Heterospecific timing of waving display in ocypodid crabs Ilyoplax pusilla and Uca lactea

This study explores whether timing adjustment in ocypodid waving also occurs between heterospecific pairs. Analysis of the dyadic interactions between neighbouring males of Ilyoplax pusilla and Uca lactea in the field showed that the former tended to wave with some delay after each U. lactea wave, while the latter was little influenced by I. pusilla waves. The heterospecific wave timing of I. pusilla by U. lactea waves can be viewed as a weakened form of the conspecific wave timing mechanism in this species.

Haemocyanin Oxygen Transport in Ocypode Spp.: Modulation of Oxygen Affinity?

The present study confirms the findings that in the two ocypodid crabs Ocypode saratan and O. ryderi haemocyanin oxygen affinity is increased in ‘replaced’ or dialysed blood compared to whole haemolymph and that this difference can be attributed to a plasma factor. After the replacement of the plasma, the haemocyanin of both species showed up to a 39% increase in oxygen affinity. The change in oxygen affinity was proportional to the logarithm of the amount of native plasma present. Further investigations have shown that this difference is not due to changes in plasma urate or bicarbonate concentrations. Using plasma exchange experiments it could be shown that the factor acts specifically on the haemocyanin of Ocypode spp. and not on Carcinus maenas haemocyanin. Fast protein liquid chromatography (FPLC) techniques indicate that the molecular weight of the factor is <5000 daltons and a specific peak could be isolated. This isolated peak is linearly correlated with changes in haemocyanin oxygen affinity. The results are discussed in the light of the overall modulation of haemocyanin oxygen affinity and the need for negative effectors.