Aspidodrilus
Aspidodrilus Baylis, 1914 emend. Coates, 1990 (ref. ID; 5783, 5791 redescribed paper)
ref. ID; 5791
Descriptions
External: Enchytraeidae with postclitellar segments dorsoventrally flattened, ectocommensal on earthworms of the genus Dichogaster. Body widest posterior to clitellum. Prostomium and first segment anteroposteriorly compressed, quadrangular; mouth just subterminal. Head pore more or less terminal on prostomium. Spermathecal pores lateral at 4/5. Dorsal setae lacking, ventral setae 2 per bundle in II-XI, gradually increasing to as many as 20 per bundle. Bundles with large numbers of setae with a transverse linear form, bundles paired laterally. Setae straight, anodulate; posterior setae with laterally flared, thin, bifurcate, recurved ectal ends. Clitellum extending over XII and XIII. With a ventral, muscular, sucker-shaped genital-adhesive disc on XII and XIII (midpoint at 12/13), diameter subequal to body width. With lateral membrane-like extension of the epidermis extending from disc to anus. Male pores in XII, on posterolateral edge of disc, female pores not seen here, believed to open in 12/13 (Michaelsen 1926). Anus slightly recessed, just subterminal. (ref. ID; 5791)
Internal: Brain truncate posteriorly. Dorsal blood vessel bifurcating ventral to brain; origin preclitellar. Pharyngeal glands compact. Spermathecae paired, not communicating with gut; ectal duct thick-walled (muscular), with sperm-containing expansion in V; ampulla saccate. Peptonephridia, pharyngeal appendages, and esophageal appendages lacking. Abrupt gut expansion at 7/8; with laterally paired, many lobed diverticula at expansion. Preseptal parts of nephridia large, efferent duct origins subterminal. Testes paired ventrally in XI. Sperm contained in "vesicles" or sacs, probably laterally paired septal extensions. Egg sacs similar. Sperm funnels in XI, glandular, with eccentric canal. Penial apparatus elongate, with external muscular layer and lateral muscular attachments; ectal part of penial apparatus, bearing male pore, protrusile (?); with complex epidermal invagination at male pore. Other copulatory glands lacking. Ovaries paired in XII. Female funnels and ducts not seen. (ref. ID; 5791)
Remarks
The main difference from previous records noted here is that ovaries and testes are paired. Overall, the organs of the reproductive system were determined to have typical enchytraeid forms and locations. Diagnostic enchytraeid characteristics, as described earlier, include the following: an anterior head pore; spermathecal pores at 4/5; straight anodulate setae; anteriorly bifurcating dorsal blood vessel; male pores in XII; female pores in 12/13; paired testes and ovaries in XI and XII, respectively; and glandular sperm funnels in XI. The characteristics of 2 setae per bundle (in anterior segments), short clitellum, and free spermathecae are plesiomorphies preceding the origin of the Enchytraeidae (Coates 1987, 1989). Body form, setal tip form and setal distribution, and the genital-adhesive disc are diagnostic for the genus. The specific form of gut diverticula found in Aspidodrilus may be a shared characteristic of a suprageneric taxon. (ref. ID; 5791)
Type species (type by monotypy)
Aspidodrilus kelsalli Baylis, 1914 (ref. ID; 5791)
- Aspidodrilus eburneensis Baer, 1952
See; Aspidodrilus kelsalli (ref. ID; 5791)
- Aspidodrilus kelsalli Baylis, 1914 (ref. ID; 5791)
Syn; Aspidodrilus eburneensis Baer, 1952 (ref. ID; 5791); Aspidodrilus kesalli Brinkhurst & Jamieson, 1971 (ref. ID; 5791)
- Aspidodrilus kesalli Brinkhurst & Jamieson, 1971
See; Aspidodrilus kelsalli (ref. ID; 5791)
Synonym
Aspidodrilus eburneensis Baer, 1952 (ref. ID; 5791); Aspidodrilus kesalli Brinkhurst & Jamieson, 1971 (ref. ID; 5791)
Descriptions
Description is based on material examined or, where data are given in brackets, on Baer 1952. (ref. ID; 5791)
External: Mature, whole-mounted and unmounted specimens 5-6 [2.5-3.6] mm long, with 47, 50, 56 [32-34] segments. Width at IV-V 0.60-0.68 [0.6] mm, at clitellum 1.05-1.13 [0.9] mm, at widest postclitellar point 1.22, 1.38 mm (n=2). Posterior segments anteroposteriorly compressed, 54, 60 µm (n=2) long and about twice as wide. Setae absent in XII, 2 or 4 perbundle in XIII and XIV, increasing in number more posteriad, from 5, 9, 14, 18 to 20 per bundle; most posterior segments all with 14-20 setae per bundle. Setae about 54 µm long in anterior segments; setal tips with two approximately equal, laterally acute teeth. (ref. ID; 5791)
Internal: Pharyngeal pad with a deep, dorsally extending medial groove; pad probably protrusile. Pharyngeal glands united dorsally at 4/5 and 5/6, with small ventral lobes in IV, V, and VI. Spermathecal ectal duct muscular, without glandular collar at pore or free glands along duct, but with a thickened area of glandular epidermis around ectal pore and with a short, thickened ectal art on duct. Canal of ectal duct with elongate expansion containing sperm, with infolded walls. Spermathecal ampulla relatively small, restricted to VI. Nephridia large, paired in preclitellar segments from 6/7, absent in clitellar segments, paired to XVII, irregularly present posterior to this, rarely single. Dorsal blood vessel origin in posterior of VII or anterior of VIII. Diverticula at intestinal region (7/8) each with 4 or 5 [6] lobes, directed anteriad, achlobe with ciliated canal. Intestine with S-bend in VIII; gut walls folded and thickened in XII-XIII. Clitellum extending over XII and anterior of XIII, small gland cells more or less regularly distributed. Genital-adhensive disc diameter about one-half body width at XII. Sperm extending into X, in small vesicle-like sacs. Sperm funnel about 2 times as long as wide, collar subequal to funnel width but very distinct. Vas deferens with thick, muscular walls throughout length, total diameter about 30-35 µm, canal diameter only 4-6 µm; only 2 or 3 times as long as funnel. Penial apparatus about 220 µm long (high) from ental gland to male pore at tip of protrusile part; glandular part penetrated about 60 µm form ental end by vas deferens; vas deferens extending to epidermal invagination at male pore. (ref. ID; 5791)
Remarks
Baer (1952) differentiated Aspidodrilus eburneensis from A. kelsalli on the basis of shorter, narrower body dimensions and correspondingly fewer segments of the former, and on the different collection locations, nothing that Sierra Leone is about 800 km northwest of the Ivory Coast. The smaller size noted by Baer for A. eburneensis cannot be appraised here as a specific difference because I have no information on inter- to intra-population variations. The specimen illustrated by Baer (1952) is shorter posterior the clitellum than the specimens seen here, but the widths of anterior and clitellar segments reported for all specimens are similar, the distance between the collection sites of the nominal species of Aspidodrillus is not greater than the known distributions of many earthworm species. Unfortunately, the specific identity of only one host species is known, although it is very likely that both hosts are species of Dichogaster. No type depiository was designated or is presently known for Aspidodrilus eburneensis, but the original figures and description are quite informatice. The resemblance of the type material of A. kelsalli to the figures of Baer (1952) is strong enough to support the conclusion that a single species in involved. Aspidodrilus eburneensis was not acknowledged by Nielsen and Christensen (1959) but this probably was an oversight, as previous publications refuting or synonymzing it are unknown. My observations support Michaelsen's (1926) record of bifid-looking setae in Aspidodrilus; however, there are no genital setae and setae are bifid throughout. There is a distinct medial division of the setal tips, which becomes less obvious as the setal tip becomes worn. In the specimens examined here the tips of the setae were notably more worn in anterior segments. The only other enchytraeid genus with bifid setal tips is Barbidrilus. The setae of Barbidrilus and Aspidodrilus are different form each other in form, and in both these taxa the setae are anodulate, unlike the nodulate bifid setae known in her oligochaetes. (ref. ID; 5791)
Type locality
Sierra Leone, West Africa; exterior of large earthworms, probably of genus Dichogaster. (ref. ID; 5791)
Material examined
Syntypes, BMNH 1923.1.4.1-2 and 1923.1.4.3 through 8; 1923.1.4.1-2 is a single, whole mature specimen in alcohol, 1923.1.4.3, 4, and 5 are whole mounts: dorsal side uppermost, stained with haematoxylin, ventral side uppermost, stained with paracarmine, and ventral side uppermost, juvenile, stained with haematoxylin, respectively; 1923.1.4.6, 7, and 8 are longitudinal sagittal sections, 6 and 7 appear to be of one specimen, L'1, and 8 one-half of a second specimen. Collected by Major H. Kelsall, R.A., in Sierra Leone. (ref. ID; 5791)