Alcyonidium, Lamoroux, 1813

SchWaha, Thomas, Cometti, Valentina, Saadi, Ahmed J., Cecchetto, Matteo & Schiaparelli, Stefano, 2024, Alcyonidium kuklinskii sp. nov., a new species of Antarctic ctenostome bryozoan with a key to all Antarctic species of the genus, Organisms Diversity & Evolution 24 (1), pp. 85-94 : 87

Description of new Antarctic species of Alcyonidium

Gymnolaemata

*Ctenostomata* (paraphyletic)

Alcyonidioidea

Genus Alcyonidium .

Alcyonidium kuklinskii sp. nov.

Alcyonidium sp. Cecchetto et al., 2019, Fig. 1

Etymology: Named after bryozoologist Piotr Kuklinski for his contribution to polar bryozoan research.

Type locality: Ross Sea , Terra Nova Bay, “Zecca” diving site, Latitude: 74°41′24.972″ S , Longitude : 164°6′9.18″ E .

Types: Holotype: MNA-02733, Paratype: MNA-02904.

Diagnosis: Colony erect and non-pedunculate, cylindrically branching forming thick main branches and sometimes thin smaller ones ( Figs. 1 , 2a–c , see also Fig. 1 in Cecchetto et al., 2019). Thick branches consisting of internal medullary, old zooids ( Fig. 3a ). Zooids hexagonal to polygonal, measuring between 490 and 610 µm in length and 370–530 µm width ( Fig. 2d–f ). Small kenozooids of triangular or polygonal shape irregularly present on frontal surface ( Fig. 2d, e ). Apertural papilla missing, vestibular wall extends to basal side of zooid ( Fig. 3b ). External cuticle thick and multi-layered ( Fig. 3d ). Lophophore with 21–22 tentacles ( Fig. 3c ), digestive tract with short foregut, very elongated cardia, prominent elongated caecum folding into proximal direction almost until cardiac valve, anus vestibular ( Fig. 4 ). Reproduction unknown.

Remarks: From all Antarctic alcyonidiid species four are encrusting ( A. antarcticum Waters, 1904 , A. eightsii Winston & Hayward, 1994 , A. epispiculum Porter & Hayward, 2004 , A. simulatum Porter & Hayward, 2004 ), five erect ( A. austral e D’Hondt & Moyano, 1979, A. flabelliforme Kirkpatrick, 1902 , A. kuklinskii sp. nov., A. scolecoideum Porter & Hayward, 2004 , A. torpedo D’Hondt, 2006 ) and one pelagic ( A. pelagosphaerum Porter & Hayward, 2004 ), A. kuklinskii is the only erect, cylindrical form with 21–22 tentacles. Alcyonidium australe is colony-wise the most similar species but easily identifiable by its lower number of tentacles (16–17). Tentacle-wise only A. eightsii and A. epispiculum have similar numbers (20–21 and 22–23, respectively), but differ in being encrusting species (see Table 1). In addition, zooids are much longer in A. eightsi (0.8–1 mm) contrary to A. kuklinskii , 0.49–0.61 mm. The length of A. epispiculum , 0.43–0.54 mm, is more similar to A. kuklinskii but are much broader, 0.51–0.71 mm, compared to 0.37–0.53 mm. Details of gut morphology have been previously used for alcyonidiid species discrimination ( Le Brozec, 1955), but remain unstudied in all other Antarctic species.

Figures

Fig. 1 Live specimens of Alcyonidium kuklinskii sp. nov., modified from Cecchetto et al. (2019). a Holotype MNA-02733 Overview of a large colony showing thick and thinner erect branching (scale bar=1 cm). b Paratype, MNA-02904. Detail of few branches with partially extended lophophores

Fig. 2 Stereomicroscopic images of Alcyonidium kuk- linskii sp. nov. Images a–c, e–f from holotype MNA-02733, d from paratype MNA-02904, a and b Colony pieces of the holotype, c Close-up showing thinner and thicker branches of the colony. d and e Zooidal shapes and few small kenozoo- ids in between. f More cleared colony piece showing internal, functional polypides. Abbre: ap – aperture, az – autozooid, kz – kenozooid, ply - polypide

Fig.3 Histological sections of Alcyonidium kuklinskii sp. nov. a Multiple internal zooids filling the internal branch. Note only close to the colony wall there are functional polypides. b Apertural area showing deep vestibular wall and medium- sized collar at its bottom. Parts of the remaining polypide are also visible. c Cross- sectioned lophophore showing 21 tentacles. d Detail of the thick, multi-layered colony wall. Abbre: az – autozooid, c – collar, cae – caecum, cow – colony wall, db – duplicature band, izw – interzooidal wall, ply – polypide, ts – tentacle sheath, v – vestibulum, vw – vestibular wall

Fig.4 Schematic drawing of the digestive tract anatomy of Alcyonidium kuklinskii sp. nov. Abbre: ca – cardia, cae – caecum, int – intestine, mo – mouth opening, ph/es – pharynx/ esophagus, py – pylorus, ts – tentacle sheath