Tylolaimophorus de Man, 1880

Ghaderi, Reza, Asghari, Ramezan & Eskandari, Ali, 2020, Systematics of the genus Tylolaimophorus de Man, 1880 (Nematoda Diphtherophoridae), with description of T. minor (Thorne, 1939) Goodey, 1963 from Iran, Zootaxa 4755 (2), pp. 322-340 : 323-326

Genus Tylolaimophorus de Man, 1880

= Triplonchium Cobb, 1920

Diagnosis

[After Brzeski (1994) with some modifications]. Small to medium-sized nematodes (0.4-2.1 mm), with exceedingly dense, granular bodies which obscure the details of the internal anatomy. Anterior sensilla in two labial circles of six sensilla in each and a cephalic circle of four sensilla. Amphidial apertures large, perpendicular to the body axis. Lip region continuous, slightly or deeply offset. Buccal cavity with thickened plates anteriorly, serving as attachments for spear protractors. Dorsal tooth needle-like, projecting from the basal part of the buccal cavity. Narrow stoma extension ending with three small thickenings. A pair of lateral pores may occur posterior to spear in some species. Pharynx usually anteriorly swollen, then narrowing, ending with short, rounded to pyriform enlargement. Three large cardiac cells between pharynx and intestine. Female reproductive organs paired, reflexed, with germinal zones directed toward vulva. Oviduct composed of four cells. Vagina short, with thick walls. Male reproductive system monorchic, spicules paired and variable in shape: straight, arcuate or strongly bent ventrally, each spicule surrounded by a muscular capsule. Ventromedian papillae may occur in precloacal and in neck region. Rectum often thick walled. Intestine extending into the tail region as a post-rectal sac in some species. Tail usually short and cylindrical with rounded terminus, rarely longer and conical with pointed terminus, similar in both sexes. A pair of caudal pores may sometimes be observed.

Taxonomic remarks: J. B. Goodey (1963) made Triplonchium a synonym of Tylolaimophorus , but this act was not recognized as valid by Thorne (1974). Since then, various authors attributed species to either genus. Jairajpuri (1964) didn’t concur with Goodey’s synonymy of Tylolaimophorus and Triplonchium on the grounds that Triplonchium does not have the perioral circlet of minutely mammiform papillae typical of Tylolaimophorus , and the spear illustrated by de Man (1880) has little resemblance to that of Triplonchium . Jairajpuri regards Tylolaimophorus as genus inquirendae in the Tyleptine. However, Jairajpuri & Ahmad (1992) accepted synonymy.

The designation of a neotype of Tylolaimophorus typicus by Brzeski (1994) helped to clarify the taxonomic position of the species. Brzeski (1994) presented a good synopsis of the genus. He also redescribed the type species, accepting notes from published works by de Coninck (1932) and Arpin (1973).

Sauer (1968) mentioned that the eight described species of Tylolaimophorus known at that time seem to fall into two groups which show some striking differences. T. cylindricus ( Cobb, 1920) Goodey, 1963 , T. bulgaricus ( Andrássy, 1958) Goodey, 1963 and T. pileatus ( Andrássy, 1961) Sauer, 1968 are relatively large species, over 1 mm, with characteristically curved spicules surrounded by conspicuous musculature. T. rotundicauda Paesler, 1955 (now considered as Longibulbophora rotundicauda (Paesler, 1955) Yeates, 1967 ), T. digitatus Husain & Khan, 1967 and T. indicus Husain & Khan, 1967 are under 0.5 mm in length, with cephalated spicules. T. minor ( Thorne, 1939) Goodey, 1963 (0.6 mm) and T. typicus de Man, 1880 (0.8 mm) are intermediate in size but unfortunately, no males are known for either species. He further noted that T. constrictus Sauer, 1968 and T. pugio Sauer, 1968 link the two groups in some respects.

Thorne (1961), Husain & Khan (1967), Jairajpuri & Ahmad (1992) and Zullini (2006) all agreed that the males of this genus are monorchic, with a single outstretched testis, whereas Brzeski (1994) illustrated the male of Tylolaimophorus typicus as possessing an anteriorly and a posteriorly directed testis. Andrássy (2009) concluded that Brzeski’s observation may be incorrect. However, Eroshenko & Tepljakov (1977) also reported two testes for T. corpulentus Eroshenko & Tepljakov, 1977 .

T. obtusicaudatus ( Schuurmans Stekhoven & Teunissen, 1938) Arpin, 1973 is inadequately described, and Goodey (1963), after studying type specimens, doubted its generic status. Therefore, the species is here considered species inquirendae. Although not designating it as a new combination, Arpin (1973) was the first to use the binomen T. obtusicaudatus .

List of species

Type species

Tylolaimophorus typicus de Man, 1880 = T. pannonicus Andrássy, 1988

Other species

T. bulgaricus ( Andrássy, 1958) Goodey, 1963

= Triplonchium bulgaricum Andrássy, 1958

T. cavicaudatus Eroshenko & Tepljakov, 1977

T. constrictus Sauer, 1968

T. corpulentus Eroshenko & Tepljakov, 1977

T. cylindricus ( Cobb, 1920) Goodey, 1963

= Triplonchium cylindricum Cobb, 1920

T. digitatus Husain & Khan, 1967

= Triplonchium digitatum ( Husain & Khan, 1967) Ivanova, 1977

T. indicus Husain & Khan, 1967

= Triplonchium indicum ( Husain & Khan, 1967) Ivanova, 1977

T. kasbegi ( Eliashvili, 1986) Brzeski, 1994

= Triplonchium kasbegi Eliashvili, 1986

T. minor ( Thorne, 1939) Goodey, 1963

= Triplonchium minor Thorne, 1939

= Triplonchium parvum Thorne, 1974

T. pileatus ( Andrássy, 1961) Sauer, 1968

= Triplonchium pileatum Andrássy, 1961

T. pugio Sauer, 1968

T. tegmentum ( Ivanova, 1980) Jairajpuri & Ahmad, 1992

= Triplonchium tegmentum Ivanova, 1980

Species inquirendae

T. obtusicaudatus ( Schuurmans Stekhoven & Teunissen, 1938) Arpin, 1973

= Triplonchium obtusicaudatum Schuurmans Stekhoven & Teunissen, 1938

Nomina nudum

T. curvicaudatus Eroshenko & Tepljakov, 1977 : appears in Jairajpuri & Ahmad (1992), and Andrássy (2009).

Key to the species of Tylolaimophorus (After Brzeski (1994) with slight modifications)

1. Rectal walls distinctly thickened; tail broadly rounded; anterior part of pharynx with median swelling.................. 2

- Rectal walls thin; tail conical; anterior part of pharynx cylindrical............................................. 12

2. Lip region offset by a deep groove....................................................................... 3

- Lip region continuous, narrower or offset by a depression..................................................... 4

3. Spicules strongly bent; spear protractor attachments sclerotized......................................... T. pileatus

- Spicules arcuate; spear protractor attachments non-sclerotized....................................... T. constrictus

4. Female body length less than 0.7 mm ..................................................................... 5

- Female body length more than 0.8 mm .................................................................... 6

5. Spear 10-12 µm; males do not occur................................................................ T. minor

- Spear 15-17 µm; spicules almost straight, cephalated; males common................................. T. tegmentum

6. Spicules wide, almost straight........................................................................... 7

- Spicules narrow, arcuate to strongly bent.................................................................. 9

7. Pair of subventral papillae on male tail.................................................................... 8

- No subventral papilla on male tail.................................................................. T. pugio

8. a = 15.................................................................................... T. corpulentus

- a = 20-25................................................................................ T. cavicaudatus

9- Body length less than 1 mm ........................................................................... 10

- Body length more than 1 mm .......................................................................... 11

10- Spicules arcuate, with ventrally directed processus................................................... T. typicus

- Spicules strongly bent, no processus............................................................... T. kasbegi

11. Five distinct ventromedian precloacal supplements................................................ T. bulgaricus

- At most a single ventromedian precloacal supplement.............................................. T. cylindricus

12. Spear 16-17 µm; a = 16-18..................................................................... T. digitatus

- Spear 18-23 µm; a = 19-21...................................................................... T. indicus

Diagnostic compendium of species

Species of Tylolaimophorus can be distinguished by 12 morphological and morphometric characters ( Table 1 ). Data are obtained from the original descriptions and other reported populations worldwide.

Description and differential diagnosis of species

For each species, measurements, description of females and males, diagnosis and relationships with closely related species and distribution are provided here. Data in parentheses are calculated from the drawings in the relevant papers.

Tables

TABLE 1. Diagnostic compendium for Tylolaimophorus species (measurements are in µm, except L is in mm).

Species\ Character †	Spear	L	a	b	c	c´	V	Spicules	Tail	Head	Pharynx	Male supplements
T. bulgaricus	15	1.3	32	7	30	1.4	-††	39	2	1	2	5
T. cavicaudatus	15	1.1	25	8	29	1.2	63	21	2	1	2	5
T. constrictus	13-14	0.8-1.6	22-29	7-10	21-34	1.2	52-60	27-33	2	2	2	4-9
T. corpulentus	13	1.0-1.3	15	8-9	33	1.1	57-63	21	2	1	2	13
T. cylindricus	18	1.2-2.1	30	8-12	30-40	0.8	53-54	40	2	1	2	1
T. digitatus	16-17	0.4-0.5	16-18	4-5	14-20	1.8	53-65	23	1	2	1	0
T. indicus	18-21	0.4-0.5	18-23	4-5	15-22	1.4	52-58	25	1	1	1	0
T. kasbegi	13-15	0.8-0.9	18-19	7	24-25	1.0	58-59	31-34	2	1	2	7
T. minor	9-12	0.3-0.7	10-23	4-7	12-23	0.9-1.7	43-61	-	2	1	2	-
T. pileatus	13-17	0.8-1.5	20-28	5-9	23-36	0.9-1.7	54-58	30-47	2,3	2	2	1 or more
T. pugio	12-13	1.0-1.5	26-37	9-12	33-46	1.1	48-57	30-40	2	2	2	4-7
T. tegmentum	15-17	0.6-0.7	11-17	3-5	25-39	0.6-0.9	51-57	23-27	2,3	1	2	0
T. typicus	10-13	0.6-1.1	18-28	4-8	23-35	0.8-1.2	48-58	24-29	2	1	2	2-4

† Diagnostic characters for species identification: tail shape: 1) conical with pointed to finely rounded terminus, 2) cylindrical with broadly rounded terminus, 3) digitate; head: 1) continuous or slightly offset, 2) deeply offset; Pharynx with anterior part: 1) cylindrical, 2) with median swelling.

†† Unknown.