Metabolic Status and Respiratory Physiology ofGecarcoidea natalis, the Christmas Island Red Crab, During the Annual Breeding Migration

Abstract

With the arrival of the monsoonal rains and after months of inactivity during the dry season, the terrestrial crab Gecarcoidea natalis embarks on its annual breeding migration to the coast. The physiological demands of the migration were assessed by determining respiratory gases in the hemolymph, key metabolites, and energy stores in G. natalis during two migratory seasons. At the end of each day of migration the pulmonary hemolymph PO2 decreased by 1-2.5 kPa, but the hemocyanin remained saturated with O2 and the venous reserve was largely unchanged (O2 > 0.4 mmol x l(-1)). The breeding migration of red crabs was accomplished without recourse to anaerobiosis, even though at times walking speeds (up to 6.2 +/- 0.5 m x min(-1)) exceeded those that promoted anaerobiosis in non-migrating crabs and in crabs exercised in the laboratory. In contrast to all previous studies, at the end of each day of migrating, red crabs experienced an alkalosis (up to 0.1 pH units) rather than any acidosis. This alkalosis was removed overnight when the crabs were inactive. Although there were seasonal fluctuations in the glycogen, glucose, and triglyceride stores, crabs engaging in the migration did not draw on these stores and must have fed along the way. In contrast, crabs returning from breeding activities on the shore terraces had significantly depleted glycogen stores. Additionally, in 1993, the male crabs returning from the breeding activities on the terraces were dehydrated and experienced a decrease in muscle tissue water of 11%. In contrast to the breeding migration per se, fighting for burrows in which breeding occurs produced severe anaerobiosis in males, especially the victors: after 135 s of combat, the maximum L-lactate concentration in the hemolymph was 35 mmol x l(-1). It appears that burrowing, courtship, and mating are more demanding than the migration itself. Furthermore, the data provide evidence that the metabolic responses of migrating individuals of G. natalis might be different from those at other times of the year.

The adaptive significance of crustacean hyperglycaemic hormone (CHH) in daily and seasonal migratory activities of the Christmas Island red crab Gecarcoidea natalis

“…This crab undergoes extensive annual migrations of several km in order to mate and spawn; these migrations are triggered by monsoonal rains, and this activity is the most energetically demanding and extreme rapid migration known in crustaceans. Furthermore, during the dry season, this crab must also undergo extended periods of inactivity in a xeric environment (Hicks, 1985;Green, 1997;Adamczewska and Morris, 2001a;Adamczewska and Morris, 2001b). So clearly, physiological demands related not only to energy mobilisation, but also to ionic homeostasis are germane, particularly when the proposed ionoregulatory functions of CHH are considered.…”

Threats to migratory birds, and actions for their conservation

“…The development of new tracking technologies has led to increased knowledge of how migratory species as varied as insects (Chapman et al, 2015), crustaceans (Adamczewska & Morris, 2001), fish (Steinhausen, 2007), birds (Hedenström, 2010), reptiles (Southwood & Avens, 2010) and mammals (Braithwaite et al, 2015) exploit seasonal changes in resources (Grothues, 2009;Jellyman, 2009;Hebblewhite & Haydon, 2010). Greater and greater migratory distances are being recorded for a variety of species.…”

“…Typically, migration is perceived as a long-distance, endurance activity; yet there are a variety of migratory behaviours ranging from long-distance, to repetitive short-distance movements, which can take place over generations (Adamczewska & Morris, 2001;Steinhausen, 2007;Hedenström, 2010;Southwood & Avens, 2010;Braithwaite et al, 2015;Chapman et al, 2015). Insects, crustaceans and reptiles fall into the latter category due to short life-cycles or physiological constraints (Adamczewska & Morris, 2001;Southwood & Avens, 2010;Chapman et al, 2015).…”

“…Insects, crustaceans and reptiles fall into the latter category due to short life-cycles or physiological constraints (Adamczewska & Morris, 2001;Southwood & Avens, 2010;Chapman et al, 2015). Indeed, many insects such as monarch butterflies (Danaus plexippus) migrate over multiple generations (Chapman et al, 2015), while ectothermic reptile migrations are small-scale and dependent on temperature, thus reserved for warmer seasons (Southwood & Avens, 2010).…”

“…Christmas Island red crab (Gecarcoidea natalis) migration, on the other hand, coincides with monsoonal rain. This minimises dehydration, maximises food availability during migration, and ensures animals arrive at coastal breeding grounds able to fight for breeding territories (Greenaway & Linton, 1995;Adamczewska & Morris, 2001).…”