SHORT COMMUNICATIONS

USE OF LEGS AS DISSIPATORS Cape turtle dove StreptopeliD capicokl OF HEAT IN FLYING grey-backed finch lark Eremopteryx verticalis red-capped lark Call1lldre/la cinerea red-breasted swallow Hirundo semirll/a ant-eating chat Myremcocichkl /ormici- P. O. H. FROST and w. R. SIEGFRIED vora Percy FitzPatrick Institute, University 0/ Cape fiscal flycatcher Sigelus silens Town buffy Anthus vtllllensis whi~browed sparrow Steen & Steen (1965) demonstrated the role of weaver Plocepasser mahali unfeathered parts of ' legs as dissipators of heat. A rapid flow of air over bare legs increases These observations were not quantified. However, convective heat-loss by reduction of the boundary in all species, with the exception of Myremcoci­ layer of still air acljacent to the skin. Tucker chla /ormicivora, the behaviour occurred fre­ (1968) observed the budgerigar Melopsitticus quently enough to be strikingly obvious. Con­ undulatus extending its legs into the slip-stream versely, during the relatively cooler post-dawn when flying in a wind-tunnel at ambient tempera­ period (0600-0900 hrs) when ambient tempera­ tures of 36-37°C. We know of no published tures averaged 30°C (24-37°C) all birds were descriptions of this behaviour in heat-stressed, observed flying with their legs in normal retrac­ wild birds. ted positions. In November 1973, near Kimberley, C.P., we Subsequently, we observed similar behaviour noted a considerable number of birds flying with by greater stripe-breasted swallows Hirundo cllclIl­

.

) legs extended on days when ambient temperatures lata and whi~throated swallows Hirundo albi­ 0

1 averaged 37°C (33-16°C) during the period 0900- gularis at SteUenbosch, C.P. Observations were 0 2

1500 hours. made on two pairs of H. cucul/ata and one pair of d e t a d ( r e h s i TA8LE l 1 b u P

Percentage frequency of leg extension in two swallows e h t

y • b H. cucullata H. alblgularis d e t

n Mean air a r Time temperature % with legs No. % with legs No. g

e (hours) ("C) extended Observations extended observations c n e c i l

1500-1600 41 88 43 93 27 r e (39-44) d n 1600-1700 38 90 50 100 20 u

y (41-36) a

w 1700-1800 33 0 35 0 19 e t (36-28) a

G 32 0830-0930 27 0 0 15 t e (31-24) n i b a Zoologica A/ricana 10(1): 101-108 (1975) 101 S y b d e c u d o r p e R 102 ZOOLOGICA AFRICANA VOL 10

H. alhigularis during 1500-1800 hrs and between over the whole body surface, as has been reported 0830--0930 hrs on the following day. Table 1 by Marder (1973) for the brown-necked raven summarizes the relevant data. No was Corvus corax. recorded more than once per minute. All three pairs of birds were feeding large ACKNOWLEDOEMENTS young at the time. In neither series of observa­ We thank the De Beers Consolidated· Mining tions were the flights display flights. All involved Corporation for permission to conduct fieldwork either feeding flights, flights to a water hole or on their Rooiport estate near Kimberley. away from a source of disturbance. We believe that under certain conditions of high ambient REFERENCES temperature, high incident radiation and intense MARDER, 1.1973. Body temperature in the brown­ activity (flying), birds become heat-stressed to the necked raven (Corvus corax ruficollis) II. point where normally employed heat-dissipating Compo Biochem. Physiol. 45:431-440. mechanisms become overloaded. The extension of STEEN, I. & STEEN, 1. B. 1965. The importance of legs into the slip stream, while creating extra drag, the legs in thermoregulation of birds. Acta appears to facilitate the unloading of, at least, physiol. scand. 63 :285-291. part of this heat-load. It seems unlikely that the ruCKER, v. A. 1968. Respiratory exchange and birds deliberately undertook flights to increase evaporative water loss in flying budgerigars. convective cooling through increased air flow J. expo Bioi. 48:67-87.

. ) 0 1 0 2 d e tion properties, lubricating properties, osmotic t THE CUTICULAR LAYER OF THE a regulating effects, nutrition and the protection d SKIN OF CERTAIN CYPRINIDAE ( from attack by bacteria and fungi (van Oosten r e

h 1. HATTINOH and K. T. VAN WARMELO 1957). In the latter instance it is not clear exactly s i l Departments of Zoology and Botany, how the mucous layer protects the and the b u Rand Afrikaans University possibility had to be considered that the cuticle P

e may have an antimicrobial or such like function. h t It is well known that SQme fish are sensitive to The used in this study were all fresh­ y

b rough handling and that when part of the water teleosts of the family Cyprinidae. Mudfish

d mucous covering the skin, including scales if the (Lobeo umbratus and Lobeo capensis), yellowfish e t

n fish has scales, is removed accidentally the fish (Barhus holuhi) and carp (Cyprinus carpio) were a r usually die, especially when kept in confinement used. In the first instance the normal flora occur­ g

e (see van Oosten 1957 for review). According to ring in the mucous layer of these fish was investi­ c n Whitear (1970) the cuticular layer in bony fish gated and compared to that of water. On difco e c i

l has a dual origin; one part is secreted from the deoxycholate agar and phenylethyl alcohol agar r

e surface epidermal cells and the other from the it was found that mucus supports a broad spec­ d

n goblet mucous cells which spread over the skin. trum of gram negative and positive bacteria, u The two components are not histologically dis­ including lactose fermenting bacteria, seemingly y a guishable and the cuticle is a homogeneous in larger numbers than in water. This is not sur­ w e

t mucous layer containing mucopolysaccharides, prising considering the composition of mucus. a albumin, lipids, various ions and n-acetyl neur­ No antibiotic or bacteriostatic effects were ob­ G t

e aminic acid (pickering 1974; van Oosten 1957). served. n i The functions assigned to this layer include the In the second place, an unidentified zygomy­ b a lessening of body friction in water, mud coagula- cetous fungus was isolated from lake water and S y b d e c u d o r p e R