Latrunculia biformis Kirkpatrick 1908

Latrunculia biformis (Kirkpatrick, 1908) (Figs 4 A, 5 A; Tab. 1)

Latrunculia apicalis var. biformis Kirkpatrick, 1908: 14. Latrunculia apicalis; Ridley and Dendy, 1887: 234 (BMNH 1887.5.2.84a). Latrunculia apicalis var. biformis; Burton 1929:444. Latrunculia apicalis; Koltun 1955:1–6. Latrunculia biformis; Boury­Esnault and Van Beveren 1984: 44

Material examined. BMNH 1908.2.5.70 (Holotype): Winter Quarters, Antarctica, 77 49'S, 167 7'4"E, National Antarctic Expedition (1901–1904), H. M. S. Discovery, 18–27 m; BMNH 1908.2.5.69b (Paratype): Winter Quarters, Antarctica, 77 49'S, 167 7'4"E, National Antarctic Expedition (1901–1904), H. M. S. Discovery, 18–27 m; BMNH 1908.2.5.69c (Paratype): Winter Quarters, Antarctica, 77 49'S, 167 7'4"E, National Antarctic Expedition (1901–1904), H. M. S. Discovery, 18–27 m; BMNH 1887.5.2.84a (labelled Latrunculia apicalis Ridley & Dendy, 1887): off mouth of Rio de la Plata, Argentina, 37° 17'S, 53° 52'W, 1080 m, H. M. S. Challenger Expedition, 14 February 1876; MDO3 50D D.NBE 1388: Latrunculia apicalis in Boury­Esnault & van Beveren (1984), spicule slide, NW of Kergeulen, stn 17, 585 m; SAM H­ 4959: Rheeders Bay, Tsitsikamma National Park, South Africa, 34° 10'S, 23° 54'E, 28 m, collected by M. K. Harper, Scripps Institute of Oceanography, California, 25 February 1995.

Description. Hemispherical to globular sponge, 6.5 x 4 x 4 cm (length x width x height), with ectosomal layer easily detachable from the underlying choanosome. Surface microscopically smooth, crowded with conical volcano­shaped oscules, 1 x 0.2 mm wide and high, and numerous flattened mammiform areolate porefields 1 x 0.2 mm wide and high. Texture firm, resilient, slightly fleshy. External colour in life mottled chocolate brown, interior dark chocolate brown, in preservative dark chocolate brown.

Spicules. Megascleres— Styles: smooth, centrally thickened, hastate, slightly sinuous, 558 (528–576) x 12 (12–16) m. Microscleres— Anisodiscorhabds (Fig. 4A”): With four whorls of spines, median whorl 45 m diameter, subsidiary whorl phyllamentous, slanted upwards towards apical whorl; 65 (55–72) x 7.2 m. Aciculodiscorhabd I (Fig. 4A’): Manubrium short with a regular expanded spinose base, armoured with separate horizontal whorls of short spines, above which is a short, stout, shaft 12 m long, 7 m wide. Median whorl broad, flat, with denticulate margins, 45 m diameter. Subsidiary whorl slanting upwards, 30 m diameter. Apical whorl spines reduced and slanted upwards, protruding from apex is a short, spined projection that gradually tapers to a fine point; 102 (82–137) x 7.2 m. Aciculodiscorhabd II (Fig. 4A”’): Hypertrophied, verticillate; 245 (200–260) x 7.2 m (specimen SAM H­4959)

Ecology. Found on rocky substrata sheltered by algal cover and other invertebrates around 18 m.

Remarks. Ridley and Dendy (1887) collected three specimens that were identified as Latrunculia apicalis on the H. M. S. ‘Challenger’ expedition, one off Christmas Harbour, Kerguelen (BMNH 1887.5.2.88a), and two specimens from Rio de la Plata, Argentina (one being BMNH 1887.5.2.84a). Examination of these samples by us revealed that BMNH 1887.5.2.84a from Argentina differed from the Kergeulen sample (BMNH 1887.5.2.88a) in possession of an additional type of acanthodiscorhabd with an apical projection termed an aciculodiscorhabd (Fig. 4’,’’’, Table 1) (Samaai & Kelly 2002). In their description of Latrunculia apicalis, Dendy and Ridley (1886) and Ridley and Dendy (1887), failed to mention the presence of these spicules. Aciculodiscorhabds were first observed in L. apicalis, by Kirkpatrick (1908), in samples dredged in Antarctica. He named this new material Latrunculia apicalis var. biformis.

Spiculation and histology of Tsitsikamma National Park material (SAM H­4959) is very similar to Kirkpatrick’s material (Kirkpatrick 1908) and that of Ridley & Dendy (1887) and Dendy and Ridley (1886b) in possessing aciculodiscorhabds. The possession of these microscleres in the ectosomal microsclere palisade is consistent between specimens and unique within the genus, justifying our elevation of the varietal status to species status.

Other records. Rio de la Plata, Argentina; Antarctica (Winter Quarters, Kerguelen).

FIGURE 4. Anisodiscorhabd microsclere morphologies: A, Aciculodischorhabds’,’’’ anisodiscorhabds2 (Latrunculia biformis SAM H­4959); B, Anisodiscorhabd (L. lunaviridis sp. nov., BMNH 1996.7.3.6); C, Anisodiscorhabd (L. microacanthoxea sp. nov., BMNH 1996.7.3.1); D, Acanthomicrorhabd (L. bellae sp. nov., BMNH 2003: 1. 10. 1); E. Isochiadiscorhabd and terminations (T. favus, BMNH 1997.7.3.2); F. Isochiadiscorhabd with two whorls and terminations (T. pedunculata sp. nov., BMNH 2003.1.10.2); G. Isochiadiscorhabd and terminations (T. scurra sp. nov., BMNH 2003.1.10.3); H. microacanthoxea of L. microacanthoxea sp. nov..

Sample Megascleres Aciculoacanthodiscorhabd I Anisoacanthodiscorhabd

BMNH 1908.2.5.70 473 (436–482) x 11 m 72 (62–83) x 7 x 23 m 57 (50–60) x 7 x 34.5 m (Holotype)

SAM H­4959 558 (528–576) x 12 m 102 (82–137) x 7 x 46 m 65 (55–72) x 7 x 46 m

MD03 (D.NBE 1388) 504 (482–518) x 18 m 82 (73–85) x 7 x 42 m 56 (55–57) x 7 x 37 m

BMNH 1887.5.2.84a 527 (500–546) x 16 m 92 (70–99) x 7 x 34 m 51 (46–52) x 7 x 39 m