Building blocks of a fish head: Developmental and variational modularity in a complex system

Abstract

Evolution of the vertebrate skull is developmentally constrained by the interactions among its anatomical systems, such as the dermatocranium and the sensory system. The interaction between the dermal bones and lateral line canals has been debated for decades but their morphological integration has never been tested. An ontogenetic series of 97 juvenile and adult Amia calva (Actinopterygii) was used to describe the patterning and modularity of sensory lateral line canals and their integration with supporting cranial bones. Developmental modules were tested for the otic canal and supratemporal commissure by computing correlations in the branching sequence of groups of pores. Landmarks were digitized on 25 specimens to test a priori hypotheses of variational and developmental modularity at the level of canals and dermal bones. Branching sequence suggests a specific patterning supported by significant positive correlations in the sequence of appearance of branches between bilateral sides. Differences in patterning between the otic canal and the supratemporal commissure and tests of modularity with geometric morphometrics suggest that both canals form distinct modules. The integration between bones and canals was insufficient to detect a module. However, both components were not independent. Groups of pores tended to disappear without affecting other groups of pores suggesting that they are quasi-independent units acting as modules. This study provides evidence of a hierarchical organization for the modular sensory system that could explain variation of pattern of canals among species and their association with dermal bones.

The tracheal system in post‐embryonic development of holometabolous insects: a case study using the mealworm beetle

“…According to Wagner's () conception, such structured biological systems should be treated as modular units of evolutionary transformation. A modular arrangement of the tracheal system can lead to higher rates of evolvability (Yang, ; Lehoux & Cloutier, ; Londe et al. ), as modular units enable changes of certain body parts without interfering with the functions of the other parts (Wagner, ; Klingenberg, , ; Sharma et al.…”

“…According to Wagner's (1996) conception, such structured biological systems should be treated as modular units of evolutionary transformation. A modular arrangement of the tracheal system can lead to higher rates of evolvability (Yang, 2001;Lehoux & Cloutier, 2015;Londe et al 2015), as modular units enable changes of certain body parts without interfering with the functions of the other parts (Wagner, 1996;Klingenberg, 2002Klingenberg, , 2009Sharma et al 2016). Moreover, it is hypothesised that this phenomenon contributes to optimisation of the whole network by lowering connection costs compared with non-modular builds (Clune et al 2013) and a high rate of co-option of modules (Monteiro & Podlaha, 2009).…”

Breaking Symmetry: Fluctuating Asymmetry and Geometric Morphometrics as Tools for Evaluating Developmental Instability under Diverse Agroecosystems

“…So, what is intended to be evaluated with GM is the effect of development on the shape of an individual, where the variations are a response from the organism to developmental instability. A different type of application of FA, also with a major use of GM, is to infer the origin of morphological structures [10,38,41,49,[54][55][56].…”

Morfometría Geométrica y sus Nuevas Aplicaciones en Ecología y Biología Evolutiva. Parte 2

“…Los estudios de integración morfológica y modularidad difieren de los análisis de redes en otros contextos, porque las interacciones responsables de la integración no son directamente observables y, en cambio, deben inferirse a partir de los patrones de covariación entre rasgos. Debido a esta razón, la modularidad ha sido temática de particular relevancia en la última década, en especial en estudios de evolución del desarrollo, donde varios autores argumentan que proporciona la flexibilidad suficiente para que diferentes rasgos evolucionen más fácilmente bajo demandas funcionales diferentes y/o contrastantes (Andjelkovic et al;Asahara, 2013;Goswami & Polly, 2010;Lehoux & Cloutier, 2015;Maga et al, 2017;Maiorino et al;Randau & Goswami, 2017, 2018Simons et al, 2018;Stefanello et al;Tamagnini et al, 2018;Zollikofer et al). Por consiguiente, la delimitación de módulos a partir de datos sobre patrones de covariación es una preocupación clave para la evolución del desarrollo de la forma (Klingenberg, 2010).…”

“…Por ende, lo que se busca evaluar con el uso de la MG es el efecto del desarrollo sobre la forma (shape) del individuo, siendo las variaciones una respuesta del organismo a la inestabilidad del desarrollo. Otro tipo diferente de aplicación de la FA, también con el uso mayoritario de la MG, es la utilización de la FA para inferir el origen del desarrollo de la integración dentro y entre estructuras morfológicas (Debat et al, 2009;Klingenberg, 2008;Klingenberg et al, 2002;Lehoux & Cloutier;Maestri et al).…”