Nearest-neighbor Distance Analysis Research Articles

Kin recognition and sibling association among wood frog (Rana sylvatica) tadpoles

1. Wood frog (Rana sylvatica) tadpoles, hatched from egg masses collected in the field, were reared either with siblings only or in mixed groups of eight sibships. Sibships were marked with vital stains, released in a laboratory test pool, and their spatial distributions recorded over a 4-day period. 2. An analysis of nearest-neighbor distances suggests that tadpoles preferentially associated with familiar siblings over both familiar and unfamiliar non-siblings. Kinship preferences of R. sylvatica tadpoles, unlike those of other anurans that have been tested, thus appear largely unaffected by prior social experience. 3. Tadpoles reared in mixed sibship groups preferentially associated with the siblings with which they were reared over unfamiliar siblings exposed to a different set of sibships. In contrast, tadpoles did not discriminate either between siblings reared in different baskets within the same mixed group tank, or between siblings housed in different singlesibship containers. 4. Because R. sylvatica egg masses are usually deposited in communal clumps, an ability to recognize relatives not dependent on post-embryonic experience may have been selected. The possible adaptive significance of kin association among wood frog tadpoles is unknown; their schools probably do not represent kin groups, but larval distributions in natural ponds might reflect sibling association tendencies. 5. Kin recognition “labels” of non-sibling R. sylvatica tadpoles reared together, like those of R. cascadae tadpoles similarly reared, may converge as a result of social interactions. R. sylvatica tadpoles, unlike R. cascadae tadpoles, retain an ability to discriminate between familiar siblings and familiar non-siblings; hence label transference may be incomplete.

Evaluation of the corneal endothelial mosaic using an analysis of nearest neighbor distances

A technique for the rapid measurement of cell size in the corneal endothelium is demonstrated. The technique involves the measurement of nearest-neighbor distances by centering a circular target within the cell boundaries. Measurements of mean cell area as a function of age were performed and compared with similar planimetric area measurements. The age independence of a dimensionless shape factor indicates that the average cell shape remains unchanged even though the endothelium becomes increasingly pleomorphic with age.

Calling Behavior and Spatial Distribution of Two Species1 of Mole Crickets in the Field2

The calling behavior of 2 species of mole crickets ( Scapteriscus acletus Rehn and Hebard and S. vicinus Scudder) was studied in a north central Florida field. Chamber openings of calling males were marked for 15 consecutive evenings. Males seldom called from the same chamber more than once. Marked individuals moved their chambers an avg of 0.34 m from night to night. Statistical analysis of nearest neighbor distances showed the calling males of the 2 species together and S. acletus alone to be clumped in their distribution.

The role of microtubules in the movement of pigment granules in teleost melanophores.

When microtubules in teleost melanophores are disrupted with antimitotic agents, colchicine, high hydrostatic pressure, low temperature, and vinblastine, the alignment and movement of the pigment granules in these cells disappear; during recovery, the return of alignment and movement corresponds in both time and space with the repolymerization of microtubules. Furthermore, analysis of nearest neighbor distances in untreated melanophores reveals that pigment granules are closely associated with microtubules. Other structures such as microfilaments, the endoplasmic reticulum, and the cytoplasmic matrix do not appear to be involved. Thus we conclude that microtubules determine the alignment and are essential for the selective movements of the pigment granules in these cells. Investigations of the mechanism of movement show that microtubules are required for both centrifugal and centripetal migrations and that they do not change in number or location during redistribution of pigment. Our results further indicate that microtubules in melanophores behave as semistable organelles as determined by investigation with colchicine and hydrostatic pressure. These observations and others rule out a push-pull mechanism based on the polymerization and depolymerization of microtubules or one which distinguishes two operationally different sets of microtubules. We propose instead that particles move by sliding along a fixed array of microtubules.