Diplotrema chajulensis, Fragoso & Rojas, 2018

Fragoso, Carlos & Rojas, Patricia, 2018, New Diplotrema and Lavellodrilus earthworm species from southern Mexico (Annelida, Crassiclitellata, Acanthodrilidae), Zootaxa 4496 (1), pp. 414-430 : 415-420

Diplotrema chajulensis sp. nov.

( FigurES 1 , 2 )

Localities and material. MExico, ChiapaS, Chajul villagE, municipality of MarquES dE ComillaS, in front of town and croSSing thE rivEr Lacantun, 2 km NW inSidE MontES AzulES BioSphErE RESErvE, tropical rain forESt ovEr alluvial SoilS at 10–30 cm dEpth, 16°07'24"N, 90°56'24"W, 180 m aSl, thrEE non-clitEllatEd adultS 07/12/1982, C. FragoSo; onE juvEnilE, 12/17/1984, C. FragoSo ( Fig. 6 ).

Holotype. EntirE non-clitEllatEd adult in rEgEnEration with gEnital markS (GM) and pEnial SEtaE (PS) collEctEd 07/12/1982: IEOL 3101.

Paratypes. Two EntirE SEmi-adultS with PS and/or GM, 07/12/1982: IEOL 4433, IEOL 4432; onE juvEnilE with incipiEnt PS, 12/17/1982: IEOL 3182.

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Description. External. LEngth 20–27.7 mm (avEragE 23.2, n=4), holotypE 20 mm (laSt 29 SEgmEntS in rEgEnEration); onE paratypE alSo in rEgEnEration (laSt 20 SEgmEntS). Width, middlE body: 0.66–1 mm (avEragE= 0.95, n= 4); holotypE 1 mm. NumbEr of SEgmEntS 73–78 (avEragE= 75, n= 4); holotypE 75 SEgmEntS. FurrowS numErouS, bEforE and aftEr clitEllum; oftEn intErruptEd. REgEnErating SEgmEntS 3.5 timES widEr than long; middlE body non-rEgEnEratEd SEgmEntS 2 timES widEr than long ( Fig. 1A ). PigmEnt abSEnt. ProStomium cloSEd EpilobouS. SEtaE Eight pEr SEgmEnt, viSiblE from 2; cloSEly pairEd throughout ( Fig. 1A ). SEtal formula (avEragES, n=4) (aa:ab:bc:cd:dd) at 10: 3.5:1:3.8:0.8:12.2 and 1.15 dd =1/2 C; at 30: 5:1:6.1:1:15.8 and 1.15 dd =1/2 C; tEn SEgmEntS bEforE anuS (only non-rEgEnErating individualS): 3.8:1:3.2:1:6.5 and 1.6 dd =1/2 C. Thin (width 17 µm) and vEry long (1.86, 2.1 mm) pairEd pEnial SEtaE (a and b) in 17 and 19 ( Fig. 2A,B ); all with Similar ShapE, color (orangE) ( Fig. 1C ), and dimEnSionS. PEnial SEtaE ExtErnally not viSiblE. PEnial SEtaE with a hair appEarancE duE to itS limitEd width and largE lEngth ( Fig. 2A,B ). No Strong curvaturES wErE obSErvEd until thE diStal part, whErE thE apEx iS Spiral-ShapEd ( Fig. 2A–C ). Faint ornamEntation limitEd to diStal part, juSt bEforE thE SpiralEd apEx; it conSiStS of two oppoSitE rowS of longitudinal tiny thornS ( Fig. 2D ). GEnital SEtaE abSEnt.

ClitEllum not dEvElopEd in any of thE thrEE ExaminEd SEmi-adultS. DorSal porES prESEnt, firSt porE in 10/11 (2 ind.) or 11/12 (1 ind.). SpErmathEcal porES pairEd in AB, in 7/8 and 8/9. FEmalE porES not obSErvEd. Two pairS of proStatic porES in 17 and 19, joinEd by SEminal groovES which run in AB ( Fig. 1A,B ). MalE porES not SEEn, probably within SEminal groovES and, aS dEducEd from malE gonoduct, in thE Equator of 18. GEnital markS incipiEnt, and only obSErvEd in two individualS; in thE holotypE two pairEd and mESial circular papillaE in thE Equator of 18 with a Smooth innEr SurfacE ( Fig. 1A,B ); in paratypE IEOL-4433 a SwElling in 16, poStSEtal and ExtEnding in AB -AB.

Internal. SEpta 5/6 and 13/14 thin and mEmbranouS; SEpta 6/7–11/12 Slightly muScular; all SEpta aS opEn funnElS, ExtEnding only onE SEgmEnt backwardS. OnE largE gizzard in 5. Gizzard dimEnSionS (lEngth by width): 0.35 by 0.59 mm, 0.48 by 0.54 mm, and 0.38 by 0.49 mm). ESophaguS in 7–12 tubular, without dilatationS or intErnal lamEllaE; in SomE of thESE SEgmEntS, ESophagEal wallS thickEnEd and with a clEar ExtErnal vaScularization. IntEStinE Starting in 12/13 (holotypE and 2 paratypES.), 13/14 (paratypE 4432). DorSal typhloSolE Starting in 14 or 15, laminar, Small, rEaching maximal SizE aftEr 3–5 SEgmEntS.

SinglE dorSal vESSEl viSiblE throughout. Supra-ESophagEal vESSEl viSiblE in SEgmEntS 10–12; in onE individual viSiblE alSo in SEgmEnt 9. LatEral hEartS in 9; latEro-ESophagEal hEartS in 10, 11 and 12; laSt two of grEatEr SizE. VEntral vESSEl prESEnt. Infra-ESophagEal vESSElS obSErvEd in thE holotypE in SEgmEntS 7–12; alSo viSiblE in onE paratypE in 9–12. Holoic without vESiclES. ThE ExonEphric, apparEntly StomatE holonEphridia arE SEptal bEforE SEgmEnt 10 and pariEtal from SEgmEnt 11 backwardS. NEphroStomES and nEphroporES not SEEn. Holandric. IridiScEnt malE funnElS in 10 and 11, largEr in 11; tEStES not SEEn. MalE gonoduct doublE, almoSt Straight and running ovEr thE body wall of SEgmEntS 13–18 in or Slightly outSidE B, EntEring body wall in 17/18 or thE Equator of 18. Two pairS of acinouS, iridEScEnt and dorSo-latEral SEminal vESiclES in 11 and 12, projEcting from 10/11 and 11/12, rESpEctivEly. Two pairS of coilEd tubular proStatES in 17 and 19 ( Fig. 1C ), ExtEnding 1–2 SEgmEntS backwardS; glandular part 4 timES largEr than thE muScular rEgion. PEnial folliclES of a and b vEry largE, clEarly SEparatEd, fixEd to dorSal mid-linE and ExtEnding fivE SEgmEntS backwardS (thoSE of 17 ExtEnding to 22 and thoSE of 19 to 22, 24) ( Fig. 1C ).

PairEd ovariES and fEmalE funnElS in 13 (both obSErvEd only in thE holotypE). OvariES Small, ovulES not clEarly SEEn; fEmalE funnElS in thE floor, mESial and cloSE to 13/14. Two pairS of SpErmathEcaE in 8 and 9, inSErting in 7/8 and 8/9, rESpEctivEly; ampulla joining duct at right anglE, divErticulum joining duct along thE SamE axiS ( Fig. 1D,E ). Ovoidal ampulla almoSt thE SamE lEngth aS divErticulum; in SomE individualS width of ampulla and divErticulum almoSt Equal. In ParatypE IEOL 4433 iridiScEncE obSErvEd in diStal part of divErticulum ( Fig. 1E ). Total lEngth of SpErmathEca 0.43 mm (holotypE), 0.46 mm (paratypE IEOL 4433; Fig. 1E ) and 0.54 mm (paratypE IEOL 4432; Fig. 1D ).

Etymology. ThE namE of thE SpEciES rEfErS to thE MExican typE locality whErE all individualS wErE found. Chajul mEanS "SacrEd jEwEl" in GuatEmalan Ixil languagE or "EnlightEn with pinE" in GuatEmalan K'ichE' languagE ( Sazo 2010).

Remarks. D. chajulensis sp.nov. bElongS to thE group of SpEciES with ampulla orthogonal to duct, and divErticulum joining duct orthogonally [ D. jenniferae ( Righi, 1994) ( REynoldS & Righi 1994)] or along thE SamE axiS [ D. murchiei JamES, 1990 and D. oxcutzcabensis ( Pickford, 1938) , TablE 1]. From all of thEm, thE nEw SpEciES iS SEparatEd by itS SmallEr SizE (20–28 mm lEngth and 0.7–1 mm width vs. 40–75 and 2–3.2 mm), itS firSt dorSal porE (10/11 vs. 4/5, 8/9, 9/10) and thE poSition of SEminal vESiclES (11 and 12 vs. 9 and 11 or 12) (SEE TablE 1). It iS alSo Similar to D. zilchi ( Graff, 1957) by Sharing a Similar SizE, a firSt intEStinal SEgmEnt in 13 and SEminal vESiclES in 11 and 12 ( TablE 1), but diffErS by thE ShapE of thE SpErmathEca. From all thE nEotropical SpEciES it iS clEarly SEparatEd by thE Spiral-ShapEd apEx of thE pEnial SEtaE; only thE Cuban D. ulrici ( MichaElSEn 1923) prESEntS Similar hair typE pEnial SEtaE, diffEring by an undulatEd diStal part.

Figures

FIGURE 1. Diplotrema chajulensis sp. nov. External. A. Ventral view of anterior region (Holotype IEOL 3101; scale 1.4 mm). B. Latero-ventral view of segments 16–20 showing genital papillae (Gp) and prostatic pores (Pp) (Holotype IEOL 3101; scale 650 µm). Internal. C. Dorsal view of segments 17–22 showing esophagus (Es), dorsal vessel (Dv), parietal holonephridia (H), prostates (Pr) and penial setae (PS) within penial follicles (Holotype IEOL 3101; scale 0.8 mm). D. Right spermatheca from segment 9, (Paratype IEOL 4432). E. Right spermatheca from segment 9, (Paratype IEOL-4433); in both D and E scale: 0.5 mm and A= ampulla, Di= diverticulum, Du= duct.

FIGURE 2. Diplotrema chajulensis sp. nov. Paratype IEOL 4432. SEM photographs. A. Right penial setae a of segment 17 (scale 200 µm). B. Right penial setae b of segment 19 (scale 200 µm). C. Apex of penial seta 19b (scale 50 µm). D. Distal ornamentation of penial seta 19b (scale 10 µm).

FIGURE 6. Geographic distribution of Diplotrema chajulensis sp. nov. and Lavellodrilus sheylae sp. nov.