"Dicyemennea antarcticensis sp. n.
(Figs. 2-21)
Description
Dicyemennea: Peripheral cell number of vermi-form stages (from counts on vermiform embryos within axial cells of nematogens): usually 34 to 36, less often 31, 32, and 37 (Table I).
Nematogens (Figs. 2, 9, 10): Body narrow, elongate, usually tapering gradually toward the calotte which is relatively small, but noticeably wider than adjoining region of parapolar cells. Lengths of 10 longest nematogens, 2,653 to 5,394 µ. Maximum width of body usually at uropolar region, occasionally at level of posterior diapolars or near midbody; widths of 10 longest specimens, 37 to 100 µ.
No verruciform cells; no conspicuous granules in peripheral cells.
Calotte more or less triangular from side view, pointed to rounded anteriorly; distinctly set off from narrower adjoining region of parapolar cells. Posterolateral edges of metapolar cells separated from parapolars, forming a velumlike extension (Fig. 10). Calotte lengths 15 to 21 µ; ratios of calotte lengths to widths, 1:0.6 to 1:1.0. Propolar cells about equal in length to metapolars; ratios of propolar lengths to metapolar lengths, 1:0.8 to 1:1.9. Base of propolar tier characteristically sur-rounded laterally by anterior edges of metapolars. Nuclei of propolar and metapolar cells usually about equal in size; ratios of diameters 1:0.8 to 1:1.4. Nuclei of propolar and metapolar cells often pycnotic, with one to few large clumps of chroma-tin (Figs. 9, 10).
Parapolar cells of medium to large individuals usually about 3 to 4 times the length of calotte; ratios of calotte lengths to parapolar lengths, 1:2.1 to 1:7.0 (19 calottes, 38 parapolars). Parapolar cells with characteristic striations of an undeter-mined nature in the cytoplasm (Fig. 10), tapering anteriorly, extending into calotte, and ending in a point between bases of propolar cells or near their midlevel.
Axial cell of medium to large nematogens ending anteriorly in a point, sometimes very sharp; not reaching calotte, but ending between the posterior ends of parapolar cells or slightly posterior to parapolars.
Stem nematogens: None seen.
Vermiform embryos (Figs. 3-8): Body of full-grown embryos relatively thin and elongate; calotte more or less pointed anteriorly and wider than adjacent region of parapolar cells; posterolateral edges of metapolars typically separated from para-polar cells (Figs. 3, 4C). Measurements of 20 longest embryos within axial cells of parent nematogens: lengths, 217 to 341 µ; widths, 15 to 31 µ; ratios of body lengths to body widths, 1:0.1; calotte lengths, 9 to 32 µ; ratios of calotte lengths to calotte widths, 1:0.6 to 1:1.0; ratios of calotte lengths to total body lengths, 1:10.3 to 1:16.2.
Trunk cells arranged apparently in opposed pairs or whorls of 4.
Parapolar cells unusually large in comparison with trunk cells, especially in younger embryos (Figs. 5, 6); parapolar cells of older embryos pointed anteriorly and extending to propolar cells, sometimes to halfway between their bases and tips. Axial cell in younger embryos (Figs. 5, 7, 8) extending well into calotte, reaching propolar cells; in older individuals axial cell ending posterior to calotte, at the level of the parapolar cells (Figs. 3, 4C). Nucleus of axial cell generally near the cell's middle. Number of axoblasts of largest embryos variable; in 10 longest embryos within parent axial cells: 5 had 8 axoblasts (4 on each side of axial cell nucleus, Fig. 4C); 1 had 4 axoblasts (2 on each side of axial cell nucleus); 2 had 7 axo-blasts (4 on one side of axial cell nucleus, 3 on the other); and 2 had 15 axoblasts (8 on one side of axial cell nucleus, 7 on the other, Fig. 3). Axo-blasts more or less fusiform.
An anterior abortive axial cell present in smaller embryos (Figs. 5, 7), absent in larger ones (Fig. 4C).
Rhombogens (Figs. 11-13): Similar in general shape and size to nematogens. Length of 10 longest individuals, 2,214 to 4,199 µ; lengths of 10 shortest rhombogens with mature infusorigens, 570 to 1,125 µ. Widths of 10 longest rhombogens, 59 to 119 µ. Accessory nuclei numerous in diapolar and uropolar cells. No verruciform cells, no conspicuous granules in peripheral cells. Calottes similar in shape to those of nematogens, lengths of 20 calottes (small to large individuals), 15 to 23 µ; ratios of calotte lengths to widths, 1:0.8 to 1:1.1. Ratios of lengths of propolar cells to metapolars, 1:0.7 to 1:1.1. Ratios of nuclear diameters, propolar to metapolar, 1:1.0 to 1:1.5. Nuclei tending to be pycnotic as in nematogens.
Parapolar cells generally similar in size and pro-portions to those of nematogens. Ratios of calotte lengths to parapolar lengths, 1:3.7 to 1:6.8 (20 calottes, 20 parapolars of small to large rhom-bogens). Parapolars extending anteriorly into ca-lotte and with striations (Fig. 12) as in nematogens. Axial cell not extending to calotte, ending ante-riorly near midlevel of parapolar cells, between bases of parapolar cells, or sometimes more pos-teriorly.
Infusorigens (Fig. 14): With relatively few cells. In 25 mature infusorigens: number of oogonia and oocytes usually 5 to 10 (range, 3 to 17; mode, 10); number of spermatogonia and spermatocytes usually 3 or 4 (range, 1 to 4).
Infusoriform larvae (Figs. 15-21): Ovoid. Dimensions (excluding cilia) of apparently full-grown specimens within axial cells of rhombogens: lengths of 50 larvae, 51 µ (42 to 65); widths of 25 larvae, 38 µ (32 to 45); depths. of 25 larvae, 35 µ (31 to 46).
Refringent bodies present, solid, appearing about equal in size to urn contents in dorsal view and slightly larger in lateral view; one or more satellite refringent bodies (Figs. 20, 21) seen rather frequently in formalin-seawater preparations.
Composed typically of 39 cells: 35 somatic, 4 germinal. Cell counts on 21 larvae: 17 with 39 cells, 3 with 40 cells, 1 with 42 cells. Each of 4 urn cells typically containing 2 nuclei and 1 germinal cell [i.e., um cell formula is 4 (2 + 1)]. Ventral internal cells bearing cilia of urn cavity. Generally similar to infusoriform of Dicyema aegira (see Short and Damian, 1966) in distribution of cells as well as total numbers.
Host: Pareledone turqueti (Joubin, 1905).
The above description is based on material from 3 hosts of this species (744, 993, and 1002). Other octopod hosts infected with D. antarcticensis are 998 and 1001, which have been determined to date as Pareledone sp., and 821, which has not yet been determined.
Localities: All near the Antarctic Peninsula (Fig. 1).
Host 744: At 101 m depth, 62°01.7' lat S, 59°04.7' long W; Station 445, Eltanin cruise 6 (12, 13 January 1963).
Host 821: At 769 m depth, 61°44.3' lat S, 55°56.1' long W; Station 997 Eltanin cruise 12 (14 March 1964).
The following hosts were taken on the 1965-66 cruise of the Eastwind.
Host 993: At 144 m depth, 64°30.0' lat S, 56°57.0' long W (15 February 1966).
Host 998: At 99 m depth, 61°11.8' lat S, 54°44.0' long W (17 February 1966).
Host 1001: At 180 m depth, 61°14.8' lat S, 54°48.0' long W (17 February 1966).
Host 1002: At 720 m depth, 61°20.2' lat S, 55°01.0' long W (17 February 1966).
Syntypes: On slides 993-13 and 1002-4 (USNM Nos. 24073 and 24074), other slides of the 993 and 1002 series, and also slides of the 744 series (authors' collections).”
(Short & Hochberg, 1970)
