Cosmocephalus pelecani , Mutafchiev, Yasen, Halajian, Ali & Georgiev, Boyko B., 2010
Mutafchiev, Yasen, Halajian, Ali & Georgiev, Boyko B., 2010, Two new nematode species of the genus Cosmocephalus Molin, 1858 (Spirurida: Acuariidae), with an amended generic diagnosis and an identification key to Cosmocephalus spp., Zootaxa 2349, pp. 1-20: 8-10
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Cosmocephalus pelecani n. sp.
Type-locality: Mansfield, Victoria, Australia (collected on 9 July 1972).
Intensity of infection: 5 specimens (3 males and 2 females).
Etymology: The name of the new species reflects the generic name of the host species.
Description ( Fig. 4 A –GView FIGURE 4 A – G)
General. Medium-sized acuariids. Anterior end with two triangular pseudolabia, each bearing single amphid and pair of prominent papillae. Pair of swellings situated dorsally and ventrally at bases of pseudolabia. Cordons arise dorsally and ventrally between pseudolabia; each cordon forming loop adjacent to its base and then continuing its course along longitudinal body axis; at level of posterior end of buccal cavity, cordons recurrent in anterior direction and reach level of anterior quarter of buccal cavity where they anastomose laterally ( Figs 4 A, BView FIGURE 4 A – G). Cordons consisting of a single row of cuticular plates (each plate c. 2 µm long) and longitudinal cuticular ridge along outer rims of plates; deep, almost closed longitudinal groove between plates and longitudinal ridge. Plates of descending cordon arm of unequal width, thus forming wide portions with notches between them. Deirids 14–20 long, bicuspid. Lateral alae absent. Buccal cavity elongate. Excretory pore situated posteriorly to deirids. Nerve ring surrounding narrow anterior portion of muscular oesophagus. Phasmids subterminal.
Male (n= 3 except otherwise stated). Body length 11.9–12.3 mm (12.0 mm). Maximum body width 115– 116, about mid-body; width 107–116 (112) at level of cloaca. Tail 294–302 (298, n= 2) long. Cordons 415–469 (442) long, recurrent in anterior direction to 116–132 (123) from anterior body end, 30–36 wide. Deirids and excretory pore at 482–561 (520) and 595–693 (640), respectively, from anterior body end. Buccal cavity 411– 434 (419) long and 18–20 wide. Muscular oesophagus 952–1,135 (1,040) long and 50–56 (53) wide. Glandular oesophagus 4,003–4,265 (4,141) long and 116–143 (123) wide. Nerve ring at 453–516 (479) from anterior body end. Cuticle 18–20 thick. Distance between cuticular striations 4–5 μm. Caudal alae 597–660 (n= 2) long. Single ventral cuticular ridge extending between level at 2,520–2,573 (n= 2) from posterior body end to beginning of caudal alae. Single median sessile precloacal papilla present. Nine pairs of pedunculate caudal papillae, 4 precloacal and 5 postcloacal ( Fig. 4 FView FIGURE 4 A – G). Anterior four pairs of pedunculate postcloacal papillae with almost equal distance between them; fifth pair near posterior extremity of tail. Sixth pair of postcloacal papillae sessile, smaller, situated between bases of last pedunculate papillae. Left spicule 658–665 (n= 2) long, 11–13 wide, with prominent projection on its distal end. Right spicule 151–155 (n= 2) long, 30–36 (n= 2) wide ( Fig. 4 EView FIGURE 4 A – G). I CL/BL 0.035–0.038 (0.037); I mOE/gOE 0.238–0.273 (0.251); I OE/BL 0.417–0.445 (0.431); I CA/BL 0.050–0.056 (n= 2); I LSP/RSP 4.290–4.358 (n= 2).
Female (n= 2 except otherwise stated). Body length 14.5–15.8 mm. Maximum body width 385–493, about mid-body; width 129–130 at anus and 385–460 at vulva. Tail 233–237 long. Cordons extending to 516–539 from anterior body end, recurrent in anterior direction to 125–129 from anterior body end, 52–54 wide. Deirids and excretory pore at 584–596 and 688–791, respectively, from anterior body end. Buccal cavity 482– 539 long and 24–28 wide. Muscular oesophagus 939 (n= 1) long and 72 (n= 1) wide. Glandular oesophagus 4,149–4,706 long and 112–125 wide. Nerve ring at 505–612 from anterior body end. Cuticle 14–18 thick. Distance between striations 6–7 μm. Vulva at 7.1 –8.0 mm from anterior body end. Reproductive system didelphic. Vagina vera short, posteriorly directed, separated from vagina uterina by well-developed circular musculature ( Fig. 4 CView FIGURE 4 A – G). Vagina uterin а longer, with muscular walls. Posterior extremity of tail with nipple-like projection ( Fig. 4 GView FIGURE 4 A – G). Eggs oval, 36–39 × 22–24 (37 × 23, n= 20), containing first stage larva ( Fig. 4 DView FIGURE 4 A – G). I CL/BL 0.034–0.036; I mOE/gOE 0.200 (n= 1); I OE/BL 0.357 (n= 1); I V/BL 0.491–0.509.
Remarks. The presence of lateral alae has been described in C. obvelatus (see Anderson & Wong 1981; present study), C. capellae (see Yamaguti 1935; present study), C. jaenschi (present study) and C. podicipis (present study). It was not mentioned in the original description of C. imperialis but was shown in the accompanying illustration ( Morishita 1930). C. pelacani can be distinguished from all these species by the absence of lateral alae.
Cosmocephalus pelecani is similar to C. obvelatus in its morphometrical characters (Table 1). In addition to the absence of lateral alae, C. pelecani can be differentiated by its more prominent appendage of the distal end of the left spicule than that in C. obvelatus ( Fig. 4 FView FIGURE 4 A – G and Fig. 5 FView FIGURE 5 A – H).
The new species can be differentiated from C. capellae by the longer body of males and the longer spicules (Table 1). C. pelecani has longer and markedly wider cordons. Moreover, C. capellae exhibits tricuspid deirids (compared to bicuspid deirids in C. pelecani ).
The absence of lateral alae and the bicuspid deirids of C. pelecani differentiate it from C. jaenschi ; the latter has lateral alae and tricuspid deirids. C. jaenschi also has a prominent appendage on the distal apex of the left spicule, much bigger than in the new species ( Fig. 7 BView FIGURE 7 A, B and Fig. 4 FView FIGURE 4 A – G).
The new species has longer males but a shorter right spicule than those of C. imperialis (Table 1).
Cosmocephalus pelecani is characterised by cordons consisting of plates of unequal width, forming a descending arm of wide series of plates separated by notches; in addition, the cordon loop is short. In contrast, C. faridi has no scalloped cordons and a very elongate loop ( Khalil 1931). The males of C. pelecani can also be distinguished from those of C. faridi by their longer body and longer left spicule (Table 1).
Compared to C. podicipis , the males of C. pelecani have a longer left spicule (Table 1) and a greater spicule ratio, i.e. I LSP/RSP (4.290–4.358 vs 2.770–3.360). The eggs of C. podicipis are more elongate than those of C. pelecani ( Fig. 1 FView FIGURE 1 A – G and Fig. 4 DView FIGURE 4 A – G).
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