Gonodactylus smithii
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Stomatopoda
Family:	Gonodactylidae
Genus:	Gonodactylus
Species:	G. smithii
Binomial name
Gonodactylus smithii Pocock, 1893 [1]

Gonodactylus smithii, also known as the purple spot mantis shrimp or Smith's mantis shrimp, is a species of the smasher type of mantis shrimp.^[2] G. smithii are the first animals discovered to be capable of dynamic polarization vision.^[3] They are identified by their distinctive meral spots ranging from maroon to purple with a white ring, though those that inhabit depths below 10 meters tend to be colored maroon.^[4] They also have raptorial dactyles, specialized forelimbs that are pigmented green and red, and antennal scales that are yellow.^[4]

Gonodactylus smithii are aggressive benthic marine predators that exhibit highly specialized color vision.^[5] On average, they are around 60 millimeters in length, but have been found to be as large as 380 millimeters.^[5][4] The morphology of both males and females are isometrically proportional to their respective body masses.^[6] Their mass ranges between 10 and 300 grams, with the average being around 60 grams.^[4] Their basal metabolic rate ranges from 0.0125 to 0.02 cm3.02/g/hr, with the average being around 0.0175 cm3.02/g/hr.^[4]

Gonodactylus smithii are found in tropical littoral zones in the Indo-Pacific Ocean, and widespread in Australia, India, and eastern Africa.^[2][5] They are also found in regions south of Japan and around Guam.^[4] Gonodactylus smithii reside in coral reef flats in both shallow waters and low intertidal depths ranging from 1 to 60 meters, but are most commonly found in the low intertidal zone.^[2] Gonodactylus smithii typically dwell in the cavities they create in either live coral or coral rubble.^[4]

Gonodactylus smithii reproduce all year long, but breeding is more concentrated during warmer months.^[4] They are generally monogamous, though some are polygynous.^[4] Males usually pursue females in their native habitats.^[5] Initially, males, using an external copulation organ, insert gonadopods into female gonadopores.^[4] Sperm is released, with females holding the males briefly.^[4] Females then release both the males and their eggs, with fertilization occurring.^[4] Males typically leave after copulation and do not invest in the females nor their offspring.^[4] Females are oviparous, laying eggs that eventually hatch.^[4]

Gonodactylus smithii have a bipartite life cycle.^[7] They begin with a larval phase, during which dispersal occurs, then mature into an adult phase.^[7] There are 7 larval stages, with the first 3 stages taking between 1 and 3 days, the fourth stage taking between 6 and 8 days, and the final 3 stages taking up to 38 days.^[8]

Gonodactylus smithii utilize their smashing raptorial claws as a mechanism to catch prey.^[4] The claws can easily shatter shells, stunning the prey.^[4] Gonodactylus smithii are generally carnivorous, specifically preying on fish, molluscs, non-insect arthropods, crustaceans, bivalves, and gastropods.^[4]

Gonodactylus smithii are capable of many signaling behaviors and exhibit offensive and defensive actions while doing so.^[5] Offensive actions include pushing the telson into the domicile of the resident, grasping the body of another using maxillipeds, and using dactyls to pierce through another.^[5] Defensive actions include simply avoiding, and bending the abdomen so that it brings the telson underneath and up to the front.^[5]

A behavior unique to Gonodactylus smithii is that they are capable of dynamic polarization vision.^[3] Unlike other organisms, stomatopods only fixate their gaze on objects of interest from time to time.^[3] They are able to focus their eyes with a series of rotations, and their eyes are capable of moving independently of the other.^[3] One type of rotation they use is torsional rotation, in which their ability to see the polarization of light is amplified.^[3] They rotate their eyes so that certain photoreceptors are aligned with the angle of polarization of a linearly polarized visual stimulus.^[3] This allows them to isolate the contrast between the object of interest and its background.^[3] The study of the eye structure of Gonodactylus smithii can generate more information on digital and visual storage capacity.^[4]

Gonodactylus smithii are essential to their ecosystem as they provide habitats for other organisms.^[4] The cavities that they create are left behind for other organisms to dwell in, and some host parasites, though this has led to the contracting of diseases in their shells.^[4]

• Barber, Paul, and Boyce, Sarah L. (2006). Estimating diversity of Indo-Pacific coral reef stomatopods through DNA barcoding of stomatopod larvae. Proc. R. Soc. B.^[7]
• Cheroske, Cronin, T. W., Durham, M. F., & Caldwell, R. L. (2009). Adaptive signaling behavior in stomatopods under varying light conditions. Marine and Freshwater Behaviour and Physiology.^[5]
• Daly, I., How, M., Partridge, J. et al. (2016). Dynamic polarization vision in mantis shrimps. Nat Commun.^[3]
• Luff, J. 2019. "Gonodactylus smithii" (On-line), Animal Diversity Web.^[4]
• McHenry, Claverie, T., Rosario, M. V., & Patek, S. N. (2012). Gearing for speed slows the predatory strike of a mantis shrimp. Journal of Experimental Biology.^[6]
• Morgan, Steven G., and Goy, Joseph W. (1987). Reproduction and Larval Development of the Mantis Shrimp Gonodactylus Bredini (Crustacea: Stomatopoda) Journal of Crustacean Biology.^[8]
• Yang, Mingqui, Liu, Hongtao, Wang, Rong, & Tan, Wei (2021). The complete mitochondrial genome of Purple Spot Mantis Shrimp Gonodactylus smithii (Pocock, 1893), Mitochondrial DNA Part B.^[2]