Pernambucano worm (Spirobolbolaimus pernambucanus) and Graciele worm (Ixonema gracieleae) from South Atlantic

NEWS - New species of Microlaimidae were discovered in sediment samples collected in the South Atlantic, along the continental shelf separating Northeastern Brazil. Pernambucano worm (Spirobolbolaimus pernambucanus) has six outer labial setae and four cephalic setae of almost equal length. Graciele worm (Ixonema gracieleae) has somatic setae on peduncles.

Both are the first species of the genus described from the South Atlantic and greatly contribute to the knowledge and variability of these two genera. The number of Microlaimidae species initially described from sediment samples collected on the Brazilian coast shows that great efforts are still needed to fully understand the richness of continental margins such as the Brazilian coast.

Pernambucanus is the Latin form of the term “pernambucano”. In Brazil, “pernambucano” refers to something or someone originating from the state of Pernambuco. I. gracieleae received its specific epithet in honor of Graciele Mariza dos Santos Alves, wife of the first author.

S. pernambucanus differs from S. undulatus in its length of 1,686-1,848 µm (vs. 2,035-2,558 µm in S. undulatus), absence of articulated outer labial setae (vs. articulated outer labial setae), presence of an outer labial setae nearly as long as the cephalic setae (vs. longer outer labial setae than the cephalic setae), 12 pore-like precloacal supplements (vs. 18-19 precloacal supplements in a series of mid-ventral elevations with pores at the top) and absence of additional teeth (vs. present).

S. pernambucanus differs from S. boucherorum in having 12 precloacal appendages (vs. 7 in S. boucherorum), a gubernaculum length of 19-19.5 µm (vs. 23-30 µm) and the presence of an outer labial seta that is nearly as long as the cephalic seta (vs. the outer labial seta being longer than the cephalic seta).

I. gracieleae differs from Bathynox in having three caudal glands that open through separate outlets in papilla-like extensions (vs. three glands opening in a single outlet), males are diorchid (vs. monorchic) and the gubernaculum lacks an apophysis (vs. the presence of a dorsal apophysis).

I. gracieleae differs from I. powelli by the circular shape of the amphidia fovea (vs. pouch-like in I. powelli), 6 rows of cervical setae (vs. 4 rows of cervical setae) and a gubernaculum 11.5–14.5 µm long (vs. ca. 6 µm). I. gracieleae differs from I. sordidum by having long somatic setae alternating with short somatic setae along the body and the presence of a precloacal supplement.

I. gracieleae differs from I. deleyi by the presence of a gubernaculum (vs. absent in I. deleyi) and a ventral jointed seta located immediately behind the pharynx + two jointed setae closer to the cloaca and a smaller non-continuous seta further away (vs. one non-continuous ventral precloacal seta).

Original research

Manoel A, Neres PF, Esteves AM. 2024. Two new species of Microlaimidae (Nematoda: Microlaimida) from the Continental Shelf off Northeastern Brazil (Atlantic Ocean) with emended diagnosis and dichotomous key. PeerJ 12:e17976, DOI:10.7717/peerj.17976

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