Antennapeachia jambio, Izumi, Fujita & Yanagi, 2017

Izumi, Takato, Fujita, Toshihiko & Yanagi, Kensuke, 2017, Antennapeachia jambio (Cnidaria: Actiniaria: Haloclavidae), the Second Species of Genus Antennapeachia, with Revision of the Diagnosis of the Genus, Species Diversity 22, pp. 109-115 : 110-113

Antennapeachia jambio sp. nov.

[New Japanese name: Misaki-no-antena] ( Figs 2–4 , Table 1)

a biological dredge onboard the R/V Rinkai-Maru, during the twelfth Coastal Organism Joint Survey of JAMBIO. The specimen was processed by the completely same way as the holotype except the place where that was preserved; the all process was undergone in Misaki Marine Biological Station.

The holotype specimen was deposited at the CMNH ( CMNH-ZG 06546 ) . The paratype one was at the National Museum of Nature and Science, Tsukuba (NSMT-Co 1596) .

Preparation of histological sections. The holotype specimen (CMNH-ZG 06546) was processed to histological sections by standard methods ( Presnell and Schreibman 1997). The dissected specimen preserved in 5% formalin was dehydrated with ethanol, dissected some tissues by tweezers and scissors, dehydrated by xylene, embedded in paraffin, sliced into serial sections (8 µm thick) by using a microtome, mounted on glass slides, and stained with hematoxylin and eosin.

Observation of cnidae. Cnidae on the tentacles (both antenna tentacles and marginal tentacles), column, actinopharynx (above tissues were from both specimens), and filaments (only from CMNH-ZG 6456, because the NSMT- Co 1596 was too damaged in proximal end to take tissue of filament for analysis) were observed. Images of the cnidae were obtained by differential interference contrast microscopy ( Yanagi et al. 2015), and the length and width were measured using the software ImageJ v. 1.49 ( Rasband 1997 – 2012). Cnida nomenclature followed Mariscal (1974).

Material examined. Holotype: CMNH-ZG 06546 ; dissected specimen, embedded tissues in paraffin, histological sections (3 slides), prepared nematocysts (5 slides); February 19, 2014, off Jogashima , Kanagawa Prefecture, 35°06.082′N, 139°34.232′E, at 238–309 m in depth collected by Kensuke Yanagi. Paratype: NSMT-Co 1596; whole specimen, somewhat damaged in proximal end; February 15, 2017, off Miura Peninsula , Kanagawa Prefecture, 35°08.0383′N, 139°33.731′E, at 95–97 m in depth collected by Takato Izumi .

Etymology. This species was named, because the type specimens were collected in the second and twelfth JAMBIO Coastal Organism Joint Survey. JAMBIO stands for “Japanese Association for Marine Biology.”

Description. External anatomy. Column smooth, cylindrical or barrel-like, rich in expansibility, length ca. 9 mm, diameter ca. 7 mm in alive, and length 8 mm diameter 6 mm in preserved specimens. Color of body orange ( Fig. 2A, B ). Column surface smooth, papillae absent, with numerous discontinuous wavy wrincles running direction of transversal and pale white patches ( Fig. 2B ). Aboral end flattened or slightly concaved, like a shape of donut, with tiny hole in center, semitransparent, so that line of mesenteries visible from outer side. Pedal disk absent, but somewhat sticky so that particles of mud adhered to column or aboral end ( Fig. 2B ). Two circles of tentacles on oral disc; 16 tentacles. Fourteen marginal tentacles in outer circle; two antenna tentacles in inner circle ( Fig. 3A ). Marginal tentacles protruding outside or hanging along column. Antenna tentacles rising straight upward. Marginal tentacles approximately 4–5 mm in length when fully expanded. Antenna tentacles 1–2 mm in length, far shorter than marginal tentacles. Both tentacles simple, without acrospheres. Coloration of marginal tentacles brownish, obscure cross-bands of yellow and brown; surface complicatedly wrinkled. Antenna tentacles without cross-bands; surface wrinkled ( Fig. 2A ). Oral disk diameter ca. 4 mm, same color as tentacles. Mouth at center of oral disk, a little swelled, with well-extended and robed conchula on ventral side ( Fig. 2A ).

Internal anatomy. Eight pairs of macrocnemes, six of first cycle and extra two pairs between ventro-lateral mesenteries and ventral directives; two independent microcnemes between ventro-lateral mesenteries and ventral directives ( Figs 2C , 3B ). All macrocnemes perfect and continuing along whole length of body. Microcnemes present from proximal end to middle part of body, but absent near oral end. Antenna tentacles between ventro-lateral endocoels ( Fig. 3B ). Seven marginal tentacles of outer cycle on dorsal half of body; one of them arised from dorsal endocoel; two (one on each side) from dorso-lateral exocoels; two from dorso-lateral endocoels; other two from lateral exocoels. Other seven on ventral half of body; one of them arised from ventral endocoel; two from endocoel between two extra pairs of macrocnemes; the other four in ventrolateral exocoel ( Figs 2A , 3B ). Tentacular circular muscle endodermal ( Fig. 2D ); tentacular longitudinal muscle ectodermal ( Fig. 2E ). Retractor muscles strongly circumscribed, limited at the center of each macrocneme ( Fig. 2C, F ), with approximately 15–30 a little branched muscular processes; parietal muscles of macrocnemes distinct, with around ten simple muscular processes ( Fig. 2F, H ). Mesoglea in body wall far thicker than ectoderm and endoderm, thinner in actinopharynx and siphonoglyph ( Fig. 2F ). Actinopharynx smooth, comparatively long in column, with huge siphonoglyph on ventral side, which always connected to it ( Fig. 2C ). Sphincter muscle absent ( Fig. 2G ). On aboral end, basilar muscle absent ( Fig. 2I ). Filaments at the tips of macrocnemes, small and limited near aboral end. Matured gametes not observed, so sexuality of specimens not clear.

Cnidom. Spirocyst in both tentacles, basitrich in every tissue, microbasic amastigophore in actinopharynx and filament, microbasic p -mastigophore in actinopharynx and filament ( Table 1, Fig. 4 ). Basitrichs in filament distinguished as two types by their size. Microbasic p -mastigophore in actinopharynx morphologically distinguished as two types (“ Type 1” and “ Type 2”; Fig. 4H, I ): Type 1 comparatively shorter than Type 2 ( Figs 4 , 5 ); ratio of shaft length for capsule length of Type 1 smaller than that of Type 2 (0.65–0.76 [n =10] vs. 0.92–1.01 [n =5]); and slight middle expansion on shaft present in Type 1 but not in Type 2.

Remarks. This species resembles A. setouchi in having antenna tentacles, forming a siphonoglyph (which is connected to conchula) beside their actinopharynx and having wrincled orange color column. Antennapeachia jambio , however, has many different features from A. setouchi ; antenna tentacles are far smaller than marginal tentacles, in contrast those of A. jambio are bigger and more prominent than marginal ones ( Fig. 2 , Izumi et al. 2016); A. jambio has a different type of cnidae from A. setouchi , especially the microbasic p -mastigophores are only in actinopharynx and filament of A. jambio ( Table 1, Figs 4 , 5 ); the two pairs of macrocnemes between ventro-lateral mesenteries and ventral directives are only formed in the column of A. jambio . The last difference is most characteristic, that is why we judged that A. jambio is appropriate to be treated as new species, and we revised the diagnosis of genus (see the Discussion part).

Figures

Fig. 2. Antennapeachia jambio sp. nov., holotype, CMNH-ZG 06546, external morphology in living state (A, B) and internal morphology of the preserved specimen (C–I). (A) Oral view; the conchula is located on the ventral side of the mouth. (B) Lateral view of the whole body. (C) Cross section of the column. (D) Longitudinal section of a tentacle. (E) Cross section of a tentacle showing the ectodermal longitudinal muscles (indicated by arrowheads). (F) Cross section of the column, enlargement of a part of (C). (G) Longitudinal section of the oral end of the column. (H) Cross section of the mesentery with filament. (I) Longitudinal section of the aboral end. Abbreviations: a, actinopharynx; at, antenna tentacle; c, conchula; f, filament; me, mesoglea; mi, microcneme; mt, marginal tentacle; pm, parietal muscle; rm, retractor muscle; s, siphonoglyph; tcm, tentacular circular muscle; tlm, tentacular longitudinal muscle. Scale bars indicate 5mm in A and B, 1mm in C, and 100µm in D–I. (Position: the center of upper or lower of the page, nearby the Result part.)

Fig. 3. Schematic representation of the arrangements of the tentacles (A) and mesenteries (B) in Antennapeachia jambio sp. nov. There are two antenna tentacles and fourteen marginal tentacles in the cycles, and one tentacle communicates with each endo- and exocoel (A and M means the position of antenna and marginal tentacle, respectively). The antenna tentacles are between the ventrolateral mesenteries. Two microcnemes (broken line) disappear near the mouth. (Position: the left or right of the page, nearby the Result part.)

Fig. 4. Cnidae of Antennapeachia jambio sp. nov., holotype, CMNH-ZG 06546. (A) Spirocyst in an antenna tentacle. (B) Basitrich in an antenna tentacle. (C) Spirocyst in marginal tentacles. (D) Basitrich in marginal tentacles. (E) Microbasic amastigophore in marginal tentacles. (F) Basitrich in the actinopharynx. (G) Microbasic amastigophore in the actinopharynx. (H) Microbasic p-mastigophore type-1 in the actinopharynx. (I) Microbasic p-mastigophore type-2 in the actinopharynx. (J) Basitrich in the column. (K) Short basitrich in the filament. (L) Long basitrich in the filament. (M) Microbasic amastigophore in the filament. (N) Microbasic p-mastigophore in the filament. (Position: the center of upper or lower of the page, nearby the Result part.)

Fig. 5. Size distribution of nematocysts of Antennapeachia jambio sp. nov., holotype, CMNH-ZG 06546. For letter abbreviations (A–N) refer to Fig. 4. (Position: under the Fig. 4, the center of upper or lower of the page.)