Redescription of Cytherissa pennata Mazepova 1990 and Cytherissa latirecta Mazepova 1985 (Ostracoda, Podocopida, Cytherideidae) from Lake Baikal

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Resumo

Illustrated redescription of females and males of two rare species of the genus Cytherissa Sars 1925, both endemic to Lake Baikal, Siberia, are provided: Cytherissa pennata Mazepova 1990 and Cytherissa latirecta Mazepova 1985. The work was carried out on the basis of syntypes from the type collection of G. F. Mazepova, lectotypes and paralectotypes being designated. The shell morphology of these species was studied in detail using scanning electron microscopy. The limb structure of both species is described in detail, and the ecology is briefly characterised. Using these two endemic species with different shell morphology as examples, the interspecific differences of Baikalian Cytherissa are shown to not be limited to shell structure. The transformed (geniculate) legs of males of C. pennata are located on the right side of the body, vs on the left side in C. latirecta; and in C. pennata the hinge teeth are on the right valve, vs on the left valve in C. latirecta. As a result, both these species belong to different lineages of Baikalian Cytherissa. In addition, the limb structure of C. pennata shows fusion of the two distal segments of both legs L5 in both sexes, vs the segments are clearly separated in C. latirecta. Taking four species (C. pennata, C. latirecta, Cytherissa sp. 1 and Cytherissa sp. 2) as examples, the structural differences in the hemipenises and brush organs of males are considered: they differ in size, the length to width ratio and some other characters. The distal segment of the transformed L6 of males in four different species is shown to have structural features peculiar to each species. These features may well be considered species-specific.

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Sobre autores

T. Alekseeva

Limnological Institute, Russian Academy of Sciences

Autor responsável pela correspondência
Email: atm171@mail.ru
Rússia, Irkutsk, 664033

R. Krivorotkin

Limnological Institute, Russian Academy of Sciences

Email: atm171@mail.ru
Rússia, Irkutsk, 664033

O. Timoshkin

Limnological Institute, Russian Academy of Sciences

Email: atm171@mail.ru
Rússia, Irkutsk, 664033

Bibliografia

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  2. Бронштейн З. С., 1930. К познанию фауны Ostracoda озера Байкал // Труды Комиссии по изучению оз. Байкал. Т. 3. С. 117–157.
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2. Fig. 1. Cytherissa pennata Mazepova 1990, schematic drawings of shells (A, B, G, H) and individual valves (C–F, I–L) of females (A–F) and males (G–L): A, G – dorsal; B, H – ventral; C, I–LV laterally, from the outer side; D, J – RV laterally, from the outer side; E, K – LV laterally, from the inner side; F, L – RV laterally, from the inner side. From here on in the figures, arrows indicate the anterior end of the body, unless otherwise indicated. Scale bar is 1000 µm.

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3. Fig. 2. Cytherissa pennata Mazepova 1990, SEM photographs of shells (A–D) and individual valves (E, F) of females: A – dorsal; B – ventral; C, D – laterally, from the outer side; E – LV laterally, from the inner side; F – RV laterally, from the inner side. Scale bar 500 µm.

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4. Fig. 3. Cytherissa pennata Mazepova 1990, SEM photographs of shells (A–D) and separate valves (E, F) of males: A – dorsally; B – ventrally; C, D – laterally, from the outer side; E – LV laterally, from the inner side; F – RV laterally, from the inner side. Scale bar 500 µm.

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5. Fig. 4. Cytherissa pennata Mazepova 1990, SEM photographs of some morphological structures of females (A–D) and males (E, F): A – posterior end of RV, laterally; B – anterior end of RV, laterally; C – semicircular process of RV, lateral view; D – oral appendages; E – arrangement of appendages and hemipenis in LV (RV is retracted), F – hemipenis. Scale bar, µm: A–D – 100; E – 500; F – 200.

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6. Fig. 5. Cytherissa pennata Mazepova 1990, drawings of female oral appendages: A – Md from the outside; B – gnathobase of Md, ventral view; C – palpa of Md, from the inside; D – Mxl (setae not plumose); E – palpa of Mxl; F – first endite of Mxl; G – diagram of setae insertion at the distal end of the first endite of Mxl, ventral view; H – second endite of Mxl; I – diagram of setae insertion at the distal end of the second endite of Mxl; J – third endite of Mxl; K – diagram of the insertion of setae at the distal end of the third endite of Mxl. In D, the lines separate the tips of the setae of the palp and each of the endites. Scale, µm: A, D – 200; B, C, E–K – 100.

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7. Fig. 6. Cytherissa pennata Mazepova 1990, drawings A1 (B) and A2 (A) of the female. The exopodite A2 with the seta is separated from A2, the blue arrow indicates the place of its insertion. Scale is 200 µm.

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8. Fig. 7. Cytherissa pennata Mazepova 1990, drawings of the limbs of the female (A–C) and male (D–J): A – L5; B – L6; C–L7; D – L5, left; E – L5, right (transformed); F – L6, left; G – L6, right (transformed); H – distal segment of right (transformed) L6; I–L7, left; J – brush-like organ. Scale bar 200 µm.

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9. Fig. 8. Cytherissa pennata Mazepova 1990, SEM photographs of juvenile shells at different stages of development: A–F – dorsal. Scale bar 500 µm.

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10. Fig. 9. Cytherissa latirecta Mazepova 1985, drawings of shells (A–D, I–L) and individual valves (E–H, M–P) of females (A–H) and males (I–P): A, I – dorsal; B, J – ventral; C, D, K, L – laterally; E, M – RV laterally, from the inner side; F, N – LV laterally, from the inner side; G, O – LV laterally, from the outer side; H, P – RV laterally, from the outer side. Scale bar 400 µm.

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11. Fig. 10. Cytherissa latirecta Mazepova 1985, SEM photographs of shells (A–D) and individual valves (E, F) of females: A, B – laterally, from the outer side; C – ventral; D – dorsally; E – LV laterally, from the inner side; F – RV laterally, from the inner side. Scale bar 400 µm.

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12. Fig. 11. Cytherissa latirecta Mazepova 1985, SEM photographs of the shell (A–D) and individual valves (E, F) of males: A, B – laterally, from the outer side; C – ventrally; D – dorsally; E – LV laterally, from the inner side; F – RV laterally, from the inner side. Scale bar 400 µm.

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13. Fig. 12. Cytherissa latirecta Mazepova 1985, SEM photographs of parts of the shells (A–D) and hemipenes (E, F) of males: A – posterior end of RV, lateral; B – anterior end of RV, lateral; C – microrelief in the central part; D – ventral, anterior end of the body; E, F – lateral. Scale bar 100 µm.

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14. Fig. 13. Cytherissa latirecta Mazepova 1985, SEM photographs of the hinge on the valves of females, laterally from the inner side: A – LV, hinge teeth and opening for the roller; B – RV, openings for hinge teeth and roller; C–LV, anterior hinge tooth; D – RV, opening for the anterior hinge tooth; E – LV, posterior hinge tooth; F – RV, opening for the posterior hinge tooth. Scale bar, µm: A, B – 200; C–F – 100.

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15. Fig. 14. Photomicrographs of male hemipenises of different species of the genus Cytherissa from Lake Baikal: A – Cytherissa pennata Mazepova 1990; B – Cytherissa sp. 1; C – Cytherissa latirecta Mazepova 1985; D – Cytherissa sp. 2. Scale bar 200 µm.

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16. Fig. 15. Schematic drawings of the transformed L6 of males (A–C) and brush-like organs (D–F), photomicrographs of the distal segments of L5 of males: A, D, G – Cytherissa pennata Mazepova 1990; B, E, H – Cytherissa latirecta Mazepova 1985; C – Cytherissa sp. 1; F – Cytherissa sp. 2. In A–F the details are not drawn; in G and H the arrows indicate the area where the segments are fused in C. pennata, while in C. latirecta there is a distinct separation of the segments. Scale bar 100 µm.

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