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Cyphotilapia Talk General Discussion of Cyphotilapia frontosa & gibberosa.

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Old 01-06-2013, 04:43 AM
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Default Do Cypho moms feed during pregnancy and at what tradeoffs ?

Fishes usually fast whilst carrying their oppspring in their mouth. However, in some cichlids, active or sporadic food intake has been observed under aquarium conditions or in the wild. It was revealed (Yanagisawa & Sato - 1990) that active browsing by mouthbrooding females of T.Dubiosis & T.Moorii in Lake Tanganyika has a detectable effect on the nourishment of the females and/or their young. Examination showed that T.Dubiosi females took food for both their young and themselves and T.Moorii, solely for their young.

Cyphotilapia Frontosa has one of the largest eggs among mouthbrooders so far examined, and its mouthbrooding period extends over 54 days. Cyphotilpias exhibit the most advanced reproductive style within the mouthbrooding group. The yolksac contains sufficient food for the young to develop into a definitive phenotype whilst still being protected inside the buccal cavity due to a combination of large, dense yolk and buccal feeding.

Feeding behavior :
Studies were conducted by Yasunobu Yanagisawa & Haruki Ochi at Bemba, 25 Kms south of Uvira in the DRC. The summary of their study is given below.

It was observed that the Frontosa took food on the sandy or rocky bottom or in midwater (1-5m above the bottom at a depth of more than 13 m). On the bottom, they scooped up algae and deposits from the surface while moving forward a few centimeters, or picked up prey from the surface. In midwater, they picked or inhaled suspended particles. Brooding females fed in midwater, usually in a loose school composed of several brooding & nonbrooding conspecifics. Only once was a brooding female observed to take food from the bottom.

Gut contents of adult Frontosas consisted of detritus, small crustaceans (probably atyid shrimps), insect larvae, filamentous and unicellular algae and small fish. The amount of inorganic matter such as sand was relatively small; ignition loss of gut contents was high compared to T.Duboisi and T.Moorii (25.7% +/- 8.9 SD, n = 27) which took sand together with filamentous algae.

During the experiments, of the 12 mouthbrooding females, 11 had some food in the stomach and intestine.
But first, lets define Gut Fullness Index :
Gut Fullness Index = {[dry weight of gut contents (mg)]/[standard length(cm)]3 x 100}

The Gut fullness index was not different between females in the first and second halves of the brooding period, see below -

Gut fullness index in Cyphotilapia Frontosa :

Mean +/- SD (n)
Female at first half brooding phase - 4.99+/- 5.28 (6)
Female at second half brooding phase - 3.38+/- 2.46 (6)
Nonbrooding female - 18.06+/- 14.12 (5)
Male - 16.15+ 6.80 (4)
Note : The boundary between the first and second half of mouthbrooding phase was set at 15 mm TL (TL = Total Length) of young.

a) The mean index of brooding females was about 1/4th as large as that of nonbrooding females and males. No definite difference could be detected in food items between brooding females and nonbrooding adults other than a lack of fish debris in brooding females.
b) Gut fullness of young increased as they grew. A bit of sand and detritus appeared from the gut of a free embryo 8.6 mm total length (TL = Total Length). A substantial amount of food was found in young 12.5 mm TL, in which yolk plus the yolksac still accounted for 92% of the whole body in dry weight and development of scales had not yet started. In young larger than 20 mm TL, more than half of the gut was filled with food; the stomach was usually full or nearly full with food. Young 20 mm TL had already become fully formed phenotypes but still retained a large quantity of yolk; yolk plus fat in the abdominal cavity amounted to 40% of the whole body in dry weight. Remnants of yolk were still evident in the largest young (25.1 mm TL).

a) Maximum and minimum diameters of fertilized eggs were 6.66mm (+0.15 SD) and 5.03mm (+0.12 SD), respectively. The egg sizes were slightly larger than that of fertilized eggs that Balon reared in his aquarium experiment (5.6 x 4.0 mm).
b) The number of offspring in a female's mouth ranged from 11 to 44 and was positively correlated with wet body weight (g) of the female (regression line, y = - 6.854 + 0.542x).

Weight change of offspring during mouthbrooding period :
a) The wet weight of offspring gradually increased with development; the weight ratio of the earliest embryos (less than 7.2 mm TL) to young just before independence (more than 22.5 mm TL) was 1 : 2.8
b) Dry weight of offspring, on the other hand, tended to decrease in the middle of the brooding period and recovered later to the initial level. The dry weight ratio of the earliest embryos to young just before independence was 1 : 0.99

Buccal feeding of young :
The occurrence of food in the guts of young in the parent's mouth is not sufficient proof of buccal feeding, because they might have taken food outside of the mouth when they were temporarily released. However, in Cyphotilapia Frontosa, a substantial amount of food appeared in guts of young whose yolk weight accounted for more than 90% of their total body weight. Even in young about 20 mm TL whose guts were sometimes full of food, yolk weight amounted to about 40% of their total weight. Such young cannot be agile swimmers and must be vulnerable to predators. Therefore, the young in such early stages are less likely to eat outside of the buccal cavity.

In the aquarium observations by Balon, the female of Cyphotilapia Frontosa did not release the young even when they had almost reached independence. In the experiments by Yasunobu Yanagisawa & Haruki Ochi, such behaviour too, was not seen. Feeding in the buccal cavity must be the primary way the young of Cyphotilapia Frontosa take food, although the possibility of feeding outside of the buccal cavity by grown young still remains.

Effect of buccal feeding on the nutrition of young during the mouthbrooding period can be estimated from change in dry weight in the young nearing independence. In Cyphotilapia Frontosa, the dry weight ratio of earliest embryos to young just before independence was 1 : 0.99. In (T.Duboisi = 1 : 0.94 & T.Moorii = 1 : 0.79). The results show that buccal feeding of young, is effective in their nutrition, probably at about the same level as in T.Duboisi.

Mouthbrooding females of Cyphotilapia Frontosa took food for their own nourishment as well as that of their young. This result is different from Balon's aquarium observation that a female of Frontosa did not swallow food particles until the final release of the young. This difference could be due either to unnatural conditions in the aquarium observation or a behavioral variation between different populations.

Advantage of large-sized eggs :
1) improved survival of independent young due to large body size
2) accelerated differentiation
Disadvantage of large-sized eggs :
1) the prolongation of mouthbrooding period which will cause the young to use greater
metabolic energy

Buccal feeding of young involves some costs. Some of the costs involved are -
1. Reduction of brood size in order to leave some space in the buccal cavity for feeding activity
2. Energy and risks involved in foraging while mouthbrooding

Such costs are relatively small for species that utilize small and accessible food. It explains why buccal feeding of young has been found only among species having eggs of the largest size and feeding on small and ubiquitous food such as epilithic algae, microbenthos and detritus (e.g. Cyphotilapia, Petrochromis, Simochromis and Tropheus).

Food intake by mouthbrooding females for themselves, together with that for the young, benefits them nutritionally in comparison with fasting. But, it also involves costs in terms of a greater food demand, resulting in further reduction of brood size and yet more foraging energy and risks.This trade-off between benefits and costs may be influenced by the quality of the feeding territories. For example, females occupy feeding territories of higher quality than males in T.Duboisi, and the reverse is true in T. Moorii. For females of T.Duboisi, therefore, active foraging through the mouthbrooding period will be benefitial, because it facilitates maintenance of territories. But it is not so for females of T.Moorii. Mouthbrooding Frontosa are not territorial. Therefore, in its natural habitat (deep water with few available shelters for small young) the release of large, well developed young would be favoured. The resultant prolonged mouthbrooding period may have led brooding females to feed for themselves as well as for their young in order to maintain good physical condition.

Ref : Food intake by mouthbrooding females of Cyphotilapiafrontosa (Cichlidae) to feed both themselves and their young Yasunobu Yanagisawa & Haruki Ochi. (For educational purpose only)
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Last edited by jaideep; 01-06-2013 at 08:49 AM.
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Old 01-06-2013, 08:51 AM
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There was a similar post in Cichlidae.com by Ron Coleman
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feed, moms, pregnancy, tradeoffs

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