I've been going through Lucretius line by line in Latin. (Latin Per Diem on YouTube is an excellent resource for this if you're curious.) I noticed an interesting pattern in the early lines;
Aeneadum genetrix, hominum divomque voluptas,
alma Venus, caeli subter labentia signa
quae mare navigerum, quae terras frugiferentis
The verb concelebras clearly acts on mare and terras as the objects. But the word also seems to echo aurally (to my ear at least) the earlier phrase, caeli subter labentia signa. (Under the sliding signs of heaven [i.e. the stars]). I spent four years studying poetry, and it's possible I'm reading too much into this; but it seems to me that the poet is attempting to draw a connection between these two elements in the text. Note the significant consonants.
Caeli subter LaBentia Signa
If there is a connection, it's a fascinating one. Concelebras means "cause to teem" or "cause to be filled with", here in reference to Venus filling the sea and land with life. But the subtle echo with "the sliding stars of heaven" might stretch the verb here, to include the indirect object. Thus, under my new interpretation, he is hinting that Venus (meaning generative passion) also "caused to teem" with life the other worlds!
As a side note; I've tried to "crack" Latin in a number of different ways over the years, but I've never studied it with so much pleasure as when I study Lucretius. My process here is to
1. Memorize sections of text
2. Learn to "read" each sentence in Latin for understanding, in Latin.
3. Work through the passage throughout the day (like when I'm driving), saying each word slowly and really "seeing" it in my mind. So when I read mare navigerum, I "see" the sea laden with ships instead of thinking "sea laden with ships" in English in my head.
And even if I never learn enough Latin to read Cicero, I will in compensation always have a little Lucretius wherever I go. It's been great fun!