Ramiellona americana Gates 1957

Ramiellona americana (Gates, 1957)

Figure 10

Ramiella americana Gates, 1957: 1.

Ramiellona americana: Gates 1962: 215. Ramiellona americana: Gates 1978: 442.

Locality and material. Guatemala, Puerta parada, Municipality of Santa Catarina Pinula, outside Guatemala City and 0.5 km from Panamerican Hwy. Forest of Cupressus in regeneration, property of J. Schuster. In a pond. 14°33’27.69”N, 90°29’10.12”W, 1800 m a.s.l.. 1CA (posterior amputee). 06/06/1993, P. Reyes, IEOL 3098.

Description. External. Length nearly 200 mm, coiled and amputee; width postclitellar 13.5 mm. Segments more than 232. Pigment absent. Color gray-brownish, probably due to conservation in alcohol for 19 years. Prostomium evaginated, probably prolobous. One secondary annulation visible from segment 4, but more evident in 5; behind clitellum hardly visible, completely absent in last segments. Setae eight per segment, closely paired, minute and difficult to see; ab visible from 7, cd visible in 13 and then only behind clitellum; towards the posterior region the setae still minute but thicker. Setal formula (aa:ab:bc:cd:dd): segment 30: 8.4:1:8.4:0.8:48; segment 225: 6.8:1:5:0.8:41; dd <1/2U. Paired penial setae (a and b) in 17 and 19, all similar in shape and size (Fig. 10 D– G). Both setae a and b characterized by three regions: a basal slightly curved zone, a straight region which represents the main body and a distal part, curved between 45° and 90°. The distal apex slightly twisted, ending as a very thin filament. No ornamentation present in any region of the setae. Size of the straight region c. 2.44 mm. Setae a and b of 18 small and difficult to see. Clitellum saddle-shaped in 1/2 13 –20 (8.5 segments), hardly visible, ventrally reaching AB. Dorsal pores present all along the body, first pore in 13/14. Paired spermathecal pores as transverse slits in AB of 7/8 and 8/9; very small (1 mm) in relation to the size of the worm, and slightly larger than ab. Female pores in equator of 14, just to the level of ab. Male pores not recognized. Two pairs of minute prostatic pores in 17 and 19, on small protuberances, in A, joined by parenthesis-shaped seminal grooves, which run in AB. Unpaired elliptical genital marks in the mid-ventral line of 16/17, 20 and 21, extending from AB to AB (Fig. 10 A).

Internal. Septa 5/6–11/12 strongly muscular, funnel-shaped and imbricated, joined by large muscular fibers; posteriorly thin and membranous. Four muscular fibers at septa 5/6–7/8, two dorsal and two lateral; eight fibers at septa 8/9, 9/10 and 11/12, four dorsal (two on each side), four lateral (two in each side). All septa joined to body wall except septum 10/11 which is completely united to 11/12. One large gizzard in 5. Calciferous glands absent; esophagus in 9–11 with thin lamellae projecting from the entire esophageal wall. Intestinal origin not recognized, somewhere in the region of segments 14–16. Dorsal typhlosole starting abruptly in 20, as a single and big lamina; from 30 on the free edge with two slight folds (i.e. typhlosole bifid), the main lamina with lateral dorso-ventral folds, ending in 189. Paired and dorsal intestinal caeca in each of segments 20–25 (n =6).

Single dorsal vessel visible throughout. Supra-esophageal vessel visible in 9–12. Lateral hearts in 9 and 10; large latero-esophageal hearts in 11 and 12. The excretory system characterized by three different kinds of nephridia: i) paired tufts of micronephridia on the floor of segments 2, 3 and 4, at both sides of the pharynx; ii) four clusters of tufted micronephridia in each of segments 5–11, two fixed dorso-laterally to the posterior septum, and two on the floor at both sides of the mid-ventral line; iii) closed parietal meronephridia from 13 on backwards, c. 18 at each side (=36 per segment), joined by a transverse cord. The median-ventral nephridium of last segments with a nephrostome.

Metandric, testes and male funnels only in 11, within a closed testicular chamber formed by the total union of septa 10/11 and 11/12, which also encloses all the somatic structures of this segment. Testes large, tuft-like; male funnels small, slightly iridescent and plicate. Male gonoducts thick and large, entering the body wall in 13 at AB; due to their size, they can be observed posteriorly even inside the body wall. One pair of large acinous dorso-lateral seminal vesicles in 12, fixed to septum 11/12 and completely covering the esophagus and dorsal vessels. Paired tubular prostates in 17 and 19, small, folded and extending one or two segments backwards, fixed to the floor by connective tissue of the involved septa; muscular duct and glandular part almost the same width, but the latter 4–5 times longer than duct. Penial setae a and b within separate follicles, each one with two or three undeveloped extra setae. Follicles with some muscular stripes extending to body wall.

Ovaries in 13, very small, bushy and with numerous eggs dispersed all over, not in rows; female funnels not recognized. Two pairs of spermathecae in 8 and 9, tightly attached to the floor, without diverticle and measuring in total length 3.3 mm. Ampulla ovoid, projecting posteriorly, its anterior part covering the underlying muscular duct, posterior part with a mesial curvature; no iridescence or external seminal chambers observed (Fig. 10 B,C).

1978 and the single individual found in Puerta Parada, Guatemala currently assigned to R. americana.

Remarks. R. americana and R. lavellei are very similar species which were both described from a single specimen, the first intercepted in soils supposedly from Guatemala (Gates 1957) and the second collected in pine forests of central Chiapas, Mexico (Gates 1978). The Puerta Parada individual of this study presents similarities with both species, mainly by the complete metandry (loss of testes and male funnels of segment 10). The metandric condition (complete or incomplete, i.e. only the loss of testes) is common in the majority of the Central American species of Ramiellona, and hitherto only recorded in one Mexican species. Other changes that accompany metandry are the testicular chamber of segment 11 and a single pair or seminal vesicles in segment 12. In R. americana Gates (1957) stated that the testicular chamber is complete and that it encloses digestive and circulatory systems of segment 10, making them visible only after separating completely the fused septa 10/11 from that of 11/ 12. Table 2 shows some characters shared by R. americana, R. lavellei and the Puerta Parada individual. It can be seen that the Puerta Parada specimen has characters in common with R. americana (clitellum, testicular chamber, type of septal nephiridia, size of penial setae) and with R. lavellei (setal distances, amount of parietal nephirida, type of spermathecae), but also that this individual presents some unique characteristics such as the kind of genital marks, the intraparietal male gonoduct, the amount and location of intestinal caeca and the bifid typhlosole. With more individuals available, it will be possible to evaluate the fixation of characters, and a new species or at least a new subspecies may be named. Search of type material of R. americana was unsuccessful: The species is not included in the catalogue of Oligochaeta types (Reynolds & Cook 1976) and nor was it found, on requesting the curators, in the main museums where G. Gates used to deposit his type specimens (Smithsonian National Museum of Natural History, Harvard University Museum of Comparative Zoology, Canadian Museum of Natural History). For now we consider it better to assign the single individual of Puerta Parada to R. americana. Finally, similarities between the Puerta Parada individual and R. americana suggest that the latter species really inhabits Guatemala. Considering that all the Guatemalan species of Ramiellona have been found in the west high mountains of the region of Huehuetenango, the record of Puerta Parada extends the distribution of this genus in Guatemala, nearly 100 km southeast (Fig. 11).