As Cyrano already said, this photo was taken after the German Africa Corps surrendered in Tunis. This soldier wasn't a member of the DAK, he served in Russia and his unit was subordinate to Heeresgruppe A. It was taken on June 21, 1943 and during this time not only the military situation was hot in this area (Kuban bridgehead, Kerch strait), but the weather was too.
Actually the Tropenbluse (jacket) should be closed and the sleeves long, not rolled up. The Heeresgruppe A war diary says that day temperatures were exceptionally high, it was cloudy and very humid, the unit commander had probably "ordered summer" because of this.
The commander of the German command in the capital of Crimea issued an order regarding the dress code for tropical uniform. The period for wearing the tropical uniform in this area was ordered between May 1, 1943 and September 30, 1943. If the soldiers were given holiday or ordered to another location during this period, they had to wear their tropical uniform or their field gray uniform, they were not allowed to mix them.
Now back to the topic of DAK, Africa and VZ24 rifles. I have looked into the documents of the High Command of the Wehrmacht and for the DAK here is a small excerpt with the following losses:
64,348 Karabiner 98k
1,189 Karabiner 98k m. Zf. (K98k with scope)
498 Gewehr 41 u. Gewehr 43
0 Other German rifles
0 Captured rifles
4,287 MG 34
1,063 MG 42
103 Other German MG
360 Captured MG