Shell utilization pattern by the hermit crab Diogenes custos (Fabricius, 1798) along Gulf of Kachchh, Gujarat, India

Present work aims to study the gastropod shell utilization pattern of hermit crab Diogenes custos in the intertidal zone of Gulf of Kachchh, Gujarat, India. Hermit crab specimens were collected randomly during the low tide timings using hand picking method in February 2019 and November 2019. Data on abundance of common gastropod species were also collected using a quadrate sampling method. Hermit crab wet weight (HW) and their shield length (SL) (represent the size of the hermit crabs) were measured. Gastropod shells were identified up to species level and different morphological characters such as shell dry weight (DW), shell length (SHL), shell volume (SHV), shell aperture length (SAL), and shell aperture width (SAW) were measured. Total 2000 individuals of D. Custos, 1171 males (58.6%), 763 females (38.1%) and 66 ovigerous females (3.3%) occupying 49 species of gastropods were collected. Pollia undosa (21.9%) was highly occupied by D. custos followed by Cantharus spiralis (14.5%), Tenguella granulata (9.9%), Chicoreus virgineus (6.45%), Cerithium caeruleum (6.05%) and Nassarius distortus (6.05%). Regression analysis carried out between D. custos morphological characters and gastropod shell morphological characters showed a strong relationship which suggests that shell architecture plays an important role in shell utilization pattern of Diogenes custos. The abundance of Pollia undosa was very high in the intertidal zone as compared to other commonly occupied gastropods species which also suggests that gastropod shell availability in the habitat also has pronounced effect on shell utilization pattern of D. custos.