External morphological characteristics and Identify subcutaneous glands structure of Sepiella inermis (Van Hasselt, 1835) found in the waters of Thailand.

Abstract

Abstract The external morphological characteristics and proportion variability of spineless cuttlefish, Sepiella inermis, were investigated at seven locations along the coastal waters of Thailand for one year. A total of 396 specimens were collected from Trat (30), Chonburi (61), Samut Songkhram (80), Phetchaburi (75), Surat Thani (30), Songkhla Province (45) and Ranong Province (75). The results showed that the dorsal mantle length (DML) measurement ranged from 32–92 mm (59.07 ± 10.51), and the body weight ranged from 8.74–133 grams (39.37 ± 18.40). The sexuality has a significant impact on morphological indices, with statistically significant differences at (p < 0.05). The dorsal mantle length can be used to identify sexuality at (p < 0.05), with a range of 40–49 (45.21 ± 2.41) mm for females and 30–39 mm (37 ± 2.82) for males. The morphometric characters at all stations were found to be correlated; Chonburi station stood out significantly from the other stations. Additionally, the description structure of the subcutaneous gland exterior, which had four lobes and was deeply grooved, were examined using Scanning Electron Microscopy (SEM) in the larvae stage. Internally, the wall of the gland consists of four layers: 1) the outer wall is the epidermis, 2) connective tissue, 3) muscle fibers, and 4) the inner wall is mucosa lines and cuboidal in shape. The basal portion of the gland produced an ink source and had four trabeculae branches retaining melanin granule cells. This study of external morphology offers numerous advantages and represents the first reported description of the subcutaneous gland in Sepiella.