Brachyrhynchus oosterlyncki Willems, Reygel & Artois

Artois, Tom, Willems, Wim, Reygel, Patrick & Schockaert, Ernest, 2013, Brachyrhynchus n. gen. n. sp., a new genus of Polycystididae Graff, 1905 (Rhabdocoela: Kalyptorhynchia), with the description of three new species from the Mediterranean and the Indian Ocean, Zootaxa 3635 (2), pp. 127-136 : 132-134

Brachyrhynchus oosterlyncki Willems, Reygel & Artois n. sp.

( Figs 3 C; 4C–E)

Localities. South-Africa, KwaZulu-Natal, iSimangaliso Wetland Park, Eastern Shores, Mission Rocks, 28°16'50.4"S, 32°29'06.5"E), highly-exposed tidal area with sandstone terrace covered with a high diversity of organisms (barnacles, mussels, limpets, corals, tunicates, algae), sand and green algae from rock pool in lower eulittoral zone, 0 5 December 2009 (TYPE LOCALITY). India, Goa, Anjuna beach, 15°34’2.8”N, 73°44’28.5”E, algae and sand, salinity 35‰, 0 3 December 2008; same locality, green and brown algae, salinity 35‰, 0 3 December 2008; same locality, algae and sponges from exposed part of beach, salinity 35‰, 12 December 2008; same locality, coarse-grained sand and shell gravel in protected bay, salinity 35‰, 12 December 2008.

Studied material. Three animals studied alive. One whole mount from South-Africa, designated holotype (SMNH, no. 7833). Two whole mounts from India, deposited as voucher specimens (HU, nos VI.1.45–VI.1.46). Etymology. Species dedicated to Mr. Kristof Oosterlynck, a close friend of W. Willems.

Description. Colourless and slender animals, 0.5–1 mm long (measured on whole mounts). Habitus and internal organisation identical to that of both other species of Brachyrhynchus n. gen., based on observations of live individuals ( Fig. 4 C–D). Differences are to be found in the size and detailed structure of the hard parts in the male genital system and the stylet-to-stylet ratios.

The prostate stylet ( Figs 3 C; 4E: pst) is a single-walled, hollow tube, which has approximately the same width over its entire length. Distally, the tube narrows asymmetrically, forming a narrow opening. In the South-African specimen, this stylet is 77 µm long and 8 µm wide proximally, whereas it is 71–72 µm long and 9–12 µm wide proximally in the Indian specimens (n = 2). Both accessory stylets ( Figs 3 C; 4D: ast1 & 2) are needle-like, widening proximally. Observations on live material did not allow us to identify which of the two accessory stylets is connected to the larger of the two accessory vesicles. These accessory stylets differ slightly in length, and are slightly to heavily curved, depending on the degree of squeezing. In the South-African specimen they measure 40 and 42 µm, in the Indian specimens 41–42 µm (n = 2) and 44–48 µm (n = 2) respectively. With the shortest one arbitrarily considered first accessory stylet, and using the same symbols as in the description of B. triplostylis n. sp., the stylet-to-stylet ratios are: α = 52%; β = 55%; γ = 105% in the specimen from South Africa and α = 57–59%; β = 61–67%; γ = 107–114% in the specimens from India.

Diagnosis. Species of Brachyrhynchus with an obliquely cut-off prostate stylet type IV, 71–88 µm long. Accessory stylets 40–42 µm and 42–48 µm long. Stylet ratios (see description): α = 52–59%, β = 55–67%, γ = 105–114%.

Figures

FIGURE 3. Hard parts of the male genital system with, from left to right: ast 2, ast 1 and pst. (A) Brachyrhynchus triplostylis n. sp. (B) Brachyrhynchus acutus n. sp. (C) Brachyrhynchus oosterlyncki n. sp. (All from the holotypes).

FIGURE 4. B. acutus n. sp. (A) Hard parts of the male genital system (from the holotype). B. triplostylis n. sp. (B) Hard parts of the male system (from the holotype). B. oosterlincki n. sp (C) Habitus of a live specimen. (D) Proboscis from a live specimen. (E) Hard parts of the male genital system (from the holotype).