Lacandodrilus Fragoso & Rojas, 2023

Fragoso, Carlos & Rojas, Patricia, 2023, A new semiaquatic worm (Annelida, Oligochaeta) from southeastern Mexican tropical rain forests, Zootaxa 5255 (1), pp. 136-156 : 137

Lacandodrilus Fragoso & Rojas gen. nov.

Type species: Lacandodrilus paludosus Fragoso & Rojas sp. nov.

Diagnosis: Setae eight by segment, closely paired, ab ventral, cd dorsolateral; all setae straight, with a nodulus and simple. Clitellum annular. Septal glands in pregonadic segments. Gizzard, esophageal glands and typhlosole absent. Dorsal vessel simple. Long and contorted vascular commissures embedded with septal glands and located before segment 12. Holoic, ovoidal nephridia covered by a granular peritoneal layer. Holandric, with testes and sperm funnels in 10 and 11 and paired male pores in 13. Male gonoducts intraparietal. Seminal vesicles long, extending several segments backwards within ovisacs. Genital lobular glands in 13 and 14. Metagynic, with large ovaries in 13 and paired female pores in 14. Paired spermathecae before segment 11, without diverticula and with ventral pores. Segment 12 without gonads.

Etymology: The name of the new genus refers to the Lacandon forest region, one of the last large remnants of tropical rain forest in Mexico.

Remarks: The position of a pair of male pores in segment 13 and the segment 12 without gonads is a condition rare in opisthoporous Oligochaeta. In Crassiclitellata it occurs only in a few cases, like the Lumbricidae species Eiseniella tetraedra (Savigny) and in monospecific family Biwadrilidae . From Biwadrilus bathybates (Stephenson) ( Brinkhurst & Jamieson 1971; Jamieson 2006; Blakemore 2006), the new genus is separated by the type of prostatic glands (lobulated only vs. lobulated with a copulatory gland) and seminal vesicles (one pair extending several segments backwards vs. two pairs limited to one segment) ( Table 1 ). From this family is also separated by the clitellar condition, which in Lacandodrilus gen.nov. is assumed to be single cell layer. In aquatic non Crassiclitellata worms, male pores in 13 are also present in the monospecific family Syngenodrilidae and in Alluroididae . From Syngenodrilus lamuensis (Smith & Greene) (Smith & Greene 1919; Gates 1945; Pickford 1945) the new genus is separated by the testicle sacs (new genus, absent vs. present), the gizzards (absent vs. present) and the amount and type of genital prostatic-like glands (two pairs lobulated in 13 and 14 vs. three pairs tubular in 11, 12 and 13) ( Table 1 ). With Alluroididae the new genus shares the presence of septal glands and (assumed) the type of clitellum, as well as the pair of male pores in 13 and a single pair of ovaries in 13. However, from the six genera and 11 species recognized so far in this family, it is separated from all of them by the atria (absent vs. present in all species) and the male gonoduct (intraparietal vs. in the coelom or attached to atria and accessory glands); from all but one species ( Alluroides lauzannei Ljungstr ̂m 1971) by the number of testes (holandric, two pairs in 10 and 11 vs. proandricone pair in 10 or metandric-one pair in 11) ( Table 2 ). Even that the new genus is clearly separated from the non Crassiclitellata family Haplotaxidae by the number and position of males pores (new genus a pair in segment 13 vs. one or two pairs of pores in segments 11 and 12, but never in segment 13), it shares some somatic (presence of septal glands, large vascular anterior commissures) and genital (type of seminal vesicles, absence of atrium) characters with the genus Metataxis (the only genus in the family without gonads in segment 12) ( Table 3 ). As far as this family is polyphyletic ( Anderson et al. 2017; Erseus et al. 2020), we did not include the new genus in it. Considering former comparisons, that there are still several characters that should be confirmed and or added by histological techniques, and with the expectations of further sampling, we tentatively decided placing the new taxon in Alluroididae . However, it could be that future morphological and molecular evidence will render it as the type of a new family within order Alluroidida (as considered by Timm & Martin 2015 and Schmelz et al. 2021).