Comparative Embryology of the Vertebrates.Olin E. Nelsen

Jane Oppenheimer

doi:10.1086/400304

Heterokairy: a significant form of developmental plasticity?

Biology Letters ◽

10.1098/rsbl.2016.0509 ◽

2016 ◽

Vol 12 (9) ◽

pp. 20160509 ◽

Cited By ~ 4

Author(s):

S. D. Rundle ◽

J. I. Spicer

Keyword(s):

Research Agenda ◽

Developmental Plasticity ◽

Potential Role ◽

Research Effort ◽

Adaptive Significance ◽

Research Interest ◽

Adaptive Plasticity ◽

Comparative Embryology ◽

A Current

There is a current surge of research interest in the potential role of developmental plasticity in adaptation and evolution. Here we make a case that some of this research effort should explore the adaptive significance of heterokairy, a specific type of plasticity that describes environmentally driven, altered timing of development within a species. This emphasis seems warranted given the pervasive occurrence of heterochrony, altered developmental timing between species, in evolution. We briefly review studies investigating heterochrony within an adaptive context across animal taxa, including examples that explore links between heterokairy and heterochrony. We then outline how sequence heterokairy could be included within the research agenda for developmental plasticity. We suggest that the study of heterokairy may be particularly pertinent in (i) determining the importance of non-adaptive plasticity, and (ii) embedding concepts from comparative embryology such as developmental modularity and disassociation within a developmental plasticity framework.

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Structure of the insect head as revealed by the EN protein pattern in developing embryos

Development ◽

10.1242/dev.122.11.3419 ◽

1996 ◽

Vol 122 (11) ◽

pp. 3419-3432 ◽

Cited By ~ 3

Author(s):

B.T. Rogers ◽

T.C. Kaufman

Keyword(s):

Drosophila Melanogaster ◽

Pattern Formation ◽

Protein Pattern ◽

Related Protein ◽

Specific Expression ◽

Tissue Specific Expression ◽

Single Segment ◽

Dorsal Ridge ◽

Insect Embryos ◽

Comparative Embryology

The structure of the insect head has long been a topic of enjoyable yet endless debate among entomologists. More recently geneticists and molecular biologists trying to better understand the structure of the head of the Dipteran Drosophila melanogaster have joined the discourse extrapolating from what they have learned about Drosophila to insects in general. Here we present the results of an investigation into the structure of the insect head as revealed by the distribution of engrailed related protein (Engrailed) in the insect orders Diptera, Siphonaptera, Orthoptera and Hemiptera. The results of this comparative embryology in conjunction with genetic experiments on Drosophila melanogaster lead us to conclude: (1) The insect head is composed of six Engrailed accumulating segments, four postoral and two preoral. The potential seventh and eighth segments (clypeus or labrum) do not accumulate Engrailed. (2) The structure known as the dorsal ridge is not specific to the Diptera but is homologous to structures found in other insect orders. (3) A part of this structure is a single segment-like entity composed of labial and maxillary segment derivatives which produce the most anterior cuticle capable of taking a dorsal fate. The segments anterior to the maxillary segment produce only ventral structures. (4) As in Drosophila, the process of segmentation of the insect head is fundamentally different from the process of segmentation in the trunk. (5) The pattern of Engrailed accumulation and its presumed role in the specification and development of head segments appears to be highly conserved while its role in other pattern formation events and tissue-specific expression is variable. An overview of the pattern of Engrailed accumulation in developing insect embryos provides a basis for discussion of the generality of the parasegment and the evolution of Engrailed patterns.

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