C. ornatus was assessed by these enzymes in order to test previous hypotheses based on morphological similarity. The morphometric and genetic evidence showed that there is no reason to justify the subspecific status of C. c. sapidus and C. s. acutidens, showing that their slight morphological differences are determined by the environment. Arenaeus cribrarius showed low genetic similarity to Callinectes spp., which justified its generic status (I = 0.252–0.396). The most closely related species within Callinectes were C. danae and C. ornatus, as previously suggested by their general morphology, showing a genetic identity of 0.762. According to the “sloppy molecular clock,” their divergence happened before the elevation of the Isthmus of Panamá, at the end of the Pliocene, about 3.8 Myr, which is in accordance with the fossil record.

Three species of the varunid crab genus Cyrtograpsus (Brachyura: Grapsoidea) occur in apparent sympatry along temperate coastlines of the southwestern Atlantic. Two of them, C. angulatus Dana, 1851, and C. altimanus Rathbun, 1914, are common in intertidal habitats and are easily separable by their morphology. In contrast, there is very limited knowledge on the ecology and distribution of the third species, C. affinis (Dana, 1851). In the present study, several specimens of C. affinis were collected in the Río de la Plata Estuary between Argentina and Uruguay. The study of these specimens showed that C. affinis tends to be smaller than the other two species of the genus and seems to be restricted to subtidal habitats. However, morphometric comparisons suggest the existence of a continuous gradient rather than discrete differences between specimens of C. affinis and C. altimanus. Morphometric differences were as common among subtidal samples as between subtidal and intertidal samples. Likewise, comparison of mitochondrial DNA sequences (16S rRNA) did not reveal diagnostic differences between the two putative species, suggesting a very close relationship between C. altimanus and C. affinis. Possibly the two forms represent a single species with a high ecological and phenotypic plasticity.

Two new species of freshwater crabs of the genus Tehuana from the states of Tabasco and Oaxaca, Mexico, are described, and a new diagnosis for the genus is presented. Tehuana chontalpaensis, new species, was collected in a mountain river in southwest Tabasco at 900 m above sea level; it is distinguished by a first gonopod with an elongated mesial process and a large laminar lateral process with a strong lateral spine. Tehuana jacatepecensis, new species, was collected in the Jacatepec river, in central Oaxaca; it differs from other species in the genus by the first gonopod, which has a reduced, spoon-like lateral process and an ax–shaped mesial process that projects beyond the marginal process.

Geothelphusa dehaani (White, 1847) is an amphibious crab inhabiting rivers and streams in Japan. Its gill complement consists of nine phyllobranchiate gills, which are cleaned by the passive action of setiferous epipods on all maxillipeds. Epipodal setae are of two types; anchor setae distally have two rows of stout outgrowths with opposing recurved ends (anchor-like), and brush setae have dense needle-like setules distally surrounding the setal shaft. Both setae project from the epipod margins mostly onto gill surfaces, with a few setae inserting between the lamellae. The functional morphology of epipodal grooming in brachyurans is inferred to be a better design solution than in other decapod taxa. Subjecting crabs to dehydration resulted in severe fouling and breakage of epipodal setae, thus indicating the importance of branchial water to gill grooming. Form-function analysis suggested that the use of setiferous epipods as a common gill-cleaning mechanism in the Brachyura was secondarily derived as a result of evolution to a crab-like body form, which caused the tight enclosure of the gills in and the exclusion of the limb bases from the branchial chambers. The epipodal setae, especially anchor setae, of G. dehaani were morphologically compared with those of several brachyuran taxa, including other Japanese potamoid species.

We recorded the incidence of predation on snakes by the amphibious freshwater land crab Eudaniela garmani (manicou crab) in the rainforests of the Caribbean island of Tobago during 168 days of field observation (spanning a 4-year period) conducted between the hours of 08.00 AM and 12.00 noon and 21.00 PM and 23.30 PM. Six instances of manicou crabs eating snakes were observed and photographed. Field notes are given for each predation event, and photographs are presented for three of these: clouded slug-eating snake, Sibon nebulata nebulata, three-lined snake, Atractus trilineatus, and vine snake, Oxybelis aeneus. We conclude that the potential predation pressure placed on local snake populations by manicou crabs merits investigation.