Anaplectus has a muscular tubular mouth for engulfing bacteria and no spear.
Bactivorous nematodes have tubular mouths and graze on bacteria by swallowing them or scraping them from soil substrates using structures on top of their head. Grazing of bacteria increases the rate of decomposition of the chemical compounds in organic matter (carbon and nitrogen mineralisation) in soil. There is also evidence that grazing on bacteria can positively affect the plant root growth. These animals have generation times ranging from a few days to a week, which is advantageous for colonising new habitats.
(Source: Global Soil Biodiversity Atlas|Chapter II – Diversity of soil organisms)