title: Is Juvenile Hormone a potential mechanism that underlay the "branched Y-model"?
abstract: Trade-offs are a central tenet in the life-history evolution and the simplest model to understand it is the "Y" model: the investment of one arm will affect the investment of the other arm. However, this model is by far more complex, and a "branched Y-model" is proposed: trade-offs could exist within each arm of the Y, but the mechanistic link is unknown. Here we used Tenebrio molitor to test if Juvenile Hormone (JH) could be a mechanistic link behind the "branched Y-model". Larvae were assigned to one of the following experimental groups: (1) low, (2) medium and (3) high doses of methoprene (a Juvenile Hormone analogue, JHa), (4) acetone (methoprene diluents; control one) or (5) näive (handled in the same way as other groups; control two). The JHa lengthened the time of development from larvae to pupae and larvae to adults, resulting in adults with a larger size. Males with medium and long JHa treatment doses were favored with female choice, but had smaller testes and fewer viable sperm. There were no differences between groups in regard to the number of spermatozoa of males, or the number of ovarioles or eggs of females. This results suggest that JH: (i) is a mechanistic link of insects "branched Y model", (ii) is a double ended-sword because it may not only provide benefits on reproduction but could also impose costs, and (iii) has a differential effect on each sex, being males more affected than females.
authors.affiliation: Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, Noria Alta, 36050 Guanajuato, Mexico.
authors.forename: Armando
authors.initials: A
authors.lastname: Márquez-García
authors.affiliation: Posgrado en Ciencias Biomédicas, Instituto de Ecología, UNAM, Mexico.
authors.forename: Jorge
authors.initials: J
authors.lastname: Canales-Lazcano
authors.affiliation: Turku Brain and Mind Center, Department of Biology, University of Turku, FIN-20014 Turku, Finland.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Rantala
authors.affiliation: ENES, UNAM, unidad Morelia, Antigua Carretera a Pátzcuaro No.8701, Col. Ex-Hacienda San José de la Huerta, Código Postal 58190 Morelia, Michoacán, Mexico. Electronic address: jcg@enesmorelia.unam.mx.
authors.forename: Jorge
authors.initials: J
authors.lastname: Contreras-Garduño
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D007605:Juvenile Hormones / Q000494:pharmacology / Q000502:physiology*; D007814:Larva / Q000187:drug effects; D008297:Male; D008726:Methoprene / Q000494:pharmacology; D008954:Models, Biological; D011679:Pupa / Q000187:drug effects; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000187:drug effects; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects; D013712:Tenebrio / Q000187:drug effects / Q000254:growth & development*
chemical_list: D007605:Juvenile Hormones; D008726:Methoprene
keywords: Branched Y-model; Condition dependence; Female choice; Life-history; Sexual selection; Sperm competition