Mesomyzostoma lanterbecqae n. sp. Summers & Rouse

Fig. 2 I–L

Holotype: SIO-BIC A3651 hologenophore (1 spm: ½—in 70% ethanol after formalin fixation; ½—95% ethanol). Padoz Reef, Madang Harbor, Papua New Guinea (5° 9' 34.8006"S, 145° 48' 46.2096"W), 5– 20 m. Collected using scuba on 27 November 2012 by MMS and GWR. Genbank (COI—KM014176).

Host. Clarkcomanthus alternans (Carpenter) ( Comatulidae, Comatulida, Crinoidea). MNHN-IE-2013-8114 (dried voucher); SIO-BIC E5879 (tissue subsample in 95% ethanol). Genbank (COI—KM491773).

Paratypes: SIO-BIC A3652 syngenophores (3 spms: 2—in 70% ethanol after formalin fixation; 2—95% ethanol). Same location as holotype. Genbank (COI—KM491743). Host: Clarkcomanthus mirabilis (Rowe et al.), MNHN-IE-2013-8174 (dried voucher) & SIO-BIC E5880 (tissue subsample in 95% ethanol); Genbank (COI—KM491774). SIO-BIC A3653 syngenophores (2 spms: 95% ethanol). South Padoz Reef, Madang Harbor, Papua New Guinea (5° 9' 43.1994"S, 145° 48' 59.3922"W), 5– 20 m. Collected using scuba on 1 December 2012. Genbank (COI—KM491744). Host: Comatella nigra (Carpenter), MNHN-IE-2013-8064 (dried voucher) & SIO- BIC E5891 (tissue subsample in 95% ethanol); Genbank (COI—KM491775).

Etymology. Named for Deborah Lanterbecq, who first sequenced DNA from a Mesomyzostoma and led the work resulting in the first molecular phylogeny for myzostomids (Lanterbecq et al. 2006).

Diagnosis and description. Located within host’s coelom. Holotype body thin and elongate. Length ~ 2.5 mm following fixation (specimen cut and curled) [paratypes 2–4 mm]. Body margin acirrate. Mouth and cloaca terminal. Five pairs of small parapodia, with large hooks (Fig. 2 L). Color cream in life, white in preservative.

Remarks. There are nine other species of Mesomyzostoma —two described, Mesomyzostoma katoi Okada, 1933 and Mesomyzostoma reichenspergeri Remscheid, 1918, and four currently being described Eeckhaut et al. (in prep) and three undescribed species in Summers & Rouse (2014). All of these species have a similar body form and occupy the coelom and/or gonads of feather star crinoids. The species are best distinguished by molecular data, followed by host use. This is likely a highly undersampled lifestyle due to the requirement of dissection.