Fourteen New Species of Dicyemids (Phylum: Dicyemida) from Seven Species of Decapodiformes (Mollusca: Cephalopoda) in the Kumano Sea, Japan Author Furuya, Hidetaka Department of Biology, Graduate School of Science, Osaka University, 1 - 1 Machikaneyama, Toyonaka, Osaka 560 - 0043, Japan E-mail: hfuruya @ bio. sci. osaka-u. ac. jp & Corresponding author hfuruya@bio.sci.osaka-u.ac.jp Author Moritaki, Takeya Marine Biological Laboratory, Toba Aquarium, 3 - 3 - 6 Toba, Toba, Mie 517 - 8517, Japan E-mail: moritaki @ aquarium. co. jp moritaki@aquarium.co.jp text Species Diversity 2022 2022-04-28 27 1 181 226 http://dx.doi.org/10.12782/specdiv.27.181 journal article 10.12782/specdiv.27.181 2189-7301 7175176 03A070DC-A02C-4FF8-A00D-FD59C7614189 Dicyema lorigeroeceum Furuya , sp. nov. [New Japanese name: Usubeni-nihaichū] ( Figs 10 , 11 ; Tables 1–3 ) Diagnosis. Medium-sized dicyemid; body length reaching 1590 µm. Calotte conical in shape. Vermiform stages with 23–30 peripheral cells: 4 propolar cells+4 metapolar cells+2 parapolar cells+13–20 trunk cells. Infusoriform embryos with 39 cells; refringent bodies solid; and two nuclei present in each urn cell. Description. Nematogens ( Figs 10a, b , 11a, c, d ). Body length 500–1100 µm, width 40–52 µm; widest in region of parapolars; trunk width mostly uniform. Peripheral cell number 23–30 ( Table 2 ): 4 propolar cells+4 metapolar cells+2 parapolar cells+11–18 diapolar cells+2 uropolar cells. Calotte conical in shape, rounded anteriorly; cilia on calotte about 4 µm long, oriented anteriorly. Propolar cells and their nuclei equal to or smaller than metapolar cells and their nuclei. Propolar cells occupying anterior 30–40% of calotte length when viewed laterally ( Fig. 10a, b ). Cytoplasm of propolar and metapolar cells contain small granules, more darkly stained by hematoxylin than cytoplasm of other peripheral cells ( Fig. 10a, b ). Axial cell cylindrical, pointed anteriorly; cell extending forward to base of metapolar cells ( Fig. 11d ). About 10 vermiform embryos present per axial cell of large individuals. Accessory nuclei seen in trunk peripheral cells. Vermiform embryos ( Figs 10c, d , 11f, g ) . Full-grown vermiform embryos length 45–68 µm, width 10–13 µm. Peripheral cell number 23–30 ( Table 2 ); trunk cells arranged in opposed pairs. Anterior end of calotte acutely pointed. Axial cell pointed anteriorly, extending to the base of propolar cells ( Figs 10d , 11f, g ). Axial cell of full-grown embryos with one agamete. Rhombogens ( Figs 10e, f , 11b, e ). Body length 500– 1590 µm, similar to that of nematogens, width 50–70 µm. Peripheral cell number typically 23–29 ( Table 2 ). Calotte shape, axial cell shape, and anterior extent similar to those of nematogens. Cytoplasm of propolar and metapolar cells contain small granules ( Fig. 10e, f ). A maximum of 2 infusorigens present in the axial cell of each parent individual. About 30 infusoriform embryos present per axial cell of large individuals. Fig. 10. Dicyema lorigeroeceum sp. nov. , photographs of syntype specimens on slide NSMT-Me-64: a, b, Nematogen, anterior region; c, body part of transitional stage from nematogen to rhombogen, note that both vermiform embryos and infusoriform embryos present within axial cell; d, vermiform embryos within axial cell; e, f, rhombogen, anterior region; g, infusorigen; h, infusoriform embryo, horizontal section. Scale bars: 10µm. Infusorigens ( Figs 10g , 11h; n =20) . Mature infusorigens medium-sized, composed of 6–14 (mode 8) external cells (oogonia and primary oocytes)+3–5 (mode 4) internal cells (spermatogonia, primary spermatocytes, and secondary spermatocytes)+4–12 (mode 8) spermatozoa. Mean diameter of fertilized eggs 12.7 µm; that of spermatozoa 2.4 µm. Axial cell ovoid or round, diameter 13–17 µm. Infusoriform embryos ( Figs 10c, h , 11i–k; n =50) . Fullgrown embryos large, length 28.3±2.1 µm (mean±SD, excluding cilia); length–width–height ratio 1.0: 0.84: 0.83; ovoid, bluntly rounded to pointed posteriorly; cilia at posterior end 7 µm long. Refringent bodies present, solid, occupying anterior 30–35% of embryo length when viewed laterally ( Fig. 11k ). Cilia project from ventral internal cells into urn cavity ( Fig. 11k ). Capsule cells contain small granules ( Fig. 11k ). Mature embryos with 39 cells: 35 somatic+4 germinal cells. Somatic cells of several types present: external cells covering large part of anterior and lateral surfaces of embryos (2 enveloping cells); external cells with cilia on external surfaces (2 paired dorsal cells+1 median dorsal cell+2 dorsal caudal cells+2 lateral caudal cells+1 ventral caudal cell+2 lateral cells+2 posteroventral lateral cells); external cells with refringent bodies (2 apical cells); external cells without cilia (1 couvercle cell+2 anterior lateral cells+ 2 first ventral cells+2 second ventral cells+2 third ventral cells); internal cells with cilia (2 ventral internal cells); and internal cells without cilia (2 dorsal internal cells+2 capsule cells+4 urn cells). Each urn cell contains two nuclei and single germinal cell ( Fig. 11k ). All somatic nuclei pycnotic in mature infusoriform embryos. Fig. 11. Dicyema lorigeroeceum sp. nov. , drawn from syntype specimens on slide NSMT-Me-64: a, Nematogen, entire; b, rhombogen, entire; c, d, nematogen, anterior region; e, rhombogen, anterior region f, g, vermiform embryo within axial cell, cilia omitted (f), optical section (g); h, infusorigen; i–k, infusoriform embryos, dorsal view (i: cilia omitted), ventral view (j: cilia omitted), sagittal section (k). Scale bars: 10 µm. Remarks. Dicyema lorigeroeceum sp. nov. is the first species of the genus found in Sepia lorigera . This new species is characterized by an acutely pointed calotte of vermiform embryos, numbers of peripheral cells, and a variable number of peripheral cells that ranges from 23 to 30 ( Table 2 ). This new species is very similar to D. conocephalum sp. nov. , D. gozaense sp. nov. and D. oxycephalum , in the shape of the calotte in vermiform stages and the number of peripheral cells ( Furuya 2009 ). However, D. lorigeroeceum sp. nov. differs from D. conocephalum sp. nov. in the cell number of infusoriform embryos (39 vs. 37). Dicyema lorigeroeceum sp. nov. can be distinguished from D. oxycephalum in the number of agamete in full-grown vermiform embryos (1 vs. 2) and a smaller number of peripheral cells (28 vs. 30, 32) ( Furuya 2009 ), and is very similar to D. gozaense sp. nov. , from which it differs in the number of peripheral cells (28 vs. 29) and in the anterior extent of adult vermiform stages (metapolar cells vs. propolar cells). Etymology. The species name “ lorigeroeceum ” is composed of the epithet of the host, Sepia lorigera , and the Ancient Greek word oiceon , meaning “inhabiting”. Taxonomic summary. Type material : a syntype slide (NSMT-Me-64) collected on 14 February 2018 ; additional syntypes on slide series No. SL5779 (5 slides) in the author’s collection. Type locality : off Minami-Ise ( 34°08′N , 136°04′E ), Mie Prefecture , Honshu , the Kumano Sea , Japan , depth 180 m . Other materials examined : None. Host : symbiotype, Sepia lorigera Wülker, 1910 (Mollusca: Cephalopoda : Sepiida ), male (mature), 157 mm ML (NSMT-Mo-85907). Collector of host : T. Moritaki. Site : anterior ends (calottes) inserted into crypts of the renal appendages within the renal sacs. Prevalence : in 10 of 10 host specimens examined (100%). Dicyema miense sp. nov. [New Japanese name: Mie-nihaichū] ( Figs 12 , 13 ; Tables 1–3 ) Diagnosis. Medium-sized dicyemid; body length reaching 1210 µm. Calotte conical in shape. Vermiform stages with 26–34 peripheral cells: 4 propolar cells+4 metapolar cells+2 parapolar cells+16–24 trunk cells. Infusoriform embryos with 39 cells; refringent bodies solid; and two nuclei present in each urn cell. Fig. 12. Dicyema miense sp. nov. , photographs of syntype specimens on slide NSMT-Me-68: a, b, Nematogen, anterior region; c, vermiform embryo within axial cell; d, rhombogen, anterior region; e, infusorigen; f, g, infusoriform embryos, horizontal section (f), sagittal section (g). Scale bars: 10µm. Fig. 13. Dicyema miense sp. nov. , drawn from syntype specimens on slide NSMT-Me-68: a, nematogen, entire; b, rhombogen, entire; c, d, nematogen, anterior region; e, f, vermiform embryo within axial cell, cilia omitted (e), optical section (f); g, rhombogen, anterior region; h, infusorigen; i–k, infusoriform embryos, dorsal view (i: cilia omitted), ventral view (j: cilia omitted), sagittal section (k). Scale bars: a, b, 50 µm; c–k, 10 µm. Description. Nematogens ( Figs 12a, b , 13a, c, d ). Body length 800–1180 µm, width 32–40 µm; widest in region of parapolars; trunk width mostly uniform. Peripheral cell number 26–34 ( Table 2 ): 4 propolar cells+4 metapolar cells+2 parapolar cells+14–22 diapolar cells+2 uropolar cells. Calotte conical in shape, rounded anteriorly; cilia on calotte about 4 µm long, oriented anteriorly. Propolar cells and their nuclei equal to or smaller than metapolar cells and their nuclei. Propolar cells occupy anterior 30–40% of calotte length when viewed laterally ( Fig. 13c, d ). Axial cell cylindrical, rounded anteriorly; cell extending forward to middle of metapolar cells ( Fig. 13d ). About 10 vermiform embryos present per axial cell of large individuals. Accessory nuclei present in trunk peripheral cells. Vermiform embryos ( Figs 12c, d , 13e, f ) . Full-grown vermiform embryos length 40–57 µm, width 12–14 µm. Peripheral cell number 26–34 ( Table 2 ); trunk cells arranged in opposed pairs. Anterior end of calotte acutely pointed. Axial cell pointed anteriorly, extending to the base of propolar cells ( Fig. 13f ). Axial cell of full-grown embryos with one agamete. Rhombogens ( Figs 12d , 13g ). Body length 900–1210 µm, similar to that of nematogens, in length, width 60–75 µm. Peripheral cell number typically 26–34 ( Table 2 ). Calotte shape, axial cell shape, and anterior extent similar to those of nematogens. A maximum of 3 infusorigens present in the axial cell of each parent individual. About 30 infusoriform embryos present per axial cell of large individuals. Infusorigens ( Figs 12e , 13h; n =10) . Mature infusorigens medium-sized, composed of 5–8 (mode 6) external cells (oogonia and primary oocytes)+2–4 (mode 2) internal cells (spermatogonia, primary spermatocytes, and secondary spermatocytes)+4–8 (mode 4) spermatozoa. Mean diameter of fertilized eggs 13.3 µm; that of spermatozoa 2.5 µm. Axial cell ovoid or round, diameter 13–15 µm. Infusoriform embryos ( Figs 12f, g , 13i–k; n =20) . Fullgrown embryos large, length 28.3±2.1 µm (mean±SD, excluding cilia); length–width–height ratio 1.0: 0.84: 0.81; ovoid, bluntly rounded to pointed posteriorly; cilia at posterior end 7 µm long. Refringent bodies present, solid, occupying anterior 35–40% of embryo length when viewed laterally ( Fig. 13k ). Cilia project from ventral internal cells into urn cavity ( Fig. 13k ). Capsule cells contain small granules ( Fig. 13k ). Mature embryos with 39 cells: 35 somatic+4 germinal cells. Somatic cells of several types present: external cells covering large part of anterior and lateral surfaces of embryos (2 enveloping cells); external cells with cilia on external surfaces (2 paired dorsal cells+1 median dorsal cell+2 dorsal caudal cells+2 lateral caudal cells+1 ventral caudal cell+2 lateral cells+2 posteroventral lateral cells), external cells with refringent bodies (2 apical cells); external cells without cilia (1 couvercle cell+2 anterior lateral cells+ 2 first ventral cells+2 second ventral cells+2 third ventral cells); internal cells with cilia (2 ventral internal cells); and internal cells without cilia (2 dorsal internal cells+2 capsule cells+4 urn cells). Each urn cell contains two nuclei and a single germinal cell ( Fig. 13k ). All somatic nuclei pycnotic in mature infusoriform embryos. Remarks. Dicyema miense sp. nov. is the first species of the genus found in Sepia subtenuipes and is characterized by an acutely pointed calotte of vermiform embryos and numbers of peripheral cells, and a variable number of peripheral cells that ranges from 26 to 34 ( Table 2 ). It is very similar to D. gozaense sp. nov. , D. lorigeroeceum sp. nov. and D. oxycephalum in the shape of the calotte in vermiform stages, the number of peripheral cells, and the number of infusoriform embryos ( Furuya 2009 ). However, D. miense sp. nov. can be distinguished from D. gozaense sp. nov. and D. oxycephalum in an anterior extent of adult vermiform stages (metapolar cells vs. propolar cells). Dicyema miense sp. nov. can also be distinguished from D. lorigeroeceum sp. nov. by the maximum number of peripheral cells (34 vs. 30): it has no clear maximum in its distribution of peripheral cells, while D. lorigeroeceum sp. nov. has a maximum of 28 peripheral cells. Etymology. The species name “ miense ” refers to the location of the Mie-Island off Minami-Ise, Mie Prefecture , in Kumano Sea. Taxonomic summary. Type material : a syntype slide (NSMT-Me-68) collected on 25 October 2016 ; additional syntypes on slide series No. SS3618 (5 slides) in the author’s collection. Type locality : off Kii-Nagashima ( 34°01′N , 136°39′E ), Mie Prefecture , Honshu , the Kumano Sea , Japan , depth 150 m . Other materials examined : slide series No. SS3614- 3617 (each 5 slide) collected off Kii-Nagashima ( 34°01′N , 136°39′E ), Mie Prefecture , Honshu , the Kumano Sea , Japan , depth 150 m , 25 October 2016 , in the author’s collection . Host : symbiotype, Sepia subtenuipes Okutani and Horikawa, 1987 (Mollusca: Cephalopoda : Sepiida ), female (immature), 68 mm ML (NSMT-Mo-85910). Collector of host : T. Moritaki. Site : anterior ends (calottes) inserted into crypts of the renal appendages within the renal sacs. Prevalence : in 19 of 30 host specimens examined (63.3%).