Stylatula diminutiva Williams and Matsumoto, 2015

Williams, Gary C. & Matsumoto, Asako K., 2015, A Review of the Pennatulacean Genus Stylatula, with the Description of a New Species from Japan (Cnidaria: Octocorallia), Proceedings of the California Academy of Sciences 62 (8), pp. 257-266 : 258-261

Stylatula diminutiva Williams and Matsumoto , sp. nov.

Figures 1–9.

SPECIES DIAGNOSIS.— Virgulariid pennatulaceans; mature colonies <65 mm long; number of polyps per polyp leaf 2–4; number of large sclerites comprising fan-shaped polyp leaf armature <7; sclerites three-flanged throughout.

MATERIAL EXAMINED.— HOLOTYPE: CASIZ 198016 ; Japan, Iwate Prefecture, Sanriku, Otsuchi Bay ; 39°20,710′N x 141°56,923′E; 44 m depth; 28 April 2009; collection number AKM 1414; collector Asako K. Matsumoto on board R / V Yayoi with 1 m biological dredge; remarks – mud bottom inside bay, water temperature 9.6° C: one whole specimen preserved in 95% EtOH . PARATYPES: CASIZ 198017 ; same data as holotype . CASIZ 203514 ; Japan, Iwate Prefecture, Sanriku, east Otsuchi Bay ; approximate coordinates 39°24′ – 39°34′N, ca. 142°10′– 142°41′E; 118–120 m depth; 12 November 1993; collection number AKM 1627 (= 1618b); collector S. Ohta on board R / V Tansei-maru KT 93–15 cruise, St. 01 with 1 m biological dredge; remarks – separated from AKM 1618a; one whole specimen fixed in formalin and preserved in 95% EtOH . OTHER MATERIAL (non-type): CASIZ 203513 ; same data as holotype .

DESCRIPTION.— The wet-preserve holotype measures 36 mm in length and 2. 5 mm at it widest point (across the second polyp pair from the terminal apex. The internal axis is thin and extends the length of the colony. It is cylindrical, round in cross section, and contains numerous surface pores, which are often narrow and elongated. The composition of the axis is that of radially-arranged, wedge-shaped columns of calcareous matter, as in other pennatulaceans ( Figs. 2 –4), which is similar to the axial structure of ellisellid gorgonians ( Bayer, 1956: 224). Of the approximately thirty-five pairs of polyp leaves that are distinguishable, nine of these at the upper end of the rachis are fully developed, have mature polyps and conspicuous fan-shaped basal armature. The other twenty-six polyp leaf pairs are incipient, or not fully mature, and are not separated from apex. Small, cross-like sclerites may also be present. Some sclerites may also have a short side branch ( Figs. 5 –6).

ETYMOLOGY.— The specific epithet is derived from the Late Latin, deminutivum (indicating small size); in reference to the miniature size of the colonies relative to those of other species in the genus.

DISTRIBUTION.— Otsuchi Bay, Iwate Prefecture, Japan; 44–120 m depth range.

VARIATION.— The polyp leaves that comprise a single pair can be arranged oppositely (as in the holotype CAS 198016) or sub-alternately (as in CAS 203513). The four entire specimens examined ranged in length from 36–60 mm.

Figures

FIGURE 1. Stylatula diminutiva sp. nov. A-B. Living colony. C. Wet preserved holotype (CAS 198016). D-F. Wet preserved paratype (CAS 203514). Scale bars = 2.5 mm.

FIGURE 2. Stylatula diminutiva sp. nov. SEM of sur- face of axis (CAS 203513), showing surface pores. A. Portion of axis; scale bar = 0.2 mm. B. Detail of axial FIGURE 3. Stylatula diminutiva sp. nov. SEM of surface; scale bar = 0.02 mm. C. Ultrastructural detail internal morphology of the axis (CAS 203513). A. of axial surface; scale bar = 0.01 mm. Transverse section of axis, 0.23 mm in diameter, showing elongated pores; scale bar = 0.02 mm; lightened rectangle is shown enlarged in B below. B. Internal structural detail of axis; scale bar = 0.01 mm. adjacent pairs in the proximal region of the rachis, or are separated by <2 mm of bare rachis in the middle portion of the rachis. The uppermost polyp leaf pairs on the distal part of the rachis are separated from adjacent pairs of polyp leaves by approximately 2 mm of bare rachis (Fig. 1C). In the largest polyp leaves of the upper rachis, there are 2–4 polyps comprising each leaf. The peduncle is approximately 7 mm in length (Fig 7E). The sclerites are predominantly threeflanged spindles and rods (0.04–0.85 mm in length). Each polyp leaf is subtended by a conspicuous V-shaped or fan-shaped polyp leaf armature of relatively large sclerites (Fig 1). The fan-shaped armature is narrowly V-shaped and gradually tapers proximally. The ends of each FIGURE 4. Stylatula diminutiva sp. nov. SEM of internal morphology of the axis 203514), show- sclerite may be acute and pointed or truncated (CAS ing radial arrangement of calcareous material. Trans- and blunt. Some sclerites are minutely toothed verse sections of axis; scale bars = 0.02 mm. on a portion of the margins or on one terminal

FIGURE 5. Stylatula diminutiva sp. nov. SEM of scle- FIGURE 6. Stylatula diminutiva sp. nov. SEM of scle- rites from region of the polyp leaf armature (Non-type rites from region of the polyp leaf armature (Paratype CAS 203513); scale bars = 0.10 mm. CAS 203514); scale bars = 0.10 mm.

Figure 7. Wet-preserved colonies of Pacific Ocean species of Stylatula. A-C. Stylatula elongata (CAS 173213); scale bars: A = 40 mm, B & C = 15 mm. D-F. Stylatula diminutiva sp. nov.; scale bar = 10 mm. D. (CAS 203513). E. Holotype (CAS 198016). F. Paratype (CAS 198017). G. Stylatula austropacifica Paratype (CAS 173209); scale bar = 30 mm.

FIGURE 9. Map of the Pacific and Indian Oceans showing the known geographic distribution of the genus Stylatula. Arrows point to type localities of 11 of the species. Localities of S. lacazi and S. kinsbergi are not known.