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<p>The paper focuses on the lip region variation during the successive juvenile stages and adults of ten species representing ten genera of family Cephalobidae Filipjev, 1934. The cephalobids show worldwide distribution with remarkable survival abilities in nutritionally-stressed soils. These bacterivores show remarkable heterogeneity in their labial morphology demonstrating adaptive radiation within the representative confamilial species or polymorphism within different life stages of a species. The structural variations in the labial appendages of selected species as elucidated by Scanning Electron Microscopy revealed the fact that the species can be categorized as those possessing simple lips with very small or indisctinct labial probolae (e.g., <i>Eucephalobus</i> sp.) or absent labial and cephalic probolae (e.g., <i>Heterocephalobellus</i> sp., <i>Pseudoacrobeles</i> sp., <i>Acrobeloides ellesmerensis</i> Yeates 1967, <i>Stegelleta</i> sp., <i>Zeldia punctata</i> (Thorne 1925, 1937) and those having well developed and complex labial and cephalic probolae (e.g., <i>Stegelletina</i> sp., <i>Nothacrobeles borregi</i> Poiras, Baldwin, Mundo-Ocampo and Bumbarger, 2002, <i>Cervidellus doorsselaeri</i> (De Clerck &amp; De Ley 1990) Boström &amp; De Ley 1996, <i>Acrobeles complexus</i> Thorne 1925). Besides being absent or underdeveloped, some of these features are convergent in the selected species; the labial probolae vary from simple, conical, trapezoid, forked to deeply incised/ branched with or without tines. Likewise, the cephalic probolae appear simple lip-like, or rectangular with marginal tine, or leaf-like with many tines. The species also differ in Primary and Secondary cephalic axils with or without guard process/s. A great degree of congruence was observed between the phylogenetic trees constructed using morphological characters and those plotted using 28S rRNA sequences by Nadler et al. (2006). This underscores that the selection of high-weight morphological characters remains crucial for effective delineation and identification of species.</p>

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Insights into diversity of the lip region in Cephalobidae Filipjev, 1934 (Nematoda)

  • 期刊论文

  • 发表日期：

    2025年6月27日

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  • Qudsia Tahseen,
  • Mohammad Mahboob,
  • Irfan Ahmad

摘要

The paper focuses on the lip region variation during the successive juvenile stages and adults of ten species representing ten genera of family Cephalobidae Filipjev, 1934. The cephalobids show worldwide distribution with remarkable survival abilities in nutritionally-stressed soils. These bacterivores show remarkable heterogeneity in their labial morphology demonstrating adaptive radiation within the representative confamilial species or polymorphism within different life stages of a species. The structural variations in the labial appendages of selected species as elucidated by Scanning Electron Microscopy revealed the fact that the species can be categorized as those possessing simple lips with very small or indisctinct labial probolae (e.g., Eucephalobus sp.) or absent labial and cephalic probolae (e.g., Heterocephalobellus sp., Pseudoacrobeles sp., Acrobeloides ellesmerensis Yeates 1967, Stegelleta sp., Zeldia punctata (Thorne 1925, 1937) and those having well developed and complex labial and cephalic probolae (e.g., Stegelletina sp., Nothacrobeles borregi Poiras, Baldwin, Mundo-Ocampo and Bumbarger, 2002, Cervidellus doorsselaeri (De Clerck & De Ley 1990) Boström & De Ley 1996, Acrobeles complexus Thorne 1925). Besides being absent or underdeveloped, some of these features are convergent in the selected species; the labial probolae vary from simple, conical, trapezoid, forked to deeply incised/ branched with or without tines. Likewise, the cephalic probolae appear simple lip-like, or rectangular with marginal tine, or leaf-like with many tines. The species also differ in Primary and Secondary cephalic axils with or without guard process/s. A great degree of congruence was observed between the phylogenetic trees constructed using morphological characters and those plotted using 28S rRNA sequences by Nadler et al. (2006). This underscores that the selection of high-weight morphological characters remains crucial for effective delineation and identification of species.