Giant clams are among the most spectacular but also the most endangered marine invertebrates. Their large size and easy accessibility has caused overfishing and collapse of the natural stocks in many places and local extinction in some of the species [1, 2]. The diversity of giant clams is extremely low because of reliction in this Tethyan group [3, 4]. The latest additions of living species date back almost two decades [5-7], fixing the number of extant Tridacna at seven species [3]. Here, we report the discovery of a new species of giant clam: Tridacna costata sp. nov. features characteristic shells with pronounced vertical folds, is genetically distinct, and shows an earlier and abbreviated reproduction than its Red Sea congeners. This species represents less than 1% of the present stocks but up to >80% of the fossil shells. The decline in proportion and shell size (20x) indicates overharvesting [8] dating back to the early human occupation of the Red Sea >125,000 years ago [9]. This earliest depletion reported so far of a shallow-water megafaunal invertebrate has important ramifications for human dispersal out of Africa [10]. Its oversight in one of the best-investigated reef provinces [11-13] illustrates the dearth of knowledge on marine biodiversity.
Collectively known as eucheumatoids, Eucheuma denticulatum, Kappaphycus alvarezii, K. malesianus, and K. striatus are the main farmed seaweed species in the Philippines. The success of seaweed farming for over five decades in the country is due, in part, to the high diversity of cultivars maintained by the Filipino farmers. Notwithstanding the fact that many eucheumatoid cultivars are presently (and consistently) recognized by the Filipino farmers, there has been no attempt to summarize the current state of the local traditional knowledge about the diversity of this seaweed group, especially with reference to the taxonomy, cultivar designation and distribution. Factors based on present day local knowledge on the eucheumatoid cultivars and what is known on genetic identification in the Philippines were also discussed. A total of 66 cultivars recognized across 58 provinces in the Philippines were documented. Most of these cultivars were morphologically identified as either K. alvarezii or K. striatus, however, the majority were yet to be genetically identified. In part, due to higher demand of kappa-carrageenan extract as compared from the iota type, K. alvarezii and K. striatus were widely cultivated in the Philippines than that of E. denticulatum. Only in the southern Philippines that K. malesianus is currently cultivated. The diverse cultivars identified in this study suggest that the Filipino farmers possess important traditional knowledge that can be useful for future crop selection and breeding.
There is a need for adaptive measures more to increase its natural resilience (e.g., marine protected areas) to both natural and man-made disturbances.
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