Immergentia cheongpodensis Seo & Chae & Winston & Zágoršek & Gordon 2018, n. sp.
Creators: name: Seo, Ji-Eun
name: Chae, Hyun Sook
name: Winston, Judith E.
name: Zágoršek, Kamil
name: Gordon, Dennis P.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Bryozoa
Gymnolaemata
Ctenostomatida
Immergentiidae
Immergentia
Immergentia cheongpodensis

description: Immergentia cheongpodensis n. sp.
(Figs 9A, B, D, 10, 11)
Immergentia [sp.] Seo et al. 2016: 9.
Etymology. The species is named for the location where it was found, Cheongpodae Beach, Yellow Sea.
Material examined. Holotype: MBRMKH7, Cheongpodae, Taean Coast National Park, Korean west coast, 36.6334° N, 126.2997° E, intertidal, 16 June 2017. Paratype: MBRBKP7, same data as holotype.
Description. Colony boring in shells of dead mollusks. Impression of narrow branching stolonate connections and elongate zooid openings seen at surface of eroded shells (Figs 9A, B, 10, 11). In more-translucent, freshly bored and less-eroded shells, the delicate branching pattern of submerged colonies is visible, especially if shells are wet. Colony extent hard to determine but stolons can trail within or over much of dead shell surface. Zooids have elongate teardrop- to sausage-shaped opening, centered along midline of branch at shell surface (Fig. 9A, B). Resin casts of colonies examined by SEM show that, below this opening, buried zooids develop first as bulge along very narrow (10 µm or less) stolonal branch (Fig. 10A, B). Mature zooids c. 150 µm long, 50 µm wide, widest at orificial end, non-pedunculate, with narrow, round-tipped basal end. Zooid excavation orientated at oblique angle, some even curving upward toward shell surface. Stoloniform processes branch from abanal and anal ends of zooid tubes and may come to shell surface where they are visible as tiny pores. Casts of structures resembling gonozooids also found; these are expanded, more-triangular than autozooids, with two basal ends, one shallower than the other (Fig. 10E, F).
Remarks. Gonozooids have not previously been reported for Immergentia. According to Pohowsky (1978) they are known only in Penetrantia, but the SEM illustrations here show that the gonozooids are connected only to Immergentia cheongpodensis n. sp. and its narrow stolons, rather than to the broader stolons of Penetrantia colonies. Perhaps gonozooids are ephemeral or seasonally produced.
Immergentia species are the smallest of boring ctenostomes, and they are seldom recorded in surveys as it takes careful study of numerous empty mollusk shells under a stereo microscope to find them. Their colonies may be intermingled with the colonies of larger boring taxa such as Penetrantia on a shell, making it hard to separate the traces of the different species. The traces of the present material at the shell surface, as well as zooidal morphology (non-pedunculate) and branching are typical of Immergentiidae, which is monogeneric.
Pohowsky (1978) discussed and illustrated several living and fossil species, three of which occur in the Pacific north of the Equator. Immergentia californica Silén, 1946 differs from Immergentia cheongpodensis n. sp. in having much longer zooids (c. 350 µm) that are pointed proximally, not rounded; Immergentia philippinensis Soule, 1950 also has a proximal end and a surface trace differing from that in I. cheongpodensis n. sp. Zooids of Immergentia angulata Soule & Soule, 1969 from Hawaii are 180–200 mm long, bent sideways, and pointed proximally.
Distribution. Korea: in dead mollusk shells, particularly oysters and clams, from the low-intertidal zone at Cheongpodae beach, west coast of Korea.
description: Published as part of Seo, Ji-Eun, Chae, Hyun Sook, Winston, Judith E., Zágoršek, Kamil & Gordon, Dennis P., 2018, Korean ctenostome bryozoans-observations on living colonies, new records, five new species, and an updated checklist, pp. 251-283 in Zootaxa 4486 (3) on pages 264-269, DOI: 10.11646/zootaxa.4486.3.3, http://zenodo.org/record/1453233