A new species of the alpheid shrimp genus Athanas Leach, 1814 (Decapoda: Caridea) from the Sea of Japan.

A new species of the alpheid shrimp genus Athanas Leach, 1814 is described based on a holotype from Wakasa Bay, Sea of Japan side of Honshu, Japan, at a depth of 90 m. Athanas exilis n. sp. appears close to A. sydnyensis Anker & Ahyong, 2007, but is distinguished from the latter by some morphological features, including the different shape of the telson, the shorter antennular stylocerite, more strongly produced distal lamella of the antennal scaphocerite, and less developed armature of the merus of the major cheliped. Preliminary genetic analysis using the mitochondrial 16S rRNA gene was performed to compare interspecific genetic divergence within the genus.

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).

Effects of forest cover on richness of threatened fish species in Japan.

Estuaries--one of the most vulnerable ecosystems globally--face anthropogenic threats, including biodiversity loss and the collapse of sustainable fisheries. Determining the factors contributing to the maintenance of estuarine biodiversity, especially that of fish, is vital for promoting estuarine conservation and sustainability. We used environmental DNA metabarcoding analysis to determine fish species composition in 22 estuaries around Japan and measured watershed-scale land-use factors (e.g., population size, urban area percentage, and forest area percentage). We sought to test the hypothesis that the richness of the most vulnerable estuarine fish species (i.e., registered by the Japanese Ministry of the Environment in the national species red-list) is determined by watershed-scale land-use factors. The richness of such species was greater, where forest cover was highest; thus, forest cover contributes to their conservation. The proportion of agriculture cover was associated with low species richness of red-listed fishes (redundancy analysis, adjusted R2 = 43.9% of total variance, df = 5, F = 5.3843, p = 0.0001). The number of red-listed species increased from 3 to 11 along a watershed land-use gradient ranging from a high proportion of agriculture cover to a large proportion of forest cover. Furthermore, the results showed that throughout Japan all the examined watersheds that were covered by >74.8% forest had more than the average (6.7 species per site) richness of red-listed fish species. This result can be attributed to the already high average forest cover in Japan of 67.2%. Our results demonstrate how the land use of watersheds can affect the coastal sea environment and its biodiversity and suggest that proper forest management in conjunction with land-use management may be of prime importance for threatened fish species and coastal ecosystems in general.

Efectos de la Cobertura Forestal sobre la Riqueza de Especies Amenazadas de Peces en Japón Resumen Los estuarios-uno de los ecosistemas más vulnerables a nivel mundial-enfrentan amenazas causadas por el hombre, incluyendo la pérdida de biodiversidad y el colapso de las pesquerías sustentables. La determinación de los factores que contribuyen al mantenimiento de la biodiversidad estuarina, especialmente la de los peces, es vital para fomentar la conservación y sustentabilidad estuarinas. Usamos un análisis de metasecuenciación de ADN ambiental para determinar la composición de especies de peces en 22 estuarios de Japón y medimos los factores del uso de suelo a nivel de cuenca (p. ej.: tamaño poblacional, porcentaje de área urbana y porcentaje de área forestal). Buscamos probar la hipótesis de que la riqueza de las especies de peces más vulnerables (es decir, aquellas registradas por el Ministerio Japonés del Ambiente en la lista roja de especies a nivel nacional) está determinada por los factores de uso de suelo a nivel de cuenca. La riqueza de dichas especies fue mayor en donde la cobertura forestal era la más alta; por lo tanto, la cobertura forestal contribuye a la conservación de estas especies. La proporción de la cobertura agrícola estuvo asociada con una baja riqueza de especies de peces en la lista roja (análisis de redundancia, R2 ajustada = 43.9% de la varianza total, gl = 5, F = 5.3843, p = 0.0001). El número de especies en la lista roja incrementó de 3 a 11 a lo largo del gradiente de uso de suelo de la cuenca, yendo desde una proporción alta de cobertura agrícola a una proporción alta de cobertura forestal. Además, los resultados mostraron que, en Japón, todas las cuencas analizadas que contaban con una cobertura forestal >74.8% tenían mayor riqueza de especies de peces en la lista roja que el promedio (6.7 especies por sitio). Este resultado puede atribuirse a la ya de por sí elevada cobertura forestal de Japón (67.2%). Nuestros resultados demuestran cómo el uso de las cuencas puede afectar al ambiente costero marino y a su biodiversidad y sugiere que la gestión adecuada de los bosques en conjunto con el manejo del uso de suelo puede ser de suma importancia para las especies amenazadas de peces y los ecosistemas costeros en general.

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.

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.