Abstract
BackgroundThe clade Diplogastridae Micoletzky 1922 largely represents the bacterivorous or predatory nematodes that very often demonstrate phoretic, necromenic or parasitic associations with insects (Sudhaus and Fürst von Lieven 2003). That is the reason, much of the diversity of the family remains undocumented because of their absence from routine soil samples. Due to their variable habitats and niches, these nematodes show ample variation in their stomal armature, feeding behavior and life cycle patterns.New informationThe paper describes and illustrates a new diplogastrid species of genus Acrostichus Rahm 1928 that appears to be the link between the genera Diplogastrellus Paramonov et al. 1952a and Acrostichus. Acrostichus medius n. sp. is characterised by hermaphroditic females and males having faintly striated longitudinal ridges, demarcated lateral fields, amalgamated lips, six adradial cheilostomal plates, moderately-built dorsal tooth, relatively smaller posterior genital branch; large oval uterine pouch and males with robust, heavily cuticularised spicules, each with hood-like capitulum, deeply forked distal end with fine extensions and a ventral attenuated arm; gubernaculum 2/3 of spicule length and rudiments of bursa confined to posterior four pairs of genital papillae. The biogeographical distribution of Acrostichus has been mapped and the relationship between congeners has been analysed cladistically and discussed.
Highlights
About the genus Acrostichus Rahm, 1928The genus Acrostichus was raised by Rahm (1928) when he reported and described Acrostichus toledoi as its type species. Goodey (1951) synonymised it with the genus Diplogaster Schultze in Carus 1857
Acrostichus medius n. sp. is characterised by female hermaphrodites having a mediumsized body with cuticle bearing faintly striated longitudinal ridges; lateral fields demarcated with two conspicuous ridges; lips amalgamated, labial sensilla small, papilliform; cheilostom with six adradial plates; dorsal tooth moderately-built slightly larger than subventrals; posterior genital branch relatively smaller; dorsal uterine pouch large, multilocular, oval to rounded occasionally filled with sperms and males with robust, heavily cuticularised spicules with hood-like capitula, appearing deeply forked distally with fine extensions and a ventral attenuated arm; gubernaculum 2/3 of spicule length with curved and tapering proximal end and distal end with slight protuberances; bursa almost absent with rudiments confined to posterior four genital pairs
The new species resembles A. lazarevskajae (Lazarevskaja 1964) Sudhaus and Fürst von Lieven 2003 in most allometric ratios but differs from it in having larger body size (L= 764-867 μm vs 365-430 μm in females and 611-715 μm vs 290-441 μm in males); greater 'ć' value (9.2-15.8 vs 6.6) and large-sized spicules (36-44 μm vs 23-25 μm) in males; spicules massive with elongated hood-like and distal part deeply bifurcated and presence [vs absence of an attenuated ventral arm separated from main body of spicules in A. lazarevskajae apud Lazarevskaja 1964]
Summary
The clade Diplogastridae Micoletzky 1922 largely represents the bacterivorous or predatory nematodes that very often demonstrate phoretic, necromenic or parasitic associations with insects (Sudhaus and Fürst von Lieven 2003). Much of the diversity of the family remains undocumented because of their absence from routine soil samples. Due to their variable habitats and niches, these nematodes show ample variation in their stomal armature, feeding behavior and life cycle patterns. The biogeographical distribution of Acrostichus has been mapped and the relationship between congeners has been analysed cladistically and discussed
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