Asteromyzostomum grygieri Summers, Al-Hakim & Rouse, 2014, n. sp.

Asteromyzostomum grygieri n. sp. Summers & Rouse

Fig. 1

Asteromyzostomum sp.— Grygier (1988); Grygier (2000); Lanterbecq et al. (2006)

Holotype: SIO-BIC A3801 (S6950) hologenophore (1 spm: 95% ethanol). Elephant Island, Antarctica (Stn. E1- 82) (61°09.0527’S, 54°11.8609’W), 222– 247 m. Collected via the R/V Nathaniel B. Palmer using a Blake trawl on 22 October 2011 by Nerida Wilson, GWR, MMS, and science team. Genbank (COI—KM014170).

Host. Labidiaster annulatus Sladen (Heliasteridae, Forcipulatida. Asteroidea).

Paratypes: SIO-BIC A3232 (S4392) syngenophores (2 spms: in 70% ethanol after formalin fixation). Elephant Island, Antarctica (Stn. EI-79) (61°10.4189’S, 54°11.9508’W), 223– 242 m. Collected via the R/V Nathaniel B. Palmer using a Blake trawl on 22 October 2011 by Nerida Wilson, GWR, MMS, and science team. Host: Labidiaster annulatus. SIO-BIC A3836 (S6947) syngenophore (1 spm: 95% ethanol). Elephant Island, Antarctica (Stn. EI-79) (61°10.4189’S, 54°11.9508’W), 223– 242 m. Collected via the R/V Nathaniel B. Palmer using a Blake trawl on 22 October 2011 by Nerida Wilson, GWR, MMS, and science team. Host: Labidiaster annulatus. SIO-BIC A3554 (S20195) syngenophores (2 spm: 1—in 70% ethanol after formalin fixation; 1—95% ethanol). South Georgia, Antarctica (Stn. SG4-5) (53° 42' 54.4"S, 36° 50' 8.5"W), 190 m. Collected via the R/V Nathaniel B. Palmer using a Blake trawl on 16 April 2013 by Nerida Wilson, GWR, and science team. Host: Labidiaster annulatus, SIO-BIC E6160 (S20209).

Etymology. Named for Mark Grygier, who first discovered this species. We also name this species to acknowledge his significant contributions to myzostomid taxonomy.

Diagnosis and description. Specimens recovered on sides of arms and in ambulacral groove, mouth piercing through body wall of host (Fig. 1 A–C). Holotype body wider than long, approximately 6 mm long and 8 mm wide following fixation. Posterior margin composed of convoluted, lobular folds. Body margin acirrate. Five pairs of parapodia on ventral side on either side of mouth, third pair farther from the edge (Fig. 1 E–F). Mouth surrounded by ring of circumoral tentacles (Fig. 1 D). Color peach in life, faded in preservative.

Remarks. Asteromyzostomum comprises three other species— Asteromyzostomum arcticum Wagin, 1954, A. multiplicatum Wagin, 1954, A. witjasi Wagin, 1954 —all described from seastars in Arctic waters (Table 1). Specimens most likely to be Asteromyzostomum grygieri n. sp. were previously recorded, but not described, from Labidiaster sp. outside of McMurdo Sound, Antarctica (Grygier 2000). These specimens were catalogued at the Smithsonian (NMNH). One of these specimens (NMHN 98554 or 98555) was sequenced in Lanterbecq et al. (2006), but this sequence has been shown to be incorrect in Summers & Rouse (2014). Asteromyzostomum grygieri n. sp. is the first myzostomid described from a seastar in Antarctica. All Asteromyzostomum species insert their mouth through the integument of the host, and are found attached to the sides of the arms or in the ambulacral grooves of the host (Wagin 1954; Grygier 2000). An additional specimen has been reported from Atlantic waters, though it was found disassociated from its host and has not been described (Wagin 1954; Grygier 1988).