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 : 92-93

Characters in Alcyonidium systematics

As mentioned, Alcyonidium represents one of the largest genera of ctenostome bryozoans (www.bryozoa.net) and has traditionally been one of the most difficult to identify and many species have been wrongly addressed or identified in the past (see references above). Particularly, features such as reproduction and tentacle number have proved to be very important for species discrimination. Also, internal features of the digestive tract have long been pointed out as very informative character for species identity ( Le Brozec, 1955, see also D’Hondt, 1983). Unfortunately, this information is seldom recorded in more recent species description, but has proven also very useful in closely-related families such as the Pherusellidae ( Decker et al., 2021) .

Soft-tissue or reproductive characters remain the most useful characters for species determination in all ctenostome bryozoans ( Jebram, 1986; Schwaha, 2020). The current assessment on Antarctic bryozoans shows that colony morphology and tentacle number essentially can provide the necessary features for species discrimination. In many preserved material or broken pieces of colonies this will practically be difficult to test without dissection or histology. Also, some broken pieces of colonies might either lack polypides or be insufficient altogether for proper species identification (see also Porter & Hayward, 2004). Polypide features especially the variable gut structure would be important to evaluate in the future, as it could represent an easy and reliable tool for species discrimination by simple mounting of bryozoan guts.

Reproduction is likewise a character of important species assignment, but very difficult to assess in most cases as it often required histology to check: size and number of gonads (oocytes), presence of an intertentacular organ (ITO, used in planktotrophic species), presence of brooded large embryos. Also, in many species the mode of reproduction is not evident when lacking embryos or distinct gonads as encountered in our current analysis on Alcyonidium kuklinskii sp. nov..

Ultimately, it will be crucial that more genetic data along with proper morphological identification will be provided for many species of Alcyonidium . This would ease the difficulties in species identification and biodiversity assays in the future.