Manayunkia godlewskii ( Nusbaum, 1901 )

Bick, Andreas & Bastrop, Ralf, 2025, Revision of the genus Manayunkia Leidy, 1859, and establishment of two subfamilies within Fabriciidae (Annelida, Sabellida), Zootaxa 5661 (1), pp. 1-58 : 31-33

Manayunkia godlewskii ( Nusbaum, 1901)

( Figures 17–18 )

Dybowscella godlewskii Nusbaum, 1901: 16–18 . – Dybowski 1929: 461–463.

Garjaiewella godlewskii Dybowski, 1929: 485–486 .

Trichosobranchella novobaicalensis major Dybowski, 1929: 463–474 , 484–485.

Manayunkia godlewskii . – Zenkevitsch 1925: 34–36. – Sitnikova et al. 1997: 23–24, fig. 1, 2, 4, 7–10. – Pudovkina et al. 2016: 132–136.

Material examined. Russia, Lake Baikal : 53°07.173’N, 109°04.289’E, depth 35–40 m, coll. 24.07.2006, 15 specimens ( ZSRO-P1942 ) .

Description (based on the description of Nusbaum (1901), Dybowski (1929), Sitnikova et al. (1997) and own observations). Total length of specimens, including radiolar crown, between 9 and 16 mm (on average about 10 mm long); width about 0.4–1.6 mm; (on average about 0.9 mm); length of radiolar crown between 0.5 and 1.7 mm (on average 1.2 mm); ratio between length of radiolar crown and body length, without radiolar crown, between 0.06 and 0.2; body slender, posteriorly tapered ( Fig. 17B ).

Radiolar crown with three pairs of radioles and one pair of unbranched vascularized ventral filamentous appendages; surface of radioles and ventral filamentous appendages wrinkled ( Fig. 17A ); dorsal radioles unbranched, median and ventral radioles with large number of branches, usually 2 (or more?) branches arise from a common base, so that the branches appear to be arranged in two rows; radiolar crown with 72–104 branches in total (on average about 80); ventral filamentous appendages and almost all branches of the radioles end at about the same height, dorsal radioles sometimes slightly shorter ( Fig. 17A ).

Peristomium distinctly longer than the first chaetiger, with anterior and posterior rings; anterior margin of anterior peristomial ring developed as low membranous collar ventrally, indented laterally, and narrowly separated mid-dorsally; border between anterior and posterior peristomial rings clearly visible ( Fig. 17A ); one pair of black peristomial eyes present.

Chaetigers 1–5 or 6 successively longer, chaetigers 7 and 8 successively shorter; abdomen about as long as chaetiger 3 or 4; margins of chaetigers 6–8 often not clearly visible in adult specimens.

Thoracic notopodia with rounded or triangular prechaetal lobes ( Figs 17C, E, F , 18B ); first chaetiger inferiorly with 5–7 short, and superiorly with 6–10 elongate, narrowly hooded notochaetae, neuropodial uncini absent; notopodia of chaetigers 2–8 posteriorly with about 12–16 elongate, narrowly hooded chaetae, about 1–1.2 mm long, and anteriorly with about 10–12 short, narrowly hooded chaetae ( Fig. 17C, E, F ); neuropodia of chaetigers 2–8 (males) or 2–5 (females) with 5–12 (on average 8) uncini, about 0.36 mm long, with main fang and apical with about 5–6 rows of progressively smaller teeth ( Fig. 17D ); neuropodia of females with 5–8 transitional chaetae on chaetigers 6–8 ( Fig. 17F ); abdominal neuropodia with 5–8 narrowly hooded chaetae; abdominal notopodia with about 20–42 uncini, about 0.15 mm long, dentate region with about 5–6 rows of equal-sized teeth, about 4–6 teeth per row ( Fig. 17G, H ); dentate region about 10–14 µm long.

Brood chamber of females formed by bulge-like protrusions ventrally on chaetigers 6 and 8 ( Fig. 18A, B ).

Pygidium triangular, pointed, but not elongated ( Figs 17B , 18A ).

Anterior chaetigers with little pigment, blood greenish.

Remarks. In addition to the very short original description of M. godlewskii by Nusbaum (1901), there are detailed descriptions by Zenkevitsch (1925) and Dybowski (1929). However, these descriptions can only be used with some reservations. As Zenkevitsch (1925) synonymised M. godlewskii with M. baicalensis , the characters of both species are therefore obviously mixed. Dybowski (1929) also did not separate the two species. It is possible that these descriptions also include characters of M. zenkewitschii . This species was first described by Sitnikova et al. (1997). However, Sitnikova et al. (1997) were also able to show that M. godlewskii and M. baicalensis differ morphologically. Manayunkia godlewskii is much less pigmented than M. baicalensis , it is larger and has significantly more branches of the radiolar crown, and this species colonises muddy bottoms, in contrast to M. baicalensis , which prefers sandy substrates. Pudovkina et al. (2016) confirmed the separation of both species by using genetic methods.

With a length of up to 16 mm, M. godlewskii is by far the largest species of the genus. Only M. baicalensis , with a length of up to 8 mm, is also significantly larger than the other Manayunkia species.

Manayunkia godlewskii is the only species of Manayunkia in which the thoracic notopodia have prechaetal lobes. It is possible that the significantly greater length of this species compared to the related species requires such a structure. Similar lobes are found, for example, in species of Sabellidae (cf. Bick & Randel 2012).

The number of branches of the median and ventral radioles is comparatively high, at least in comparison to most of the smaller species. This is explained by the fact that immediately after branching, the branches divide further, so that 2 or even more branches branch off from a common base. Zenkevitsch (1925) and Sitnikova et al. (1997) then concluded that the branches of the tentacle crown are arranged in two rows.

Manayunkia godlewskii is characterised in particular by a triangular but not elongated pygidium. The pygidium of the other two species from Lake Baikal is either elongated and pointed or oval. In addition, the pigment is almost completely absent or at most present on first two chaetigers. In M. baicalensis the first 6 chaetigers are distinctly pigmented, and in M. zenkewitschii all chaetigers are pigmented.

There is a sexual dimorphism in this species. Mature females have transitional chaetae on neuropodia of chaetigers 6–8 instead of regular thoracic uncini. A brood chamber, which is formed by bulge-like protrusions ventrally on chaetigers 6 and 8, is also present in females. These characters are also found in M. baicalensis ( Zenkevitsch 1925) and M. zenkewitschii ( Sitnikova et al. 1997) . Zenkevitsch (1925) also stated that the number of thoracic chaetae and thoracic and abdominal uncini differ between males and females. Males have more chaetae and uncini than females. We did not have enough material to confirm this. However, the number of thoracic and abdominal uncini is significantly lower in smaller individuals. Specimens with a length of about 2 mm have only about 2–4 thoracic uncini, and 11–15 abdominal uncini on chaetiger 9, 8-–12 on chaetiger 10 and 6–10 on chaetiger 11.

Geographic distribution. Known from Russia, Lake Baikal and probably from Lake Baunt, which is located about 200 km east of Lake Baikal.

Biology. The reproduction period is in September and October. However, some females with embryos in the tube have also been found in November and December. In some years, reproduction has also taken place at the end of March/beginning of April. The eggs are between 350 and 425 µm long and 270 and 300 µm wide. The maximum number of eggs and embryos in the tube was 48 ( Sitnikova et al. 1997).

Ecology. Manayunkia godlewskii occurs throughout Lake Baikal. It inhabits mainly muddy bottoms with detritus, muddy sand, but also pebbles and rocky areas. The depth distribution ranges from about 3 to 80 m.

Figures

FIGURE 17. Manayunkia godlewskii (Nusbaum, 1901), SEM micrographs. A. Anterior end, dorso-lateral view. B. Posterior end, lateral view. C. Notopodium of chaetiger 2. D. Thoracic uncini of chaetiger 2. E. Parapodium of chaetiger 3. F. Parapodium of chaetiger 6, with transitional chaetae in the position of thoracic uncini. G, H. Frontal view of abdominal uncini. Scale bars. A, B 200 µm, C, E, F 100 µm, D 10 µm, G, H 5 µm.

FIGURE 18. Manayunkia godlewskii (Nusbaum, 1901), SEM micrographs.A. Posterior end of female with bulge-like protrusion on chaetigers 6 and 8, ventral view. B. Posterior end of chaetiger 6 in a female with bulge-like protrusion. Scale bars.A 200 µm, B 100 µm.