Manayunkia speciosa Leidy, 1859

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 : 37-40

Manayunkia speciosa Leidy, 1859

( Figures 1 and 21 )

Manayunkia speciosa Leidy, 1859: 90 . – Leidy 1883: 204–212, pl. 9, fig. 1–13. – Potts 1884: 21–22. – Foulke 1884: 303–304.

– Zenkevitsch 1925: 36–38. – Meehan 1929: 479–480. – Pettibone 1953: 149–153, fig. 1. – Hiltunen 1965: 183–185.

– Wilson 1965: 175–176. – Schloesser et al. 2016: 1072–1082, fig. 2–9. Manayunkia eriensis, Krecker 1939: 153–154 .? Manayunkia speciosa . – Holmquist 1967: 297–302, fig. 1. 1973: 497–507, fig. 1–5. Not: Manayunkia speciosa . – Armendáriz et al. 2011: 282–283. – Armendáriz et al. 2012: 81–84, fig. 4,5. – Hazel 1966: 533–

535, fig. 1. – Paola et al. 2013: 523–527, fig. 2,3. – Verner 1981: 182–183. – Wilson et al. 2010: 183–191, fig. 2.

Material examined. USA, North Carolina, Lake Norman, 35°26’N, 80°56’W, coll. 6. or 7.10.1981, 7 specimens ( USNM 68726 ); Western Lake Erie , coll. 1963, 137 specimens ( USNM 31015 ) .

Description (based on the descriptions of Leidy (1883), Potts (1884), Pettibone (1953), Atkinson et al. (2020) and own observations). Total length of specimens about 2.5–4.9 mm, width about 0.25–0.3 mm; length of radiolar crown about 0.4–0.8 mm; ratio between length of radiolar crown and body length, without radiolar crown, about 0.2–0.3. Body cylindrical, posteriorly rounded ( Figs 1.1 , 21A–C ).

Radiolar crown with three pairs of radioles and one pair of unbranched vascularized ventral filamentous appendages; dorsal radioles unbranched, median and ventral radioles with a maximum of 10 branches each in adults but lower in juveniles; vascularized ventral filamentous appendages slightly wider and longer than radioles ( Figs 1.1 , 21A, B ).

Metanephridium in peristomium and chaetigers 1–2 ( Fig. 1.1 ). Peristomium about as long as wide, with anterior and posterior rings; anterior ring distinctly shorter than posterior ring; anterior margin of anterior peristomial ring developed as low membranous collar ventrally, narrowly separated mid-dorsally; border between anterior and posterior peristomial rings indistinct; with one pair of black rounded peristomial eyes ( Figs 1.1 , 21A, B ).

Chaetigers 1 to 5 almost same length or successively longer, chaetigers 6 and 7 longest, chaetiger 8 shorter again; first 5 thoracic chaetigers wider than long, last 3 thoracic chaetigers distinctly longer than wide; abdomen, including pygidium, as long as chaetiger 8, often separated from thorax by a widening at chaetiger 9 ( Fig. 21A, C ); chaetigers 9 to 11 successively shorter; borders between thoracic chaetigers usually visible and between abdominal chaetigers indistinct; pygidium as long as chaetiger 10 ( Figs 1.1 , 20A, C ).

Thoracic notopodia with about 4–6 elongate, and about 2–4 short, narrowly hooded chaetae, length of chaetae 100–250 µm ( Figs 1.3, 1.4 , 21D–G ); thoracic neuropodia of males with 2–4 (sometimes 5) uncini, neuropodia of females with same uncini on chaetigers 2–5, followed by transitional chaetae on chaetigers 6–8; thoracic uncini about 50–60 µm long, with main fang and apical with about 5–6 rows of progressively smaller teeth ( Figs 1.5 , 21I ); abdominal neuropodia with elongate, narrowly hooded chaetae, decreasing posteriorly from 5–7 to 2–4 per fascicle ( Fig. 21H ); abdominal notopodia with about 20–24 (max. 30) uncini on chaetiger 9, 16–18 on chaetiger 10, and 12–14 on chaetiger 11; abdominal uncini about 20–30 µm long, with about 5–7 rows of equal-sized teeth, and about 4–6 teeth per row ( Figs 1.6, 1.7 , 21J ).

Pygidium short and rounded ( Figs 1.1 , 21A, C ).

Body wall translucent olive-green, radioles with minor brown pigmentation; base of radioles with 6–10 brownish pigment spots ( Fig. 1.1 ); spots not visible when preserved.

Remarks. Manayunkia speciosa most closely resembles M. occidentalis . For the differences between these two species, see the Remarks in M. occidentalis . Females and males differ in the presence or absence of transitional chaetae on segments 6–8, as already described by Atkinson et al. (2020).

Leidy (1883) described and illustrated the occurrence of an expansion at the beginning of chaetiger 6 ( Fig. 1.1 ), which he interpreted as the possible beginning of paratomy (transverse division with head formation). Zenkevitsch (1925) already referred to this structure and its possible function as a brood chamber in this species when he described a brood chamber in M. baicalensis ( Nusbaum, 1901) .

Pettibone (1953) also described a thickened semicircular band on the ventral side of the anterior part of chaetiger 6, and mentioned Zenkevitsch's (1925) assumption that it could be part of a brood chamber. Holmquist (1973), on the other hand, found no evidence of a brood chamber in specimens from Alaska. In the material available to us from North Carolina (from October) and from Western Lake Erie (without any exact date of collection) we also did not find any indication of a brood chamber in females.

The occurrence of Manayunkia speciosa has been documented from several regions of North America. However, it has been shown that the specimens found in the north-west of the United States, far from the type locality in the eastern part of the USA, belong to a different species. This species has been described as M. occidentalis (see Remarks in M. occidentalis ). It would also be interesting to know whether the individuals from the southern states of the USA, e.g. North Carolina, really belong to M. speciosa and whether there is a genetic difference between these specimens and those from the north-east of the USA. It can be also assumed that the specimens found in freshwater lakes of northern Alaska, which were recorded by Holmquist (1967, 1973) and labelled as M. speciosa , must be assigned to another, undescribed species.

Geographic distribution. Northeastern United States: Pennsylvania, New Jersey, North Carolina , Great Lakes, northern Alaska (?).

Biology. Abundances of more than 45,000 specimens per square meter have been reported for M. speciosa in the mouth of the Detroit River, western Lake Erie ( Hiltunen 1965). Males have sperm and spermatids in chaetigers 6–8. Eggs develop in females in chaetiger 4. The oviduct opens between the 4th and 5th chaetiger. Eggs are oval, and have a length of 0.135 mm and a width of 0.095 mm ( Meehean 1929). The eggs are laid in the tube, where they develop into young worms that leave the tube with 8 to 9 chaetigers ( Fig. 1.8–1.13 ). The reproduction of this species was described by Schloesser et al. (2016). According to these authors, mature specimens were found from April to October. The sex ratio was approximately 1:1 on average, but with a higher proportion of males (72%) in April and a higher proportion of females in October (80%). This means that males become sexually mature earlier than females, and females remain mature longer than males. Reproduction is continuous from May to September, but a first peak recruitment occurs between late June and mid-July and second peak in early September. But in October, females with eggs and males with sperm were still found in North Carolina (own observation). The mean number of larvae found in the tubes of females is approximately 5, and the maximum number is 20. Schloesser et al. (2016) assumed a minimum life span of approximately 10 months for this species.

Mechanical disturbances or lack of oxygen result in an exit from their tubes or deep withdrawal. When they left their tubes, they often took with juveniles as well. Schloesser et al. (2016) concluded from their observations from western Lake Erie that a large proportion of individuals occur outside of their tubes most of the time during warmer months and that their tubes are not maintained in colder months.

Manayunkia speciosa was long confused with M. occidentalis . However, only M. occidentalis is an obligate intermediate host for myxozoan parasites, but not M. speciosa , which has long been incorrectly described as an intermediate host (see Remarks on biology of M. occidentalis ).

Ecology. Tubes composed of mud or fine particles, attached partly along their length to fixed objects but the greater part free, pendant. According to Leidy (1883), most of the tubes of M. speciosa occur as single tubes, but two to five tubes connected together have been found in some cases ( Fig. 1.2 ).

Figures

FIGURE 1. Manayunkia speciosa Leidy, 1859. Original plate of external and internal morphologies and development of larvae (Fig. 1–13) by Leidy (1883).

FIGURE 20. Manayunkia occidentalis (Atkinson, Bartholomew & Rouse, 2020), SEM micrographs. A. Complete specimen without radiolar crown, dorsal view. B. Two branches of radiolar crown with short median and long latero-frontal cilia. C. Anterior end, lateral view. D. Notopodium of chaetiger 5 with short, and elongate, narrowly hooded chaetae. E. Thoracic chaetae of chaetiger 1. F. Notopodium of chaetiger 6 with short, and elongate, narrowly hooded chaetae. G. Short, narrowly hooded chaetae of chaetiger 6. H. Posterior end ventro-lateral view. I. Thoracic uncini of chaetiger 4. J. Thoracic uncini of chaetiger 6, frontal view. K. Thoracic uncini of chaetiger 4 frontal view. Scale bars. A 200 µm, B 10 µm, C, H 50 µm, D–F 20 µm, G, I 5 µm, J, K 2 µm.

FIGURE 21. Manayunkia speciosa Leidy, 1858, SEM micrographs. A. Complete specimen, ventro-lateral view. B. Anterior end, ventro-lateral view. C. Posterior end, lateral view. D. Thoracic chaetae of chaetiger 1. E. Notopodia of chaetigers 1–3. F. Notopodium of chaetiger 3 with short, and elongate, narrowly hooded chaetae. G. Notopodium of chaetiger 6 with short, and elongate, narrowly hooded chaetae. H. Abdominal neurochaetae of chaetiger 11. I. Thoracic uncini of chaetiger 3, lateral view. J. Frontal view of abdominal uncini. Scale bars. A 200 µm, B, C 50 µm, D, F–H 10 µm, E 50 µm, I 2 µm, J 5 µm.