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Relative Growth of Three Chionoecetes Crabs (decapoda, Majidae) in the East Sea, Korea
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Snow crabs, Chionoecetes spp., are among the commercially most important species of Decapoda in the world, and proper stock assessment and management are required for their sustainable use. In the present study, morphological characteristics of three snow crabs, Chionoecetes japonicus, Chionoecetes opilio and a hybrid form exhibiting characteristics intermediate between those of the parent species, Chionoecetes japonicus/opilio, have been compared. The ratio of carapace length including rostral horn (CL(RL)) to carapace width (CW) in C. japonicus, C. opilio, and the C. japonicus/opilio hybrid was 0.973 ± 0.020, 0.983 ± 0.019, and 0.956 ± 0.019, respectively. The only significant difference in regression slope among the three crabs, was between CW and chela height (CH), indicating that at a given size, the hybrid form is the fastest in the growth of chela height in relation to carapace width. In C. japonicus and C. opilio, the relationship between CW and total weight (TW) was significantly negatively allometric, while in the hybrids, it was significantly positively allometric. This indicates that at a given size, the hybrid form is heavier than the others.
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Population Dynamics of the Western Australian Soldier Crab Mictyris Occidentalis Unno, 2008 (brachyura, Mictyridae) in the Dampier Archipelago — 30 Years of Observations
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The previously undescribed population dynamics of the Western Australian soldier crab, Mictyris occidentalis Unno, 2008, in King Bay, north-western Australia are elucidated, with annual observations and sampling over a 30-year period from 1980 to 2010. This is the longest recorded study of a single inter-tidal brachyuran population and shows long-term persistence of soldier crab populations in stable, sheltered habitats. The life cycle of M. occidentalis follows a cryptic subsurface juvenile and immature adult (= adolescent) phase and an emergent adult phase. Population densities were generally 500 crabs/m2 for the early 1980s, late 1980s, and during the early 2000s. Maximum population densities were high in the mid 1980s (800 crabs/m2). The spatial and temporal variability in the distribution of the population was consistent over the study period. Juvenile recruitment extends for up to 7 months of a given year between May and November with the main influx of juveniles usually in June and occasional minor influxes in August or October. Juvenile recruitment is followed by incremental growth of individuals at a rate of 1 mm/month reaching sexual maturity in the first year at 6.0-6.9 mm carapace length (CL). Adult males are larger than females with a maximum size of 15.0 mm CL compared to 12.0 mm CL, respectively. Ovigerous females are low in numbers throughout most of the year but reach a peak in February. During swarming, M. occidentalis populations partition not only by size class, with surface crabs being adults only and subsurface crabs mainly adult females and juveniles, but also by sex in that swarms are male-dominated in varying ratios.
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Artificial Settlement of Sea Lice, Caligus Rogercresseyi Boxshall & Bravo, 2000 (copepoda, Caligidae), on Tissues of Fish Used As Substrate
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Caligus rogercresseyi is the main ectoparasitic copepod affecting salmon and trout farming in Chile. The aim of this study was to evaluate under laboratory conditions the ability of copepodids of C. rogercresseyi to settle on fin, scale, and skin tissues taken from a wild host, the rock cod (Eleginops maclovinus) and an exotic host (Oncorhynchus mykiss), and evaluate the effects of inductors, such as conditioned water and fish mucus, on the process. The assessment was carried out simultaneously for each host and inductor, using a single pool of larvae (N = 1800). Three replicates per treatment were done and the settlement as well as the development stage of the frontal filament were recorded after 24 h. A total of 341 copepodids were able to settle on the different tissues and hosts. The host showing the higher settlement was E. maclovinus (N = 215; 23.9%) compared to O. mykiss (N = 126; 14%); the tissue showing the higher number of settled copepodids was the skin (N = 126; 48.4%), followed by fin (N = 140; 41.1%) and scales (N = 36; 10.5%). Regarding inductors, neither conditioned water (N = 112; 32.8%) nor mucus (N = 113; 33.1%) showed significant differences with the control without inductor (N = 116; 34%). Inductors did not have a significant effect on the development of the frontal filament, neither for E. maclovinus, nor for O. mykiss tissues, thus suggesting the tissues used were able to induce a positive response on these processes. This is the first work reporting a successful settlement of a species of sea louse in tissue extracted from fish.
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Freshwater Prawns of the Genus Macrobrachium (decapoda, Palaemonidae) with Abbreviated Development from the Papaloapan River Basin, Veracruz, Mexico: Distribution and New Species
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In the Papaloapan River two freshwater prawns with abbreviated development have been recorded: Macrobrachium villalobosi (a stygobitic species) and Macrobrachium totonacum (an epigeal species). In this paper we describe four new species from this genus, and the distribution of these six species along the river basin. M. oaxacae nov. sp. occurs in the River La Junta, and together with M. cosolapaense nov. sp. is geographically close to the stygobitic species and M. totonacum, but differs from these in the following aspects: pigmentation, the number of rostral spines, and the relative proportions of the articles of the second pereiopod, of appendix masculina and appendix interna, and the number of spines on the appendix masculina. Macrobrachium mazatecum nov. sp. lives in two streams in Veracruz: the first close to Tierra Blanca Veracruz and the second on the Zapotal Veracruz near Mpio. Lerdo de Tejada. This species was also recorded in two springs near Valle Nacional Oaxaca, and differs from M. oaxacae nov. sp. and M. cosolapaense nov. sp. in the number of rostral spines, and the relative proportions on the articles of second pereiopod, of appendix masculina and appendix interna, and of the spines on the appendix masculina. Finally, Macrobrachium jacatepecense nov. sp. occurs only in a spring near Jacatepec, Oaxaca. This species differs from the other species in the relative proportions of the articles of the second pereiopod: however, it is very close to Macrobrachium oaxacae nov. sp. in the number of rostral spines, but based on the geographical distribution of both species and other features, it is clearly a different species. In this Papaloapan River basin, the distribution of this complex of species is very limited, because the various populations live in very restricted areas associated with springs or small streams, and without direct interconnections. All these new species are comparable with the epigeal Macrobrachium species in the southeast of Mexico that have abbreviated larval development.
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Is Corophium Multisetosum Stock, 1952 an Exotic Invasive Species in Europe? Distribution, Habitat, and Recent Observations in the Netherlands
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Corophium multisetosum Stock, 1952 has been found in several estuaries and water bodies in Europe ranging from fresh and brackish to salt water. The species appeared to be distributed over a wide geographic range from the Iberian Peninsula to the southern Baltic region and is recently found in the Mediterranean and Gulf of Mexico, showing remarkable differences in ecology between populations. The recorded observations of the species in the Netherlands, however, remained restricted to a few smaller waters, and were published in grey literature. Recently, the species has been observed in a variety of waters in the southwestern part of the Netherlands and appears to be relatively common. The current study gives an overview of the recordings of C. multisetosum within its geographic range and its habitat preferences.
The recent observations on distribution and habitat preferences of C. multisetosum in the Netherlands are compared with the findings in other parts of Europe. Seeming discontinuities in recorded ecology of the species in the Netherlands and over Europe are discussed. C. multisetosum appears to be very flexible in its behaviour and appears to tolerate a broad range of environmental conditions. Local environmental conditions (e.g., salinity and substrate) and related communities (in the Netherlands particularly the presence of the seemingly competing species Corophium volutator (Pallas, 1766) and Chelicorophium curvispinum (G. O. Sars, 1895)) determine the presence of C. multisetosum and the local behaviour and abundance of the species in the system. As the species shows a typical distribution pattern with many recent recordings, its origin and possible dispersal routes are discussed.
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Eurydice Personata Kensley (isopoda, Cirolanidae) on a Caribbean Leptocephalus Fish Larva: an Intriguing Case Report
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Corrigendum
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