How a sharp rostral dimorphism affects the life history, population structure and adaptability of a small shrimp: the case study of Hippolyte sapphica

Abstract

The rostrum shows a large variation across caridean shrimps; however, our knowledge about the biological significance of this morphological structure is very limited, and information on its genetic control is completely absent. The present study concentrates on an unusual rostral dimorphism in a population of small Mediterranean caridean shrimp and combines laboratory and field observations. Analysis of lab‐reared offspring supports the hypothesis that the post‐larval elongation of the rostrum is controlled by a single genetic locus, with the long dentate rostrum representing the recessive state and the short larval‐like rostrum representing the completely dominant state. The short rostrum is a sparsely distributed character; our results obtained from field studies suggest that it reduces the viability and probability of egg‐bearing among large females but, unexpectedly, the specimens with a short rostrum show consistently more rapid sex differentiation and a significantly higher propensity to become males. Therefore, it has to be concluded that, under certain conditions, a single emergent character could influence the species evolution in a rather complex manner, thus affecting the life history, population structure and dynamics and mortality in certain subgroups. In turn, the genetic factors responsible for the different phenotypes would tend to be segregated through different subpopulations and size classes, thus partially escaping the negative selective pressure.

Global biogeography, cryptic species and systematic issues in the shrimp genus Hippolyte Leach, 1814 (Decapoda: Caridea: Hippolytidae) by multimarker analyses

“…Hippolyte sapphica was described 43 with two distinct morphs (A and B), separated on the basis of rostral morphology, with no known intermediate forms 1 . This species inhabits shallow seagrass meadows in the central and eastern Mediterranean 2 , 44 , although forma B has only been reported from the Amvrakikos Gulf (Greece) and Venice Lagoon (Italy), always sympatric with forma A 45 . Larval development studies of both forms concluded that females of both forms can generate larvae ultimately developing in adults of either form 46 .…”

Eco-morphological consequences of the ‘rostral loss’ in the intertidal marine shrimp Hippolyte sapphica morphotypes

“…(2010) confirmed the conspecific status of the two forms and later Liasko et al . (2015) suggested that rostral length is genetically regulated by a simple locus, with allele b (morphotype B) being dominant. Furthermore, it has been shown that morphotype A specimens had a high propensity to become female (A/B ratio in females ~1 : 0.63), while the opposite was true for morphotype B specimens (A/B ratio in males 0.49 : 1).…”

“…Furthermore, it has been shown that morphotype A specimens had a high propensity to become female (A/B ratio in females ~1 : 0.63), while the opposite was true for morphotype B specimens (A/B ratio in males 0.49 : 1). Likewise, A-phenotype turned out to be superior, in terms of viability, for big ovigerous females (Liasko et al ., 2015).…”

“…In this way, we attempt to benefit from this unique discontinuous rostral variability to draw eco-morphological conclusions about the adaptation of the species and its morphotypes. We expected that, since form A benefits females (Liasko et al ., 2015), the females of form B must develop some compensatory traits, which would substitute for the lack of a long rostrum.…”

Peer Review #1 of "Recognizing two new Hippolyte species (Decapoda, Caridea, Hippolytidae) from the South China Sea based on integrative taxonomy (v0.1)"

“…Most Hippolyte species inhabit seaweed beds, but some are obligate or facultative symbionts of other organisms, such as gorgonians and crinoids (D'Udekem d'Acoz, 2007;Marin et al, 2011). The taxonomy, phylogeny, and biology of Hippolyte taxa have attracted considerable attention in recent years (Manjón-Cabeza et al, 2011;Marin et al, 2011;Terossi & Mantelatto, 2012;Liasko et al, 2015;Gan & Li, 2017a;2017b;Liasko et al, 2017;Terossi et al, 2017). Currently, a total of 35 valid species are recognized worldwide (D'Udekem d'Acoz, 1996;2007;De Grave & Fransen, 2011;Marin et al, 2011;Gan & Li, 2017a, 2017bTerossi et al, 2017), of which about 12 species occur in the Indo-West Pacific region.…”