Phonorhynchoides minor Diez, Sanjuan, Reygel & Artois, 2018

Diez, Yander L., Hernández, Claudia Sanjuan, Reygel, Patrick, Roosen, Paulien & Artois, Tom, 2018, First record of Polycystididae (Platyhelminthes, Kalyptorhynchia) from Cuba, with the description of a new genus and five new species, and remarks and the description of one new species from Panama, Zootaxa 4514 (1), pp. 107-125 : 110-111

Phonorhynchoides minor Diez, Sanjuan, Reygel & Artois sp. n.

( Fig. 1 A–C)

Material and distribution in Cuba. Two specimens studied alive and whole mounted afterwards, one of which designated holotype (FMNH http://id.luomus.fi/KV.601), the other one reference material (HU VIII.2.39). Both specimens were collected in Siboney (type locality) (February 7, 2016 & June 5, 2017), the holotype on Gracilaria sp., 0.5 m deep, salinity 32 ‰; the other specimen in the upper layer of fine sand in the intertidal, salinity 35 ‰.

Etymology. The epithet reflects the fact that the new species has the smallest stylets of all species in the genus (Lat. minor = smaller).

Diagnosis. Species of Phonorhynchoides with a slightly curved prostate stylet type IV, proximally rounded and distally obliquely cut, 53–58 µm long, 4 µm wide. Accessory stylet type IV 45 µm long, 3 µm wide proximally, twisted distally, tapering into a distal sharp tip.

Description. Living animals 1 mm long, with a pair of eyes and a translucent body. Proboscis 1/10 to 1/12 of the body length ( Fig. 1A : pr), and pharynx situated at about 25% ( Fig. 1A : ph). General internal morphology as in other species of the genus.

Atrial organs in the posterior two-thirds of the body. Paired testes caudally from the pharynx ( Fig. 1A : t). Prostate vesicle type IV spindle shaped ( Fig. 1A : pv4), with only one type of secretion visible in live animals. Prostate stylet type IV ( Fig. 1A : ps4, Fig. 1B ) slightly curved, 53–58 µm long and 4 µm wide, proximally rounded and with a subterminal distal opening. Accessory vesicle type IV ( Fig. 1A : av4) rounded and connected to a straight accessory stylet type IV ( Fig. 1A : as4, Fig. 1C ), which in both specimens is 45 µm long and 3 µm wide proximally. It tapers to a sharp distal tip, showing a twist just proximal from this tip. Accessory stylet to prostate stylet ratio is 80%.

Paired vitellaria ( Fig. 1A : vi) extend at both sides of the body, from behind the proboscis to the end of the body. Small oval ovaries are present in the midbody ( Fig. 1A : ov), with the oocytes in a row. Globular bursa not bipartite ( Fig. 1A : fb), posterolateral to the male sclerotized organs and connected to the common genital atrium ( Fig. 1A : cga) through a sphincter ( Fig. 1A : sph). Distal to the sphincter, the common genital atrium receives the male genital duct. Common gonopore at approximately 90% ( Fig. 1A : cg).

Discussion. The new species shows the typical features of Phonorhynchoides (as diagnosed by Willems et al. 2017): male system with two stylets, a prostate stylet type IV and an accessory stylet type IV, the prostate stylet being longer than the accessory stylet, and a bursa that is not bipartite (as opposed to that of Phonorhynchopsis Willems & Artois, 2017 ). In P. flagellatus Beklemischev, 1927 and P. japonicus Ax, 2008 the prostate stylet is more or less straight, as it is in P. minor sp. n., but in P. minor sp. n. it is ± 3 times shorter than in the other two species. In the remaining species of the genus ( P. carinostylis Ax & Armonies, 1987 , P. gondwanae Willems & Artois, 2017 , and P. somaliensis Schockaert, 1971 ), the prostate stylet shows a typical undulation ( P. carinostylis and P. gondwanae ) or is corkscrew-shaped in its midpart ( P. somaliensis ). In these three species, the prostate stylet is 3.5 to 4.8 times longer than it is in P. minor sp. n.. The prostate stylet of P. minor sp. n. does not show ornamentations, which are present in the prostate stylet type IV of P. carinostylis (spiral ridge over whole length) and P. japonicus (short spiral ridge). A unique feature of P. minor sp. n. within the genus is the oblique distal end of the prostate stylet. In all the other species the prostate stylet ends in a sharp point.

The accessory stylet type IV of the described species in the genus is 1.7 (in P. carinostylis and P. flagellatus ) to 2.5 (in P. gondwanae ) times longer than it is in P. minor sp. n.. The relative length of the accessory stylet compared to the prostate stylet in P. minor sp. n. is the highest in the genus (82%), compared with 74% in P. japonicus , 45– 55% in P. somaliensis , 50% in P. flagellatus , 42–46% in P. gondwanae , and 33–36% in P. carinostylis (see Willems et al. 2017).

Figures

FIGURE 1. Phonorhynchoides minor sp. n. A, Habitus (from the live animal). B, prostate stylet type IV. C, accessory stylet type IV. Phonorhynchopsis capillaris sp. n. D, prostate stylet type IV. E, proximal end of the accessory stylet type IV. F, distal end of the accessory stylet type IV. Phonorhynchopsis sublinguatus sp. n. G, prostate stylet type IV. H, proximal end of the accessory stylet type IV. I, distal end of the accessory stylet type IV. Drawings of the stylets are from the holotypes of the respective species.