Tripneustes gratilla (Linnaeus, 1758) is aspecies of sea urchin under the phylum Echinodermata; class Echinoidea; orderTemnopleuroida; family Toxopneustidae. This is commonly known as collectorurchin and locally called as “sowaki” all throughout the island of Leyte. Thespines of this species are dark or white to bluish-purple in color and some specimenshave orange-tipped spines (Lyman, 1921). It is widely distributed in the Indo-Pacific Region, Hawaii and in the RedSea (Rahman et al., 2014). Itis usually found at 1 to 30 m depths, in shallow seagrass beds and also incoral reef areas.
The individuals are always covered with collected debris,weeds or other subjects, hence the name collector urchin (Schoppe, 2000)Seaurchins play a vital role in the ecosystem by controlling the population ofinvasive algae in coral reefs, and have high economic value by providing foodand source of livelihood, generating up to millions of pesos per annum to thefisher folks (Talaue-Mcmanus & Kesner, 1995). Unfortunately, edibleechinoids like T. gratilla are threatened by overexploitation (Micael et al.,2009) and continuous rise of temperature due to climate change (Brennand etal., 2010).Climatechange is one of the major challenges in the present time causing stress to theenvironment. From shifting weather patterns that threaten food production, torising sea levels that increase the risk of catastrophic flooding, and therising global temperature that threaten the lives of marine organisms, theimpacts of climate change worldwide is in unprecedented scale (UNEP, 2013).According to the Intergovernmental Panel on Climate Change (IPCC) in 2014, asmuch as 4°C increase in ocean temperature is predicted by the end of thecentury.
High levels of water temperature and CO2 concentration caused by bothnatural and anthropogenic activities and processes are expected to be first experiencedin the coastal areas in the future. It has been noted that some parts of theglobe are already experiencing these phenomenon (Talmage & Gobler, 2011).Several marine ecosystems and the living organisms in it, especially in theintertidal and subtidal zones, are in great danger because of the continuousincrease of temperature (Sherman, 2015; Brennand et al., 2010; Nguyen et al.,2011). One of the important abiotic components of the ecosystem that affectsthe survival, growth, biological processes and distribution of organisms istemperature (Kinne, 1964).
In echinoderms, increasing temperature can inducechange in the position of its body and could greatly affect the growth anddevelopment of the larvae due to its fragility, and because planktonic stagedepends on the water temperature and chemistry (Brennand et al., 2010). Fertilizationof T.
gratilla is not directly affected by ocean warming and acidification(Byrne, 2010) but the early embryonic and larval stages are said to be highlysusceptible to increased temperatures because it produces a fragile calciteskeleton, and because this life stage has a planktonic period of days or weeksin the water column where seawater chemistry and temperature have a majorimpact on development (Brennand et al., 2010). Echinoplutei larvae support their body by producing calcite rods whichare also used for locomotion and feeding. Temperature has great influence onthe development of echinoplutei by shortening its planktonic stage whichdecreases the risk of predation (Byrne, 2010; O’Connor et al., 2007). Calciterods and arm length have direct effect on the larval feeding efficiency andvulnerability to predation (Soars et al., 2009; Allen, 2008). Information onthe development and survival of embryo and larvae particularly to hightemperature will provide insights on the impact of increasing temperature andultimately climate change to T.
gratilla, hence this study. The informationfrom this research will eventually help in conservation efforts and foraquaculture purposes.