Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAGNOLIA PRESS  

Two species of the cumacean genus Atlantocuma from the southern coast of Honshu, Japan, 781-861 m depth, A. gamoi sp. nov. and A. ojii sp. nov., and Pseudopicrocuma japonicum gen et sp. nov. from Nansei Islands, 566-1769 m depth, are described. Atlantocuma gamoi is characterized by (1) carapace elevated in preparatory and ovigerous female, (2) antero-lateral angle of carapace with 3 teeth in females, and (3) pseudorostrum of carapace of adult males truncate, anterolateral angle without teeth. Atlantocuma ojii is characterized by (1) carapace not elevated in preparatory females, but elevated in ovigerous females, (2) inferior margin of carapace in ovigerous female serrated for entire length, (3) pseudorostrum of carapace in adult males truncate, (4) uropod exopod with 1-2 spiniform setae on inner margin, except for subterminal one. The new genus Pseudopicrocuma, which is similar to Picrocuma from shallow waters of eastern Australia, is characterized by (1) well-developed exopods present on maxilliped 3 and pereopods 1-3 in both sexes, (2) antenna 1 of adult males with many aesthetascs-like sensory setae on peduncle articles 2 and 3, (3) male antenna 2 of clasping form, and (4) uropod slender, peduncle shorter than rami. Pseudopicrocuma shows affinity to Atlantocuma except for (1) arrangement of well-developed exopods on pereopods, (2) male antenna 2 flagellum of clasping form, and (3) uropod peduncle shorter than rami. In addition, P. japonicum and the new Japanese Atlantocuma species are characterized by a similar trend in degeneration of mouthparts (mandibles - maxillipeds 2) in ovigerous females, suggesting a rather close relationship of these genera with quite different arrangements of exopods on pereopods. These 2 genera are currently placed in Nannastacidae. Other possible relatives of Pseudopicrocuma are Spilocuma (Bodotriidae) and Claudicuma (Nannastacidae).

DOI： 10.11646/zootaxa.3400.1.2

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Cumacean crustaceans in the genus Eudorella (Leuconidae) from Japanese waters, in the Northwest Pacific, were examined and the following 15 species were recognized: E. acuticaudata sp. nov.; E. oe quiremis Hansen, 1920; E. bathyalis Vassilenko & Tzareva, 2004; E. bathyhwanghaensis sp. nov.; E. breviflagella sp. nov.; E. dentata Lomakina, 1955; E. emarginata (Kroer, 1846); E. fusafusa sp. nov.; E. haradai sp. nov.; E. hwanghaensis Hong & Park, 1999; E. ohtai sp. nov.; E. orientalis sp. nov.; E. parahirsuta sp. nov.; E. ryukyuensis Akiyama & Gamo, 2005; and E. setoensis Akiyama & Gamo, 2006. In addition, Eudorella suluensis sp. nov., was collected from the Sulu Sea, Philippines, Indo-West Pacific, 688-693 m. These species include 2 groups on the basis of shared morphological characters. Eudorella bathyalis, E. breviflagella sp. nov., E. fusafusa, E. orientalis, and E. setoensis are characterized by a row of simple setae on each side of the carapace, with both E. breviflagella and E, setoensis also characterized by a short flagellum on antenna 2 in adult males. The other group consists of Eudorella hwanghaensis, E. bathyhwanghaensis, and E. ryukyuensis, from southern Japan, and E. suluensis; with E. hwanghaensis and E. bathyhwanghaensis also characterized by a peculiar secondary sexual character on the tip of the 3rd pereopod in adult males.

DOI： 10.11646/zootaxa.3319.1.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAGNOLIA PRESS  

The distribution of the cumacean family Pseudocumatidae is restricted to the North Atlantic, Mediterranean and brackish waters of the Pont-Caspian region, except for three known species of the genus Petalosarsia. The present study describes nine species of Petalosarsia from Japanese waters, the Sulu Sea, the North-west Pacific, the Indo-West Pacific, and the Tasman Sea, Australia. The occurrence of P. declivis (Sars, 1865) in northern Hokkaido agrees with the reported circumpolar distribution of this species. Four species from the Pacific coast of southern Japan and the East China Sea, P. brevirostris Gamo 1986, P. ovalis sp. nov., P. ryukyuensis sp. nov. and P. gamoi sp. nov., are characterized by prominent dorsolateral carinae with teeth anteriorly and the basis of the 2nd maxilliped with a semicircular plate on the ventral surface. Nine specimens collected from the Sulu Sea included five species, P. brevirostris, P. gamoi, P. jonesi sp. nov. P. suluensis sp. nov. and P. longicauda sp. nov. The latter three species were characterized by no or faint dorsolateral carinae on the carapace. Among them, P. jonesi was similar to P. longirostris from the eastern tropical deep Atlantic. Petalosarsia australis sp. nov. from the Tasman Sea is characterized by one faint pair of dorsolateral carinae running for the entire length of the carapace. The species richness of Petalosarsia in the Sulu Sea and the Indo-West Pacific suggests a wide distribution of ancestors of Pseudocumatidae around the ancient Tethys Sea, with the Ponto-Caspian region located near the center. The habitat of Petalosarsia was mostly deeper than 200 m.

DOI： 10.11646/zootaxa.3320.1.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAGNOLIA PRESS  

Dimorphostylis elegans Gamo, 1960 and two related new species, D. bathyelegans n. sp. and D. brevicarpus n. sp. are described. Dimorphostylis elegans were collected from the Pacific coasts of Honshu and Shikoku Islands, and the East China Sea, Japan, 74-443 m. As a result, D. latifrons Harada, 1960 from the Izu Peninsula, Japan is declared a junior synonym of D. elegans. Morphological variation of the carapace is discussed. Dimorphostylis bathyelegans, from southern coast of the Honshu Island and the East China Sea, is very similar to D. elegans, but is distinguished from the latter by the long telson and the third peduncle article of antenna 1 with more short setae. Depth of the habitat ranges from 495-918 m, which is the deepest known species in the genus. Dimorphostylis brevicarpus was collected from Kyushu and Nansei Islands, East China Sea, on sandy bottoms, 165-236 m deep. This species also resembles D. elegans, but is distinguished from the latter by (1) short carpus of pereopods 3-5, (2) anterior end of dorsolateral carina with 2 or 3 teeth, and (3) max-illiped 1 with a group of sharp spines on the ventral surface of basis, and (4) carapace covered with numerous small pits, with a tiny seta in each.

DOI： 10.11646/zootaxa.2994.1.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CRUSTACEAN SOC  

A new species of cephalocarid, Sandersiella kikuchii, is described from central Japan, 300 m depth. It differs from congeners primarily based on the following points: 5-9 hooks on each ventrolateral side of cephalon; exopod proximal segment of thoracopod 6 with long finger-like lateral process (with narrow base) on the dorsal margin; exopodal distal segment of thoracopod 6 pointed distally, not divided into 2 lobes; exopodal proximal segment and pseudopipod of thoracopod 8 furnished with 2 and 2-3 setae respectively. Sandersiella acuminata Shiino, 1965 is redescribed and illustrated based on the holotype.

DOI： 10.1651/07-2864R.1

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOL SOC WASHINGTON  

Katianira platyura, new species, is described from the mid-bathyal zone of the Kumano Basin, southern Japan, the first record for the family from the North Pacific. Katianira platyura differs from its congeners by having the head with a pair of broad, deeply divided, bilobed lappets; pereonite 1 laterally rounded; anterior and posterior corners of pereonites blunt; mandibular molar process rudimentary; pereopod 3 flattened and broad; distal part of pleopod 1 with 32 setae; protopod of pleopod 2 trapezoidal; tip of endopod of pleopod 2 reaching to approximately 0.9 of protopod; and broad, leaf-shaped uropods.

DOI： 10.2988/0006-324X(2006)119[576:ANSOTD]2.0.CO;2

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The great majority of Nippoleucon hinumensis (Gamô) in the Seto Inland Sea of Japan enters a long-term summer diapause from May to November. We identified a minor subpopulation of N. hinumensis (0.7% of the total population) that became adults in a short period without diapause. Small-sized ovigerous females (15% shorter than the ordinary-sized ovigerous females) appeared from January to early February, a month earlier than the appearance of the ordinary-sized ovigerous females that produce diapausing offspring. These precociously ovigerous females released offspring from early February to early March. The offspring developed from 1st manca larvae to 2nd manca larvae, 1st juvenile stage and 2nd juveniles stage in that order, and in mid-April they reached the adult stage (5th instar) without diapause. In the non-diapausing subpopulation, sexual dimorphism was apparent from the 1st manca instar and the sex ratio (males:females) was 2 to 4:1. The molts, occurring at intervals of ca. 10 d, were not highly synchronous among individuals. The non-diapausing females mostly disappeared in April without producing offspring, but many non-diapausing males survived until the ordinary-sized ovigerous females started incubation of the second brood in late April. Possibly, the non-diapausing subpopulation is maintained through mating of non-diapausing males with ordinary-sized ovigerous females. The non-diapausing mode of life in N. hinumensis may represent the ancestral life mode before this species acquired a summer diapause mechanism.

DOI： 10.3354/meps284227

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The life history of the cumacean Nippoleucon hinumensis was investigated in the Seto Inland Sea of Japan from August 1998 to February 2002. The population produced 1 generation per year and recruitment of offspring occurred in April. The post-marsupial period consisted of 8 instars in males and 9 (plus generally 2 repeated instars) in females. Post-marsupial development up to the 4th instar (2nd juvenile stage) was characterized by periodic molting at intervals of 10 d, slow growth rate, and suppression of sexual dimorphism. Thereafter, the juveniles entered a long-term summer diapause from mid-May to early December, during which the ambient seawater temperature ranged from 15 to 28°C. Ninety-nine % of the population during the diapause were at the 2nd juvenile stage, and 1 % were at the 1st juvenile stage. In December, the cumaceans resumed growth, characterized by a fortnightly molt cycle, until the females began to incubate the first brood in late February. Each molting was highly synchronized among individuals and phased with the lunar cycles. After the end of the summer diapause, sexual dimorphism became apparent, with ovigerous females becoming about 1.2 times larger than adult males. After release of manca larvae in early April, most females incubated a second brood in late April, and then rapidly disappeared due to mortality probably caused by high water temperature. Clutch size was 57.9 ± 9.4 for the first brood and 42.4 ± 7.3 for the second.

DOI： 10.3354/meps284211

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The cumacean Dimorphostylis asiatica (Crustacea) exhibits a circatidal swimming activity rhythm. The animals were exposed to a 12.5 hr sinusoidal change of hydrostatic pressure of 0.3 atm amplitude in the laboratory. Under constant dark conditions, most of the specimens were entrained to a daily bimodal swimming activity rhythm by the hydrostatic pressure cycle. A small number of individuals exhibited a unimodal daily rhythm, with no apparent entraining from the administered cycles. A marked feature was a flexible phase relationship between the entrained daily bimodal rhythm and the hydrostatic pressure cycles: the swimming activity of most of the specimens occurred around the pressure-decreasing phase, but for a small number of individuals it coincided with the pressure-increasing phase. Such flexibility suggests a weak entraining effect of hydrostatic pressure on the circatidal rhythm of this species. When exposed to 24 hr light-dark cycles and a hydrostatic pressure cycle simultaneously, the specimens exhibited a rhythmic activity entrained by the hydrostatic pressure cycle during the dark period, which closely resembles the temporal activity pattern of this species in the field. The light cycles entrained the swimming activity via direct inhibition and induction of activity (i.e., masking). Under light-dark conditions, the specimens exhibited activity on the pressure-increasing phase more frequently compared with specimens kept in constant darkness.

DOI： 10.2108/0289-0003(2004)21[29:EOTCSA]2.0.CO;2

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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Cumacean Dimorphostylis asiatica exhibits an endogenous swimming rhythm, free-running period of which spontaneously changes from circa 12-hr to circa 24-hr in the laboratory. Administration of a 4-hr pulse of hydrostatic pressure stimulus and a 4-hr light pulse confirmed that the circa 12-hr rhythm is circatidal and the circa 24-hr rhythm circadian, with respect to the phase setting characteristics. The activity records provide evidence of a "splitting" phenomenon, which suggests that these two types of rhythms are governed by (an) identical pacemaker(s). This species appears to have acquired tidal synchrony by making use of flexibly coupled circadian pacemakers, accompanied by expansion of their subtidal habitat to shallow, tide-affected area.

DOI： 10.2108/zsj.14.901

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Dimorphostylis asiatica, a cumacean crustacea inhabiting the sublittoral line of the Seto Inland Sea, shows a rhythmic pattern of swimming activity coinciding with daily and tidal components in the field. This activity pattern was bimodal at first, i.e., circatidal activity coinciding with high tides at their habitat. The mean free-running period (i.e., bitidal interval) of this endogenous rhythm was 23.1 h at 10°C, which was significantly shorter than the environmental tidal cycle. In most cases (90% of the records) this bimodal activity became unimodal within 10 d. The unimodal period was 24 to 27.5 h, which is markedly longer than the preceding bimodal period. The bimodal pattern observed in the present study was not observed in the field. The difference between field and laboratory activity patterns can be explained in terms of direct response of the bimodal circatidal rhythm to the day-night cycle in the field. Field observations were made and laboratory experiments conducted between 1988 and 1992. © 1995 Springer-Verlag.

DOI： 10.1007/BF00353616

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DOI： 10.2307/1542082

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Dimorphostylis asiatica actively swims in the water at night. Males are positively phototaxic. Nearshore collections of males have demonstrated a clear rhythmic pattern, with emergence synchronized with both day-night and tidal cycles. While emergence was strongly synchronized with high tide during the winter and spring, tidal synchrony was scarcely detected in summer and autumn. -from Authors

DOI： 10.2307/1541766

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