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The nuclear ssu rRNA gene of several isopods (Crustacea, Peracarida) was sequenced to study its phylogenetic information content. Several areas had to be cut out of the alignment of 31 isopod sequences and selected outgroup arthropod sequences due to the lack of alignable patterns. The final alignment had 2,533 positions and 43 sequences. The length of the isopod nuclear ssu rRNA genes varies between 2,098 and 3,402 bp. In some clades the gene length increases; in others like the cymothoids and bopyrids, long deletions occur. Some insertions are specific for major groups (e.g., amphipods, isopods). Most elongation areas evolve rapidly and are not alignable among higher taxa. Information content is visualized with spectra of supporting positions. Only a few groups are unambiguously supported with a signal distinctly higher than background noise. The results of maximum parsimony analyses are congruent with major aspects of earlier hypotheses on isopod phylogeny. Some contradictions are discussed. The latter are mainly based on a lack of reliable information. A major monophyletic group found in the molecular phylogenies and also supported by distinct morphological characters is named Scutocoxifera tax. nov., composed of the Oniscidea, Valvifera, Sphaeromatidea, Anthuridea, and Cymothoida. SEM photographs are presented to document the apomorphic state of the coxa in the Scutocoxifera.
The intertidal barnacle Balanus zhujiangensisRen, 1989, is reported from Okinawa, Japan, for the first time. A supplementary description of this species is provided, and the specimens are compared to those from the Zhujiang River estuary which empties into the South China Sea. Several morphological characteristics of the shell, mouthparts, and armature of cirrus III suggest that B. zhujiangensis is related to the B. amphitrite complex rather than to B. trigonus by consistently having but a single row of pits on the external surface of the scutum and lacking an adductor ridge. The presence of scutal pits is interpreted as a means of facilitating the transmission of light through the valve thereby allowing the photoreceptors to detect changes in light intensity while the operculum is closed.
Two species of blue crabs were investigated with regard to infestation of the branchial chambers by the pedunculate cirriped Octolasmis lowei. In Callinectes danae, the frequency of infestation was 22.4%, and the mean intensity of infestation was 2.2 ± 0.2 (range: 1–8). Prevalence and mean intensity of infestation did not differ significantly between males and females of C. danae. Significant differences in prevalence were observed between juveniles and adults, between ovigerous and nonovigerous adult females, and among blue crabs in different molt stages. No correlation was observed between the prevalence of infestation by O. lowei and the carapace width of male or female blue crabs. In Callinectes ornatus, the prevalence of infestation by O. lowei was 12.1%, and the mean intensity observed was 4.0 ± 1.3 (range: 1–49). Prevalence of infestation did not differ significantly among crabs in different molt stages but differed between juveniles and adults and between male and female crabs. A positive correlation was observed between the percentage of infestation by O. lowei and the carapace width of C. ornatus males.
The female of Haplostomides scotti Chatton and Harant is redescribed, and the male is described for the first time, on the basis of specimens living in the compound ascidian Polyclinum aurantium collected at Roscoff (Brittany, France). Some morphological characters of the female are at variance with the original description, which was based on one specimen from the type locality (Penpoul, near Roscoff). (?) Enterocola beaumonti Scott and Scott may be a synonym of H. scotti. The male of H. scotti is compared with males of species of Botryllophilus with respect to the armature formula for legs 1–4. Similar comparisons are attempted for seven other species of haplostomatins (in the genera Haplostoma, Haplostomides, Haplosaccus) in order to establish morphological differences between males of haplostomatins and botryllophilins.
The maxillae (fourth limbs) of myodocopine Ostracoda are difficult to interpret correctly because of their complexity, which has led to inaccurate descriptions of the limb in the literature. Maxillae of species of the Sarsiellinae are described and illustrated herein in their natural orientation on the body of the animal, and clues are presented to assist in more accurate descriptions of the limb when compressed under a cover slip. It is shown that the anterior-to-posterior sequence of the three endites of the protopod in the Sarsiellinae is the reverse of that in the Cypridinidae, Philomedidae, and Rutidermatidae.
A new genus and species, Galathocrypta acaudata, infesting the galatheid Munidopsis erinaceus is described based on a pair collected from the outer continental slope off the Coatzacoalcos River, southwestern Gulf of Mexico, at a depth of 502 m. The female in the new genus differs from those of its most similar genera Pseudione, Pleurocryptella, and Parapleurocryptella in having a maxilliped with an unarticulated palp and no uropods. Males of Galathocrypta acaudata lack pereomeral ventral tubercules, maxillipedal palps, pleopods, and uropods.
Tanaidacean material collected from Mundel Lake, Sri Lanka, in 1997 included the first recorded males of ‘Apseudes’ srilankaensisBăcescu, 1981. From the morphology of the male cheliped (inter alia) the species is reassigned to the genus HalmyrapseudesBăcescu and Guţu, 1974. The species which have been associated with this genus have been analyzed. The genus, which is rediagnosed, is currently composed of seven species, characterized in particular by carpal apophyses on the male cheliped and a reduced dactylus on the fourth pereopod.
Calcinus verrilli, a hermit crab endemic to Bermuda, is unusual in that it inhabits both gastropod shells (Cerithium litteratum) and gastropod tubes (Dendropoma irregulare and Dendropoma annulatus; Vermicularia knorrii and Vermicularia spirata). A significant difference was observed between the uropod symmetry of shell dwellers and tube dwellers. Tube dwellers were found to have more symmetrical uropods than shell dwellers. Regardless of shelter, the abdomens of naked individuals coiled to the right, and the left uropod was always longer than the right when their uropods were not perfectly symmetrical, suggesting the C. verrilli may be a descendant of a shell-dwelling ancestor, most likely one that inhabited dextrally coiled shells. Shelter type was manipulated, so that individuals collected in shells were forced to inhabit tubes, while those collected in tubes were forced into shells. Over several molts, uropod symmetry of the forced shelter dwellers did not differ from that of individuals inhabiting the same types of shelters in the field. This may be the first experimental evidence of an alternative shelter affecting symmetry in a hermit crab species.
Nineteen species and subspecies of freshwater crabs from the anomuran family Aeglidae are represented in Chile, 16 of which are endemic to this country. We sequenced ∼2,600 nucleotides of the 12S, 16S, COI, and COII genes from mitochondrial DNA to estimate phylogenetic relationships among the Chilean aeglids. We sampled 16 putative Chilean species and subspecies and one morphologically unrecognized taxon according to the most recent Aeglidae classification. In addition to the Chilean aeglids, one sample of Aegla riolimayana and two samples of Aegla affinis were collected from Argentina to check previous hypotheses about the origin of the group. Two other anomurans, one galatheid (Munida subrugosa) and one porcellanid (Pachycheles haigae), were sequenced to serve as outgroups in our phylogenetic analysis. Our results show the clear separation of Aegla papudo from the other Aegla species, as has been suggested previously based on morphology. Its basal position in the Aeglidae trees also supports a Pacific origin for the Aeglidae. Our phylogenies provide strong monophyletic support for the currently recognized species, with the exception of Aegla laevis and Aegla cholchol samples, which form nonmonophyletic groups.
The spider crab Pyromaia tuberculata was introduced into southeastern Brazil; ovigerous material was collected and reared in the laboratory. Morphologic changes and growth patterns of postlarval development are reported. Results show that within-stage size variation is lowest in mature stages, especially in the case of females in which there is an apparent size threshold for the last juvenile stages to undergo the puberty molt. A prepuberty molt taking place at the fourth crab stage is indicated by analyzing the allometric growth of the abdomen in females. In contrast, the same procedure using the allometric growth of chelae failed in detecting both the prepuberty and puberty molts in males. Conversely to females, which develop a complex brood chamber at the puberty molt, the enlargement of chelae was not consistent in all postpuberty males. The short instar sequence of this species, in no case exceeding nine stages, is marked by conspicuous morphologic alterations achieved at each molt. Almost all stages can be identified by examining diagnostic features of rostrum, abdomen, sternum, and pleopods.
Austinotheres new genus and Raymondia new genus are erected to receive as type species the oyster crab Pinnotheres angelicusLockington, 1877, which is redescribed, and the knife-clam crab Pinnotheres clavapedatusGlassell, 1935, respectively. Austinotheres can be separated from other Pinnotheridae by the combination of the following characters: walking legs 2 asymmetrical in length, and the third maxilliped having a carpus that is larger than the combined propodus and dactylus. Raymondia differs from other Pinnotheridae in having a clavate propodus of the first and second walking legs of the female and in the large dactylus of the third maxilliped that inserts on the midlength on the ventral margin of this article and extends far beyond the tip of the propodus.
In this study, Penaeus monodon hemocytes were identified and characterized on the basis of morphology, labeling by monoclonal antibody markers (mAbs Z5E10, Z6A5, Z6A6, and Z6H8), and cellular defense reactions. Using light and transmission electron microscopy (LM and TEM), three hemocyte types were identified based on the number and size of the cytoplasmic granules and the nucleus-to-plasma (N/C) ratio: hyaline cells (HC) are round or ovoid small cells with a high N/C ratio (0.58–0.77), and although they are clear under LM, a small number of granules can be seen with TEM; semigranular cells (SGC) are irregular in shape with medium-size granules (0.31–0.9 µm); and granular cells (GC) are round or ovoid in shape, and contain the most and the largest (0.54−1.9 µm) granules. Immunofluorescence staining showed that separately the four mAbs labeled some of the HC, SGC, and GC. Results from double staining with Z6A5 and Z6H8 showed that all three types of shrimp hemocytes could be divided into two subclasses, one labeled by both mAbs (Z6A5Z6H8) and the other labeled by neither (Z6A5−Z6H8−). Beads (0.5 µm in diameter) were engulfed by both HC subclasses, but not by any of the SGC or GC. Acid phosphatase and phenoloxidase were expressed only in some of the Z6A5−Z6H8− hemocytes, and not in any of the Z6A5Z6H8 cells. These results suggest that cellular morphology and two of the four mAb markers (Z6A5 and Z6H8) can be used to classify P. monodon haemocytes into six functionally distinct subclasses.
Petrolisthes laevigatus is commonly found in the intertidal zone from southern Peru to southern Chile. Its geographic distribution and its location in the intertidal zone suggest that this species should have ample physiological and biochemical adaptability to environmental change. Several experiments were conducted on P. laevigatus specimens collected in south-central Chile (Coliumo Bay) to determine: (i) the relationship between specific oxygen consumption rate and temperature; (ii) the presence and activity of lactate dehydrogenase (LDH), octopine dehydrogenase (OPDH), strombine dehydrogenase (STRDH), alanopine dehydrogenase (ALPDH), and alcohol dehydrogenase (ADH); and (iii) resistance to hypoxic conditions in sea water. The specific respiration rate at temperatures frequently found in Coliumo Bay was 0.054 and 0.058 ml O2h−1g−1 at 10.5°C and 13°C, respectively. LDH and OPDH activities were found in muscle tissue, heart, and visceral mass (midgut gland, gonad); OPDH presented a lower activity than LDH. Both enzymes presented high activities in comparison to other decapods. No activity was detected for ALPDH, STRDH, and ADH. Crabs subjected to low dissolved oxygen concentrations (i.e., 0.79 to 0.96 ml O2 l−1) died after three hours of exposure, and no oxygen consumption was detected during this period. Accordingly, P. laevigatus is not adapted to long-term conditions of environmental hypoxia. Nevertheless, compared to other decapod species, P. laevigatus can cope well with short-term environmental and/or functional hypoxia due to the high activity levels of LDH and OPDH and the presence of both enzymes in the heart.
The shape of sternal calcium carbonate deposits (CCD) preceding moult was used as a diagnostic character to distinguish between reproductive and non-reproductive females in six species of terrestrial isopods belonging to different families. Samples in the wild at the beginning of the reproductive season revealed females with CCD of incomplete shape, with a diamond-shaped opening at the level of central furrow. All the females showing this pattern made a parturial moult a few days later, while all females showing complete CCD made a normal moult. A laboratory experiment confirmed that these characteristics were diagnostic for females performing a secondary vitellogenesis. These females were receptive to mating at that time, provided the stage of the intermoult cycle was not too early. Screening the CCD shape is therefore a non-destructive method that can be used for routine diagnosis of females' reproductive status in terrestrial isopods.
The growth and reproductive biology of the freshwater shrimp Exopalaemon modestus were studied in Young-am Lake, Korea, from January to December 1999. Female maturity was determined by the size of ovigerous females and of females with maturing ovary. The size at which 50% of females are mature is estimated as 11.55 ± 1.95 mm carapace length. Brood size was isometric functions of female body size. Based on dry weight, the reproductive output (mass of incubating eggs/mass of female) averaged 0.17. Ovigerous females occurred in May–September. Higher gonad index was observed from May–June (percentage ovigerous > 50%). Significant difference in ovarian weight between females with noneyed eggs and eyed-egg stage was found. This indicates that ovarian maturation occurs during the incubation time, suggesting that females were potentially consecutive breeders, capable of multiple spawning during a reproductive season. Spawning by a single female seems to occur consecutively in a single reproductive period. The length-frequency distribution showed that the population had two modal size groups per year, displaying similar pattern in both males and females. Parameters of growth were estimated using the von Bertalanffy growth function (VBGF). Females grew faster and reached a larger size at age than males (K = 0.58 yr−1 and L∞ = 21.39 mm CL for females, and K = 0.62 yr−1 and L∞ = 18.40 mm CL for males). Longevity was estimated to be 1.1–1.3 yr.
A two-year field study of the population of Macrobrachium olfersi from the Guaecá River, São Sebastião, Brazil, revealed a predominance of adult females over adult males, which is expressed by an overall sex ratio of 4.3:1. Relationship between sex-ratio is a function of body size and is related to differential growth with males attaining larger body size than females. Ovigerous females were present in every monthly collection, indicating that reproductive activity was continuous. Periods of higher reproductive activity were observed during the warmer and rainy months. The smallest ovigerous female sampled was 28.1 mm of total body length. Mean fecundity was 1,227 eggs per female (mean total length: 39.9 mm) with a positive correlation between fecundity and female body size. Mean egg sizes (shortest and longest axes) were 0.449 and 0.579 mm at early embryonic development and 0.489 × 0.648 mm at late embryonic development. Based on color and size of ovaries, five distinct developmental stages were recognized. Embryonic development of incubated eggs was usually accompanied by concomitant ovarian maturation, indicating consecutive spawnings during reproductive life span. Fully developed spermatozoa were recognized in histological preparations in males as small as 15.3 mm of body length while previtellogenesis was detected in a female of 26.5 mm of body length.
The problem of intersexuality was studied in the freshwater crayfish Samastacus spinifrons by examination of sexual characters of 1,114 specimens captured at nine fluvial populations and a lake population in southern Chile. The existence of this phenomenon was verified in the populations of rivers Contaco, Forrahue, Chico, and Hueyusca. In the first three cases, the percentage of intersexes was 1.5%, 2.7%, and 12.5%, respectively, and in the fourth case it ranged between 0% and 9.8%. A total of 41 intersex specimens was captured in which six gonopore patterns were identified. The dissections showed that 30 of them had testes, seven had ootestes, and four had ovaries. Moreover, all had gonoducts of both sexes, except for one of those with testes which had only sperm ducts, and one of those with ovaries that had only oviducts. It was also found that all intersex specimens had an abdomen with masculine morphological characteristics. This evidence, added to those found in the literature, confirm that in river populations of S. spinifrons, there is a variable percentage of intersex individuals, probably corresponding to transitional stages of a sex change from male to female.
The aim of the present study was to characterize the total and seasonal fecundity of the hermit crab Paguristes tortugae as well as the influence of shell type on fecundity using the morphometric relationship. Ovigerous females were collected monthly from January to December, 1998, in the infralittoral region of Anchieta Island. Samplings were performed using SCUBA. The hermit crabs and the gastropod shells were measured. Hermit wet weight and shell dry weight were recorded. For the fecundity analysis, only ovigerous females with the eggs in the early phase of development were selected. The number of eggs carried by individuals of several sizes (shield length), condition of development, and egg size were determined. A high percentage (69.88%) of ovigerous females with eggs in the early phase of development were captured, with a low frequency (4.29%) of females with eggs in the final stage of development. Size-frequency distribution during the months showed two peaks in the ovigerous female population (2.5 to 3.4 mm and 4.0 to 5.4 mm of SL). Mean ± SD fecundity was 132 ± 102 eggs and tended to increase with increasing SL. No significant difference in fecundity occurred among the various seasons of the year. The results showed continuous and elevated reproduction of P. tortugae, with a high reproductive potential for the population. The pattern of the frequency distribution of ovigerous females tending to bimodality may be characteristic of a population with a two-year life cycle. Considering the four shells most occupied by P. tortugae (Pisania auritula, Cerithium atratum, Morula nodulosa, and Leucozonia nassa), the highest fecundity was observed for ovigerous females occupying larger shells (P. auritula and L. nassa). The reproductive aspects of P. tortugae were related to strategies developed to compensate for interspecific competition, i.e., high and continuous reproductive effort, early maturity, low fecundity, and larger eggs produced.
In the mole crab Emerita asiatica, the female reproductive cycle is repetitive; when the pleopodal embryos undergo development, there is a concurrent maturation of oocytes within the ovary making it ready for the next spawning. However, molting occurs after hatching of the larvae from the pleopods and before spawning. In E. asiatica, the developmental changes of setae on the pleopods and the extent of epidermal retraction were used to define the molt cycle stages. Contrary to earlier reports on embryo-carrying decapods, in E. asiatica the first sign of molting, viz., the retraction of epidermis, is evident even before the hatching of the embryos. The premolt stages advance further up to D1, at a time when the pleopodal embryos hatch. No female at the time of embryo hatching is in the intermolt. Both ovarian index and total ovarian proteins gradually increase from the intermolt stage C1 to C3, thereupon maintaining the same level up to spawning. In continuously reproducing females (size class 23–33-mm CL), the hemolymph protein level is also high during the entire intermolt period, but increases sharply during premolt stage with a drastic decline just before ecdysis. Furthermore, hemolymph protein of both immature females (size class 10–17-mm CL) as well as females in the first maturation (18–22-mm CL) sharply rises during premolt stages (D0–D2), with an ensuing decline in stage D3–4. Evidently, the changes in the total hemolymph protein reflect on its role in vitellogenesis as well as new cuticle synthesis. Whereas the protein rise during the intermolt stage is coincident to the active vitellogenic phase, the second ramp in the increase of hemolymph protein during premolt stage may be related to new cuticle synthesis. A common endocrine basis of such a synchronous molting and ovarian cycle in Emerita is evident, but a substantial nutritional status, owing to filter-feeding habit of the sand crab, is attributed to the year-round reproduction and molting.
Changes of the gonad, survival rate, and life span of the precocious (i.e., sexually mature in their first October–November, at the age of 5 or 6 months) Chinese mitten crab (Eriocheir sinensis) were studied in a small, shallow, macrophytic, freshwater lake along the middle reaches of the Changjiang River, China. The gonosomatic index (GSI) reached peak during the next March when the female GSI was 12.32 ± 1.75 SD% and the male GSI was 4.24 ± 0.19%. The sexual glands degraded from then on. In the first ten-day period of the following July, there was no complete ovum in the ovary, and the sperm became thin and lost adhesion. The population declined sharply from November to July, and the last one (a female) died in the middle of July, which indicated that the life span of the precocious crab was about 12 months (from larval hatching in June to death in July of next year). The survival curve might be expressed as Y = 1.09exp(−0.018x) (Y: survival rate; x: days) for the precocious crabs stocked in experimental cages.
The reproductive biology of Arenaeus cribrarius from Ubatuba, São Paulo State, Brazil, was studied. Swimming crabs were sampled monthly for two years with otter trawls in two bays. A total of 941 males and 1,012 females were examined. Mating took place mainly in autumn involving postmolt females and intermolt males. At that time, gonad regression was verified in adult males, due to spermatophore transfer, and the molting of adult females. Ovigerous females or females with mature gonads were present year-round but more frequently captured during spring and summer. We found that 1% of all adult females were premolt, which indicated the occurrence of another mature instar and thus the absence of a well-defined terminal molt after puberty. Intermolt males were captured throughout the whole study period.
Fiddler crabs (Uca thayeri) on Florida's east and west coasts show temporally distinct hatching rhythms, correlated with differences in tidal form. Our purpose in this study was to determine whether these differences were fixed or could change in response to variation in the tides. West coast crabs (but not east coast crabs) showed seasonal variation in their hatching rhythms correlated with seasonal variation in the tides. In the spring, they released larvae at night. In the summer, hatching occurred during the day. West coast crabs transferred to Florida's east coast within four weeks released larvae at night in a rhythm similar to resident crabs but different from the spring nocturnal rhythm shown at their home beach. We conclude that this species has a flexible hatching rhythm that changes under natural, as well as under experimental, conditions. Such flexibility may permit the crabs to time larval release optimally over a range of tidal forms. This study and others published recently suggest that “plasticity” may be characteristic of behavioral rhythms shown by many intertidal crabs.
The memory capabilities of individuals of four species of crayfish (two invasive species and two native species) were tested in the laboratory. Individuals of the invasive Orconectes rusticus and the native O. virilis were tested in Michigan, and the invasive Procambarus clarkii and the native Austropatmobius pallipes were tested in Italy. Following pairing of conspecific alarm odour and a novel odour (goldfish odour), individuals were tested one day, one week, and either three weeks later (Italy) or two and four weeks later (Michigan) for inhibition of feeding responses by goldfish odour. In all four species, exposure of animals for just two hours was sufficient to establish an association between the novel odour and elevated predation risk. In both species pairs, individuals of the invasive species showed evidence of retention of the learned association longer than did individuals of the native species. The results are consistent with the general hypothesis that invasive species have a greater capacity for behavioural plasticity.
This study investigated the social behaviors of blind cave-adapted crayfish and compared them to the behaviors of sighted crayfish. Because blind cave crayfish display phototactic behavior, presumably mediated by the caudal photoreceptors in the sixth abdominal ganglion, we tested whether light, a disturbance in the crayfish's normal cave environment, altered their normal social behaviors. Observations were made in infrared or dim-white light to quantify social interactions. Exposure to white light reduced the amount of interaction time as compared to infrared light. The results revealed that blind crayfish did not exhibit behaviors usually associated with visual displays and posturing (i.e., the raised meral spread was absent). Same-sized individuals, previously housed in isolated conditions for two weeks, were paired. Both individuals tended to tail flip or move apart immediately after initial antennae contact. This is the same behavior observed within the natural cave environment. After repeated interactions between them, the rapid tail flip behavior became less frequent, while avoidance became an automatic reaction. Ethograms were constructed to determine the differences in the observed behaviors between the aggressive and submissive cave crayfish.
Seasonal zonation patterns of amphipods with various life styles and feeding habits were analyzed in a temperate sandy shore surf zone using a sledge net. The range in distribution of the burrowers Synchelidium lenorostralum and Urothoe convexa did not change seasonally: the former was usually found in the sandy shore from 1.0 to 3.0 meters below mean sea level (MSL) and the latter from 3.0 to 0 m below MSL. On the other hand, the distribution ranges of the nestlers Pontogeneia rostrata and Allorchestes angusta and the epifaunal tube-dweller Jassa slatteryi were restricted from 1.0 m above to 2.0 m below MSL, showing seasonal movement from below MSL in winter to above MSL in summer. Distribution centers of P. rostrata and A. angusta were located at 1.0 m below MSL and at 1.0 m above MSL in summer, respectively. This implies that habitat segregation occurred in summer. Gut contents analysis revealed that S. lenorostralum fed mainly on harpacticoid copepods, while P. rostrata, A. angusta, and U. convexa fed on phytoplankton and detritus. It is likely, therefore, that in summer, the segregation between P. rostrata and A. angusta may reduce competition for food. We suggest that feeding habits and life styles of amphipods in the sandy shore surf zone may be important factors controlling seasonal zonation patterns.
Secondary production of the amphipod Synchelidium lenorostralum was examined on a temperate sandy shore, southern Korea, on the basis of monthly samples from July 1996 to June 1997. Secondary production was estimated by the size-frequency method. Biomass structure showed two peaks in fall and spring, with maximum biomass in April. Biomass in the spring breeding period was higher than that in the fall. The annual secondary production of S. lenorostralum was 1.09 g DW m−2 yr−1 with an annual P/B ratio of 5.68. Secondary production of S. lenorostralum fell within the range observed for other amphipods from intertidal sandy shores, whereas the P/B ratio was higher than that recorded previously. The combination of high abundance and a high P/B ratio suggests an important role for S. lenorostralum in the sandy shore ecosystem as a trophic link from primary producers to higher consumers.
Burrow structure of the thalassinidean mud shrimp Upogebia major (de Haan) was investigated on a tidal flat in Tokyo Bay, central Japan, using in situ resin casting. Burrow structure consisted of two sections, an upper U-shaped part and a lower I-shaped part, with chambers and short branches on each. Depth of the burrow reached 208 cm, and extrapolations from the data on two incomplete burrows indicate that the maximum depth may exceed 250 cm. The depth of the burrow increased exponentially with carapace length of the inhabiting shrimp. This increase was accounted for principally by vertical extension of the lower I-shaped section. Each burrow was occupied by only a single shrimp. Even small new recruits occupied their own independent burrows. In this respect the mud shrimp proved different from some other thalassinidean shrimps, in which juveniles attach their burrows to those of adults. Feeding and excavating habits of the mud shrimp were considered as explanations for this behavior. Numerous tubes of suspension feeding phoronid worms attached to the burrows. Burrows of the mud shrimp play an important role in oxygenating deeper sediments and structuring the local tidal flat benthic community.
Aspects of the behavior of ovigerous Dungeness crabs (Cancer magister) were studied in Fritz Cove, Alaska. To test fidelity and homing ability of crabs to their brooding site, we ultrasonically tagged eight ovigerous crabs and transplanted them 1.4 km from their brooding site. Eight ultrasonically tagged control crabs were returned to the brooding site. Crab movements were subsequently monitored weekly from late February to October to determine activity patterns and seasonal shifts in depth distribution and habitat use. Seven females transplanted away from the brooding site homed back to that site within 13 to 20 d. Ovigerous female crabs showed fidelity to the head of the cove and ranged a maximum of 3.4 km. Crabs had distinct seasonal patterns of depth distribution, habitat use, and activity which were related to reproductive status. The general pattern for female crabs was: (1) a relatively inactive period during winter and early spring at depths greater than −16 m; ovigerous crabs were typically buried during this period in a dense aggregation; (2) an abrupt movement into shallow water (less than −10 m) during mid-April and residence there until late June; this movement was coincident with the spring phytoplankton bloom and initiation of larval hatching; and (3) increased activity beginning in July with movement back to deeper water presumably to forage. Females that molted prior to oviposition did so between late May and September. Females occupied depths between 1.6 and −107.3 m. Home ranges were small (< 4% of the total cove habitat) and varied with crab size; smaller crabs had larger home ranges. Ovigerous females brooded embryos in a small, discrete area of unconsolidated, homogeneous, fine sand. These sediments were also highly permeable. Annual use of the main brooding area was documented for a 12-year period and emphasizes the importance of this essential habitat.
Radio tracking technology has, for many years, been applied successfully to studies of vertebrates, particularly mammals and birds. Recent reductions in transmitter size have enabled these techniques to include invertebrates. However, perhaps because the radio tracking of invertebrates is especially problematic, relatively few studies have been carried out. In particular, there are relatively few radio tracking studies of decapod crustaceans, especially terrestrial species. Here we report the practical use of radio transmitters to track a tropical, amphibious fresh-water land crab, Eudaniela garmani, in the rainforests of the Caribbean island of Tobago. We include a method for gluing tags to the crabs' carapaces which allows individuals to be tracked for periods of up to 12 months.
Local inhabitants of the Caribbean island of Tobago catch land crabs Cardisoma guanhumi (Herbst, 1796) in an ingenious tube trap made from bamboo. The trap bears a remarkable resemblance to bamboo land-crab traps used in the Philippines. The bamboo-tube trap reported here has not previously been reported from the New World. Tobagonian bamboo-tube traps are baited with local fruits and are positioned on the surface adjacent to crab burrow entrances. In contrast, Old World bamboo-tube traps are reportedly used unbaited and are inserted into the mouths of crab burrows. The striking structural similarity between Caribbean and Philippine bamboo traps lends ethnographic interest, while the traps' simple design and ability to catch land crabs alive and unharmed make them a viable research tool in population studies of land crabs. Similar traps could be made from modern plastic drainage piping.