Myobulla armenterosi Diez, Sanjuan, Reygel & Artois sp. n.

(Fig. 5, 7B)

Material and distribution in Cuba. Observations on live animals, whole mounted afterward. Six whole mounts from Bueycabón (type locality) (March 3, 2016), one of which is designated holotype (FMNH http://id.luomus.fi/ KV.605), fine-grained sand with organic matter, 0.5 m depth, salinity 32–33 ‰. The other five specimens reference material (HU VIII.3.33–VIII.3.37). One whole mount from Aguadores (February 14, 2017), on Cladophoropsis macromeres, 0.3 m depth, salinity 35 ‰ (HU VIII.3.38).

Etymology. Species dedicated to Prof. Dr. Maickel Armenteros (Marine Research Centre, Havana University, Cuba).

Diagnosis. Species of Myobulla with a prostate stylet type III 68 µm long, with a 90° curve at its midpoint and its distal tip more or less hook shaped.

Description. Animals 0.6–1 mm long (x̄ = 0.9 mm; n = 7) (measured on the whole mounts), with two eyes (Fig. 5A: e) and colourless, except for some long, pink glands along both sides of the body. Habitus and internal morphology similar to that of other species of Myobulla, hence, with unpaired gonads and a typical bursal stalk provided with an asymmetrical muscular bulb with a ring of four hard teeth. For a detailed description we refer to Artois & Schockaert (2000). Proboscis (Fig. 5A: pr) 91–131 µm long (x̄ = 110 µm; n = 7). Pharynx (Fig. 5A: ph) 113–186 µm in diameter (x̄ = 162 µm; n = 7), located at 40%.

Prostate stylet type III (Fig. 5 A–B: ps3, 5D–E) 58–86 µm long (x̄ = 68 µm; n = 7). Proximal part gutter shaped, with a thickened proximal end, 11–18 µm wide (x̄ = 17 µm; n = 7). Distal part tubiform, more or less perpendicular to the proximal part in more or less strongly-squeezed animals (Fig. 5 D–E) whereas the entire stylet is more straight in less-squeezed ones (Fig. 7B). Distal tip of the stylet somewhat hook-shaped. Proximal part represents 45–59% of the length of the stylet (x̄ = 53%; n = 7). The seminal duct enters the male atrium at the level where the stylet becomes tubiform, as in the other species of Myobulla .

Female system as in other species of Myobulla . Ovary kidney shaped, with the oocytes in a row, diminishing in diameter from the most distal to the most proximal. Bursa globular, with the muscular seminal receptacle with a ring of four teeth characteristic of the genus.