Cienfuegia, Armenteros & Vincx & Decraemer, 2009

Armenteros, Maickel, Vincx, Magda & Decraemer, Wilfrida, 2009, Cienfuegia gen. nov. (Xyalidae) and Pseudoterschellingia gen. nov. (Linhomoeidae), two new genera of free-living marine nematodes from the Caribbean Sea, Journal of Natural History 43 (17 - 18), pp. 1067-1081 : 1069-1070

Genus Cienfuegia gen. nov.

Etymology

Refers to Cienfuegos Bay, Cuba, Caribbean Sea where the specimens were collected.

Diagnosis

Xyalidae . Cuticle coarsely striated. Head with six low lips, buccal cavity conical with two chambers marked by a constriction, without tooth or other cuticularized structures; inner labial sensilla not visible in light microscopy, six outer labial setae shorter than four cephalic setae, second and third circles of anterior sensilla at the same level or very close; amphidial fovea rounded, relatively small and positioned anteriorly in head region, at level of buccal cavity; cardia without pericardial cells. Female reproductive system with one outstretched anterior ovary; male reproductive system monorchic, i.e. with one outstretched anterior testis; gonads in both sexes at left of intestine; gubernaculum with well-developed dorsocaudal apophyses; tail with three caudal glands and without terminal setae at tail tip.

Type species

Cienfuegia cachoi gen. nov., sp. nov.

Discussion and relationships

Cienfuegia gen. nov. is classified within the family Xyalidae based upon the position of the anterior gonad constantly left of the intestine (holapomorphy for the family), cuticle striated, second and third circle of anterior sensilla inserted at the same level or very close, and buccal cavity surrounded by pharynx. Cienfuegia gen. nov. shows some affinities with the genera Diplolaimella Allgén 1929 and Diplolaimelloides Meyl 1954 (Monhysteridae) with the presence of a bipartite buccal cavity. However, in Cienfuegia gen. nov. the two chambers are indicated only by a slight constriction and a change in orientation of their walls compared with two clearly differentiated chambers in the two other genera. Cienfuegia gen. nov. is characterized by the following characters: structure of buccal cavity, and four cephalic setae longer than the six outer labial setae. Nicholas and Trueman (2002) made a cladistic analysis of the family Xyalidae based on maximum parsimony, using eight species of Monhysteridae and four species of Sphaerolaimus (Sphaerolaimidae) as outgroups. The data matrix used is not based on any prior judgement as to which character states are primitive and which derived. Transformation series simply define separate observable conditions, only treated as an ordered series where a change implies that the lineage has passed through an intermediate condition. In the parsimony consensus tree the species of the Monhysteridae formed a separate paraphyletic group; the remaining species are divided into 14 groups, a few of them representing clades including the ‘outgroup’ Sphaerolaimus (hereafter we use the same labels that these authors used for the clades).

The genus Cienfuegia has affinities with the poorly defined groups B and C of Nicholas and Trueman (2002); group B includes several genera: Daptonema Cobb 1920 (partim), Filipjeva Ditlevsen 1928 , Paramonohystera Steiner 1916 (partim), Stylotheristus Lorenzen 1977 and Theristus (Penzancia) Bastian 1865 . Group C included other species of Daptonema , Paramonohystera and Zygonemella Cobb 1920 . The shared features between Cienfuegia and the eight mentioned genera are mainly the six outer labial setiform sensilla, absence of additional cephalic setae (although they are present in Stylotheristus and in two species of Theristus : T. manicatus and T. interstitialis ), a circular amphidial fovea, an unarmed buccal cavity, a conicocylindrical tail, and a triangular cardia. An additional feature of Cienfuegia relates it to species belonging to the clade F [includes species of Theristus (Theristus) Bastian 1865 and the genera Robustnema Nicholas 1996 and Echinotheristus Thun and Riemann 1967 ]: absence of terminal setae on the tail, presence of dorsocaudal apophyses of gubernaculum.

The differentiation between the genera Daptonema and Theristus is problematic and mainly based on tail shape, presence of terminal setae and the structure of the male copulatory apparatus (see Wieser 1956). Cienfuegia gen. nov. possesses intermediate tail-related features: conico-cylindrical tail (as in Daptonema ) without terminal setae (as in Theristus ); the strong and cuticularized apophysis of the gubernaculum and the shape of spicules are close to those in several species of the subgenus Theristus (Theristus) although a few species of Daptonema also possess a well-developed gubernaculum apophysis (e.g. in D. laxus Wieser 1956 , D. setosum Bütschli 1874 ). A summary of the main shared and differentiating features between Cienfuegia gen. nov. and related genera is present in Table 1.