Morphological Characteristics and Relationships between Beak Dimensions and Length of Marbled Octopus Amphioctopus aegina (Gray, 1849)

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Sonthaya Phuynoi
Charuay Sukhsangchan
Pawida Prasopsook


Morphological characteristics and the relationship between beak dimensions and body size of marbled octopus, Amphioctopus aegina (Gray, 1849) were determined using specimens collected from the Gulf of Thailand. A total of 408 individuals, 207 males and 201 females, were measured and weighed. Their body weights ranged from 7.30 to 120.00 g (39.78±19.05), mantle length (ML) from 32 to 80 mm (54.39±8.97) and total length (TL) from 114 to 305 mm (210.04±32.19). The rostral tips of the upper and lower beaks were brown to black in color, slightly curved, short, and with a small hood. The upper beak of this species has a short wing with large lateral wall. The ratios among upper beak dimensions were 1:2.95 for upper hood length (UHL):upper crest length (UCL), 1:3.64 for upper rostral width (URW):UCL, and 1:3.05 for upper rostral length (URL):UHL. The lower beak has a long wing and narrow lateral wall. The ratios of lower beak dimensions were 1:3.44 for lower hood length (LHL):lower crest length (LCL), and 1:1.25 for lower rostral width (LRW):LCL. Regressions of body size on beak dimensions were statistically significant (p<0.05). The best equations for determining mantle length (ML) and total length (TL) were ML = 0.531+2.108UHL (R2 = 0.704, MSres = 0.238) and TL = 3.574+2.539UCL (R2 = 0.731, MSres = 2.791), respectively.


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