By Binu Varghese
Marine Products Exports Development Authority
Parental care in Clownfishes is well known, mouthing and fanning are the important behaviours apart from defending eggs from predators. They fan the egg mass using pectoral and caudal fins and thus provide necessary water movement to the densely packed clutch and thus help in faster removal of metabolic wastes (fig.1). Clownfishes also remove unfertilized and unhealthy eggs from the clutch (egg batch). The care is mostly done by male, and on the day of hatching eggs are vigorously fanned after sunset which helps larva to break open the thick walled egg capsule. This activity also assures that the hatching is complete, which is not the case in artificial incubation.
The description given above is the normal parental care behaviors in Clownfishes. However, the alloparental care i.e., care given to non-descendant egg or young one is rarely observed in fishes. In a study using true Sebae (Amphiprion sebae) selected from the earlier broodstock nutrition experiment, where different feeds were used to find its influence on the egg and larval quality. Two clutches spawned on the same day with distinctly different pigmentations were used (table 1 & fig.2). The pairs fed deep sea prawn gave pinkish red eggs and the formulated diet imparted yellowish colour to eggs. The egg colour typically reflects the dietary pigment and the initial colour of egg remains only for first two days and later it turns dark with the embryo development. On the day of spawning the clutches were allowed to be with original parents and on the second day noon the clutches were interchanged.
Table 1. Alloparental Care Experiment
After interchanging the PVC pipes with clutch the fishes were observed for their behaviour. After few minutes the male partner came to inspect the clutch from distance and returned immediately without fanning. There was no activity for a while, after about half an hour he came close to the clutch and retreated. This continued for a while and after this initial hesitation surprisingly the pair accepted the clutch. The pairs cared for the clutch as normal and the clutches hatched completely and the larvae were also found normal and healthy.
This behaviour might be an adaptation to ensure the survival of species governed by their social instincts. As the clown parents care for their eggs continuously it’s difficult to assume that the fishes were unaware of the change. Moreover the egg colour itself was continuing for the past six consecutive spawnings i.e. more than two months. This may be the case in nature also where the threats from predators and lose to either or both the parents are high. Step fathering in Clownfishes were observed in natural habitat which owes greatly to their tight social hierarchies. More studies are required to bring insights into the amazing behaviours in these beautiful fishes.
Alloparental care in fishes by Brian D. Wisenden (Review article in the journal Reviews in Fish Biology and Fisheries 9: 45 - 70, 1999)
Varghese, 2004. Nutritional studies on the sebae anemonefish,
Amphiprion sebae Bleeker 1853, with special reference to protein and lipid
requirements. Thesis submitted to CIFE/ICAR, Mumbai, India.