If the Dioscuri at the head of the image on f.5v were the seamens’ Saviour deities, the creature at the base was their bane. Linnaeus called it “calamitas navium” and the Greeks, teredon. It is also called the ‘termite-worm’ and that is exactly how it is depicted here: half worm and half blind ant, gripping the wood with that white ‘collar’ that is actually a pair of hard, white, thin shell “lips”.
An earlier post explained how I came to identify it, and here are two of the illustrations from that post. The creature turns brown only after exposure to the air; while alive it is soft and grey-ish. In effect the picture on folio 5v ‘kills it’ and I daresay the Dioscuri were often urged to do the same; the teredon’s boring can render a ship’s hull below the waterline as porous as sponge, and infested ships might founder with all hands, unexpectedly, in the finest weather. 
And here we come to an interesting point; another indication of the first enunciator’s environment and cast of mind.
It is evident that he knew the culture of the sea as a mariner did, and not as an urban mythographer would, for the scholars on land supposed the mariner’s greatest peril an enormous monster of some sort: a great whale, fearful dragon, a snarling long-toothed Leviathan or a sea-serpent so enormous it could overtake a ship and pick off the crew from the open deck.
Mariners might also believe such fabulae existed, but they knew that that their greatest fear apart from storm and tempest, or being becalmed was the ‘termite-worm’ teredo navalis which grows to no more than quarter- to a half an inch in diameter and from five to ten inches in length – and that it does not devour the crew one at a time, but the ship itself, so that all are lost at once. And it is the teredo which the maker pictured ‘gnawing at the root’.
Secondly, he must have lived at a time and in a cultural environment where the Dioscuri, and not any Christian saint or single deity was invoked to protect the ship, its crew and cargo and it is difficult to imagine that being so after the 3rdC AD. By contrast, the Dioscuri appear as the patron gods of the Seleucid Hellenistic kingdom, whose successive members include the Dioscuri on their coins, from the first.
Thirdly, the first enunciator effortlessly alludes to correspondences across botanical, astronomical and cultural matter in folio 5v; but in his astronomical matter includes only practical uses for the stars; there is no hint of zodiac-and-planet focus which marks the style of astrology.
Those asterisms in Gemini called the ‘turned about’ and ‘the ell’ are astronomical, and while in medieval Europe knowledge of the lunar mansions was considered not merely arcane, but positively occult, they had been common reference even in pre-Islamic Arabia and served as the horizontal axis for the mariners navigational grid as well as naming the months of the Islamic religious year and of the old agricultural roster.  Only the north African mariners, whom Ibn Majid calls his brethren, offer an exception to the rule that the navigational star grid – and knowledge of how to use it – was unknown to Mediterranean mariners. In Hellenistic times, the Phoenician or Cretan mariners might have shared that knowledge; some suggestion of it is made by the story of Pompey’s flight, but I’ll omit details as this post will be long enough without them.
Overall, then, the indications are that the person who first enunciated the image on f.5v belonged within a distinctly Hellenistic and Greek-influenced culture, but had first-hand knowledge of the seas, and probably of the eastern seas, for a majority of the plants in the manuscript are (in my opinion) ones proper to that world.
Another level of natural ‘complement-and-opposition’ which he might have associated with the Dioscuri and teredon was a geographic one.
In the world known to the Greeks, and even before Alexander reached the Indus, there existed in the far north on the eastern side of the Black Sea a town reputedly founded by the Twins themselves, and so named Dioskurias. And to the southern limit of the Seleucid kingdom, on the shore of the Great Sea, was a market town founded first by Nebuchadrezzar and which the Greeks knew as Teredon.
Quite apart from whether the first enunciator had that geographic pair in mind, each is of interest to us: Teredon as an early market for eastern goods and as the point of embarkation for India and the far east to about the tenth century AD, while Dioskurias not least because the Genoese had a factory there in the fourteenth century.
 There is a giant teredon found near Sumatra; it doesn’t live in wood as t.navalis does, but in the muddy bottom, though one doubts if foreign seamen would have trusted to that difference, even if they knew it. For those who enjoy biology, there’s an ongoing scientific study of the teredo and the site has nice photos and diagrams. (here)
 According to the Yemeni/Soqotran calendar reported by Serjeant, al Han’ah marks the lunar month beginning on January 4th, save in Hadramawt, where the month begins on January 1st. The Soqotri name, he gives as Ma’ōdīf. al-Dira’ is called in Soqotri Franzak, and begins on 17th. January. Note that the advent of Islam saw the older lunar calendar ‘frozen’ and we may not presume to apply the same dates after c. 8th-10thC AD as were in affect before that time, when irregular intercalations were permitted. R.B. Serjeant, ‘A Socotran star calendar’, Irvine et.al. (eds.), A Miscellany of Middle Eastern Articles.. (1988) pp. 94-100. Reproduced as Paper IV in R.B. Serjeant, Farmers and Fishermen in Arabia: studies in customary law and practice edited by G. Rex Smith (Variorum) (p.96)