Daptonema matrona, Neres & Fonseca-Genevois & Torres & Cavalcanti & Castro & Silva & Rieger & Decraemer, 2010

Neres, Patricia Fernandes, Fonseca-Genevois, Verônica Gomes Da, Torres, Rodrigo Augusto, Cavalcanti, Mariana Da Fonseca, Castro, Francisco José Victor De, Silva, Neyvan Renato Rodrigues Da, Rieger, Tania Tassinari & Decraemer, Wilfrida, 2010, Morphological and molecular taxonomy of a new Daptonema (Nematoda, Xyalidae) with comments on the systematics of some related taxa, Zoological Journal of the Linnean Society 158 (1), pp. 1-15 : 4-8

DAPTONEMA MATRONA SP. NOV.

Description

Material studied: 11 males; 11 females.

Material type: Material type: Holotype and allotype deposited in the National Museum of Rio de Janeiro. Paratypes slide deposited in the Laboratório de Meiofauna Departamento de Zoologia , Universidade Federal de Pernambuco, Recife, Brazil .

Type specimens: Male holotype MNRJ 337 ; Female allotype: MNRJ 338 ; male paratypes 123–132 NM LMZOO-UFPE; female paratypes 133–142 NM LMZOO-UFPE .

Locality: Pina Basin (Recife, Pernambuco, Brazil): estuarine intertidal silt-clay sediments.

Measurements: See Tables 1 and 2.

Etymology: The species’ Latin name (matrona = mother family) is based on the method of reproduction by the female i.e. intra-uterine hatching and development.

Holotype: Elongated body, hardly narrowed anteriorly ( Figs 1A, 2A); cephalic and pharynx base diameter corresponding to 40 and 84% of the maximum body diameter, respectively. Cuticle transversely striated, striations relatively fine (1.8 Mm) ( Figs 1B, 3B). Somatic setae short and distributed along the body but more concentrated/numerous in the neck and caudal regions ( Fig. 1A). Head rounded with six distinct lips, each one with a labial papilla ( Fig. 3A). Twelve cephalic setae in six pairs, the longer ones measuring 3 Mm (12% of the cephalic diameter) and the shorter ones 1.8 Mm (7% of the cephalic diameter) ( Fig. 1B; Table 1).One circle of subcephalic setae ( Fig. 1B). Buccal cavity conical, with an annular reinforcement delimiting the stoma from the anterior part of the cavity ( Fig. 1B, C). Amphidial fovea circular, 21.8% of corresponding body diameter and located 13.2 Mm behind anterior end ( Figs 1B, 2C, 3C). Secretory–excretory pore at 42 Mm and the nerve ring at 81.6 Mm from the anterior end ( Table 1). Pharynx cylindrical, surrounding stoma ( Figs 1C, 2B, D). Cardia with irregular form and partially inserted in the intestine ( Fig. 1G). Ventral gland not visualized. Single testis located on the left of the intestine, reaching almost to the base of pharynx ( Fig. 1A). Five ejaculatory glands extending 354.5 Mm anteriorly to the anal opening ( Fig. 1D). Spicules cephalate proximally, 0.7¥ anal body diameter long and almost straight ( Figs 1F, 2E). Gubernaculum without apophysis ( Fig. 1F) and with the distal region wingshaped ( Fig. 3D). Four pairs of setae posteriorly to the anal opening, next to the cylindrical region of the tail, on the ventral side ( Fig. 1E). Tail conical–cylindrical 4.8¥ anal body diameter long, the cylindrical region corresponding to 30.7% of the total tail length, with two terminal setae (9 Mm) ( Fig. 1E; Table 1). Three caudal glands present ( Figs 1E, 2F).

Allotype: Female largely similar to male ( Fig. 4) but showing sexual dimorphism in size of amphidial fovea, i.e. smaller than in male. Amphidial fovea round, its diameter 14.5% of corresponding body width and located 13.2 Mm or 0.46 cephalic diameters from anterior end ( Fig. 4B; Table 2). Secretory– excretory pore at 40.2 Mm and the nerve ring 100.8 Mm behind anterior end ( Table 2). Single ovary located left of intestine and extending almost to base of pharynx. A short prevulval uterine sac (spermatheca) in the second third of the body length. Vulva close to anus, i.e. at 73.8% of total body length from anterior end ( Fig. 4A). Reproduction apparently by ovoviviparity. Up to 45 eggs as well as first and second stage juveniles observed within the uterus of a single specimen.

GENETIC AND PHYLOGENETIC ANALYSES

Neighbour-joining topology revealed the existence of two large genetic groupings ( Fig. 5). The first characterized by the lineage of the genus Theristus and Daptonema normandicum , the latter of which is genetically closer to Theristus agilis . Such a grouping emerged as a genetic sibling lineage to the other grouping, which united Theristus acer and Theristus sp. The second large genetic grouping revealed the genetic unity of the remaining species of Daptonema and a Metadesmolaimus sp. Daptonema matrona sp. nov. emerged as a genetic sibling lineage of Daptonema oxycerca and Daptonema procerum . Such a grouping emerged as the genetic sibling lineage to the other remaining group composed of Daptonema hirsutum , Daptonema setosum + Daptonema sp. , besides Metadesmolaimus sp. ( Fig. 5). Daptonema hirsutum and D. setosum presented identical sequences. Daptonema oxycerca + D. procerum are genetically close lineages.

Maximum parsimony topology was represented by the consensus of 28 153 equally parsimonious trees. A total of 1416 characters was analysed, 945 of which were constant, 270 were parsimoniously informative, and 201 were parsimoniously non-informative. The length of the consensus tree was 887 steps; retention and consistency indexes were 0.7934 and 0.7193, respectively. The analysis revealed the existence of two monophyletic clades ( Fig. 6). The first clade was formed by Daptonema normandicum and the Theristus sp ecies, in which Theristus agilis and D. normandicum emerged as an evolutionary sibling lineage to the other grouping, which united T. acer and Theristus sp. The second clade was formed by the other Daptonema species , including the new species and Metadesmolaimus sp. Daptonema matrona sp. nov. was characterized as an evolutionarily distinct branch and a sibling group of the other congeneric species, with the exception of D. normandicum . Daptonema procerum and D. oxycerca were revealed to be sister groups. This evolutionary unit also emerged as a sister group of D. setosum , Daptonema sp. , D. hirsutum + Metadesmolaimus sp. ( Fig. 6). The analysis also revealed a putative synonymy involving D. hirsutum and D. setosum as well as a well-supported monophyletic unit (98/97) encompassing diverse species of Daptonema and Metadesmolaimus sp. ( Fig. 6).

Bayesian inference topology resulted from the majority rule consensus of 10 001 trees with a standard deviation of 0.005222, resulting from 1 000 000 generations computed in four Markov chains. The analysis also revealed the existence of two monophyletic groupings ( Fig. 7). The first was formed by D. normandicum and the Theristus sp ecies (like that revealed in the MP topology), in which T. agilis and D. normandicum emerged as sister taxa to the other grouping, which united T. acer and Theristus sp. In the second grouping ( Fig. 7) formed by the remaining species of Daptonema + Metadesmolaimus sp. , D. matrona sp. nov. exhibited the same phylogenetic status as seen in the MP topology, constituting a sibling group of D. oxycerca , D. setosum , D. procerum , D. hirsutum + Metadesmolaimus sp. Daptonema procerum and D. oxycerca were also revealed to be a sibling group of D. setosum , Daptonema sp. , D. hirsutum + Metadesmolaimus sp. ( Fig. 7). The analysis also revealed two polytomies – the first involving D. hirsutum and D. setosum (as found in the previous analyses) and the second between D. procerum and D. oxycerca ( Fig. 7).