Myzostoma hollandi Summers, Al-Hakim & Rouse, 2014, n. sp.

Myzostoma hollandi n. sp. Summers, Al-Hakim & Rouse

Fig. 4 H–I

Holotype: MZB Pol. 0 0 128 hologenophore (½—in 70% ethanol after formalin fixation; ½—in 95% ethanol following fixation in DMSO). Near Kri Eco Resort Jetty, Raja Ampat, Indonesia (0°33'27.42"S, 130°40'36.23"E), less than 20 m. Collected at night using scuba on 13 October 2013 by MMS and GWR. Genbank (COI—KM014208).

Host. Stephanometra tenuipinna (Hartlaub) (Mariametridae, Comatulida, Crinoidea). SIO-BIC E5842. Genbank (COI—KM014353).

Etymology. Named after Nick Holland, for his appreciation of all things crinoidal, including their symbionts.

Diagnosis and description. Holotype body elongate, terminating in 6 cylindrical acirrate caudal processes (Fig. 4 H–I). Entire specimen ~ 5 mm long including caudal processes following fixation. Medialmost pair of caudal processes longest, decreasing in length to outermost pair. Body margin with 16 triangular cirri, pairs 1–4 large, 5–7 very small, and pair 7 half the length of the most anterior pairs. Five pairs of parapodia, located halfway between the midpoint and body-margin (Fig. 4 I). Four pairs of lateral organs midway between parapodia and body margin, alternating with the former. Live color orange, white in preservative.

Remarks. Four other species possess 6 cylindrical caudal processes (see remarks for M. eeckhauti n. sp.), but only Myzostoma fissum Graff, 1884 has acirrate caudal processes as in M. hollandi n. sp. Myzostoma fissum was described from a specimen bent and rolled upon itself from an unknown host southwest of the Fiji Islands. This species and its potential hosts were discussed in Eeckhaut et al. (1998), which also includes a description of specimens from Dichrometra flagellata in Papua New Guinea (which we advise be considered as the host for this species). Myzostoma hollandi n. sp. can be distinguished from M. fissum based on molecular data (Lanterbecq et al. 2006) and morphology. SEM of Papua New Guinean M. fissum in Eeckhaut et al. (1998) suggests that the caudal processes of M. fissum are more robust and less cylindrical than in Myzostoma hollandi n. sp. Myzostoma fissum specimens also had 18–24 marginal cirri, with the most anterior pair shortest (sometimes only a fringe), with more posterior pairs increasing in size (Eeckhaut et al. 1998). Myzostoma hollandi n. sp. has 16 marginal cirri, the most anterior pairs being largest.