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Sacculina sinensis (Cirripedia: Rhizocephala) is a parasitic barnacle first reported in Hong Kong by Boschma (1933) to infect the intertidal crab, Leptodius exaratus. Since then, no studies have been conducted to investigate its distribution and morphology, which are important in providing background information for further taxonomic and ecological studies. In the present study, S. sinensis has shown to have a limited distribution in Hong Kong, being confined to only four out of the nine sheltered boulder shores sampled and with a mean infestation rate of 11.3 percent. The localized distribution of S. sinensis in Hong Kong is probably due to its short larval development times (four naupliar stages and one cypris stage, completed in about six days) and hence limited larval dispersal distance. The externa of S. sinensis is ovoid in shape with two distinct shoulders, and the outer cuticle surface is spinous. From histological studies, the male receptacles are located posteriorly in the visceral mass, and each male receptacle is globular in shape. The receptacle duct is folded and connected to the receptacle via a small tube with a thick cuticle lining. The larval morphology of S. sinensis was investigated using a scanning electron microscope. The appendages bear setulate setae in all naupliar stages. In the cyprid, segment III of the antennule consists of the attachment disc in both sexes, and the male has a large posterior aesthetasc which is absent in females. On segment IV, male cyprids have a large terminal aesthetasc, a subterminal aesthetasc, and three terminal setae. Segment IV of female cyprids has a subterminal aesthetasc which is smaller than that on the male cyprids. The larval sex ratio showed seasonal variation with 100 percent males in summer and 80 percent females in winter. Such seasonal variation in sex ratio would allow the female cyprids to infest the host crabs in winter, producing virgin externae by summer for the male cyprids to settle, and allow the externae to mature.
A new species of bioluminescent ostracode, Vargula morini from Carrie Bow Cay, Belize, is described on the basis of morphology and mating displays. Every night, males of V. morini produce an elaborate species-specific bioluminescent courtship display in order to attract females. These displays occur over coral or coral rubble, beginning near the sea surface and continuing as a series of rapid flashes produced in a downward direction. A nicothoid copepod was found living within the posterodorsal area of the valves of some V. morini. Scanning electron micrographs of these minute ostracode parasites are presented here for the first time.
Serbanibathynella primaindica gen. n., sp. n. is described from India. It is the sister taxon of the genus NannobathynellaNoodt, 1969. The most spectacular apomorphic feature is the mandible, which has no gnathobase. Only three teeth persist on the first segment of the palp, which is subequal to the second segment in length. Both are equipped with strong musculature, and there is a joint between them allowing a backward swing of the terminal part of the palp. This joint is unique within Bathynellidae. Only Agnathobathynella ecclesiSchminke, 1980, can rival the new species in the specialization of mouthparts. The new species is the fifth species of Bathynellidae described from the tropics.
Three new species of Parastilomysis, P. paucispina, P. prominula, and P. separata, are described from Japanese waters. Parastilomysis paucispina is different from the other species of the genus by the smaller body size and the uropodal endopod with the inner margin armed with fewer spines, P. prominula by two small protuberances on the mid-dorsal line of the carapace, and P. separata by the arrangement of spines on the lateral margin of the telson. Parastilomysis secunda is revised taxonomically, and a new genus, Hyperstilomysis, is proposed for the accommodation of this species.
Three new species of Tegano are described, two from caves on Panglao Island, Bohol, Philippines, and one from a cave on Peleliu Island, Palau. Sriha vagabunda from Sri Lanka is reassigned to the genus Tegano based primarily on the high degree of similarity between Sriha vagabunda and species of Tegano and the fact that these species exhibit a great deal of variation in the reduction of the mandibular palp. A new species of Melita with characters intermediate between those defining the genera Abludomelita, Melita, and Paraniphargus is described from a spring on Guam. The characters of the new species and studies by previous authors suggest that Abludomelita may not be as distinct from Melita as previously believed. The troglomorphic genus Paraniphargus from the Andaman Islands and Java is re-evaluated and synonymized with Melita.
A new species of Tanaidacea from the Antarctic abyssal is diagnosed and described. It has been classified to new genus Singularia, although, at present, it cannot be assigned to any of the families established by Larsen and Wilson (2002). The genus has many characters found in the family Colletteidae Larsen and Wilson, 2002. The original key to genera of Colletteidae is presented.
Three new species of the genus Typhlatya from anchialine caves in Mexico (T. dzilamensis), the Bahamas (T. kakuki), and Honduras (T. utilaensis) are described. Typhlatya dzilamensis is the fourth species to be described from the Yucatan Peninsula, Mexico, and is morphologically similar to T. mitchelli. Typhlatya kakuki is the first species of the genus to be described from the Bahamas archipelago. Its morphology departs from the patterns showed by the Cuban species, which are the closest geographically. Typhlatya utilaensis is the first species described from Central America, and is found in Utila, one of the Honduras Bay Islands. Morphologically, T. utilaensis is related to T. monae from Mona Island, Puerto Rico, and Barbuda. A revised diagnosis of the genus and a key for the 17 known species are provided.
During the past decade, quantification of the pigment lipofuscin in the olfactory lobe cell masses (OLCM) has been successfully used for age determination of crustaceans. The aim of the current study was to quantify the amount of lipofuscin in European lobsters (Homarus gammarus L.) of known age and to determine the accuracy of lipofuscin as an age predictor. Lipofuscin was quantified by confocal fluorescence microscopy and image analysis of histological sections. Our results showed that age and OLCM lipofuscin were closely and linearly related (r2 = 0.88). Furthermore, in contrast to earlier studies, age was also closely, but nonlinearly, related to carapace length (r2 = 0.78). Comparison of lipofuscin and carapace length as age predictors nevertheless showed that lipofuscin produced significantly more accurate estimates of age than carapace length. The relatively small difference in the precision of age estimation between lipofuscin and carapace length emphasises the importance of evaluating the relationship between age and carapace length/lipofuscin in studies of populations with variable environmental conditions or demographic processes. It is possible that age, in specific situations, could be satisfactorily predicted on basis of measurements of size.
Birgus latro excretes nitrogenous waste as a mixture of urate and guanine and not predominantly urate as believed previously. The presence of guanine in faeces was confirmed by enzymatic derivatisation of guanine to xanthine with guanase. This is the first report of significant excretion of guanine outside the Chelicerata. The ratios of urate to guanine within the excreta of animals in field situations (natural diets) and in the laboratory (a range of artificial diets) were ∼3:2. Rates of excretion of both urate and guanine increased when experimental crabs were fed an artificial diet high in nitrogen. Significant amounts of guanine were also measured in tissues of B. latro, but only urate was present in equivalent tissues of the closely related species Coenobita brevimanus. Coenobita brevimanus did not excrete any significant amount of purines with the faeces.
We investigated the effects of delayed mating on the reproductive success of female spiny king crabs, Paralithodes brevipes, in laboratory experiments where the duration between female molting and mating was controlled. Females mated and spawned irrespective of the number of days after their molting within 20 days. However, as the number of days after female molting increased, the fertilization rate decreased significantly. Females that spawned at 16 or more days after molting lost significantly more eggs than females that spawned at ≤12 days after molting. The percentage of detached eggs that developed normally to the morula stage decreased significantly in females mated at 20 days after their molting. The percentage of females with a few or no eggs tended to increase as time elapsed between molting and mating increased. Thus, the increased number of days after female molting influenced the reproductive success of spiny king crab females, and females had an optimal duration to mate after their molt. Our results suggest that the present fisheries of this species, in which only larger males are harvested, may affect female reproductive success by decreasing the availability of male mates. An adequate management of this species needs to include these considerations.
This study relates to the size at morphological and physiological sexual maturity of the deep sea crab Anamathia rissoana. Between August 1997 to July 2000, 469 specimens were collected at depths of between 400 and 620 m off the western coast of Sardinia (Mediterranean Sea). On the basis of cheliped morphology, the males were classified into three demographic categories: immature, adolescent, or adult. In addition, a discriminant function analysis was performed in order to classify the males (post hoc prediction) using the biometric data relating to the four distal segments of the endopod of the right cheliped. For the females, only two demographic categories were detected: juvenile females with flat abdomen and adult females with domed abdomen. Morphological maturity was estimated from the allometric relationships between carapace width and propodus length in males or maximum abdomen width in females. For both sexes, allometric relationships were established in the specimens of each of the demographic categories. Physiological maturity was determined by observing testes or ovary size, colour, morphology, and development. Functional maturity was presumed to be the minimum size at which each sex was morphologically and physiologically able to reproduce. In males, the size at physiological maturity was clearly earlier than the size at morphological maturity, unlike in females where such values were similar.
Morphological heterogeneity of the pinnotherid genera Durckheimia and Xanthasia has long been recognised. In particular, the segmentation of the third maxilliped palp, whether 2- or 3-segmented, is presently regarded as a conservative and useful generic trait. Durckheimia and Xanthasia, however, both contain species with both types of third maxilliped palps. Prior to the present study, five species were placed in Durckheimia, four bearing a 3-segmented palp and one, D. besutensis, with a 2-segmented palp. Durckheimia is restricted to three species, D. carinipes (type species), D. caeca, and D. lochi. Durckheimia yokotai is synonymised with D. caeca. The aberrant D. besutensis is transferred to a new genus, Serenotheres. Xanthasia is restricted to its type species, X. murigera, which bears a 2-segmented palp. Xanthasia whitei, with a 3-segmented third maxilliped palp and only superficially resembling X. murigera, is made the type of a new genus, Tridacnotheres. All species are illustrated and diagnosed, and a key to the species of Durckheimia is presented.
The Asian shore crab, Hemigrapsus sanguineus (De Haan, 1853), is an opportunistic omnivore with well-developed predatory tendencies and a strong preference for animal food items over algae. In laboratory experiments, 71 percent (319/448) of the crabs given a choice between macroalgae (Enteromorpha spp. and/or Chondrus crispus) and benthic invertebrates (Mytilus edulis and/or Semibalanus balanoides) consumed animals only. There were no significant differences in food preference between sexes or between juvenile and adult crabs. Relative abundance of food type, either algal or animal, in small food patches did not affect crab food preference. Crabs with prolonged starvation periods (5-d), however, consumed both food types more often than those that had been starved for 1-d only. Experiments to determine the effect of conspecifics on food selectivity showed that increased crab density leads to increased diet breadth, suggesting that competition for food can alter food selection patterns of H. sanguineus. Results reported here and in previous studies provide strong evidence that predation pressure exerted by H. sanguineus could play an important role in structuring the post-settlement population dynamics of its invertebrate prey, possibly leading to population declines of commercial shellfish, especially blue mussels.
The population dynamics and reproduction of the land crab Epigrapsus notatus were studied at Hengchun Peninsula, Taiwan. Epigrapsus is the most poorly known genus of the land crab family Gecarcinidae, and differs from other gecarcinids in its much smaller size. Epigrapsus notatus leads a cryptic life and is seldom observed outside its burrow in the coastal forest. The only time it is commonly observed is when ovigerous females migrate to the shore to release larvae. The reproductive season of E. notatus is limited to two lunar months in September and October, a relative short time in comparison with other gecarcinid crabs. Ovigerous females begin releasing larvae 3–4 d after the full moon, for 3–7 d. Larval releases occur for about a 3-h period during and immediately after high tide. Ovigerous females shake their entire body to release larvae, a unique behavior not previously documented in brachyurans. Ovigerous females prefer to release larvae inside surge channels rather than on the exposed shore. The unusual larval release behavior and choice of surge channels as release sites are suggested as adaptations to life on land, to reduce the chances of being swept away by waves.
Adult sand fiddler crabs, Uca pugilator, forage in large herds on exposed sediment during low tide. These herds form as a response to optimal foraging conditions but may have an additional benefit of water conservation. We determined water loss rates for crabs in groups of different sizes. Crabs in groups of 10 and 20, but not in a group of 5 or isolated individuals, showed a water-conserving group effect, yielding nearly a two-fold decrease in water loss rates. Other characteristics of U. pugilator (water content, dehydration tolerance, activation energies for water loss, critical transition temperature, and critical equilibrium humidity) are consistent with a hydrophilic water balance profile. Because crabs did not replenish water supplies from water vapor like some terrestrial arthropods, water conservation is vital to crab survival outside burrows. Enhanced water retention generated by herding likely permits more time for feeding outside the burrow, while also increasing feeding efficiency by minimizing frequency of water uptake. The fact that U. pugilator is semiterrestrial suggests that a reduction in water loss due to group effects may provide a mechanism for terrestrialization.
The spatial distributions of two grapsoid crabs, Helice tridens and Parasesarma plicatum, overlap broadly in salt marsh habitats in the Yoshino River Estuary, Japan. In order to clarify factors influencing the coexistence of the two species, resource utilization was compared between the two species in space, time, and food, and intraspecific and interspecific predation was evaluated. The two species showed similar distributional patterns along the length of estuary with respect to elevation and sediment, reed, and debris conditions. Most crabs of both species dwelled solitarily in burrows. Parasesarma plicatum was most active during daytime low tide, whereas the activity of H. tridens did not differ between daytime low tide and other periods. Although both crab species had broad omnivorous diets (e.g., feeding on plants, brachyurans, insects, and detritus), H. tridens tended to consume more animal food items than P. plicatum. Laboratory experiments revealed that adults of both species preyed on subadults of the same species and different species. Adults of P. plicatum preyed on more subadults of H. tridens than conspecific subadults, whereas adults of H. tridens preyed on subadults of conspecifics and P. plicatum in similar frequency. Differences in resource utilization in conjunction with effects of predation and cannibalism, which would tend to reduce resource limitation, likely contribute to the coexistence to these two ecologically similar brachyuran crab species.
A catalogue of the type specimens deposited in the reference collection of decapod crustaceans built up by the late Gilberto Rodríguez and collaborators, from 1960 to 2004, at the Instituto Venezolano de Investigaciones Científicas (IVIC), Venezuela, is presented. It contains the field data and taxonomic information for 32 holotypes and 25 paratypes of 42 species and subspecies belonging to three families (2 Palaemonidae, 3 Trichodactylidae, and 37 Pseudothelphusidae).