WEB PAGE UPDATE version 02/2017

Hello to our valuable online users.

http://sealifebase.ca/ is now updated!

Feel free to search for your top most favorite non-fish marine animals.
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HAPPY LEARNING!

Through the eyes of a peacock mantis shrimp

Odontodactylus scyllarus (peacock mantis shrimp) is neither a peacock, mantis nor shrimp but a different kind of crustacean which resembles all, regardless of its common name. It is famous for its greatly enlarged hammer-like second raptorial appendage which it uses to smash its prey and defend itself against predators, both in high speeds and with a crushing force [1].

Photo taken in Taiwan by Tim-Yan Chan.

Another great feature of this species is its eyes, which are more advanced than those in humans or in any other species. Its stalked eyes have trinocular vision, depth perception, and can move independently of each other. If humans have 4 different photoreceptors with 3 color channels which allow them to see linearly polarized light, the peacock mantis shrimp has 16 photoreceptors with 12 color channels that allow it to see both linearly and circularly (3D) polarized lights, scientifically called hyperspectral vision [2].

Photo by Steve De Neef.

With this knowledge humans have now developed new ideas that will improve the high-definition capacity of DVDs and CDs by adapting the quarter-wave plates of the mantis shrimp [3].

To know more about the peacock mantis shrimp and other crustaceans, visit SeaLifeBase.

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[1] Patek, S.N., & R.L. Caldwell. 2005. Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp Odontodactylus scyllarus. The Journal of Experimental Biology 208(Pt 19):3655–3664.
[2] Chiou, T., S. Kleinlogel, T. Cronin, R. Caldwell, B. Loeffler, A. Siddiqi, A. Goldizen, and J. Marshall. 2008. Circular polarization vision in a stomatopod crustacean. Current Biology 18:429-434.
[3] Roberts, N.W., T. Chiou, N.J. Marshall, and T.W. Cronin. 2009. A biological quarter-wave retarder with excellent achromaticity in the visible wavelength region. Nature Photonics 3:641-644.


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First record of a potentially invasive mussel Mytella charruana in Manila Bay

Human activities have, in many unprecedented ways, accelerated biological shifts and nuances in our planet. Such is the case for Manila Bay and its inhabitants. A slew of anthropogenic activities such as land and sea-based transportation, sedimentation, fisheries, and reclamation and land conversion has put the ecosystem at high risk for biological invasions.

Meet the Charru mussel Mytella charruana, a newly reported species in Manila Bay, which has been previously documented to be invasive in Florida. A team of researchers led by Dr. Benjamin Vallejo (University of the Philippines Diliman) and SeaLifeBase staff, Jeniffer Conejar-Espedido (University of the Philippines Los Banos) confirms its first recorded presence in the area. Previously identified as Mytilus spp., the bivalve was later identified via DNA barcoding to be Mytella charruana, suggesting its phylogenetic position within the Perna clade. Increasing trend in its abundance from 2014 to 2015 indicates likelihood of establishment and probable competition with the native mussel Perna viridis.  

What makes the species different from Perna and Modiolus is its dark bluish to brown hue and a bluish to purplish nacreous interior. It is also bigger (average of 2.8 cm shell length) compared to another non-indigenous mussel in the area, Mytilopsis, which only grows to 1 cm SL.

Mytella charruana from the Manila Bay PICES
collectors. Photographs by J. Conejar-Espedido.

How did M. charruana reach Manila Bay?

Researchers suggest it is likely to have been introduced via ballast water or through fouled ship hulls. Since mytilids in general adapt and highly reproduce in estuarine and coastal conditions, the persistence of M. charruana is likely.

The spat was first observed at the start of southwest monsoon rainy season. Assuming it has a similar life history profile as that of P. viridis, its introduction must have occurred between late April and early May 2014. This suggests possible competition between the two species. The increasing abundance of M. charruana also indicates its establishment in Manila Bay, but this is yet to be verified in succeeding years. How it could affect the populations of the native P. viridus is, however, is unknown. Further studies on the reproduction, ecology, community dynamics and population genetics are recommended.

Dr. Vallejo’s team also includes, Leanna Manubag, Kevin Carlo Artiaga, Amor Damatac II, Ivan Christian Imperial, Tyrll Adolf Itong, Ian Kendrich Fontanilla and Ernelea Cao.

You can access the full paper at (http://www.reabic.net/journals/bir/2017/1/BIR_2017_Vallejo_etal.pdf). 

Cheaper, faster tool may be used to assess risks posed to dolphin populations by dolphin-watching tourism

Many studies have supported the threats imposed by boat-based tourism on whale and dolphins, especially amidst poorly-enforced or lacking regulations. Tourist boats highly impact cetacean behavior, both in short- and long term aspects. Thus, there is a need to understand the ecological effects of boat-based tourism on cetaceans along with economic sustainability of the industry. Since long-term study of ecological indicators may take 15 years or more to detect, it is impractical and costly. A group of researchers then proposes a cheaper and faster approach on this issue.

To complement ecological data, they used human dimension data (which is more readily available) with insights from Driver-Pressure-State-Impact-Response (DPSIR) framework to rapidly assess the ecological impact of dolphin-watching tourism to dolphin populations across six developing Asian countries: Cambodia, India, Indonesia, Malaysia, Thailand and the Philippines. Putting the framework within the context of dolphin-watching  tourism, they identified different indicators: the driver (development potential of dolphin-watching industry) that build pressure (number of tour boats, driving behavior, engine noise, etc.) on the environment, affecting the state (local IUCN status of species), leading to impact (change in population dynamics and habitat use) on ecosystems, hence the need for response (Code of Practice, cap on daily boat trips, alternative livelihoods, etc.).

Since impact can only be measured through large historical data, the indicators of the other four components and relationships among them where used to obtain a proxy, risk, i.e. the risk of a dolphin-watching industry harming, displacing or causing local extinction to a target dolphin population. A relative value of 0 to 5 was assigned for each D-P-S-R indicator: zero risk (0), very low risk (1), low risk (2), medium risk (3), high risk (4) and very high risk (5). Based on the values of pressure, state, and response, they obtained an overall risk indicator of local extinction.

They found high risk to dolphins in India and Indonesia, intermediate risk to Cambodia, and suspected low risk (pending more ecological data) to Thailand, Philippines and Malaysia populations.

Aside from alleviating the main contributing component to the overall risk factor, the study suggests “The introduction of and compliance to a Code of Practice would significantly reduce the pressure on the local dolphin populations.”

The international research team includes scientists from Indonesia (Putu Liza Mustika), Australia (Riccardo Welters, Gerard Edward Ryan - Cambodia, Coralie D’Lima - India), Philippines (Patricia Sorongon-Yap), Thailand (Suwat Jutapruet), and Malaysia (Cindy Peter). 

This paper is now published in the Journal of Sustainable Tourism.

You can access the full paper here: A rapid assessment of wildlife tourism risk posed to cetaceans in Asia.

Underwater's Ultimate Weapon

Listen to this audio recording below from Radiolab [1]. Start from 2:00 and end at 3:25.

What did you hear?

Rice pops? Twigs being burned? Frying bacon?

No – they are snapping shrimps, or rightfully called “pistol” shrimps which belong to the family Alpheidae. Do the sound even hint to a deadly weapon?

For starters, a snapping shrimp is a tiny creature, reaching one to two inches – just half of your finger [4]. Now it gets scarier: it has a distinctive large claw which it uses to stun a prey instantaneously! The cracking sound produced is what you hear during low tide in shallow waters. Some species live mutually with gobies in burrows: the shrimp provides a home for the goby, while the fish confers protection to shrimp against predators [2].

Why do these shrimps make an incessant sound? 

In 2000, European scientists discovered that the sound is produced from the formation of cavitation bubble released when the claw rapidly snaps shut [3]. Charged with a speed of up to 100 km an hour [1,3,4], the bubble can go for a swift kill in a matter of 300 microseconds [3]. As the pressure stabilizes, the bubble pops with a loud bang reaching about 220 decibels [1, 5]. That is equivalent to the sound of a jet engine [1], enough to break small jars [4]. And yes, it’s louder than a gun shot which is around 150 decibels [7]. It actually competes with the sperm whale as the loudest animal in the ocean [4].  

It emits not only a ‘deafening’ sound but an ultra-fast light when the bubble collapses. It is thought to exhibit sonoluminiscence - emission of short bursts of light [4] caused by a strong sound field [3]. If it were to be seen at the time of collapse, the temperature inside the bubbles must be a least 5,000 degrees Kelvin, comparable to the surface of the sun at 5,800 degrees Kelvin. The ephemeral flash of light lasts no longer than 300 picoseconds (a picosecond is one trillionth of a second) [3]. 

The violence of it all is lies on the sheer extremes of temperature and pressure before bursting – a truly impressive and deadly weapon. Now that’s intimidating.

Credit: National Geographic

Below is pistol shrimp in action, releasing its deadly, supersonic bubble [6].

Here’s another interesting feat.

Pistol shrimps helped the Americans win World War II. Yes, you read it right. Since the crackling sound they produce is intense enough to disrupt underwater communication, US Navy submarines used the shrimp beds to interfere with the sonar, therefore attacking the Japanese while hiding on their makeshift invisibility cloak [1,2]. They even installed speakers on their ships to mirror the shrimps’ sounds! [1]. 

Awesome, isn't it?

To know more about snapping shrimps or pistol shrimps, visit SeaLifeBase.

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[1] Iono.fm. (2016, November 10).  Bigger than bacon [Audio file]. Retrieved from https://iono.fm/e/286830

[2] Riley, A. (2016, January 29). This shrimp is carrying a real-life working stun gun. BBC Earth. Retrieved from http://www.bbc.com/earth/story/20160129-the-shrimp-that-has-turned-bubbles-into-a-lethal-weapon

[3] Roach, J. (2001, October 3). Snapping shrimp stun prey with flashy bang. National Geographic. Retrieved from http://news.nationalgeographic.com/news/2001/10/1003_SnappingShrimp.html

[4] Anirudh (2013, February 13). 7 interesting facts about pistol shrimp or snapping shrimp. Retrieved from https://learnodo-newtonic.com/pistol-shrimp-facts

[5] Ocean Conservation Research (2016). Snapping shrimp. Retrieved from http://ocr.org/sounds/snapping-shrimp/

[6] Nat Geo Wild. (2013, April 11). World’s deadliest – amazing pistol shrimp stun “gun” [Video file]. Retrieved from https://www.youtube.com/watch?v=KkY_mSwboMQ

[7] Simon, M. (2014, July 11). Absurd creature of the week: the feisty shrimp that kills with bullets made of bubbles. Wired. Retrieved from http://www.wired.com/2014/07/absurd-creature-of-the-week-pistol-shrimp/