Cauloramphus japonicus Silén, 1941

Martino, Emanuela Di, 2023, Scanning electron microscopy study of Lars Silén’s cheilostome bryozoan type specimens in the historical collections of natural history museums in Sweden, Zootaxa 5379 (1), pp. 1-106 : 14-16

Cauloramphus japonicus Silén, 1941

( Fig. 4 ; Table 5)

Cauloramphus japonicus Silén, 1941: 33 , figs 34, 35.

Material examined. Holotype by original designation UPSZTY 2463 , Okinose , Sagami, Japan; depth 600 m; encrusting a fragment of Steginoporella magnilabris . Leg. Prof. S. Bock 1914.

Description. Colony encrusting, multiserial, unilaminar ( Fig. 4A ).

Autozooids pear-shaped with a tapering proximal gymnocyst ( Fig. 4A, B, D ), longer than wide (mean L/ W 1.44), distinct, separated by deep grooves, quincuncially arranged. Proximal gymnocyst width highly variable (42– 271 µm), narrow laterally (20–85 µm), smooth; cryptocyst almost vertical forming a narrow circumopesial rim, 20–30 µm wide, either completely obscured by spines or, in zooids with detached spines, only visible if slightly tilted, finely granular with granules <5 µm in diameter.

Opesia pear-shaped, occupying most of the zooidal length (mean OpL/ZL 0.77) ( Fig. 4C, D ); opesial spines varying in number from 20 to 24 (more commonly 20), 15–25 µm in maximum width, 140–200 µm long, with squared and open tips, fairly widely spaced, curved over the aperture but not meeting in the midline; opesial spine bases 10–25 µm in diameter; 7–8 shorter spines placed distal to the orifice, 50–80 µm long, 10–20 µm in diameter ( Fig. 4B, C ); orificial opening transversely D-shaped, 130–150 × 230–250 µm.

Avicularia adventitious, budding from pore chambers placed on the lateral gymnocyst ( Fig. 4C, E, F ) with a short peduncle expanding into the avicularian chamber; inconstant, absent in several zooids, if present usually single, rarely paired, placed latero-orally between the distal oral spines and the first pair of opesial spines, tear-drop shaped with triangular rostrum directed distolaterally inwards ( Fig. 4F ), no condyles; in a single instance an additional avicularium, of the same size and shape, observed proximolaterally ( Fig. 4B , see arrow).

Ovicells globular, kenozooidal, resting on the space between zooids or developed at colony edge ( Fig. 4A ); ooecium smooth with a visor-like proximal projection ( Fig. 4E, F ); only two distolateral oral spines visible in ovicellate zooids ( Fig. 4E, F ).

Intramural buds observed in some autozooids ( Fig. 4C, D ).

Remarks. Silén (1941) described four distal spines in non-ovicellate autozooids but this does not include all the spines around the orificial opening/operculum (i.e. distal and distolateral above the level of avicularia budding sites), which are constantly 7–8 (see Fig. 4C, D ). Those distolateral spines were not included in the count of the opesial spines, being those reported as 10 pairs. Seo (2001) mentioned the rare observation of distal spines in Cauloramphus korensis Seo, 2001 as a character shared with C. japonicus following Mawatari & Mawatari (1981, p. 43, fig. 9A). However, the 7–8 distal spines are always visible in all zooids of the type specimen of the latter species.

Other small differences between the present observations and the original description pertain to the striations of the ooecium, as in Cauloramphus costatus , which were not observed (see Fig. 4E, F ), as well as the description of the avicularian peduncle, defined as very long and very narrow at the base but which looks instead short and stout (see Fig. 4B, C, E ).

The two species of Cauloramphus described by Silén come from the same sampling station located in deep waters (i.e. 600 m) but species of the genus were reported from all depths including intertidal waters ( Grischenko et al. 2007).

Genus Corbulella Gordon, 1984

Figures

FIGURE 4. Cauloramphus japonicus Silén, 1941. Holotype UPSZTY 2463, Japan. A. Group of zooids. B. Close-up of two autozooids lacking stalked avicularia. The arrow indicates the only proximolateral avicularium observed in the specimen. C. Close-up of two autozooids with a single stalked avicularium. D. Intramural budding in autozooids. E. Ovicellate zooids with paired stalked avicularia. F. Close-up of an ovicell flanked by two stalked avicularia. Scale bars: A–E = 200 µm; F = 100 µm.