Analysis of pigmentation characteristics on beak of Berryteuthis magister shevtsovi in the Japan Sea based on artificial neural networks

The beak is the main feeding organ of cephalopods which contains abundant biological information and is widely used in cephalopod biology research. In this paper, the characteristics of pigmentation stage in the beak were studied, which provided the basis for the study of fishery ecology of Berryteuthis magister shevtsovi. Based on the 303 schoolmaster gonate squid samples collected in the Japan Sea, we measured the basic biological data which included the mantle length (ML), body weight (BW), sexual maturity stage (SMS), the external morphological parameters (lower hood length, LHL; lower rostrum length, LRL; lower lateral wall length, LLWL; lower wing length, LWL) of the beak and stomach stage (SS), divided and determined the beak pigmentation. The relationships between the beak pigmentation and the ML, BW, SMS, the external morphological parameters of the beak and SS were analyzed by artificial neural networks, and the median values of the samples were fitted linearly. The results indicated that the ML contributed the most to beak pigmentation stage, which was 22.90%, followed by the LHL, SMS, BW, LRL, LWL, which contributed 16.50%, 14.4%, 11.90%, 11.70% and 11.60% respectively, while the LLWL and SS contributed less to beak pigmentation stage, which were 6.30% and 4.70% respectively. The analysis of covariance (ANCOVA) results showed that there was no gender difference in the relationship between the beak pigmentation and ML, BW, sexual maturity stage and stomach stage (P=0.611, P=0.786, P=0.132, P=0.515). The relationships between beak pigmentation and ML (R²=0.9870), BW (R²=0.9148) and the external morphological parameters of the beak (R²=0.9082, R²=0.8768, R²=0.8329, R²=0.7807, R²=0.8938, R²=0.6877, R²=0.7474, R²=0.7787) were significantly relevant. The beak pigmentation stage also increased with the increasing of sexual maturity stage, but there was no significant relevance between the beak pigmentation and stomach stage. This research studied the relationships between various growth factors and beak pigmentation stage, in order to provide scientific basis for further study on fishery ecology and rational development of Berryteuthis magister shevtsovi. The relationships between ML, BW, the external morphological parameters and beak pigmentation stage were significantly relevant, so that we can evaluate the beak pigmentation stage by these growth factors.