Desmacystis sandalia ( Robertson, 1900 )

Grischenko, Andrei V., Dick, Matthew H. & Mawatari, Shunsuke F., 2007, Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan, Journal of Natural History 41 (17 - 20), pp. 1047-1161 : 1104-1105

Desmacystis sandalia ( Robertson, 1900)

( Figure 22 )

Membranipora sandalia Robertson 1900, p 324 , Plate 20, Figures 9, 9a , Plate 21, Figure 10 ; 1908, p 264, Plate 15, Figures 11–14 .

Desmacystis sandalia: Osburn 1950, p 32 , Plate 3, Figure 1 ; Gontar 1981, p 102; Dick and Ross 1988, p 30, Plate 1A; Gordon and Grischenko 1994, p 62, Figures 1–6 ; Kubanin 1997, p 123; Grischenko 1997, p 173; 2004, p 40.

? Desmacystis sandalia concinna Gontar 1982, p 543 , Figure 1,1 .

Material examined

ACT, two colony fragments (NHM 2006.2.27.59); KAI, colony on rock (NHM 2006.2.27.60). Additional material: 147 specimens.

Description

Colony encrusting, unilaminar, coherent, loosely attaching to substrate, irregularly circular, up to 5 cm across, bright orange or reddish when alive. Zooids ( Figure 22B–D ) irregularly hexagonal, or tapering proximally and clavate in shape, rounded distally, thinwalled, 0.60–0.80 mm long (0.71¡ 0.06 mm), 0.32–0.45 mm wide (0.38¡ 0.03 mm), separated by raised vertical walls. Frontal shield cryptocystal, ‘‘incomplete’’, occupying 40–60% of zooidal length; relatively smooth in newly formed zooids, sunken below narrow gymnocystal rim and covered by epitheca, with three to five areolar pores along each lateral margin; with age, reinforced by strong buttresses of calcification running between adjacent areolae toward centre of cryptocyst, meeting proximal and lateral margins of avicularian chamber, often confluent with a heavily calcified median buttress. A suboral avicularium with a raised chamber arises from one of distalmost areolae, asymmetrically placed and overhanging the opesia, rostrum facing obliquely laterally, mandible semicircular to subspatulate, cross-bar complete. Secondary orifice oval to nearly circular, 0.28–0.35 mm long (0.31¡ 0.02 mm), 0.27–0.33 mm wide (0.29¡ 0.02 mm), surrounded by thin, raised gymnocystal margin; with age, orifice can become partially concealed by calcification from adjacent zooids. Ovicell ( Figure 22C, D ) a small, transversely elongate hood suspended in distal curvature of aperture, with uncalcified central area that is sometimes open at proximal margin. Four small circular multiporous septula in each lateral wall; transverse wall interconnects through numerous pores in basal half, organized into two distinct septular areas. Spines absent. Ancestrula not observed.

Remarks

Gontar (1982) described a new subspecies, D. sandalia concinna , on the basis of material from Kunahsir among the southern Kuril Islands. Characters distinguishing this subspecies from the nominal subspecies include strongly calcified ridges on the proximal part of the frontal shield; the occasional presence of a small additional avicularium in the same area; and smaller zooidal dimensions. Grischenko (1997) noted a similar condition of the frontal shield in specimens from the Commander Islands, but did not observe the additional frontal avicularia. Colonies of D. sandalia from Akkeshi Bay show considerable variation in the degree of calcification of the frontal shield and avicularian chamber, and in the development of buttresses. Whereas in some colonies zooids have an inflated, relatively smooth frontal shield and reduced, shortened buttresses, in others zooids have a highly mucronate frontal, reinforced by strong buttresses. A parallel variation in characters also occurs during individual zooidal development. Except for the sporadic presence of an additional frontal avicularium, the characters considered diagnostic for D. sandalia concinna appear to comprise astogenetic, ecophenotypic, or intra-population variation. It thus remains unclear whether D. sandalia concinna represents a valid subspecies.

Distribution

This is a Boreal Pacific species, originally described from Yakutat, Alaska ( Robertson 1900) and subsequently reported from the Queen Charlotte archipelago ( Osburn 1950), Kodiak Island ( Dick and Ross 1988), the Commander Islands ( Gordon and Grischenko 1994; Grischenko 1997, 2004; Kubanin 1997), and Kunashir and Shikotan among the southern Kuril Islands ( Gontar 1981). Our record from Akkeshi is the first report of D. sandalia from Japan and represents the southernmost limit of its known distribution in the western North Pacific.

Figures

Figure 1. Map of Akkeshi Bay showing the 10 sampling stations (filled squares); 5, 10, and 20 m depth contours are indicated. Inset shows the location of Akkeshi Bay on Hokkaido Island, northern Japan.

Figure 9. Cauloramphus cryptoarmatus n. sp. (A, C, E) NHM 2006.2.27.14; (B, F) NHM 2006.2.27.31; (D) NHM 2006.2.27.13. (A) Colony margin with developing zooids, unbleached; (B) zooids at colony margin in interaction with Cribrilina annulata, showing numerous additional avicularia developing along vertical walls from pore chambers, bleached; (C) autozooids, unbleached; (D) autozooids, showing strongly developed granulated cryptocyst, bleached; (E) two zooids showing details of avicularia and spines, unbleached; (F) ancestrula surrounded by periancestrular zooids, bleached. Scale bars: 0.5 mm (A–D, F); 0.4 mm (E).

Figure 10. Cauloramphus magnus Dick and Ross, 1988. (A, C, D) NHM 2006.2.27.33–34; (B) NHM 2006.2.27.54; (E) NHM 2006.2.27.35; (F) NHM 2006.2.27.32. (A) Colony margin with developing zooids, unbleached; (B) same, bleached; (C) autozooids, unbleached; (D) close up of autozooids showing details of avicularia and spines, unbleached; (E) autozooids, bleached; (F) ancestrula and periancestrular zooids, bleached. Scale bars: 0.5 mm (A–C, E, F); 0.4 mm (D).

Figure 11. Cauloramphus multispinosus n. sp. (A) NHM 2006.2.27.36; (B, C) NHM 2006.2.27.38; (D, E) NHM 2006.2.27.37; (F) NHM 2006.2.27.40. (A) Colony margin with developing zooids, unbleached; (B) group of autozooids, unbleached; (C) close up of zooids showing details of distal erect spines and thin proximal spines strongly curved and arched over opesia, unbleached; (D) autozooids with variable form of proximal gymnocyst, bleached; (E) close up of zooids, unbleached; (F) ancestrula surrounded by periancestrular zooids, bleached. Scale bars: 0.5 mm.

Figure 12. Cauloramphus niger n. sp. (A–E) NHM 2006.2.27.16; (F) NHM 2006.2.27.17. (A) Developing zooids at colony margin, unbleached; (B) general view of group of zooids with immersed vestigial ovicells, unbleached; (C) zooids from colony periphery, showing numerous avicularia, unbleached; (D) close up of zooids with avicularia, unbleached; (E) autozooids with immersed ovicells and bases of spines, bleached; (F) ancestrula and periancestrular zooids, bleached. Scale bars: 0.5 mm.

Figure 13. Cauloramphus spinifer (Johnston, 1832). (A) NHM 2006.2.27.38; (B) NHM 2006.2.27.41; (C) NHM 2006.2.27.18; (D) NHM 2006.2.27.17. (A) Group of autozooids, unbleached; (B) distal half of zooid, showing avicularia, unbleached; (C) autozooids, bleached; (D) ancestrula and periancestrular zooids, bleached. Scale bars: 0.5 mm (A, C, D); 0.1 mm (B).

Figure 14. Tegella aquilirostris (O’Donoghue and O’Donoghue, 1923). HNM 2006.2.27.42. (A) Developing zooids near colony margin, bleached; (B) immature zooids with large frontal avicularia, bleached; (C) zooids with developing and completed ovicells, bleached; (D) mature zooids, showing ovicells with associated frontal avicularia, and also straight and curved spines, bleached. Scale bars: 0.5 mm.

Figure 22. Desmacystis sandalia (Robertson, 1900). (A, D) NHM 2006.2.27.59; (B, C) NHM 2006.2.27.60. (A) Colony margin with developing zooids; (B) immature zooids; (C) mature zooids showing transversely elongate vestigial ovicells and relatively smooth frontal walls; (D) mature zooids with frontal shields reinforced by radially arranged ridges of calcification. Scale bars: 0.5 mm.