Aoruroides cochinchinensis, Guzeeva, Elena A., Luc, Pham Van & Spiridonov, Sergei E., 2010

Guzeeva, Elena A., Luc, Pham Van & Spiridonov, Sergei E., 2010, Aoruroides cochinchinensis sp. n. (Oxyurida: Thelastomatidae) from Vietnamese Panesthiinae wood-burrowing cockroaches, Zootaxa 2477, pp. 62-68 : 63-68

Aoruroides cochinchinensis sp. n.

( Figs 1–2 )

Morphometric data: Table 1.

TABLE 1. Morphometry of Aoruroides cochinchinensis sp. n.

Adult: Long fusiform thelastomatids. Remarkable sexual dimorphism. Mouth opening hexagonal. Lateral alae absent.

Male: Cuticle smooth and thin. Maximal body diameter at proventriculus level. Tail subulate. Head capsule cylindrical, non-annulated, 15×20–23 µm. Anterior end bearing thorn-like cuticular projections posterior to head capsule to mid-corpus level. Mouth opening surrounded by 8 pseudolabia bearing no papillae. Amphids situated laterally, slightly posteriad to subventral and subdorsal pseudolabia; amphidial apertures round, 0.6 μm in diameter.

Stoma of complex structure, 10–11 µm long. Pharynx consists of clavate corpus 180–203 µm long and maximum width 33–43 µm in paratypes, 195×38 µm in holotype, thin-walled isthmus, and basal bulb 60–78 µm in diameter in paratypes and 64 µm in holotype. Anterior part of intestine broadened, forming proventriculus 75–100 µm in diameter in paratypes, 85 µm in holotype.

Nerve ring in 175–200 µm from anterior end in paratypes and 188 µm in holotype, situated on the border between corpus and isthmus.

Excretory pore situated behind proventriculus level, close to testis flexure.

Monorchic. Testis reflexes at 428–525 µm from anterior end in paratypes and 485 µm in holotype. Testis flexure ca. one third of total testis length. Posterior to flexure, testis contains several dozens of 12–17 μm long rod-like cells. Spicule absent.

Three pairs of genital papillae present: a pair of prominent elongated precloacal genital papillae in front of cloaca, a pair of smaller adanal genital papillae and a pair of postcloacal genital papillae at short distance from cloaca. Unpaired papilliform appendage present just posterior to cloaca.

Female: Cuticle prominently annulated at anterior, annules 15–18 µm wide. No thorn-like projections present. Head capsule conoid 73 µm long. Eight triangular pseudolabia of perioral area separated from each other by 8 protruding elongated plates. Perioral area off-set separated from head capsule by deep furrow. No head papillae.

Nerve ring at mid-isthmus ca. 295 µm from anterior end.

Excretory pore behind proventriculus level. Excretory vesicle large, with 4 prominent excretory canals.

Swollen ovoid pharyngeal corpus 163–165×73–80 µm with thick inner cuticular lining of lumen, thinwalled isthmus 250–275 µm long and 23–28 µm wide, and basal bulb 108–113 µm in diameter with prominent valvular apparatus. Cardia small. Distinct proventricular part of intestine ca. 200 µm in diameter. Proventriculus lumen with homogeneous brownish content. Rectum long, with three round rectal cells. Anal opening covered by anterior fold.

Didelphic, uteri opposed and reflexed. Germinative part of gonad tubes ending with well discernible terminal cap cells on anterior and posterior branches. Anterior ovary does not reach pharynx level. Vulva opening near mid-body, anterior vulva lip protruding, vagina directed anteriorward. Spherical cells on the border between vagina vera and vagina uterina. Vaginal lining strongly cuticularized.

5– 10 eggs in uteri at the moment, 155–173 µm long and 73–100 µm wide. Fully formed eggs with smooth egg-shells, unembryonated in uteri.

Sequencing data

The only sequences deposited for Aoruroides nematodes are the partial (273 bp) LSU (28S) rDNA sequences ( AM232763 and AM232755 ) for two isolates of A. queenslandensis ( Jex et al., 2006) . Constructed 273 bp long alignment for four available Aoruroides sequences demonstrated complete identity of D2D3 LSU sequences for male and female of A. cochinchinensis sp. n. (thus proving conspecificity of male and female specimens) and presence of nucleotide differences in six positions between Vietnamese and Australian specimens.

Type material

Holotype—male, № 1065; paratypes— 8 males, 2 females. Holotype is deposited in the Museum of Helminthological Collections at the Center of Parasitology, A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia. 2 paratype male specimens are deposited in the Museum voor Dierkunde, Ghent University, Ghent, Belgium ( UGMD 104140) and in the Julius Kühn-Institut, Muenster, Germany ( DNST 323/1/1).

Type host

Panesthia sp. ( Dictyoptera : Blattaria: Blaberidae ) Type species

Aoruroides philippinensis ( Chitwood & Chitwood, 1934) Travassos & Kloss, 1958 ; Philippines List of valid species

A. legionarius Kloss, 1966 ; Brazil

A. rosario Coy Otero, García & Alvarez, 1993 ; Cuba A. travassosi Coy Otero, García & Alvarez, 1993 ; Cuba A. queenslandensis Jex, Cribb & Schneider, 2004 ; Australia

Differential diagnosis

Males of A. cochinchinensis sp. n. are characterized by cylindrical head capsule, thorn-like projections densely placed and situated posterior to head capsule to mid-corpus level, smooth non-annulated cuticle further posteriad, lack of cephalic papillae, nerve ring position on the border of corpus and isthmus, excretory pore posterior to proventriculus and presence of 3 pairs of genital papillae and unpaired papilliform appendage. Females are characterized by annulated cuticle, lack of cephalic papillae, nerve ring encircling middle of isthmus and large smooth egg-shells.

The present species is easily differentiated from other nominal species of the genus by the presence of thorn-like cuticular projections at the male anterior end. By having cuticular projections on male’s anterior end it is related to A. queenslandensis but differs by its thorn-like shape vs knob-like shape in the latter. Additionally males of A. cochinchinensis sp. n. differ from A. legionarius Kloss, 1966 and A. queenslandensis with nerve ring position at the border of corpus and isthmus vs nerve ring position at mid-corpus.

By similar values of de Man indices a, b and c, females of A. cochinchinensis sp. n. are related to A. legionarius , A. rosario Coy Otero, García & Alvarez, 1993 and A. queenslandensis . They can be differentiated from A. legionarius and A. rosario by larger body size (3700–5160 µm vs 2664–3146 µm in A. legionarius and 1620–1950 µm in A. rosario , correspondingly).

The new species is also related to A. queenslandensis as well as to A. philippinensis ( Chitwood & Chitwood, 1934) Travassos & Kloss, 1958 in similar size of egg-shells (155–173×73–100 µm; 113–163×56– 91 µm and 164–166×70–80 µm, respectively). A. queenslandensis can be distinguished from the new species by striated egg-shells. A. cochinchinensis sp. n. is differentiated from A. philippinensis and A. rosario by the position of nerve ring in females. In both latter species the nerve ring of females is positioned on the anterior part of the isthmus whereas it is at mid-isthmus in the new species. From A. philippinensis the new species from Vietnam can be also distinguished by the value of de Man index a —14.3 vs 19.4. From A. travassosi Coy Otero, García & Alvarez, 1993 females of A. cochinchinensis sp. n. differ by prominently different body proportions (a = 14.3 vs 5.5; b = 8 vs 4).

Remarks

Earlier Jex et al. (2004) described knob-like cervical cuticular projections at the male anterior end of A. queenslandensis . These structures are forming irregular transversal rows on the surface of the body and disappear before nerve ring level. Males of the type species A. philippinensis , as equally of two Neotropical species A. legionarius and A. travassosi , lack any cuticular projections on the anterior end. The original description of the Cuban species A. rosario is based on female specimens only.

Few morphological features of Aoruroides nematodes from original descriptions can be used for secure species differentiation. The body size of males varies prominently between species. The shortest males are reported for A. travassosi (mean body length—724 µm) and the maximal male body length for this genus is reported for Australian species A. queenslandensis (range 1920–3010 µm). The male body length of the type species of the genus A. philippinensis is 1100–2330 µm and for A. cochinchinensis sp. n. is 1820–2490 µm. Body proportions are also different between Aoruroides males. De Man index a is the lowest in males of A. travassosi (a = 6.3), around 13.5 in A. queenslandensis , 17.4— A. legionarius , 19.1— A. philippinensis and reaching maximum in males of A. cochinchinensis sp. n. —19.5. For Aoruroides females the shortest are those of A. rosario 1620 –1950 µm, when A. cochinchinensis sp. n. together with A. philippinensis and A. queenslandensis are demonstrating average female body length over 4000 µm (see Table 2 ). Females of the Cuban and Brazilian species A. travassosi and A. legionarius are characterized by the intermediate length values (2090 µm and 2664–3146 µm, correspondingly). These morphometric data are demonstrating that together with two Australasian species newly found A. cochinchinensis sp. n. belongs to the group of Aoruroides species with maximal body length in both sexes.

An analysis of the original description revealed another feature, which helps to distinguish Aoruroides species—the position of the nerve ring. Thus, nerve ring position in males at mid-corpus was reported for A. legionarius and A. queenslandensis . In the males of A. cochinchinensis sp. n. nerve ring is situated near the border between corpus and isthmus. In Aoruroides’ females nerve ring is always situated at mid-isthmus level besides of females of A. philippinensis and A. rosario with nerve ring behind the corpus.

This work was supported by the grants of the Russian Foundation of Basic Researches №№ 08–04–00209_a and 09–04–90300-Viet_a.

Figures

FIGURE 1. Aoruroides cochinchinensis sp. n. A – D—male; E, F—female: A—anterior end; B—stoma; C—posterior end; D—excretory pore; E—anterior end; F—reproductive system.

FIGURE 2. Aoruroides cochinchinensis sp. n. A – C—male; D, E—female: A—anterior end; B—mouth opening; Ccloacal region; D—anterior end; E—mouth opening.

Tables

TABLE 2. Species of the genus Aoruroides Travassos & Kloss, 1958: comparison of female morphometric features.

Species L	Width	Pharynx	Characters a b c	V, %	V', %	Eggs
A. cochinchinensis 4430 sp. n.	310	555	14.3 8 4.6	47	60.6	155-173× 73-100
A. philippinensis 4000–4450	165–270	473–540	19.4 8.3 5.4	47.3	58.2	164-166×70-80
A. legionarius 2664 –3146	182–225	320–333	14.3 9 3	38.5	59	88-94×44
A. rosario 1620 –1950	143–156	203–207	11.9 8.7 –	47.3	–	85-92×58-61
A. travassosi 2090	378	535	5.5 4 3.4	47	66.7	42-52×31-42
A. queenslandensis 3200–4990	280–440	525–596	13.1 7.4 4	50	–	113-163×56-91
Acknowledgements