Macropthalmus sulcatus, H.Milne Edwards, 1852

Bom, Roeland A. & Ebbinge, Maaike, 2022, Simple and complex burrow morphology in two Macrophthalmus species on the intertidal mudflats of Barr Al Hikman, Sultanate of Oman, Journal of Natural History 56 (5 - 8), pp. 475-485 : 479

Macropthalmus sulcatus

All casted and excavated burrows of M. sulcatus were single tunnelled ( Figure 3 ). The casted burrows showed one or two sharp curves at the beginning, with no specific direction, after which the tunnel continued in one direction. The end of each burrow consisted of a small pool of water in which, in all but one cast, a single crab was entombed by the plaster. The mean length of the casted burrows was 21.3 cm (Standard Deviation [SD] ± 5.2; range 11.2–26.6 cm) and the mean depth was 10.3 cm (SD ± 1.5; range 8.3– 12.5 cm). In one of the casted burrows two relatively large crabs were found: a male and a female ( Figure 4 ). In total 24 crabs were entombed or captured, of which we identified 13 as males and 11 as females. There was a positive relation between burrow size at entrance and the carapace width of the crab caught inside (t = 8.972, P <0.01, R2 = 0.79; Figure 4 ). The regression equation was Y ¼ 4: 51 þ 1:16 X.

Figures

Figure 3. Drawing of a typical cast of the burrow of the two crabs studied. The ends of the burrow of Macrophthalmus depressus are open as the burrows were more extensive than our casts.

Figure 4. Relationship between crab carapace width and burrow size at entrance for the two studied crab species. The dashed red line gives the significant linear model relating Macrophthalmus sulcatus carapace width to burrow size at entrance. Symbols within the points refer to burrows in which more than one crab was encountered; similar symbols refer to the same burrow.