Bratislavia dadayi ( Michaelsen 1905 ), 2002

Gusakov, Vladimir A. & Sylaieva, Anzhelika A., 2019, Bratislavia dadayi (Michaelsen 1905) (Annelida, Clitellata, Naididae): discovery of an alien oligochaete in a technogenic fresh water body in Ukraine, Zootaxa 4711 (2), pp. 349-365 : 351-352

Bratislavia dadayi ( Michaelsen 1905)

Naidium (Nais?) dadayi Michaelsen 1905: 355–357 .

Pristina unidentata Harman 1973: 161–163 , Fig. 2 .

Bratislavia unidentata Harman & Loden 1978: 541–544 , Fig. 1 .

Bratislavia dadayi ( Michaelsen 1905) Righi & Hamoui 2002: 124–125 .

Material examined. 117 specimens: 106 sexually immature and 11 mature with developed clitellum. All these are single worms without indications of asexual reproduction.

Material storage. Three sexually mature, one premature and 12 immature individuals are deposited in the collection of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg), with slide inventory number 1/48235. Further specimens are stored in the Laboratory of Ecology of Aquatic Invertebrates of the Papanin Institute for Biology of Inland Waters of the Russian Academy of Sciences (Borok, Yaroslavl Province): four slides named “ Bratislavia dadayi (KhNPP: 2015, 2017)”, No 1–4.

Description. Medium-sized naidids without eyes, proboscis and stomachal dilation ( Fig. 2 A–C). Complete immature individuals with 17–53 segments, body length 1.2–3.7 mm and maximum diameter 162–293 μm (usually in segments X–XVII). Sexually mature individuals with 38–71 segments, body length 3.2–5.2 mm and maximum diameter 278–376 μm (in the clitellum zone). The body ends with a short, undifferentiated pygidium ( Fig. 2A ). Integument rough, slightly wrinkled, with visually smooth, numerous, irregular and relatively shallow transverse grooves ( Fig. 2D,E ).

Dorsal chaetae normally from segment II ( Fig. 2B ). As a rule, each dorsal bundle with one needle and one hair chaeta. Occasionally, individual bundles (at different parts of body) with two needles (5 occurrences in the studied material) and hairs (one occurrence) ( Fig. 3 A–C). In some specimens hairs or hairs and needles lacking in several anterior and/or posterior segments. Hairs missing anteriorly most frequently in II–III ( Fig. 2B ), more rarely in II (10 worms), II–IV (6), II–V (4), IV–V (one) or V (one), or hairs present in all segments, including II (one specimen). In a single examined immature worm the dorsal chaetae start from III, and in two, they start from VI. Posteriorly, the hairs and needles are often missing in the last 1–8 and 1–3 segments, respectively.

Hair chaetae visually smooth (occasionally with a barely noticeable serration on their convex side when observed by DIC-contrast at magnification of 900– 1500x), relatively thin and short, about 1.4–2.0 μm in width (proxi- mally) and 58–139 μm in length; shorter in some anterior segments as well as in posterior ones, longest in the front half to middle of the body. Chaetae always shorter than corresponding body diameter ( Fig. 2A,B , 3 A–C). Needle chaetae stout, simple-pointed, with a distal nodulus and more or less pronounced sickle-shaped curvature in the upper part; maximum width 2.5–3.4 μm, length 30–66 μm. Usually, smallest needles in the first 2–3 segments; be- ginning from IV–VII, length rapidly increasing to the mean-maximum values, and again decreasing in the posterior body zone (though not to the minimum lengths) ( Fig. 2B , 3 A–C).

Ventral chaetae bifid (except penial chaetae), s-shaped, curvature less pronounced in segments II–V than in the rest. In II–V they also distinctly longer and slightly thinner, 3–4 per bundle, ranging from 2.7–4.0 μm in width and 84–111 μm in length, with a proximal nodulus and upper teeth somewhat thinner and about twice as long as lower ( Figs. 2B,C , 3D ). From VI, chaetae with distal nodulus, 3.0–4.3 μm in width and 54–74 μm in length (shortest usu- ally at body end), commonly 3–4 per bundle, but posteriorly sometimes 1–2 per bundle, or none at all in the last 1–3 segments; upper teeth thinner and markedly shorter than lower ( Figs. 2D , 3E ), except in or near VI–VIII, where both teeth are nearly equal in length.

Sexually mature worms with clitellum from the middle of segment V to the border between VII–VIII ( Fig. 2C ). Most elements of the reproductive system (spermathecae, testes, ovaries, etc.) are not clearly visible on our mounts due to the poorly transparent, glandular tissues of the clitellum ( Fig. 3F,G ). Only large sperm sacs (extending up to IX–X in some specimens) and, commonly, penial chaetae are clearly discernible. The latter are in VI, 2–4 per bundle, with distal nodulus, 3.5–4.1 μm in width and 82–92 μm in length. They are almost straight, except for the hooked tip, and generally simple-pointed. In one case bifid tips with small, weakly differentiated teeth were observed ( Figs. 2C , 3 H–J).

Figures

FIGURE 1. Location of the studied water area, and sampling points (S1, S2) where Bratislavia dadayi (Michaelsen 1905) was found.

FIGURE 2. Bratislavia dadayi (Michaelsen 1905) from the Ukrainian population. A. Entire body of an immature individual, lateral view. B. Anterior body part of an immature individual, lateral view. C. Anterior body part of a mature individual, ventral view. D. Integument, ventral view. E. Integument, lateral view.

FIGURE 3. Bratislavia dadayi (Michaelsen 1905) from the Ukrainian population. A. Typical dorsal bundles with single needle and hair chaetae (XXI–XXII segments). B. A dorsal bundle with two needles. C. Dorsal bundle with two needle and two hair (normal and short) chaetae. D. A bundle of anterior ventral chaetae (IV segment). E. Typical bundles of ventral chaetae in posterior body part (XXI–XXIII segments). F. Clitellum, general view. G. Surface of clitellum. H. A bundle of penial chaetae. I. Bundles of penial chaetae with pair of bifid ones. J. Tips of the bifid penial chaetae.