A new ant-butterfly symbiosis in the forest canopy fills an evolutionary gap

Myrmecophilous butterflies can establish complex symbiotic relationships with ants. A caterpillar wandering among the brood of the aggressive ponerine ant Neoponera villosa was found inside the core of a nest built in the myrmecophytic bromeliad Aechmea bracteata. This is the first caterpillar found living inside a ponerine ant nest. Its DNA barcode was sequenced, and an integrative approach was used to identify it as Pseudonymphidia agave, a poorly known member of the subtribe Pachythonina in the riodinid tribe Nymphidiini. The cuticle of the tank-like caterpillar lacks projections or tubercles and is covered dorsally by specialized flat setae that form an armor of small plates. Ant-organs potentially related to caterpillar-ant signaling, such as perforated cupola organs and tentacle nectary organs, are present. These morphological traits, together with evidence of social integration (direct contact with host brood, protective morphology, slow movement, no host aggressiveness), suggest that P. agave is a symbiotic, social parasite of N. villosa, preying on its host brood. However, several knowledge gaps remain, including oviposition site, dependence on bromeliad association, steps to colony integration, and larval diet through development. Carnivory has been reported in all known members of the subtribe Pachythonina (caterpillars prey on honeydew-producing hemipterans) suggesting a shift to myrmecophagy inside the ant nests as a possible evolutionary transition.

Filling the gap: a new ant-butterfly symbiosis in the forest canopy

Myrmecophilous butterflies can establish complex symbiotic relationships with ants. An elusive symbiotic caterpillar wandering among the brood of the aggressive ponerine ant, Neoponera villosa, was found inside the core of a nest built in the myrmecophytic bromeliad Aechmea bracteata. This is the first caterpillar found in symbiosis with a species of the subfamily Ponerinae. Tissue sample was barcoded, and an integrative approach was used to identify it as Pseudonymphidia agave, a poorly known Pachythonina member in the riodinid myrmecophilous tribe Nymphidiini. The caterpillar has a general tank-like body morphology, without projections or tubercles, and is covered dorsally by specialized flat setae that form an armor of small plates. Ant-organs potentially related to the caterpillar-ant signaling, such as perforated cupola organs and tentacle nectary organs, are present. These functional traits, together with the stable social integration, suggest that P. agave is a specialized social parasite of N. villosa. However, several knowledge gaps remain, notably the oviposition site, dependence on bromeliad association, steps to colony integration, and the larval diet through ontogeny. Carnivory has been reported in all known members of the Pachythonina subtribe (caterpillars prey on honeydew-producing hemipterans), and a shift to myrmecophagy inside the ant nests is a possible evolutionary step.

Corallite increase and mural pores in Lichenaria (Tabulata, Ordovician)

Lichenaria may be a representative of the most primitive stock of tabulate corals. The degree of paleobiologic complexity discovered in L. globularis and L. grandis is therefore surprising. Six types of corallite increase are recognized. All are lateral, which is the predominant mode in tabulates. Most types, however, are unique or are comparable to those in few other Ordovician taxa. Only Type 1 (L. globularis), yielding a single offset with a simple basal mural pore, is typical of tabulates. In Type 2 (L. globularis), one parent produces two offsets simultaneously, whereas in Type 3 (L. globularis), two offsets arise from separate parents at nearly the same time and join via a connective mural pore. Types 4 (L. globularis, L. grandis), 5 (L. grandis), and 6 (L. globularis, L. grandis), respectively, involve one, two, and two to four corallites in addition to the parent, which join via a connective mural pore at the site of offsetting.Several features of L. globularis and L. grandis point to unexpectedly high levels of colony integration. Continuously fused common walls lacking back-to-back epithecae suggest soft tissue continuity among polyps above the corallum. Connective mural pores indicate temporary fusion of polyps. Coordinated behavior of polyps is suggested by the development of conjoined offsets from two parents during Type 3 increase, and by fusion during Types 4 to 6 increase. Attempts at certain types of increase sometimes failed to yield offsets, suggesting expendability of incipient buds, perhaps reflecting subjugation of individuals for the good of the colony.In light of this study, genera that have previously been included in Lichenariidae and Lichenariida require reassessment and their phylogenetic relationships should be reconsidered. Unfortunately, this is hindered because fundamental characters such as corallite increase and wall structure remain inadequately known in most early tabulates.