UB study proves that parental care affects embryonic development in a freshwater fish
A male of S. fluviatilis providing care to the eggs. Photo: Noëlle Fabre, UB
Research
(08/10/2014)
An article published in the journal Animal Biology indicates that parental care improves embryosʼ development in the river blenny. The article is signed by experts from the Department of Animal Biology of the University of Barcelona (UB) Dolors Vinyoles, Noëlle Fabre and Eduardo García Galea, who is also member of the Biodiversity Research Institute of the UB (IRBio).
A male of S. fluviatilis providing care to the eggs. Photo: Noëlle Fabre, UB
Research
08/10/2014
An article published in the journal Animal Biology indicates that parental care improves embryosʼ development in the river blenny. The article is signed by experts from the Department of Animal Biology of the University of Barcelona (UB) Dolors Vinyoles, Noëlle Fabre and Eduardo García Galea, who is also member of the Biodiversity Research Institute of the UB (IRBio).
The river blenny (Salaria fluviatilis) is a freshwater fish classified as endangered species in the Mediterranean area due to habitat loss (gravel extraction, river pollution, etc.). Like it happens in many other fish species, only males provide care to eggs (parental care) as they are the ones who fertilize the eggs laid by females.
Dolors Vinyoles explains that “parental care is a reproductive strategy used by many fish species, particularly freshwater ones. Its beneficial effects have been proved but it also implies high energetic expenditure. It is known that this activity improves embryosʼ survival. However, the study first shows that this strategy also has a direct effect on larvae embryology”.
When eggs are protected by males
According to the expert Noëlle Fabre, first author of the study which is based on her PhD thesis, “one of the most interesting aspects of the species is maleʼs parental behaviour”. “When the reproductive period arrives (May or June) —she explains—, the male chooses a stone (used as nest) and attracts females, which lay adhesive eggs on it. Then, the male fertilizes them and takes care of different femalesʼ egg laying: it guards and defends eggs from predators, cleans the nest and oxygenates eggs by moving its pectoral fins”.
“The male —adds Noëlle Fabre— may also secretes antimicrobial substances in order to protect eggs, like boarfish and peacock blenny (S. pavo, a marine species which is phenogenetically close to the river blenny) do”.
In the study, the UB research team designed an experimental protocol to know whether or not parentsʼ presence influences the process of embryonic development (ontogenic sequence) and embryosʼ structures. The team studied different parameters on river blenny eggs laid in aquaria where parents (male and female) were present and in others where they were absent. “To include the female in these protocols is also an important feature”, points out Dolors Vinyoles. “We know that parental care is given by males, by without femaleʼs stimuli, maleʼs reproductive behaviour will be different and it will probably affect parental care. Moreover, females are always near the nests in natural environments”, she says.
What is better: with or without parentsʼ presence?
Results show that the sequence of development in embryos reared in the presence and in the absence of parents is identical. However, head height presented lower values in larvae reared with parents than in larvae reared without them. Moreover, the yolk-sac volume of larvae with parental care is higher.
“From egg hatching to the moment when the larva feeds itself, nourishmentdepends on the yolk-sac”, stressed Dolors Vinyoles. “Everything suggests that larvae from eggs cared by fathers had a bigger reservoir and, thus, they have more possibilities of surviving”. The UB research group considers that hormones released by the male may help to optimize yolk-sac absorption during embryonic development, thus increasing survival possibilities.
Filial cannibalism: the dark side of parental care
Although parental care has obvious advantages, it also has some disadvantages: males must guard the nest permanently, so their possibilities to feed themselves are reduced, and that means a decrease in their physical condition. “This involves a certain rate of filial cannibalism, in order words, the male eats some eggs”, affirms Noëlle Fabre. “However, it is disadvantageous to a certain extent —she argues— because when the male eats part of the egg laying, it also compensates its physical condition loss and increases its possibilities to complete the cycle of parental care”. “Maleʼs survival is essential; eggs do not survive without him”, highlights Dolors Vinyoles.
The protection of an endangered species in the Mediterranean area
The research work has been carried out together with the wet laboratory, coordinated by Dr. Jordi Guinea. The lab is located at the Faculty of Biology and is part of the Science and Technology Centres of UB (CCiTUB). One of the objectives of the study is to improve future conservation programmes in Catalonia and Spain. Is it possible to substitute maleʼs parental care as a way to avoid male physical condition loss and filial cannibalism? Results indicate that it is not possible to do without maleʼs presence (although larvae have been successfully reared at the lab without parentsʼ presence). Future investigations are needed to describe paternal and maternal effects on embryosʼ sexual determination and the survival rate of larvae. According to the UB research group, “it is a study centred on an endangered species. Therefore, all new knowledge that can be applied to captive breeding promotion means a step forward in populationsʼ conservation”.