Life in the arena: infaunal gastropods and the late Phanerozoic expansion of marine ecosystems into sand

Abstract

Marine ecosystems have expanded into the infaunal realm below the surface of soft sediments throughout the Phanerozoic eon. During the Palaeozoic era, this expansion largely involved sedentary animals living in permanent resting places. Active sand-burrowing animals colonized the infaunal environment later, but when this happened and when specialization for infaunal life evolved remain open questions. Here, phylogenetic evidence, fossil occurrences and previously established criteria for recognizing the sand-burrowing habit in marine gastropods are used to determine how many gastropod clades became infaunal and when the transitions from surface-dwelling to infaunal life occurred. At least 20, and as many as 35, clades (all but one of post-Palaeozoic age) contain actively infaunal species.The overwhelming majority (15 of 20 clades) became infaunal during the Cenozoic, and clades with hundreds of infaunal species in the living fauna diversified beginning in the Early Miocene. The repeated evolution of, and specialization to, the sand-burrowing habit by gastropods and other animals was enabled by increased habitat availability and higher marine productivity, and was necessitated by intensifying predation. As a result, the infaunal realm was transformed from a marine refuge to an integrated part of the marine biosphere in which high performance in locomotion and defence has become the norm.

Struktur Komunitas dan Asosiasi Gastropoda pada Ekosistem Lamun di Pulau Harapan, Kepulauan Seribu

“…Keanekaragaman tinggi pada stasiun 1 kemungkinan berkaitan dengan substrat dasar yang cenderung pasir dan pecahan karang sehingga keberadaan nutrisinya kurang dan banyak jenis gastropoda yang lebih mudah berpindah dari satu tempat ke tempat lain sehingga keanekaragaman tinggi meskipun jumlahnya lebih sedikit. Menurut Vermeij (2017), gastropoda di perairan akan memiliki keanekaragaman tinggi karena secara aktif bergerak menguburkan diri di pasir dan bergerak di karang untuk mencari makanan, sedangkan pada substrat lumpur cenderung lebih permanen karena ketersediaan makanan melimpah. Pada stasiun 2 dan 3 ditemukan lebih dari 100 individu karena menurut pengamatan secara langsung Pulau Harapan memiliki substrat dasar pasir halus dan lumpur sehingga banyak terdapat nutrient untuk kelangsungan hidup gastropoda.…”

Predation in the marine fossil record: Studies, data, recognition, environmental factors, and behavior

“…Locomotion operates differently for organisms moving within sand, mud, or on top of hard or soft substrates , 2017); thus, life mode varies with substrate. Organisms occupy more permanent burrows in cohesive mud, exhibiting morphologies that ensure stability within the substrate, whereas sand dwellers with streamlined morphologies can burrow actively (Vermeij, 2017).…”

“…Interpretations of long-term patterns in predation must recognize that substrates themselves have evolved; increases in bioturbation, evolution of seagrasses, and the activities of organisms that break up hard substrata (e.g., parrotfishes) have modified depositional environments, especially during the Cenozoic (Vermeij, 2017). These changes have created new habitats and new opportunities for both predators and prey.…”

The efficiency paradox: How wasteful competitors forge thrifty ecosystems

“…The fossil record offers ample evidence for increasing performance among opportunists and dominant competitors. Older, lower powered opportunists and dominants were displaced to more marginal environments by higher powered species in different clades in land plants (61), phytoplankton (62), suspensionfeeders (5), sediment-dwelling animals (59,87), swimmers (65), predators (5), herbivores (83), and wood-digesting organisms (85). The evolution of endotherms permitted faster recycling of nutrients even in the cold, and therefore reduced losses of organic matter at low temperatures.…”