Junji Okuno

Inferences on mating and sexual systems of two Pacific Cinetorhynchus shrimps (Decapoda, Rhynchocinetidae) based on sexual dimorphism in body size and cheliped weaponry.

Abstract Sexual dimorphism in body size and weaponry was examined in two Cinetorhynchus shrimp species in order to formulate hypotheses on their sexual and mating systems. Collections of Cinetorhynchus sp. A and Cinetorhynchus sp. B were made in March, 2011 on Coconut Island, Hawaii, by hand dipnetting and minnow traps in coral rubble bottom in shallow water. Although there is overlap in male and female size, some males are much larger than females. The major (pereopod 1) chelipeds of males are significantly larger and longer than those of females. In these two Cinetorhynchus species, males and females have third maxillipeds of similar relative size, i.e., those of males are not hypertrophied and probably not used as spear-like weapons as in some other rhynchocinetid (Rhynchocinetes) species. Major chelae of males vary with size, changing from typical female-like chelae tipped with black corneous stout setae to subchelate or prehensile appendages in larger males. Puncture wounds or regenerating major chelipeds were observed in 26.1 % of males examined (N = 38 including both species). We interpret this evidence on sexual dimorphism as an indication of a temporary male mate guarding or “neighborhoods of dominance” mating system, in which larger dominant robustus males defend females and have greater mating success than smaller males. Fecundity of females increased with female size, as in most caridean species (500–800 in Cinetorhynchus sp. A; 300–3800 in Cinetorhynchus sp. B). Based on the sample examined, we conclude that these two species have a gonochoric sexual system (separate sexes) like most but not all other rhynchocinetid species in which the sexual system has been investigated.

First larvae of Lebbeus comanthi and Thor amboinensis (Decapoda: Hippolytidae) hatched in the laboratory

The decapodid stage of Lebbeus comanthi Hayashi and Okuno and the first zoea of Thor amboinensis (De Man) are described based on laboratory‐hatched eggs from females collected from Japan. The decapodid stage of L. comanthi is readily distinguished from that of L. groenlandicus by the carapace without anteroventral denticle and tooth behind rostrum, the absence of the antennal spine, the four‐segmented outer flagellum of the antennule, the absence of the palp of the mandible, and the telson with posterior margin concaved medially and without dorsolateral spine. The carapace with anteroventral denticle and the third abdominal somite distinctly curved in lateral view distinguish the first zoea of T. amboinensis from that of T. dobkini Chace and T. floridanus Kingsley. Larval characters of the genus Thor are summarized.

RESURRECTION OF THE GENUS LAOMENES A. H. CLARK, 1919 (DECAPODA, CARIDEA, PALAEMONIDAE)

The palaemonid genus Laomenes is re-established. The type species, Periclimenes (Corniger) ceratophthalmus Borradaile, associated with crinoids, differs from other Periclimenes Costa species at the generic level on the account of the epistome being armed with horns, the posterior rostral carina forming well developed supraorbital eaves, the presence of a supraocular tooth at the edge of the supraocular eaves, the eye with the cornea produced distally, and the mandible with a widened and multidentate incisor process. Three other crinoid associates, P. amboinensis (De Man), P. (Corniger) cornutus Borradaile, and Parapontonia nudirostris Bruce are now placed in the genus Laomenes. The monotypic genus, Parapontonia Bruce is considered to be a junior subjective synonym of Laomenes. A key and a checklist to the species of Laomenes known at present are provided.

Izucaris Masudai, New Genus, New Species (Decapoda: Caridea: Palaemonidae), a Sea Anemone Associate From Japan

ABSTRACT A new genus is proposed for Izucaris masudai, new species, a pontoniid shrimp associated with the sea anemone Nemanthus nitidus. Izucaris, new genus, is closely related to the genus Pontonides sensu stricto, but distinguished by the rostrum overreaching the midlength level of the distal peduncular article of the antennule, the pterygostomian margin distinctly tapering anteriorly, and the lack of a distinct protrusion on the medial margin of the dactyl of the second maxilliped. The type species is described and illustrated based on a male and a female collected from Izu Peninsula, Honshu, Japan. The color pattern of the new species may show a chromatic adaptation.

Cinetorhynchus Brucei, a New Species of Shrimp (Decapoda, Caridea, Rhynchocinetidae) from the Ryukyu Islands, Japan

[A new species of rhynchocinetid shrimp, Cinetorhynchus brucei sp. nov., is described and illustrated on the basis of two specimens from Kume-jima Island, Ryukyu Islands, southern Japan. The absence of an arthrobranch on the second and third pereopods links C. brucei to C. manningi Okuno, 1996, known from the western Atlantic Ocean, but the present new species differs from the latter on account of the length of stylocerite, the development of the podobranch of the second maxilliped, and the armature of the meri of the ambulatory pereopods. Eine neue Art von rhynchocenitider Garnele, Cinetorhynchus brucei sp. nov., wird anhand zweier Exemplare von der Kume-jima Insel, Ryukyu Inseln, sudliches Japan, beschrieben und illustriert. Das Fehlen einer Arthrobranchie auf dem zweiten und dritten Pereiopoden stellt die neue Art in die Nahe der westatlantischen C. manningi Okuno, 1996, sie unterscheidet sich aber von letzterer durch die Lange des Stylocerits, das Vorhandensein einer Podobranchie am zweiten Maxillipeden und die Bedornung der Schreitbein-Meri., A new species of rhynchocinetid shrimp, Cinetorhynchus brucei sp. nov., is described and illustrated on the basis of two specimens from Kume-jima Island, Ryukyu Islands, southern Japan. The absence of an arthrobranch on the second and third pereopods links C. brucei to C. manningi Okuno, 1996, known from the western Atlantic Ocean, but the present new species differs from the latter on account of the length of stylocerite, the development of the podobranch of the second maxilliped, and the armature of the meri of the ambulatory pereopods. Eine neue Art von rhynchocenitider Garnele, Cinetorhynchus brucei sp. nov., wird anhand zweier Exemplare von der Kume-jima Insel, Ryukyu Inseln, sudliches Japan, beschrieben und illustriert. Das Fehlen einer Arthrobranchie auf dem zweiten und dritten Pereiopoden stellt die neue Art in die Nahe der westatlantischen C. manningi Okuno, 1996, sie unterscheidet sich aber von letzterer durch die Lange des Stylocerits, das Vorhandensein einer Podobranchie am zweiten Maxillipeden und die Bedornung der Schreitbein-Meri.]

Rediscovery of Chirostylus dolichopus Ortmann, 1892 (Crustacea: Decapoda: Anomura: Chirostylidae) from its type locality, Boso Peninsula, Japan, with description of the colouration in life

BackgroundThe chirostylid squat lobster, Chirostylus dolichopus Ortmann, 1892, was rediscovered from its type locality, Katsuyama (Boso Peninsula, Honshu, Japan) (35°06.7′N, 139°48.8′E), since the holotype had been collected in 1880. The colouration in life of C. dolichopus is reported for the first time on the basis of a recently captured topotypic specimen.ResultsChirostylus dolichopus is characterized by the brilliant yellow ground colour and spot pattern on the meri of the ambulatory pereopods.ConclusionsThe colouration in life of C. dolichopus is diagnostic for species of Chirostylus. The examination of the present specimen revealed that C. dolichopus is distinguishable from other shallow water congeners, such as C. ortmanni, C. sandyi, and C. stellaris, by the colouration as well as morphology.

New records of two species of the coral reef shrimp genus Thor Kingsley, 1878 (Crustacea: Decapoda: Thoridae) from the Ryukyu Islands, Japan

The caridean shrimp genus Thor Kingsley, 1878 (Thoridae) is currently represented by 14 species distributed in shallow tropical to subtropical waters in the Indo-Pacific, East Pacific and West Atlantic oceans. In this study, two species of the genus are reported on the basis of material from Okinawa and Kume islands in the Ryukyu Archipelago, southern Japan. Thor leptochelus (Xu & Li, 2015) n. comb., recently described from Xisha Islands, China and originally assigned to Thinora Bruce, 1997, is transferred to Thor. Relationship of the species to three congeneric species (T. cordelli Wicksten, 1996, T. spinipes Bruce, 1983 and T. spinosus Boone, 1935) is discussed. The second is T. marguitae Bruce, 1973, representing the rediscovery since the original description and new record for Japanese waters. The four specimens of T. leptochelus were all free-living, whereas the single specimen of T. marguitae was found to be associated with a solitary fungiid coral, as previously reported.