Why grow up?Aperspective on insect strategies to avoid metamorphosis

Abstract

Abstract. 1. Insects with complete metamorphosis (holometaboly) are extremely successful, constituting over 60% of all described animal species. Complete metamorphosis confers significant advantages because it enables organisms to optimise life-history components through temporal partitioning, and thereby to exploit multiple ecological niches. Yet holometaboly can also impose costs, and several lineages have evolved life cycle modifications to avoid complete metamorphosis.2. In this review, we discuss different strategies that have evolved that result in the loss of complete metamorphosis (type I and type II paedomorphosis). In addition, the ecological pressures and developmental modifications that facilitate this avoidance are considered, as well as the importance of life cycle complexity in life-history evolution.3. Interestingly, only female holometabolous insects have entirely avoided complete metamorphosis, and it is always the ancestrally juvenile morphology that is retained. These findings point to a strong sex-biased trade-off between investment in reproduction and development. While the loss of complete metamorphosis in females has occurred independently on several occasions across holometabolous insects, only a small number of species possessing this ability have been described. 4. Thus, complete metamorphosis, which originated only once in insects, appears to have been almost fully retained. This indicates that significant modifications to the holometabolan metamorphic ground plan are highly constrained, and suggests that the transition to complete metamorphosis is evolutionarily irreversible.

Phylogenomic analysis resolves the relationships among net‐winged beetles (Coleoptera: Lycidae) and reveals the parallel evolution of morphological traits

“…Since then, larviform females have been identified in other lycid taxa. Additional presumed neotenics are currently known in a high number of males and their relationships, morphology and distribution indicate a possibility that conspecific females are larviform, although this hypothesis has not been verified (Crowson, ; Cicero, ; Bocak & Bocakova, ; Miller, ; Kazantsev, , ; Bocak et al , ; Masek et al , , ; McMahon & Hayward, ). We considered these taxa to be neotenic in our analysis in agreement with the opinion of the listed authors.…”

“…Previous studies have reported on the evolution of neoteny (Crowson, 1972;Kazantsev, 2013;Masek et al, 2015;McMahon & Hayward, 2016), speciation of neotenic lineages (Malohlava & Bocak, 2010;Bray & Bocak, 2016), chemical protection and mimicry (Linsley et al, 1961;Eisner et al, 1962Eisner et al, , 2008Moore & Brown, 1981, 1989Bocak & Yagi, 2010;Motyka et al, 2018), dispersal history (Sklenarova et al, 2013;Li et al, 2015b;Motyka et al, 2017;Bocek & Bocak, 2019) and morphological evolution (e.g. Bocak & Bocakova, 1990;Miller, 1991;Bocakova, 2001Bocakova, , 2003Bocakova, , 2005Kazantsev, 2005Kazantsev, , 2006Kazantsev, , 2013 in net-winged beetles.…”

The molecular phylogeny of Omalisidae (Coleoptera) defines the family limits and demonstrates low dispersal propensity and ancient vicariance patterns

“…Most incompletely metamorphosed beetle females (i.e. neotenic forms sensu Gould ()) are recorded from Elateroidea and only a few forms are known from other beetle superfamilies (Crowson, ; Gould, ; Bocakova et al ., ; Bocak et al ., , ; McMahon & Hayward, ). Many elateroid taxa with incompletely metamorphosed close relatives are known only in males and their fully larviform or incompletely metamorphosed females are hypothesised.…”

“…The metamorphosis of holometabolous insects is affected by gradual changes in concentration of 20‐hydroxyecdysone and juvenoide hormones (Naisse, ; Zhou & Riddiford, ; Suzuki et al ., ; McMahon & Hayward, ). In contrast with the gradual character of modifications of metamorphosis and gradually increasing degrees of imaginalisation of adult females and males, some authors discriminate neoteny as a case when sexually mature individual is completely larviform and incomplete metamorphosis in all other cases when females differ from fully sclerotised and winged relatives (e.g.…”

Eating in a losing cause: limited benefit of modified macronutrient consumption following infection in the oriental cockroachBlatta orientalis

“…However, virtually nothing is known about the relationship between macronutrient diet choice and immunity outside of a handful of holometabolous, mostly herbivorous, insect larvae. Holometabolous insects undergo complete metamorphosis consisting of distinct larval, a pupal and an adult winged phase, which are typically correlated with vastly different ecologies and corresponding physiological, morphological and immunological conditions (McMahon & Hayward 2016). By contrast, hemimetabolous insects undergo progressive molts where each larval instar closely resembles the adult (Sehnal et al .…”