Revista Chilena de Historia Natural 76 (2): 157-168, 2003
SIMPOSIUM
Brood care in Brachyuran crabs: the effect of oxygen provision on reproductive
costs
The quantification of the costs associated with parental care of marine invertebrates
requires a first and necessary step, which is the identification of the different forms of care exhibited by this group. Among marine
invertebrates, provision of oxygen to the aggregation of embryos may be critical, although most evidence on the link between oxygen
limitation and parental care is indirect. Species which show active behavior directed at providing oxygen to the brood offer a good
model to establish the direct link between behavioural patterns and oxygen provision to the embryos, and to estimate the costs
associated with this form of care. In this manuscript, we conducted a review of the current knowledge about oxygen limitation in
embryos aggregations of marine invertebrates in general and Brachyuran crabs in particular. Most of the emphasis focuses on recent
results on Brachyuran crabs and new information on Ovalipes trimaculatus. The consequences of oxygen limitation on
investment in reproduction and clutch size determination are analyzed. Temporal patterns of oxygen availability in the center of embryo
masses of Brachyuran crabs are different from other brooding species of marine invertebrates. A cyclic pattern in oxygen partial
pressure (PO2) was detected in masses of early stage embryos, and constant, high PO2 in females carrying late stage embryos, for
all crab species studied so far. As changes in PO2 in the embryo mass occurred, an increase in oxygen demand by the embryos and
an increase in abdominal flapping frequency were detected in all species. Moreover, the rate of increase in the frequency of abdominal
flapping between females carrying early and late stage embryos varied among species, depending on oxygen consumption rate of the
embryos. In spite of this, embryos of all species experience similar oxygen conditions throughout development. Abdominal flapping
seems to be the main behavior used to provide oxygen to the embryos, regardless of the habitat types inhabited by brooding females.
Recent studies have shown that ovigerous female crabs consume a substantially higher amount of oxygen than non-brooding females,
and suggested that there may be a trade-off between investment in eggs and in ventilation of the embryos. This information supports
the need for including the cost of oxygen provision in the estimation of maternal effort. A broad range of possible areas of research are
proposed to advance in this direction, concentrating either on marine invertebrates in general, or Brachyuran crabs in
particular.
Key words:
reproduction, brood
care, crabs, oxygen, marine invertebrates
