A new species of the ghost shrimp genus Callianassa Leach, 1814 (Decapoda: Axiidea: Callianassidae) from Wakasa Bay, western Japan: the first representative of the genus from the Pacific region.

The ghost shrimp genus Callianassa Leach, 1814 is currently represented by six taxa, of which five are known from the eastern Atlantic and only C. persica Sakai, 2005 from the Persian Gulf. In this study, a new species of Callianassa is described and illustrated on the basis of material from the subtidal soft sediments (at 2628 m depth) in Wakasa Bay, western Japanese coast of the Sea of Japan. Callianassa ogurai n. sp. is the first species of the genus from the Pacific region. This study discusses characters differentiating the new species and other five congeneric species. Molecular phylogenetic analysis using the mitochondrial 16S rRNA gene supports the close relationship between the new species and C. subterranea (Montagu, 1808), warranting the generic assignment of the new species to Callianassa sensu stricto. We also explore the contentious taxonomic status of C. timiris (Sakai, Trkay, Beck Freiwald, 2015).

Differences in the parasitic effects of a bopyrid isopod and rhizocephalan barnacle on the portunid crab, Charybdis bimaculata.

Bopyrid isopods and rhizocephalan barnacles are obligate parasite crustaceans which harm their decapod hosts. However, to the best of our knowledge, studies have not compared which of these parasites has a greater parasitic effect on its hosts. Here, the parasitic effect of the bopyrid isopod, Allokepon hendersoni, and an unidentified sacculinid rhizocephalan species, infesting the same population of portunid crabs, Charybdis bimaculata, was investigated and compared for the first time. Samples were collected from the bycatch of a trawl fishery in Tosa Bay, Japan. A total of 2601 crabs were collected, of which 14 (0.55%) were parasitized by the bopyrid and 21 (0.82%) by the rhizocephalan. One of the two female crabs parasitized by the bopyrid was ovigerous (with much fewer eggs than unparasitized females). No ovigerous crab was found from the eight females parasitized by the rhizocephalan. Because only two female crabs were parasitized by the bopyrid, the following analyses were made using the male crabs. Both parasites reduced the wet weight (crab condition) and the cheliped size (secondary growth) of C. bimaculata, but the impact of the parasitism did not differ between the parasite species. The size of the abdominal flap of male hosts was reduced by the bopyrid infestation; however, rhizocephalan infestation caused enlargement of the abdominal flap, which is an indication of feminization. The present study provides information on how the effect of these two parasitic castrators on the same host crab varies. A moderate decrease in crab condition and cheliped development was common among the parasites, suggesting that the degree of impact might be favorable for the survival of the two parasites species.

A new genus for "Neocallichirus" grandis Karasawa amp; Goda, 1996, a ghost shrimp species (Decapoda: Axiidea: Callianassidae) heretofore known only by fossil materials.

A new genus of the family Callianassidae, Laticallichirus, is established for "Neocallichirus" grandis Karasawa Goda, 1996, a ghost shrimp species heretofore represented only by fossil materials from the middle to upper Pleistocene of Japan. The newly collected specimens came from two Japanese localities: Numazu, Shizuoka Prefecture (Suruga Bay) and Tosa, Kochi Prefecture (Tosa Bay), included within the known geographical range derived from fossil records. The species identification was based on the close agreement in the cheliped morphology and the known fossil distributions. The new genus is assigned to the subfamily Callichirinae Manning Felder, 1991, and compared with seven genera, Balsscallichirus Sakai, 2011, Callichirus Stimpson, 1866, Callichiropsis Sakai, 2010, Grynaminna Poore, 2000, Michaelcallianassa Sakai, 2002, Lepidophthalmus Holmes, 1904 and Podocallichirus Sakai, 1999, all characterized by the antennular peduncle being longer and stouter than the antennal peduncle. The new genus is characteristic in combination of the following characters: rostrum spiniform; maxilliped 3 devoid of exopod; ischium-merus of maxilliped 3 broadly operculiform; maxilliped 3 ischium devoid of crista dentata; major cheliped devoid of meral hook or associated lobe-like structure; tergites of the pleomeres 3-5 without conspicuous ornamentation; male pleopod 2 biramous, its endopod devoid of appendices interna and masculina; uropodal endopod suboval in shape; telson distinctly wider than long, with shallowly concave posterior margin. The genetic analysis using the mitochondrial 16S rRNA places the new genus as sister to Callichirus Stimpson, 1866, although bootstrap support for major branches is generally low. The newly collected specimens were found in burrows in soft sediments of shallow subtidal zone being accessible at low tide.

Parasitic effects of the bopyrid Megacepon goetici (Crustacea: Isopoda) on the varunid crab Gaetice depressus.

The effects of infestation by the bopyrid isopod Megacepon goetici on the varunid crab Gaetice depressus were investigated. This crab is one of the most common crabs in Japanese intertidal shores where it plays a key role in structuring the benthic community. Samples were collected in Wakayama Prefecture, Japan. From a total of 1694 crabs, 61 (3.6%) were parasitized by bopyrid isopods. No ovigerous females were parasitized, which may be evidence of parasitic castration of female host crabs, as has been described in other parasitized brachyuran crabs. Total weight was reduced in both males and females, and infested crabs also exhibited subtle lateral and dorsal carapace swelling due to the presence of parasites under the carapace. We therefore conclude that the morphology and the reproductive capacity of G. depressus were significantly affected by the bopyrid isopod.

Burrow Morphology of Alpheid Shrimps: Case Study of Alpheus brevicristatus and a Review of the Genus.

The Alpheus brevicristatus De Haan, 1844 is one of the commonest shrimp species inhabiting the tidal flats in Japan. This species is sometimes accompanied by the facultative symbiotic goby, Acentrogobius spp. Here, we investigated the burrow morphology of A. brevicristatus in a tidal flat of Uranouchi Inlet, Kochi Prefecture, Japan. We also reviewed existing literature on alpheid burrow morphology using the resin casting technique, to determine how burrows vary in the presence and absence of gobies. Nine burrows were casted in situ using polyester resin. All burrows were long, but shallow in structure, with several funnel-shaped openings and short cul-de-sac branches. This species appears to use several burrow openings to access the sediment surface for feeding with high efficiency. Gobies were not associated with all burrows cast; however, 1-3 individuals of the small alpheid shrimp Athanas japonicus Kubo, 1936 were entombed in seven of the casts. A review of 12 studies on the burrow morphology of 16 Alpheus species based on resin casting techniques showed wide variation in burrow characteristics, such as burrow depth, length, and number of openings. Our findings suggest that burrow structure is influenced by species-specific characteristics and sediment type. The possibility that the presence of the symbiotic goby affects the burrow morphology of Alpheus shrimp is discussed.

On a New Species of Parasitic Barnacle (Crustacea: Rhizocephala), Sacculina shiinoi sp. nov., Parasitizing Japanese Mud Shrimps Upogebia spp. (Decapoda: Thalassinidea: Upogebiidae), Including a Description of a Novel Morphological Structure in the Rhizocephala.

The rhizocephalan Sacculina shiinoi sp. nov. parasitizes three species of Upogebia in Japan. It is described morphologically and compared with another Upogebia parasite, Sacculina upogebiae Shiino, 1943 from Japan and Korea. These two species are the only sacculinids that parasitize mud shrimps. DNA analyses clearly show the two species to be separate and not closely related. The cuticle differs in being provided with close-set, branched, and spiny excrescences in S. shiinoi, while it lacks excrescences, but forms small scales in S. upogebiae. In S. upogebiae, the bulbous sperm-producing part and the narrow receptacle duct are separated by a compartmentalized mid portion, which is missing in S. shiinoi. A ridge, having a thickened, fluffy cuticle with a U-shaped course, passes across the visceral mass between the two receptacle openings in S. shiinoi. Such a structure has never been described in other rhizocephalans, and its function is uncertain.

Burrow utilization in the goby Eutaeniichthys gilli associated with the mud shrimp Upogebia yokoyai.

We investigated the estuarine goby's (Eutaeniichthys gilli) utilization of mud shrimp (Upogebia yokoyai) burrows in laboratory experiments at Kochi, Japan. The goby utilized the shrimp burrow in the presence of the host, without predators, when the mud surface was covered with water. The goby spent one quarter to half the time in shrimp burrows in experimental tanks. The goby frequently entered and exited the shrimp burrows, with bout durations of several seconds to several minutes. The goby also utilized vacant artificial burrows in much the same manner. It is suggested that E. gilli feeds on small-sized crustaceans and other organic matter on the mud surface frequently utilizing shrimp burrows for possible predator avoidance even when no predator is present. Repeated evolution of burrow utilization in the North Pacific bay gobies in both the East and West Pacific would correlate with burrow commensalism in E. gilli, which is the most proximal outgroup of the bay gobies.

Epizoanthus spp. associations revealed using DNA markers: a case study from Kochi, Japan.

Zoanthids (Cnidaria, Hexacorallia) of the genus Epizoanthus are often found in association with other marine invertebrates, including gastropods and hermit crabs. However, little information exists on the specificity and nature of these associations due to a lack of investigation into Epizoanthus species diversity, and the taxonomy of Epizoanthus is therefore confused. In this study, analyses of morphological data (tentacle number, polyp size, etc) and molecular data (mitochondrial cytochrome oxidase subunit 1 = COI, 16S ribosomal DNA = 16S rDNA) were used to examine Epizoanthus specimens from Tosa Bay, Kochi, Japan. The Epizoanthus specimens were found on both live gastropods (Gemmula unedo) and hermit crabs (Paguristes palythophilus) inhabiting G. unedo and G. cosmoi shells. While morphological analyses did not show clear differences between examined specimens, both COI and mt 16S rDNA clearly divided the specimens into two groups, one associated only with hermit crabs (= Epizoanthus sp. C), and another associated only with living gastropods (= Epizoanthus sp. S). Unexpectedly, DNA sequences from both groups did not match with two previously reported Epizoanthus species from Japan (E. indicus, E. ramosus), indicating they both may be undescribed species. These results highlight the utility of DNA "barcoding" of unknown zoanthids, and will provide a foundation for re-examinations of Epizoanthus species diversity and specificity, which will be critical in understanding the evolution of these unique marine invertebrates.