Diplotrema kaxyebensis, Fragoso & Rojas, 2019

Fragoso, Carlos & Rojas, Patricia, 2019, More new Diplotrema earthworm species from southern Mexico (Annelida, Crassiclitellata, Acanthodrilidae, Acanthodrilinae), Zootaxa 4688 (4), pp. 483-502 : 494

Diplotrema kaxyebensis sp. nov.

( Figures 8 , 9 )

urn:lsid:zoobank.org:act:7747DFF4-3345-4018-860F-30D5D23F701A

Diplotrema sp. nov. 6: Fragoso 2001: 163, 2007: 122.

Localities and material. Mexico, Chiapas, Lagos de Montebello, municipality of La Trinitaria, 2.5 km after deviation from Road 307 in direction to “Cinco Lagos “ lake; small patch of tropical cloud forest on a NE oriented slope, over dark soils rich in organic matter, at 0–20 cm depth; 16°07’2.1”N, 91°40’8.8”W, 1500 m asl, one clitellate adult 11/28/1997, C. Fragoso and J. Bueno ( Fig.10 ) .

Holotype. Entire clitellate adult, IEOL 3334 .

Description. External. Length 23 mm. Width after clitellum 1 mm. Number of segments 75. Body cylindrical. Pigment absent. Prostomium prolobous. No secondary furrows observed. Setae eight per segment, visible from 2, closely paired throughout and highly conspicuous ( Fig. 8A ). Setal formula (aa:ab:bc:cd:dd): 10: 2.4:1:3.8:1:10.4 and 1.2 dd =1/2 C; 30: 3.5:1:4.5:1:13.5 and 1.1 dd =1/2 C; ten segments before anus: 2.8:1:3.6:1:7.6 and 1.4 dd =1/2 C. Penial setae (a and b) in 17 and 19 only visible internally; setae a and b of 18 externally visible. Seta 19 b 0.85 mm long and 10 µm wide ( Fig. 9A ), smooth without ornamentations, bracket-shaped but with an opposite curvature in the distal quarter; the claw-shaped apex slightly wider than the basal part ( Fig. 9B ). Setae a and b of segment 8 modified as genital setae, and only visible internally; they are small (length 205 µm), straight, with distal ornamentation of alternated and rounded crevices, and with a moderately pointed apex ( Fig. 9C ). Clitellum saddle-shaped in 1/2 12 –16 (4.5 segments) ( Fig. 8A,B ). Dorsal pores present all along the body, first pore in 5/6, larger and open in 6/7. Spermathecal pores minute, barely visible externally, opening in 7/8 and 8/9, medial to A, not in mid-ventral line. Female pores in 14, presetal, small and difficult to see, in A. Two pairs of prostatic pores in 17 and 19, medial to A, joined by bracket-shaped seminal grooves which run surrounding the genital marks of 17–19 ( Fig. 8A,B ). Male pores in the equator of 18, in the seminal groove ( Fig. 8B ). Genital marks: i) two slight swellings in 8, in AB; ii) two longitudinally elliptical and mid-ventral papillae in 1/2 16 –1/2 17 and 1/2 17 – 1/2 19; reaching A in its widest part. Anterior papilla smaller than posterior one; the latter enclosed by seminal grooves and prostatic pores; both papillae located in a slight depression ( Fig. 8A,B ).

Internal. Septa 5/6, 6/7 thin and membranous; septa 7/8–9/10 progressively thick and muscular; septum 10/11 less muscular; from septa 10/11 backwards membranous. Septa 7/8 funnel shaped. One large almost squared gizzard in 5, 0.56 mm length and 0.6 mm width. Esophagus in 8–13, without internal lamellae. In 9–11 esophagus vascularized, and with dilatations which give the appearance of pouches. Intestine starts in the equator of 14. A dorsal laminar typhlosole begins very small in 15, reaches its maximal size in segment 18, and continues with the same size until 30 where it drastically reduces in size.

Single dorsal vessel visible throughout. Supra-esophageal vessel seen in segments 10–11; in 12 probably present also. Latero-esophageal hearts in 10, 11; hearts of 12 clearly joining dorsal vessel, but connection with supraesophageal vessel not seen. Nephridial system holoic, avesiculate and exonephric; parietal nephridia visible from segment 12 and opening to exterior in BC, closer to C. Nephrostomes not seen. Male apparatus holandric. Testes not seen; abundant coagulum and iridescent male funnels in 10 and 11. Male gonoduct double with traces of iridescence; it runs superficially along body wall in BC of segments 13–17, entering body wall in 17/18. One pair of acinous seminal vesicles in 12. Two pairs of highly coiled tubular prostates in 17 and 19, limited to their respective segments; glandular part three times longer and two times wider than muscular region. Fibers of connective tissue from mid-ventral line to lateral walls in segments 16–19.

Large and paired ovaries in 13 with few ovules. Two pairs of spermathecae in 8 and 9, of almost equal size (0.45–0.46 mm), with duct, ampulla and diverticulum strongly attached by connective tissue between themselves and also to the floor. Duct thin and elongate, perpendicularly connecting to both ampulla and diverticulum; the last two connected along the same axis ( Fig. 8D ). Ampulla oriented laterally, larger than the mesially oriented diverticulum and divided into two sections of unequal size at the union with duct and diverticulum ( Fig. 8C, D ); stalked diverticulum with the distal part ovoid and full of seminal chambers. Under left spermatheca of segment 8, a follicle containing two genital setae was observed.

Etymology. The name of the species combines two mayan words, ka’ax, meaning forest, and ye’eb, meaning ‘fog’, referring to the cloud forest where the species was found.

Remarks. From Table 1 of Fragoso & Rojas (2018), it can be see that D. kaxyebensis is similar to the Mexican D. murchiei (one pair of seminal vesicles in 12 and unpaired genital marks in the mid-ventral region of 17–19). However, both species differ in size ( D. kaxyebensis , 23 mm length and 1.1 mm width vs. D. murchiei , 55, 75 mm length and 2 mm width), first dorsal pore (6/7 vs. 8/9, 9/10), genital setae (present vs. absent) and shape of spermatheca (long duct perpendicular to common passage connecting ampulla and diverticulum vs. ampulla perpendicular to common passage connecting short duct and diverticulum). This species was listed as “ Diplotrema sp. nov 6 ” by Fragoso (2001, 2007).

Figures

FIGURE 8. Diplotrema kaxyebensis sp. nov., holotype IEOL 3334, external (A,B) and internal (C,D). A. Ventral view of anterior region, scale 1 mm. B. Ventral view of segments 14–20 showing genital papillae (Gp), male pores (Mp) and prostatic pores (Pp), scale 1 mm. C. Spermatheca of segment 8, right side, lateral view. D. Schematic illustration of same spermatheca after raising both duct and diverticulum; in both C and D scale 0.35 mm and A=ampulla, Di=diverticulum, Du=duct.

FIGURE 9. Diplotrema kaxyebensis sp. nov., holotype IEOL 3334. A. Right penial seta b of segment 19, scale 150 µm. B. Apex of same penial seta 19b, scale 65 µm. C. Left genital seta of segment 8, scale 50 µm; the two fractures occurred during its extraction.

FIGURE 10. Geographic distribution of Diplotrema oaxacana sp. nov., Diplotrema tabascensis sp. nov, and Diplotrema kaxyebensis sp. nov. For each species locality the type of vegetation is shown: pine forest (square), tropical subdeciuous forest (triangle) and fallow of cloud forest (circle).