Morphological and molecular characterisation of Californian species of Metaporcelaimus Lordello, 1965 (Dorylaimida, Aporcelaimidae), with a new concept of the genus

Abstract

Two new and one known species of Metaporcelaimus from Californian natural habitats were studied using morphological and molecular approaches. Metaporcelaimus marinensis sp. n. is characterised by its body 1.99-2.48 mm long, lip region offset by deep constriction and 14-15 μm broad, odontostyle 13-15 μm long, neck 456-529 μm long, pharyngeal expansion occupying 47-50% of total neck length, pharyngo-intestinal junction bearing a dorsal lobe, uterus tripartite and 201-262 μm long, pars refringens vaginae well developed, V = 55-58, tail conical (43-55 μm, c = 43-52, c′ = 1.3-1.6) with its inner core somewhat notched and nearly reaching the tip, spicules 54-63 μm long and 6-7 spaced ventromedian supplements located outside the range of the spicules. Metaporcelaimus ovogranulosus sp. n. is distinguished in having body 1.54-1.96 mm long, lip region offset by deep constriction and 17-19 μm broad, odontostyle 17-19 μm long, neck 415-539 μm long, pharyngeal occupying 49-53% of total neck length, uterus simple and 27-41 μm long, uterine eggs granulate, pars refringens vaginae well developed, V = 48-51, tail conical (35-44 μm, c = 39-52, c′ = 1.4-1.6) with its inner core notched and nearly reaching the tip, and male unknown. Measurements and LM illustrations are also provided for M. capitatus. Metaporcelaimus was morphologically compared with Aporcelaimellus. The analysis revealed that these genera are barely distinguishable from each other. Aporcelaimellus species can be separated into two groups, one of them being morphologically similar to Metaporcelaimus. Molecular data and the derived evolutionary tree show that Metaporcelaimus and Aporcelaimellus do not share a recent common ancestor. Consequently, a new concept is proposed for Metaporcelaimus, M. ahmadi sp. n. is proposed for A. coomansi apud Ahmad nec Baqri & Khera, and 16 species of Aporcelaimellus are transferred to Metaporcelaimus. An updated list of Metaporcelaimus species with their synonyms, a key to their identification and a tabular compendium with important taxonomic morphometric characters are given.

Morphology, phylogeny and taxonomy of the genus Sectonema (Nematoda, Aporcelaimidae)

“…Finally, present molecular analysis strongly supports previous findings (Álvarez‐Ortega, Nguyen, Abolafia, Bonkowski, et al, ; Álvarez‐Ortega, Nguyen, Abolafia, Vu, et al, ; Álvarez‐Ortega et al , ; Álvarez‐Ortega, Subbotin, & Peña‐Santiago, ; Holterman et al ; Nguyen et al ) revealing that aporcelaims are not a natural (monophyletic) taxon, with Sectonema sequences clustering together with those of the genus Metaporcelaimus Lordello , in a larger, also highly supported (PP: 100% and BS: 99%) clade, which does not share a recent ancestor with other supposed aporcelaims as the representatives of the genus Aporcella Andrássy .…”

Two atypical new species of the genus Sectonema Thorne, 1930 (Nematoda, Dorylaimida, Aporcelaimidae) from Vietnam

“…On the one hand, it is the second in a series of papers devoted to studying the nematode diversity of aporcelaims (family Aporcelaimidae Heyns, 1965) from natural areas of Vietnam, the first one (Álvarez-Ortega et al 2015) dealing with the representatives of the genus Aporcelaimoides Heyns, 1965. On the other hand, it is part of a general revision of the taxonomy and systematics of this dorylaimid group, in which the genera Aporcelaimellus Heyns, 1965, Metaporcelaimus Lordello, 1965and Sectonema Thorne, 1930 have already received some attention (see for instance, and respectively, Álvarez-Ortega & Peña-Santiago 2013; Álvarez-Ortega et al 2013a;Peña-Santiago & Álvarez-Ortega 2014a).…”

New data on two remarkable Antarctic species Amblydorylaimus isokaryon (Loof, 1975) Andrássy, 1998 and Pararhyssocolpus paradoxus (Loof, 1975), gen. n., comb. n. (Nematoda, Dorylaimida)

“… Dorylaimidae in odontostyle aperture (indistinct vs distinct) and especially in its characteristic postembryonic development pattern – J1 with long tail, c’ decreasing in successive stages and adults caused by the increasing of anal diameter rather than shortening of tail, adults with similar tail shape - conical with distal third much narrower, finger-like vs one or more juvenile stages bearing long (filiform or conical elongated) caudal region, adults with similar (either long or short and rounded, never conical) or dissimilar (long in females, short and rounded, ex ceptionally conical, in males) tail ( Peña-Santiago and Álvarez-Ortega 2014 ). Recent studies based on molecular data ( Holterman et al 2008 ; Pedram et al 2011 ; Álvarez-Ortega et al 2013a , c ; Peña-Santiago et al 2015 ) show that the current classification of superfamily Dorylaimoidea is questionable with most families being not monophyletic taxa, as some of the genera are closer to members of other families. Further integrative studies are needed to clarify its phylogeny and systematics and to understand which characters are homologous and which are the results of convergent or parallel evolution ( Vinciguerra et al 2014 ).…”

“…Molecular studies of free-living Dorylaimida members are increasing ( Mullin et al 2005 ; Holterman et al 2006 ; 2008 ; Pedram et al 2009 ; 2011 ; Álvarez-Ortega et al 2013a , b , c ; Nedelchev et al 2014 ; Peña-Santiago et al 2015 ). Nevertheless, Antarctic dorylaimids have received little attention in this respect with only one study of this widespread order in Antarctic.…”