Structure & functions of the accessory nidamental gland in the Indian squid,Loligo duvanuceli Orbigny(Mollusca:Cephalopoda)

Abstract

Females of the Indian squid, Loligo duvauceli in different stages of sexual maturity were collected during September-November, 2007. Mantle length of the ripe females was 16.22 ± 0.487 cm and body weight was 125.3 ± 8.628 g. Accessory nidamental glands (ANG) were conspicuous only in sexually maturing females. These paired glands were located at the anterior end of the nidamental glands (NG) and were closely associated with the ventral surface of the ink sac. The colour of ANG was orange red in mature specimens. The colour has been attributed to pigments of symbiotic bacteria. The ANG-somatic index of ripe females of L. duvauceli was 0.154 ± 0.024 %. Based on the morphological changes like gross size, coloration of the gland and also histological changes like formation, distribution, size and shape of the pigment granules during the course of maturation, the accessory nidamental glands were quantified into four stages namely immature, ripening, ripe and spent. Antibacterial activity of ANG-butanol extracts (2.5 g in 5.0 ml butanol) from different stages of maturity was studied. The extracts from ripe stage ANG showed antibacterial activity against gram negative bacterial strains, Escherichia coli and Pseudomonas aeruginosa, and gram positive bacteria, Staphylococcus aureus. Immature and spent gland extracts did not show any antibacterial activity. The ANG-butanol extract of ripe ANG showed an absorbance maximum at 498.5 nm, followed by shoulders at 528.0, 290.5 and 315.5 nm. In the case of immature stage an absorbance maximum at 285.0 nm was obtained, followed by shoulders at 340.5, 358.0 and 400.5 nm. For the spent stage the absorbance spectrum was very similar to the immature stage. The peak at 498.5 nm (2.597A) obtained for the ripe stage could be attributed to the presence of carotenoid pigments. The peak obtained at 286 nm for the different stages indicated the presence of peptides/ proteins. Thin layer chromatography of the ANG- butanol extract did not show the presence of polyphenols/flavonoids or quinones, whereas neutral lipid components such as phospholipids, cholesterol, free fatty acids, triglycerides, fatty acid esters, and cholesteryl esters were detected. The total free fatty acid (FFA) content in the ripe ANG was 16.0 ± 0.143 mg oleic acid/g tissue, whereas in immature ANG, it was 10.3 ± 0.114 mg oleic acid/g tissue. The FFA content was significantly higher in the ripe stage. Gas chromatographic studies of immature and ripe stages revealed the presence of a mixture of fatty acids. The total fatty acid content was 3.925 mg/g tissue in ripe stage and 0.704 mg/g tissue in immature stage showing the high gross value in the ripe stage. The quantum of the major four fatty acid (Palmitic acid, Oleic acid, Docosahexaenoic acid and Eicosapentaenoic acid) components was clearly found to be much more in the ripe stage than in the immature stage, especially the unsaturated fatty acids and may be the factors responsible for the antibacterial activity.