Zonothrix columbianus Adamson & Buck, 1989

Carreno, Ramon A., 2018, Pinworms (Nematoda: Thelastomatoidea) from Insects Collected in Mississippi, USA, with description of a new species of Protrellus Cobb, 1920 from the Cockroach Ischnoptera deropeltiformis Brunner von Wattenwyl, 1865 (Blattaria: Ectobiidae), Zootaxa 4531 (4), pp. 567-577 : 573

Zonothrix columbianus Adamson & Buck, 1989 (Thelastomatoidea: Pseudonymidae )

Males and females of this species were recovered from Tropisternus collaris and T. blatchleyi blatchleyi (Table 1).

Measurements (in micrometers). Males (n = 9): Body length 1251 ± 165 (980–1410); maximum width 69 ± 6 (60–78); buccal cavity 7 ± 1 (5–8); length of buccal capsule 7 ± 2 (5–9); width of buccal capsule 16 ± 2 (14–18); nerve ring 159 ± 12 (135–170); excretory pore 322 ± 18 (290–338); esophagus 222 ± 12 (201–235); corpus 171 ± 10 (153–181); corpus maximum width 17 ± 2 (15–21); isthmus 14 ± 4 (10–20); bulb length 38 ± 2 (35–40); bulb width 37 ± 2 (34–40); tail 39 ± 8 (28–53); body width at tail 25 ± 2 (23–28); spicule 24 ± 4 (18–28); gubernaculum 16 ± 5 (13–20); a = 18 ± 2 (15–20); b = 6 ± 1 (5–6); c = 33 ± 7 (26–44).

Female (n = 15): Body length 3001 ± 282 (2375–3775); maximum width 206 ± 25 (169–250); buccal cavity 17 ± 2 (15–21); oral annule length 12 ± 2 (10–15); oral annule width 40 ± 3 (36–45); second annule length 21 ± 4 (17–28); second annule width 68 ± 5 (60–76); nerve ring 243 ± 25 (225–260); excretory pore 561 ± 117(415–725); esophagus 371 ± 32 (325–410); corpus length 291 ± 28 (256–340); corpus maximum width 43 ± 3 (40–49); bulb length 82 ± 8 (70–95); bulb width 82 ± 6 (73–95); vulva from anterior end 1859 ± 280 (1391–2425); vulva from posterior end 1068 ± 114 (860–1260); distance between vulva and anus 767 ± 104 (560–910); tail 286 ± 31 (250–335); body width at tail 115 ± 19 (90–145); egg length 69 ± 4 (63–78); egg width 44 ± 3 (40 – 48); a = 15 ± 2 (12–18); b = 8 ± 1(7–9); c = 10 ± 2 (8–13); V = 64 ± 4 (57–69).

The morphology of our specimens together with the measurements presented above overlap consistently with those of T. columbianus . The swollen cuticular annulations and longer tail (84 – 120 µm vs. 250 – 335 µm) differentiate this species from the only other currently known North American species, Zonothrix tropisterna Todd, 1942 , found in Tropisternus numbatus Say, 1823 ( Todd, 1942; Adamson & Buck, 1990). Reported hosts for Z. columbianus include Tropisternus columbianus , T. lateralis marginatus , and Hydrobius fuscipes ( Adamson & Buck, 1990; Adamson et al., 1992). Thus, T. collaris and T. b. blatchleyi represent new hosts for Z. columbianus . The typical presence of worms in the host has been reported as exactly one male and one female (Adamson et al., 1992). In the present study, a similar pattern was found, with the mean intensity of males of Z. columbianus in T. collaris being 1 (8 infected) and females 1.2 (11 infected). Six of the 11 infected T. collaris had one male and one female, 3 had no males and one female, two had 1 male and 2 females, and 6 were uninfected (Table 1). The 2 infected T. blatchleyi both had one male and one female Z. columbianus in each host. This pattern resembles that reported in other infected hydrophilids (Adamson et al., 1992). The broad North American distribution and multiple hosts make this species a potentially interesting subject for molecular comparison to determine whether possible cryptic species complexes may exist.