Fisheries Research Institute, Hellenic Agricultural Organization, 64007, Nea Peramos, Kavala, Greece.
Department of Biological Applications and Technology, University of Ioannina, University Campus, 45110, Ioannina, Greece.
Sci Rep. 2023 Nov 23;13(1):20581. doi: 10.1038/s41598-023-47834-x.
One of the most exceptional, loud paradigm of shape polymorphisms constitutes the "rostral loss" condition in hippolytid shrimps. The intertidal shrimp Hippolyte sapphica includes two conspecific morphotypes, one of which demonstrates a neotenic rostrum (morph-B). Morphs' rostral elongation is controlled by a single genetic locus, with long rostra (morph-A) representing the recessive state and short, larval-like ones the completely dominant state. Geometrics morphometry on the species morphotypes revealed also the homozygous/heterozygous state of the gene site along with some induced body' adaptations, which compete the micro-evolutionary disadvantage of the "rostral loss". We found recently that females' viability and maternal energy investment selectively favors morph-A. The present contribution detects and discuss comparatively demographic and reproductive traits in species mixed (both morphs) and unmixed populations. Our results show that this sharp dimorphic rostral condition is a sex-related marker and that the species is gonochoric. Presence of morph-B results to (a) lower egg production (b) higher seasonally males' percentage (c) morph-A females' earlier maturation and (d) higher fecundity in morph-A mixed populations. It seems that the "rostral loss" state induces complex adaptations between the two morphotypes through sex ratios equilibria, morphotypes' growth rates, and morphs' fecundity differentiate inputs throughout the seasons.
一种最为特殊和显著的形态多态现象范例是 hippolytid 虾类的“头部缺失”状态。潮间带虾类 Hippolyte sapphica 包括两种同物异态型，其中一种表现出幼态的头部（形态-B）。形态的头部伸长由单个遗传位点控制，长头部（形态-A）代表隐性状态，短而类似幼虫的头部则代表完全显性状态。对该物种形态的几何形态测量还揭示了基因座的纯合/杂合状态以及一些诱导的身体适应，这些适应竞争了“头部缺失”的微进化劣势。我们最近发现，雌性的生存能力和母体能量投资选择性地有利于形态-A。本研究旨在检测和比较物种混合（两种形态）和未混合种群的人口统计学和生殖特征。研究结果表明，这种明显的二态性头部条件是一个与性别相关的标记，而且该物种是雌雄同体的。形态-B 的存在导致：（a）产卵量降低；（b）季节性雄性比例升高；（c）形态-A 雌性的早期成熟；（d）形态-A 混合种群的更高繁殖力。似乎“头部缺失”状态通过性别比例平衡、形态生长率以及形态繁殖力在整个季节的分化输入，在两种形态之间诱导了复杂的适应。
