Paralithodes Platypus Research Articles

西部ベーリング海のアブラガニ資源 ＩＩ 標識放流による産卵周期と成長の検証

In observations as carried out in August and September, on recaptured females of the blue king crab, Paralithodes platypus, released with a suture tag that remains after moulting, and the leg tag which is lost when moulting, the following results were obtained as to the spawning cycle and the growth of the mature female. Female crabs do not moult and spawn in August and September. Mature females in virgin stage and the stage of no carrying eggs moult and spawn in the first year of liberation. They, when in the stage of carrying eggs, do not spawn after the carried eggs hatch out in the first year of liberation but moult and spawn in the second year, which verify spawning as taking place in every other year. Therefore mature females are composed of more than four age groups which moult and spawn more than twice. The increase in size by one moult per two years is 5-10mm in carapace width and 4-10mm in carapace length.

西部ベーリング海のアブラガニ資源に関する研究-I

In researches on the blue king crab, Paralithodes platypus BRANDT, in the Western Bering Sea, as carried out from August to October, the following results were obtained as to the spawning cycle. 1. Female crabs were classified into five groups as shown in following keys. Immature group: Eggs and thread-like substace sticking to pleopods are absent. Ovary is undeveloped. Virgin group: Ovary is fully ripe. Group of carrying eggs: Eggs are present and ovary is immature. Group of no carrying eggs: Eggs are absent but the thread-like substance is present. Ovary is fully ripe. Senile and injured group: Eggs and the thread-like substance are absent. Ovary is very thin. 2. The five developmental stages of female crabs are arranged as follows. Immature stage→ Virgin stage→ →Stage of carrying eggs ↔Stage of no carrying eggs→Senile stage It is deduced from this study that the periods of the stages of carrying eggs and of not carrying eggs are nineteen months and several months respectively and the spawning cycle is two years, which is different from the annual spawning cycle of the king crab, Parali-thodes camtschatica TILESIUS.

Description of Laboratory-Reared Larvae of Paralithodes platypus (Decapoda, Anomura, Lithodidae)

Larvae of the blue king crab, Paralithodes platypus (Brandt), were hatched and reared in the laboratory. All larval stages obtained developed in a manner similar to the development reported for other lithodid anomurans. In culture, P. platypus had four zoeal stages and a single glaucothoeal stage. The feature which distinguishes all zoeal stages of this species from zoeae of the other two North Pacific species of Paralithodes — P. camtschatica and P. brevipes — is the presence of 9 + 9 telson processes (including a hair-like second process) rather than 8 + 8 telson processes. Glaucothoes of P. platypus have one more pair of spines in the branchial region of the carapace than do those of P. camtschatica. Glaucothoes of P. platypus have 15 pairs of spines on the dorsal surface of the carapace, not including the spines of the frontal area (rostral complex) or the suborbital spines, whereas glaucothoes of P. camtschatica have 14 pairs of spines, and those of P. brevipes have 13 pairs.

Wind profiles over sea waves : Takeda A., 1963. J. Oceanogr. Soc., Japan, 19 (3): 136–142

Ocean acidification (OA) adversely affects a broad range of marine calcifying organisms. Crustaceans, however, exhibit mixed responses to OA, with growth or survival negatively affected in some species, but unaffected or positively affected in others. In crustaceans, the mineralized cuticle resists mechanical loads, provides protection from the environment, and enables mobility, but little is known about how OA or interactions between OA and temperature affect its structure or function. Here, the effects of OA on the mechanics, structure, and composition of the cuticle in two Alaska king crab species was assessed. Juvenile blue king crabs (Paralithodes platypus) were exposed for a year to three pH levels, 8.1 (ambient), 7.8 and 7.5. Juvenile red king crabs (Paralithodes camtschaticus) were exposed for ~ 6 months to two pH levels, 8.0 and 7.8, at three temperatures: ambient, ambient + 2 °C, and ambient + 4 °C. Cuticle microhardness (a measure of resistance to permanent or plastic mechanical deformation), thickness, ultrastructure, and elemental composition were assessed in two body regions, the carapace and the crushing chela (claw). In both species tested, OA reduced endocuticle microhardness in the chela, but not in the carapace. There was no effect of pH or temperature on total procuticle thickness of the chela or carapace in either species. Reductions in microhardness were not driven by reduced calcium content of the shell. In fact, calcium content was significantly elevated in the carapace of blue king crabs and in the chela of red king crabs exposed to lower than ambient pH at ambient temperature, suggesting that calcium content alone is not a sufficient proxy for mechanical properties. Reduced chela microhardness, indicative of more compliant material, could compromise the utility of crushing chelae in feeding and defense.