Dicyema shimaense, Furuya & Moritaki, 2022
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publication ID |
https://doi.org/ 10.12782/specdiv.27.181 |
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publication LSID |
lsid:zoobank.org:pub:03A070DC-A02C-4FF8-A00D-FD59C7614189 |
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persistent identifier |
https://treatment.plazi.org/id/24376AE3-7C92-41CC-BDD5-DFC682023A36 |
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taxon LSID |
lsid:zoobank.org:act:24376AE3-7C92-41CC-BDD5-DFC682023A36 |
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treatment provided by |
Felipe |
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scientific name |
Dicyema shimaense |
| status |
sp. nov. |
Dicyema shimaense sp. nov.
[New Japanese name: Shima-nihaichū] ( Figs 14 View Fig , 15 View Fig ; Tables 1–3)
Diagnosis. Medium-sized dicyemid; body length reaching 1190 µm. Calotte conical in shape. Vermiform stages with 28–30 peripheral cells: 4 propolar cells+4 metapolar cells+2 parapolar cells+18–20 trunk cells. Infusoriform embryos with 39 cells; refringent bodies solid; and two nuclei present in each urn cell.
Description. Nematogens ( Figs 14a, b View Fig , 15a, c, d View Fig ). Body length 640–1190 µm, width 38–48 µm; widest in region of parapolars; trunk width mostly uniform. Peripheral cell number 28–30 ( Table 2): 4 propolar cells+4 metapolar cells+2 parapolar cells+16–18 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 occupy anterior 30–40% of calotte length when viewed laterally ( Fig. 15c, d View Fig ). Cytoplasm of propolar, metapolar, and parapolar cells contain small granules, more darkly stained by hematoxylin than cytoplasm of other peripheral cells ( Fig. 14a View Fig ). Axial cell cylindrical, rounded anteriorly; cell extending forward to base of metapolar cells ( Fig. 15d View Fig ). About 15 vermiform embryos present per axial cell of large individuals. Accessory nuclei seen in trunk peripheral cells.
Vermiform embryos ( Figs 14c View Fig , 15f, g View Fig ). Full-grown vermiform embryos length 56–105µm, width 12–16 µm. Peripheral cell number 28–30 ( 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 14c View Fig , 15f, g View Fig ). Axial cell of full-grown embryos with one agamete.
Rhombogens ( Figs 14d–f View Fig , 15e View Fig ). Body length similar 285– 650 µm, similar that of nematogens, in length, and width 41–51 µm. Peripheral cell number typically 28–29 ( Table 2). Calotte shape, axial cell shape, and anterior extent similar to those of nematogens. Cytoplasm of propolar cells, metapolar cells, and parapolar cells contains small granules ( Fig. 14d–f View Fig ). A maximum of 2 infusorigens present in the axial cell of each parent individual. About 10 infusoriform embryos present per axial cell of large individuals.
Infusorigens ( Figs 14g View Fig , 15h; n View Fig =20). Mature infusorigens medium-sized, composed of 5–12 (mode 7) external cells (oogonia and primary oocytes)+3–4 (mode 4) internal cells (spermatogonia, primary spermatocytes, and secondary spermatocytes)+2–12 (mode 6) spermatozoa. Mean diameter of fertilized eggs 12.0 µm; that of spermatozoa 2.1 µm. Axial cell ovoid or round, diameter 13–17 µm.
Infusoriform embryos ( Figs 14h, i View Fig , 15i–k; n View Fig =12). Fullgrown embryos large, length 26.5±2.5 µm (mean±SD, excluding cilia); length–width–height ratio 1.0: 0.79: 0.85; 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. 15k View Fig ). Cilia project from ventral internal cells into urn cavity ( Fig. 15k View Fig ). Capsule cells contain small granules ( Figs 14i View Fig , 15k View Fig ). 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. 15k View Fig ). All somatic nuclei pycnotic in mature infusoriform embryos.
Remarks. Dicyema shimaense sp. nov. is the first species of the genus found in Sepia madokai . 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, an acutely pointed calotte of vermiform embryos, and the cell number of infusoriform embryos ( Furuya 2009). However, D. shimaense sp. nov. differs from D. gozaense sp. nov. and D. oxycephalum in the anterior extent of adult vermiform stages (metapolar cells vs. propolar cells). Dicyema shimaense sp. nov. has 28–29 peripheral cells, while D. lorigeroeceum sp. nov. has a variable number of peripheral cells ranging from 26 to 34 ( Table 2).
Etymology. The species name “ shimaense ” refers to the Shima Peninsula type locality, famous for its beautiful landscape in the Ise-Shima National Park at the northern end of the Kumano Sea.
Taxonomic summary. Type material: a syntype slide (NSMT-Me-70) collected on 8 March 2019; additional syntypes on slide series No. SM4024 (5 slides) in the author’s collection.
Type locality: off Kii-Nagashima (34°01′N, 136°37′E), Mie Prefecture, Honshu, the Kumano Sea, Japan, depth 180 m GoogleMaps .
Other materials examined: slide series No. SM3312 (5 slides) collected off Minami-Ise (34°12′N, 136°40′E), Mie Prefecture, Honshu, the Kumano Sea, Japan, depth 200 m, 30 November 2015, in the author’s collection GoogleMaps .
Host: symbiotype, Sepia madokai Adam, 1939 (Mollusca: Cephalopoda: Sepiida ), female (immature), 54 mm ML (NSMT-Mo-85912).
Collector of host: T. Moritaki.
Site : anterior ends (calottes) inserted into crypts of the renal appendages within the renal sacs.
Prevalence: in 5 of 21 host specimens examined (23.8%).
Dicyema tenuipoeceum Furuya , sp. nov. [New Japanese name: Udeboso-nihaichū] ( Figs 16 View Fig , 17 View Fig ; Tables 1–3)
Diagnosis. Small-sized dicyemid, body length reaching 1540 µm. Calotte cap- or disc-shaped. Vermiform stages with 22 peripheral cells: 4 propolar cells+4 metapolar cells+2 parapolar cells+12 trunk cells. Infusoriform embryos with 37 cells; refringent bodies solid; and 2 nuclei present in each urn cell.
Description. Nematogens ( Figs 16a, c, d View Fig , 17a, b View Fig ). Body length 550–1540 µm, width 50–83 µm; widest in region of parapolars; trunk width mostly uniform. Peripheral cell number 22 ( Table 2): 4 propolar cells+4 metapolar cells+ 2 parapolar cells+10 diapolar cells+2 uropolar cells. Calotte cap- or disc-shaped, rounded anteriorly; cilia about 4 µm long, oriented anteriorly. Propolar cells equal to or larger than metapolar cells, their nuclei equal to or smaller than metapolar cell nuclei. Propolar cells occupy anterior 50% of calotte length when viewed laterally ( Fig. 17d View Fig ). Axial cell cylindrical, pointed anteriorly, extending forward to base of propolar cells ( Fig. 17c, d View Fig ). About 15 vermiform embryos present per axial cell of large individuals. Accessory nuclei seen in trunk peripheral cells.
Vermiform embryos ( Figs 16c View Fig , 17e, f View Fig ). Full-grown vermiform embryos length 60–80 µm, 15–16 µm in width. Peripheral cell number 22 ( Table 2); trunk cells arranged in opposed pairs. Anterior end of calotte rounded. Axial cell pointed anteriorly, extending to the base of propolar cells ( Fig. 17f View Fig ). Axial cell of full-grown embryos with 2 agametes.
Rhombogens ( Figs 16d View Fig , 17g View Fig ). Body length 950–1450 µm, similar to that of nematogens, in length and 70–90 µm in width. Peripheral cell number typically 22 ( Table 2). Calotte, axial cell shape and anterior extent similar to nematogens. Maximum of 4 infusorigens present in the axial cell of each parent individual. About 40 infusoriform embryos present per axial cell of large individuals.
Infusorigens ( Figs 16f View Fig , 17h; n View Fig =10). Mature infusorigens medium-sized; composed of 6–14 (mode 8) external cells (oogonia and primary oocytes)+3–6 (mode 3) internal cells (spermatogonia, primary spermatocytes, and secondary spermatocytes)+4–15 (mode 6) spermatozoa. Mean diameter of fertilized eggs 12.8 µm; that of spermatozoa 3.0 µm. Axial cell round or ovoid, diameter 12–15 µm.
Infusoriform embryos ( Figs 16g, h View Fig , 17i–k; n View Fig =20). Fullgrown embryos large, length 26.2±1.5 µm (mean±SD, excluding cilia); length–width–height ratio 1.0: 0.90: 0.88; shape ovoid, and pointed posteriorly; cilia at posterior end 7 µm long. Refringent bodies present, solid, occupying anterior 50–60% of embryo length when viewed laterally ( Fig. 16h View Fig ). Cilia project from ventral internal cells into urn cavity ( Fig. 17k View Fig ). Capsule cells contain small granules ( Figs 16h View Fig , 17k View Fig ). Mature embryos with 37 cells: 33 somatic+4 germinal cells. Somatic cells of several types present: external cells covering large part of anterior and lateral surfaces of embryo (2 enveloping cells); external cells with cilia on external surfaces (2 pairs of 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 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 containing 2 nuclei and a germinal cell ( Fig. 17k View Fig ). All somatic nuclei pycnotic in mature infusoriform embryos.
Remarks. Dicyema tenuipoeceum sp. nov. is similar to D. balamuthi , D. clavatum , D. colurum , D. hadrum , D. japonicum Furuya and Tsuneki, 1992 , and D. schulzianum in the calotte shape of vermiform stages and peripheral cell numbers ( Beneden 1876; McConnaughey 1949; Furuya et al. 1992b; Furuya 1999). However, D. tenuipoeceum sp. nov. is distinguishable from D. balamuthi , D. clavatum , D. colurum , and D. hadrum in the cell number of infusoriform embryos (37 vs. 39). It also shares the same cell number of infusoriform embryos with D. japonicum and D. schulzianum . However, D. tenuipoeceum sp. nov. infusoriform embryos lack anterior lateral cells, which distinguished this species from D. japonicum . Dicyema schulzianum was recorded from Sepia elegans Blainville, 1827 , and Rondeletiola minor (Naef, 1912) in the western Mediterranean ( Beneden 1876; Nouvel 1947). Rhombogens of D. schulzianum have at most two infusorigens, while those of D. tenuipoeceum sp. nov. have four. Thus, D. tenuipoeceum sp. nov. can be distinguished from D. schulzianum in the maximum number of infusorigens and geographical distribution.
Etymology. The species name “ tenuipoeceum ” is composed of the epithet of the host, tenuipes , and the Ancient Greek word oiceon, meaning “inhabiting” in reference to its host.
Taxonomic summary. Type material: a syntype slide (NSMT-Me-62) collected on 10 April 2016; additional syntypes on slide series No. ST3503 (5 slides) in the author’s collection.
Type locality: off Minami-Ise (34°04′N, 136°36′E), Mie Prefecture, Honshu, the Kumano Sea, Japan, depth 260 m GoogleMaps .
Other materials examined: slide series No. ST3763 (5 slide) collected off Owase (34°04′N, 136°33′E), Mie Prefecture, Honshu, the Kumano Sea, Japan, depth 300 m, 22 January 2018, in the author’s collection GoogleMaps .
Host: symbiotype, Sepia tenuipes Sasaki, 1929 (Mollusca: Cephalopoda: Sepiida ), female (mature), 85 mm ML (NSMT-Mo-85905).
Collector of host: T. Moritaki.
Site : anterior ends (calottes) attach to surfaces of the renal appendages within the renal sacs.
Prevalence: in 36 of 91 host specimens examined (39.6%).
Dicyema tympanocephalum Furuya , sp. nov. [New Japanese name: Taiko-nihaichū] ( Figs 18 View Fig , 19 View Fig ; Tables 1–3)
Diagnosis. Small-sized dicyemid, body length reaching 1540 µm. Calotte disc-shaped. Vermiform stages with 22 peripheral cells: 4 propolar cells+4 metapolar cells+2 parapolar cells+12 trunk cells. Infusoriform embryos with 37 cells; refringent bodies solid; and 2 nuclei present in each urn cell.
Description. Nematogens ( Figs 18a, b View Fig , 19a, c, d View Fig ). Body length 450–1420 µm, width 42–105 µm; widest in region of parapolars; trunk width mostly uniform. Peripheral cell number 22 ( Table 2): 4 propolar cells+4 metapolar cells+ 2 parapolar cells+10 diapolar cells+2 uropolar cells. Calotte disc-shaped, rounded anteriorly; cilia about 4 µm long, oriented anteriorly. Propolar cells equal to or larger than metapolar cells, their nuclei equal to or smaller than metapolar cell nuclei. Propolar cells occupy anterior 40–50% of calotte length when viewed laterally ( Fig. 19c View Fig ). Axial cell cylindrical, pointed anteriorly, extending forward to base of propolar cells ( Figs 18b View Fig , 19c View Fig ). About 20 vermiform embryos present per axial cell of large individuals. Accessory nuclei seen in trunk peripheral cells.
Vermiform embryos ( Figs 18d View Fig , 19e, f View Fig ). Full-grown vermiform embryos length 51–79 µm, 12–20 µm in width. Peripheral cell number 22 ( Table 2); trunk cells arranged in opposed pairs. Anterior end of calotte rounded. Axial cell pointed anteriorly, extending to the base of propolar cells ( Fig. 19f View Fig ). Axial cell of full-grown embryos with 2 agametes.
Rhombogens ( Figs 18c View Fig , 19g View Fig ). Body length 550–1380 µm, similar to that of nematogens, in length and 50–95µm in width. Peripheral cell number typically 22 ( Table 2). Calotte, axial cell shape and anterior extent similar to nematogens. Maximum of 2 infusorigens present in the axial cell of each parent individual. About 25 infusoriform embryos present per axial cell of large individuals.
Infusorigens ( Figs 18e View Fig , 19h; n View Fig =20). Mature infusorigens medium-sized; composed of 10–20 (mode 12) external cells (oogonia and primary oocytes)+3–6 (mode 4) internal cells (spermatogonia, primary spermatocytes, and secondary spermatocytes)+3–7 (mode 4) spermatozoa. Mean diameter of fertilized eggs 12.7 µm; that of spermatozoa 2.6 µm. Axial cell round or ovoid, diameter 12–20 µm.
Infusoriform embryos ( Figs 18f, g View Fig , 19i–k; n View Fig =20). Fullgrown embryos large, length 26.7±2.3 µm (mean±SD, excluding cilia); length–width–height ratio 1.0:0.87: 0.84; shape ovoid, pointed posteriorly; cilia at posterior end 7 µm long. Refringent bodies present, solid, occupying anterior 50–60% of embryo length when viewed laterally ( Figs 18f View Fig , 19k View Fig ). Cilia project from ventral internal cells into urn cavity ( Fig. 19k View Fig ). Capsule cells contain small granules ( Figs 18g View Fig , 19k View Fig ). Mature embryos with 37 cells: 33 somatic+4 germinal cells. Somatic cells of several types present: external cells covering large part of anterior and lateral surfaces of embryo (2 enveloping cells); external cells with cilia on external surfaces (2 pairs of 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 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 containing 2 nuclei and a germinal cell ( Fig. 19k View Fig ). All somatic nuclei pycnotic in mature infusoriform embryos.
Remarks. Dicyema tympanocephalum sp. nov. is similar to D. balamuthi , D. clavatum , D. colurum , D. hadrum , D. japonicum , and D. schulzianum , and D. tenuipoeceum sp. nov. in the calotte shape of vermiform stages and peripheral cell numbers ( Beneden 1876; McConnaughey 1949; Furuya et al. 1992a; Furuya 1999). However, D. tympanocephalum sp. nov. is distinguishable from D. balamuthi , D. clavatum , D. colurum , and D. hadrum in the cell number of infusoriform embryos (37 vs. 39).
Dicyema tympanocephalum sp. nov. shares the same cell number of infusoriform embryos with D. japonicum , D. schulzianum , and D. tenuipoeceum sp. nov., but D. tympanocephalum sp. nov. infusoriform embryos have third ventral cells instead of the anterior lateral cells. The rhombogens of D. tympanocephalum sp. nov. have at most two infusorigens, while those of D. tenuipoeceum sp. nov. have four. Therefore, D. tympanocephalum sp. nov. can be distinguishable from D. japonicum and D. tenuipoeceum sp. nov.
Dicyema tympanocephalum sp. nov. is very similar to D. schulzianum in morphological characters except in the maximum size of adult vermiform stages. Large adult individuals of D. tympanocephalum sp. nov. reach nearly 1500 µm in length, while those of D. schulzianum are at most 1000 µm. Dicyema schulzianum is recorded from S. elegans and R. minor in the western Mediterranean ( Beneden 1876; Nouvel 1947). In dicyemids, differences found in host species and geographical distribution represent empirically distinct species. Thus, D. tympanocephalum sp. nov. can be separated confidently from D. schulzianum by differences in the maximum size of adult vermiform stages, host species and geographical distribution.
Etymology. The species name “ tympanocephalum ” is an adjective composed of two Ancient Greek roots, tympa and - kephalos, meaning “drum” and “-headed” in reference to the characteristic anterior part of adult vermiform stages.
Taxonomic summary. Type material: a syntype slide (NSMT-Me-65) 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 GoogleMaps .
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) attach to surfaces of the renal appendages within the renal sacs.
Prevalence: in 1 of 10 host specimens examined (10.0%).
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