Chromadora macrolaimoides Steiner, 1915

Neres, Patrícia Fernandes, Santos, Paulo Jorge Parreira Dos & Esteves, André Morgado, 2021, New chromadorid nematodes from Brazilian coral reefs: a taxonomic contribution to Chromadora Bastian, 1865, Zootaxa 5032 (1), pp. 47-79 : 62-67

Chromadora macrolaimoides Steiner, 1915

( Figures 9–12 , Table 3)

Studied Material. Male drawn ( MOUFPE 0005 ), female drawn ( MOUFPE 0006 ), 5 males (463–467 NM LM- ZOO-UFPE) and 5 females (468–472 NM LMZOO-UFPE) .

Locality. Serrambi beach (S 8°33’31.5” W 35°00’16.7”), located on the southern coast of the State of Pernambuco, in the Northeastern region of Brazil .

Description. Males. Body cylindrical 677–800 µm long. Maximum body diameter 29–33 µm, anterior region attenuated, head diameter 10–12 µm (38–46% of body diameter in pharynx end). Annulated cuticle with transversal rows of small dots. Lateral longitudinal differentiation represented by four rows of larger and more spaced dots. This pattern is homogeneous throughout the body extension. Cephalic arrangement 6+6+4, inner and outer labial sensilla papilliform; cephalic setiform sensilla measuring 0.6–0.8 times head diameter. Amphideal fovea transversely elliptical occupying 32–53% of corresponding body diameter, located 2–3 µm from anterior end. Buccal cavity armed with three solid teeth, one dorsal and two ventral, dorsal tooth larger. Secretory–excretory pore located near and anterior to ocelli, 2–2.2 times head diameter from anterior end. Secretory–excretory gland situated posteriorly to pharynx with two cells present, one well developed (proximal) measuring 43–53 µm long and one of reduced size (6.5–13 µm). Ocelli situated 20.5–22 µm from anterior end. Nerve ring located 57–65% of pharynx length from anterior end. Pharynx with terminal bulb, pyriform and double, occupying 28–29% of pharynx length (34–36 long vs. 20–21.5 wide). The reproductive system with a single outstretched testis. Spicules 1–1.3 times the cloacal body diameter, curved and slightly cephalated. Gubernaculum narrow occupying 62–84% of spicule length, with expanded distal portion, embracing the spicules. Two small supplements (2.5–3 µm). Distance between proximal (anteriormost) supplement (S1) and distal (posteriormost) supplement (S2) is less than distance between S2 and the cloaca. Distance between S1 and cloaca is about 0.4 times tail length. Tail conical-elongated measuring 3.8–5.5 times cloacal body diameter, with a long spinneret (5.5–8 µm).

Females. Very similar to male. Reproductive system amphidelphic with reflexed ovaries with branches bent in opposite directions. Anterior gonad to the right of the intestine and the posterior gonad to the left of the intestine. Vulva located 46–50% of total length from anterior end. Tail 5.7–6.3 times anal body diameter.

Diagnosis (measurements of the specimens of Serrambi beach). Chromadora macrolaimoides is characterized by double bulb, cephalic setae 0.6–0.9 times head diameter. Secretory-excretory pore 2–2.2 times head diameter from anterior end, near and anterior to ocelli. Spicules 1–1.3 times cloacal body diameter. Gubernaculum narrow (62–84% of spicule length), with expanded distal portion, embracing the spicules. Two small precloacal supplements. Distance between S1-S2 less than between S2-Cloaca, which can be up to half the length (S1- S2 0.14 –0.18 times tail length/ S2-Cloaca 0.21–0.25 times tail length). Tail conical-elongated with a long spinneret (3.8–5.5 times cloacal body diameter in male and 5.7–6.3 times anal body diameter in female).

Differential diagnosis (Relationships). Chromadora macrolaimoides redescribed in this study is very similar to specimens described previously ( Steiner 1915; Chitwood 1951; Wieser 1955; Wieser and Hopper 1967; Hopper and Meyers 1967; Kito 1978b). The characteristics used for its identification were: the number, size and position of the pre-cloacal supplements, the shape of the bulb (pyriform-double), as well as the narrower tail with a long spinneret. The species that most resembles C. macrolaimoides is C. brevipapillata , similar in number and shape of pre-cloacal supplements and pyriform bulb, however, the distance between supplements (S1-S2 and S2-Cloaca) is different in these two species and bulb is not double in C. brevipapillata . The comparative illustration of the bulb shape of these two species can be seen in Wieser (1955).

Figures

FIGURE 9. Chromadora macrolaimoides male (MOUFPE 0005): (A) overview, (B) anterior region (buccal cavity, cephalic setae, secretory-excretory pore, ocelli and cuticle), (C) anterior region (pharynx posterior bulb and secretory-excretory gland), (D) posterior end (pre-cloacal supplements, spicules, gubernaculum, tail and cuticle).

FIGURE 10. Chromadora macrolaimoides male (MOUFPE 0005): (A) anterior region (arrow marks secretory-excretory pore and ocelli), (B) anterior region (arrow marks amphideal fovea), (C) pharynx posterior bulb and secretory-excretory gland, (D) anterior region (buccal cavity), (E) anterior region (cuticle), (F) posterior region (cuticle), (G) posterior end (tail), (H) posterior region (spicules, gubernaculum and pre-cloacal supplements).

FIGURE 11. Chromadora macrolaimoides female (MOUFPE 0006): (A) overview, (B) anterior region (buccal cavity, cephalic setae, secretory-excretory pore, ocelli and cuticle), (C) anterior region (pharynx posterior bulb and secretory-excretory gland), (D) posterior end (tail and cuticle).

FIGURE 12. Chromadora macrolaimoides female (MOUFPE 0006): (A) anterior region (buccal cavity, arrow marks secretory-excretory pore and ocelli), (B) pharynx posterior bulb and secretory-excretory gland, (C) anterior region (arrow marks amphidial fovea), (D) posterior region (cuticle), (E) posterior end (tail), (F) reproductive system.