Keiichi Kakui

Phylogenetic relationships within Tanaidacea were analyzed based on sequence data for the 18S rRNA gene. Our results strongly supported a monophyletic group composed of Neotanaidae, Tanaoidea, and Paratanaoidea, with the first two taxa forming a clade. These results contradict three previously suggested hypotheses of relationships. Based on the molecular results, and considering morphological similarities/differences between Neotanaidomorpha and Tanaidomorpha, we demoted Suborder Neotanaidomorph

The new species Nesotanais ryukyuensis sp. n. is described from Japan. Nesotanais ryukyuensis most closely resembles N. rugula Bamber, Bird & Angsupanich, 2003, but can be distinguished by the length of simple seta on maxillipedal basis and the shape of cheliped in male. A key to species of the genus Nesotanais is given. The male chelipeds of N. rugula are redescribed. The serial ridges on the inner surface of the chelipedal propodus and dactylus in Nesotanais ryukyuensis and N. rugula are l

We describe Tanaopsis japonica sp. nov. from intertidal and nearshore habitats around Hokkaido Island, northern Japan. This species closely resembles T. chotkarakde Bird & Bamber, 2000 and T. rawhitia Bird, 2011 in having the uropod with the endopod biarticulate and the exopod uniarticulate, but differs from them in the following characters: pereonite 4 as long as pereonite 5; mandibles lacking the molar; the number of simple setae on the antenna, propodal palm, and dactylus of pereopods 1–3

Among arthropods, various insects, spiders, and crustaceans produce thread. The crustacean Tanaidacea include species that use thread mainly to construct dwelling tubes. While thread production was previously known only in Tanaoidea and Paratanaoidea, it was recently discovered in two species in Kalliapseudidae (Apseudoidea), although information on the morphology of the thread-producing system was lacking. Using histology, light and scanning electron microscopy, we found that the kalliapseudid

Tanaidaceans are small benthic crustaceans that mainly inhabit diverse marine environments, and they comprise one of the most diverse and abundant macrofaunal groups in the deep sea. Tanaidacea is one of the most thread-dependent taxa in the Crustacea, constructing tubes, spun with their silk, for shelter. In this work, we sequenced and assembled the comprehensive transcriptome of 23 tanaidaceans encompassing 14 families and 4 superfamilies of Tanaidacea, and performed silk proteomics of Zeuxo e

We report in <i>P. algicola</i> a third, novel secretory system, here termed the pleotelsonal-gland system, used for tube construction in Tanaidacea. It is similar to the secretory system in some "thalassinidean" decapods; both systems have secretory glands connecting to the gut and thence to the anal opening as the outlet; however, these gland systems likely evolved independently. Recent discoveries of novel secretory systems for tube construction in Tanaidacea suggest that information from sma

Lack of an ischium on pereiopods 1-6 was previously considered a synapomorphy for the tanaidacean superfamily Tanaoidea, although descriptions of Arctotanais alascensis (Richardson, 1899), the sole species in Arctotanais, indicated presence or absence of the ischium. To resolve this ambiguity, we examined newly collected specimens of A. alascensis (including males, which had not previously been described) from Hokkaido, Japan, using light and scanning electron microscopy. We also conducted molec

Abstract Information on the extent, diversity and connectivity of populations is lacking for most deep-sea invertebrates. Species of the order Tanaidacea (Crustacea), one of the most diverse and abundant macrofaunal groups in the deep sea, are benthic, lack a planktonic larval stage, and thus would be expected to have narrow distributional ranges. However, with molecular evidence from the COI gene, we show here that the deep-sea tanaidacean Carpoapseudes spinigena has a distributional range span

We describe a new typhlotanaid species, Hamatipeda kohtsukai sp. nov., collected from between 167 and 488 m depth in the Sagami Sea, Japan. This is the first record of Hamatipeda from the northern hemisphere. Hamatipeda kohtsukai resembles Hamatipeda trapezoida from the Subantarctic region in having pereonites 1–3 widest anteriorly (not rectangular), but differs from it in the length ratio of antennal articles 4/5; the number of setae on the dactyli of pereopods 1–3, ischia of pereopods 4–6, and

Two new species, Kudinopasternakia balanorostrata and Pseudosphyrapus quintolongus are described from Japan. Kudinopasternakia balanorostrata is characterized by an acorn-shaped rostrum. It most closely resembles K. siegi (Viskup &amp; Heard, 1989), but can be distinguished by the shape of the rostrum, the number of setae on article 2 of the mandibular palp, and the setation on the outer lobe of the fixed endite of the maxilla. Pseudosphyrapus quintolongus is characterized by an unusually large

We report on the behavior of a deep-sea tanaidacean, <i>Gigantapseudes</i> sp. (Apseudomorpha: Gigantapseudidae), recorded at the depths of 6446-6447 m by the manned submersible <i>Shinkai 6500</i>. From recordings of at least three individuals walking on the sea floor, we confirm that <i>Gigantapseudes</i> sp. is epibenthic, as previously inferred from leg shape. One individual was recorded entering a hole. All individuals in the videos kept pereopods 4 raised from the seafloor while walking, i