Hysterothylacium sp. type MD of Deardorff & Overstreet, 1981 (larval type VIII of Shamsi et al., 2011)

Gonzalez-Solis, David, Soler-Jimenez, Lilia C., Aguirre-Macedo, M. Leopoldina, McLaughlin, John P., Shaw, Jenny C., James, Anna K., Hechinger, Ryan F., Kuris, Armand M., Lafferty, Kevin D. & Vidal-Martinez, Victor M., 2019, Parasitic nematodes of marine fishes from Palmyra Atoll, East Indo-Pacific, including a new species of Spinitectus (Nematoda, Cystidicolidae), ZooKeys 892, pp. 1-26 : 1

Hysterothylacium sp. type MD of Deardorff & Overstreet, 1981 (larval type VIII of Shamsi et al., 2011)

Description.

Third-stage larva (5 specimens): medium-sized nematodes, 3.00-8.64 mm long, 100-267 wide. Cuticular lateral alae extending along whole length of worm. Poorly developed lips, small, 18 long and 19 wide. Esophagus 270-680 long, with almost spherical ventriculus at distal part, 59-75 long and 57-87 wide. Ventricular appendage 481-595 long; intestinal caecum small, anteriorly directed, 67-274 long. Ratio for length of ventricular appendage and intestinal caecum 1: 2.10-7.73. Nerve ring at 116-279 from anterior end of body. Excretory pore slightly anterior to nerve ring, 137-198 from cephalic end. Deirids 395 from anterior end (observed in only 1 specimen). Tail conical, 121-227 long, with small spine-like mucron at tip.

Hosts.

Acanthurus triostegus , C. ferdau , C. lunula , C. chanos , K. cinerascens , A. sordidus , and A. hispidus .

Site of infection.

Mesenteries and liver.

Prevalence and mean intensity.

6 and 1.7 ± 0.6 (n = 50) to A. triostegus , 40 and 1.0 ± 0.0 (n = 5) to C. ferdau , 50 and 3.3 ± 1.6 (n = 14) to C. lunula , 20 and 6 (n = 5) to C. chanos and 50 and 2 (n = 2) to K. cinerascens , 5.6 and 3 (n = 18) to A. sordidus , 20 and 7.0 ± 5.0 (n = 15) to A. hispidus .

Specimens deposited.

CHCM no. 624 (voucher) (1 vial, 1 specimen ♀) (from Chaetodon lunula ), CHCM no. 625 (voucher) (1 vial, 2 specimens ♂ ♀) (from K. cinerascens ).

Remarks.

Because of the presence of a small intestinal caecum, long ventricular appendage, rounded ventriculus and small mucron on the tail tip, these larvae are morphologically similar to those described by Deardorff and Overstreet (1981) and the type HA of Deardorff et al. (1982) in the Gulf of Mexico and the Hawaiian Island, respectively. Recently, Shamsi et al. (2011) proposed a new classification for larvae occuring in fishes off Australia according to their molecular characterization. Morphometrically, larvae from America and the Australian region were practically identical. Arothron hispidus , C. lunula , and K. cinerascens represent new host records.