Pectinidae

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Pectinidae
Temporal range: Triassic to Recent
Close up of a live scallop showing the rows of eyes on the edges of the mantle
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Ostreoida
Suborder: Pectinoida/Pectinina?
Superfamily: Pectinoidea
Family: Pectinidae
Wilkes, 1810
Genera

See text

The Pectinidae (from the Latin pecten meaning comb), common name scallops, are a family of saltwater bivalve mollusks. They are hermaphrodites, and the male gonads mature first. Numerous species of various sizes occur in all of the oceans, and a number species are of commercial importance as food species.

A small minority of pectinid species live cemented to rocky substrates as adults. Some others species are more simply attached, by means of a filament they secrete. The majority of species, however, are recumbent on sandy substrates, but when they sense the presence of a predator such as a starfish, they are able to escape by swimming swiftly but erratically through the water using a form of jet propulsion created by repeatedly clapping the valves of their shells together.

Pectinids have numerous simple eyes situated around the edges of their mantles.

Shell morphology[edit]

In general, shells of the Pectinidae consist of two valves which are circular to broadly ovate with the right valve usually more inflated than the left valve. The valves are narrower and pointed at the umbones, which have flattened triangular extensions on both sides, known as auricles or ears. The upper edge of the ears forms a somewhat straight hinge line. The umbones project only slightly above this line. Most Pectinidae have radial ribs and concentric ridges, although a few are smooth. The ctenolium, a key shell feature, separates the Pectinidae from all other families.

Distribution and habitat[edit]

Pectinidae inhabit all the oceans of the world, with the largest number of species living in the Indo-Pacific region. Most species live in relatively shallow waters from the low tide line to 100 meters, while others prefer much deeper water. Although some species only live in very narrow environments, most are opportunistic and can live under a wide variety of conditions. Pectinidae can be found living within, upon, or under either rocks, coral, rubble, sea grass, kelp, sand, or mud. Most adult specimens are either byssally attached or cemented to a substrate, while others are free swimmers.

Motility and behavior[edit]

Most species of the Pectinidae family are free-living active swimmers, propelling themselves through the water through the use of the adductor muscles to open and close their shells. Swimming occurs by the clapping of valves for water intake. Closing the valves propels water with strong force near the hinge via the velum, a curtain-like fold of the mantle that directs water expulsion around the hinge. Pectinidae swim in the direction of the valve opening, unless the velum directs an abrupt change in course direction.[1][2]

Other species of Pectinidae can be found on the ocean floor attached to objects by byssal threads. Byssal threads are strong, silky fibers extending from the muscular foot, used to attach to a firm support, such as a rock. Some can also be found on the ocean floor, moving with the use of an extendable foot located between their valves or burrowing themselves in the sand by extending and retracting their feet.

Pectinidae are highly sensitive to shadows, vibrations, water movement, and chemical stimuli.[3] All possess a series of 100 blue eyes, embedded on the edge of the mantle of their upper and lower valves that can distinguish between light and darkness. They serve as a vital defense mechanism for avoiding predators. Though rather weak, their series of eyes can detect surrounding movement and alert precaution in the presence of predators, most commonly sea stars, crabs, and snails.

Physiological fitness and exercise of Pectinidae decreases with age due to the decline of cellular and especially mitochondrial function,[4] thus increasing the risk of capture and lowering rates of survival. Older individuals show lower mitochondrial volume density and aerobic capacity, as well as decreased anaerobic capacity construed from the amount of glycogen stored in muscle tissue.[5] Environmental factors, such as changes in oxidative stress parameters, can inhibit the growth and development of Pectinidae.[6]

Seasonal changes in temperature and food availability have shown to affect muscle metabolic capabilities. The properties of mitochondria from the phasic adductor muscle of Euvola ziczac varied significantly during their annual reproductive cycle. Summer Pectinidae in May have lower maximal oxidative capacities and substrate oxidation than any other times in the year. This phenomenon is due to lower protein levels in adductor muscles.[7]

Mutualism[edit]

Chlamys hastate frequently carries epibionts like sponges and barnacles on its shell. The scallop-shell relationship is characterized as a form of mutualism. The sponge provides protection by interfering with adhesion of predatory sea-star tube feet,[8][9][10] camouflages Chlamys hastate from predators,[11] or forms a physical barrier around byssal openings to prevent sea stars from inserting their digestive membranes.[12] Sponge encrustation protects C. hastate from barnacle larvae settlement, serving as a protection from epibionts that increase susceptibility to predators. Thus, barnacle larvae settlement will occur more frequently on sponge-free shells than sponge-encrusted shells.

In fact, barnacle encrustation negatively influences swimming in C. hastata. Those swimming with barnacle encrustation require more energy and show a detectable difference in anaerobic energy expenditure than those without encrustation.[13] In the absence of barnacle encrustation, they swim significantly longer, travel further, and attain greater elevation.

Lifecycle and growth[edit]

Many Pectinidae are hermaphrodites (having female and male organs simultaneously), altering their gender throughout their lives, while others exist as dioecious species, having a definite gender. In this case, males are distinguished by roe containing white testes and females with roe containing orange ovaries. At the age of two, they usually become sexually active, but do not contribute significantly to egg production until the age of four. The process of reproduction takes place externally through spawning, in which eggs and sperm are released into the water. Spawning typically occurs in late summer and early autumn; spring spawning may also take place in the mid-Atlantic Bright.[14] The females of Pectinidae are highly fecund, capable of producing hundreds of millions of eggs per year.[15]

Once an egg is fertilized, it is then planktonic, which is a collection of microorganisms that drift abundantly in fresh or salt water. Larvae stay in the water column for the next four to seven weeks before dissipating to the ocean floor, where they attach themselves to objects through byssus threads. Byssus is eventually lost with adulthood, transitioning Pectinidae into free swimmers. There is rapid growth within the first several years, with an increase of 50 to 80% in shell height and quadrupled size in meat weight and reach commercial size at about four to five years of age.[16] The lifespans of some Pectinidae have been known to extend over 20 years.[17]

Fossil record[edit]

Fossil Pectinidae from East Timor

The fossil history of Pectinidae is rich in species and specimens. The earliest known records of true Pectinidae (those with a ctenolium) can be found from the Triassic period over 200 million years ago.[18] The earliest species were divided into two groups, one with a nearly smooth exterior: Pleuronectis von Schlotheim, 1820, while the other had radial ribs or riblets and auricles: Praechlamys Allasinaz, 1972.[19] Fossil records also indicate the existence of Pectinidae has been unstable at times; from being the most speciose family of the Mesozoic era, to almost disappearing completely by the end of the Cretaceous period. Survivors evolved rapidly during the Tertiary period. Nearly 7,000 species and subspecies names have been introduced for both fossil and recent Pectinidae.

Taxonomy and list of genera[edit]

More than 30 genera and around 350 species are in the family Pectinidae. Raines and Poppe[20] list nearly 900 species names, but most of these are considered either questionable or invalid. They mention over 50 genera and around 250 species and subspecies. While species are generally well circumscribed, their attribution to subfamilies and genera is sometimes equivocal, and information about phylogeny and relationships of the species is minimal, not the least because most work has been based on adult morphology.[21]

Evolution[edit]

The family Pectinidae is the most diversified of the pectinoideans in present-day oceans. It is one of the largest marine bivalve families and contains 300 extant species in 60 genera.[22] Its origin dates back to the Middle Triassic Period, approximately 240 million years ago, and has been a thriving family to present day. Evolution from its origin has resulted in a successful and diverse group: pectinids are present in the world’s seas, found in environments ranging from the intertidal zone to the hadal depths. The Pectinidae plays an extremely important role in many benthic communities and exhibits a wide range of shell shape, sizes, sculpture, and culture.[23]

The earliest and most comprehensive taxonomic handlings of the family are based on macroscopic morphological characters of the adult shells and represent broadly divergent classification schemes.[24][25] Some level of taxonomic stability was achieved when Waller’s studies in 1986, 1991, and 1993 concluded evolutionary relationships between pectinid taxa based on hypothesized morphological synapomorphies, which previous classification systems of Pectinidae failed to do.[26][27][28] He created three Pectinidae subfamilies: Camptonectinidae, Chlamydinae and Pectininae.

The framework of its phylogeny shows that repeated life habit states derive from evolutionary convergence and parallelism.[29][30] Studies have determined the Pectinidae family is monophyletic, developing from a single common ancestor. The direct ancestors of Pectinidae were scallop-like bivalves of the family Entoliidae.[31] Entoliids had auricles and byssal notch only at youth, but they did not have a ctenolium, a comb-like arrangement along the margins of the byssal notch in Pectinidae. The ctenolium is the defining feature of the modern family Pectinidae and is a characteristic that has evolved within the lineage.[32]

Recently, Puslednik et al. identified considerable convergence of shell morphology in a subset species of gliding Pectinidae, which suggests iterative morphological evolution may be more prevalent in the family than previously believed.[33]

There have been a number of efforts to address phylogenetic studies. Only three have assessed more than 10 species[34][35][36] and only one has included multiple outgroups.[37] Nearly all previous molecular analyses of the Pectinidae have only utilized mitochondrial data. Phylogenies based only on mitochondrial sequence data do not always provide an accurate estimation on the species tree. Complicated factors can arise due to the presence of genetic polymorphisms in ancestral species and resultant lineage sorting.[38][39]

In molecular phylogenies of the Bivalvia, both the Spondylidae and the Propeamussiidae have been resolved as sister to the Pectinidae.[40][41] A useful strategy would be to include outgroup species from two or more closely related families.

Genera[edit]

Family Pectinidae

Gallery[edit]

References[edit]

  1. ^ Cheng, J.-Y.; Davison, I. G., & Demont, M. E. (1996). "Dynamics and energetics of scallop locomotion". Journal of Experimental Biology 199 (9): 1931–1946. 
  2. ^ Joll, L.M. (1989). Swimming behavior of the saucer scallop Amusium balloti (Mollusca: Pectinidae). Marine Biology. pp. 299–305. 
  3. ^ Land, M.F. (1966). "Activity in the optic nerve of Pecten maximus in response to changes in light intensity, and to pattern and movements in optical environment". Journal of Experimental Biology 45 (1): 83–99. 
  4. ^ Philipp, E.E.R.; Schmidt, M., Gsottbauer, C., Sänger, A. M., & Abele, D. (2008). "Size- and age- dependent changes in adductor muscle swimming physiology of the scallop Aequipecten opercularis". Journal of Experimental Biology 211 (15): 2492–2501. 
  5. ^ Philipp, E.E.R.; Schmidt, M., Gsottbauer, C., Sänger, A. M., & Abele, D. (2008). "Size- and age- dependent changes in adductor muscle swimming physiology of the scallop Aequipecten opercularis". Journal of Experimental Biology 211 (15): 2492–2501. 
  6. ^ Guerra, C.; Zenteno-Savín, T., Maeda-Martínez, A. N., Abele, D., & Philipp, E. E. R. (2013). "The effect of predator exposure and reproduction on oxidative stress parameters in the Catarina scallop Argopecten ventricosus". Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 165 (1): 89–96. doi:10.1016/j.cbpa.2013.02.006. 
  7. ^ Boadas, M.A.; Nusetti, O., & Mundarain, F. (1997). "Seasonal variation in the properties of muscle mitochondria from the tropical scallop Euvola (Pecten) ziczac". Marine Biology 128 (2): 247–255. 
  8. ^ Bloom, S. (1975). "The motile escape response of a sessile prey: a sponge-scallop mutualism". Journal of Experimental Biology and Ecology 17 (3): 311–321. 
  9. ^ Pitcher, C.R.; Butler, A.J. (1987). "Predation by asteroids, escape response, and morphometrics of scallops with epizoic sponges". Journal of Experimental Marine Biology and Ecology 112 (3): 233–249. doi:10.1016/0022-0981(87)90071-2. 
  10. ^ Forester, A.J. (1979). "The association between the sponge Halichondria panicea (Pallas) and scallop Chlamys varia (L.): a commensal protective mutualism". Journal of Experimental Marine Biology and Ecology 36 (1): 1–10. 
  11. ^ Pitcher, C.R.; Butler, A.J. (1987). "Predation by asteroids, escape response, and morphometrics of scallops with epizoic sponges". Journal of Experimental Marine Biology and Ecology 112 (3): 233–249. doi:10.1016/0022-0981(87)90071-2. 
  12. ^ Forester, A.J. (1979). "The association between the sponge Halichondria panicea (Pallas) and scallop Chlamys varia (L.): a commensal protective mutualism". Journal of Experimental Marine Biology and Ecology 36 (1): 1–10. 
  13. ^ Donovan, D.; Bingham, B., Farren, H., Gallardo, R., & Vigilant, V. (2002). "Effects of sponge encrustation on the swimming behaviour energetics and morphometry of the scallop Chlamys hastata". Journal of the Marine Biological Association of the United Kingdom 82 (3): 469–476. 
  14. ^ Hart, D.R.; Chute, A.S. (2004). "Essential Fish Habitat Source Document: Sea Scallop, Placopecten magellanicus, Life History and Habitat Characteristics". NOAA Tech Memo NMFS NE-189. 
  15. ^ Hart, D.R.; Chute, A.S. (2004). "Essential Fish Habitat Source Document: Sea Scallop, Placopecten magellanicus, Life History and Habitat Characteristics". NOAA Tech Memo NMFS NE-189. 
  16. ^ Hart, D.R.; Chute, A.S. (2004). "Essential Fish Habitat Source Document: Sea Scallop, Placopecten magellanicus, Life History and Habitat Characteristics". NOAA Tech Memo NMFS NE-189. 
  17. ^ "Scallop Aquaculture". College of Marine Science. 
  18. ^ Treatise on Invertebrate Paleontology Geological Society of America, Kansas, Part N, Vol. I (1969) p. N348.
  19. ^ Waller, T. R. (1993): The evolution of "Chlamys" (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin 10 (2): 195-249.
  20. ^ Raines, B. K. & Poppe, G. T. (2006): The Family Pectinidae. In: Poppe, G. T. & Groh, K.: A Conchological Iconography. 402 pp., 320 color plts., ConchBooks, Hackenheim, ISBN 3-925919-78-3.
  21. ^ Barucca, M., Olmo, E., Schiaparelli, S. & Canapa, A. (2004): Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia)
  22. ^ Waller, T.R. (2006a). New phylogenies of the Pectinidae (Mollusca: Bivalvia): Reconciling morphological and molecular approaches. Scallops: biology, ecology and aquaculture II (Ed. S. E. Shumway): Elsevier, Amsterdam. pp. 1–44. 
  23. ^ Brand, A.R. (2006). "Scallop ecology: distributions and behavior". Scallops: Biology, Ecology and Aquaculture 35: 651–744. doi:10.1016/S0167-9309(06)80039-6. 
  24. ^ Waller, T.R. (1972). The functional significance of some shell micro-structures in the Pectinacea. Paleontology: International Geological Congress. pp. 48–56. 
  25. ^ Habe, T. (1977). Systematics of Mollusca in Japan. Bivalvia and Scaphopoda. 
  26. ^ Waller, T.R. (1986). "A new genus and species of scallop (Bivalvia: Pectinidae) from off Somalia, and the definition of a new tribe Decatopectinini". Nautilus 100 (2): 39–46. 
  27. ^ Waller, T.R. (1991). Evolutionary relationships among commercial scallops (Mollusca: Bivalvia: Pectinidae). Scallops: Biology, Ecology and Aquaculture. pp. 1–73. 
  28. ^ Waller, T.R. (1993). "Waller, T. R. (1993). The evolution of "Chlamys" (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific". American Malacological Bulletin 10 (2): 195–249. 
  29. ^ Alejandrino, A.; Puslednik, L., & Serb, J. M. (2011). "Convergent and parallel evolution in life habit of the scallops". BMC Evolutionary Biology 11 (1): 164. PMC 3129317. 
  30. ^ Waller, T.R. (2007). "The evolutionary and biogeographic origins of the endemic Pectinidae (Mollusca: Bivalvia) of the Galápagos Islands". Journal of Paleontology 81 (5): 929–950. doi:10.1666/pleo05-145.1. 
  31. ^ Dijkstra, H.H.; Maestrati, P. (2012). "Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago". Zoosystema 34 (2): 389–408. 
  32. ^ Waller, T.R. (1984). "The ctenolium of scallop shells: functional morphology and evolution of a key family-level character in the Pectinacea (Mollusca: Bivalvia)". Malacologia 25 (1): 203–219. 
  33. ^ Puslednik, L.; Serb, J.M. (2008). "Molecular phylogenetics of the Pectinidae (Mollusca: Bivalvia) and the effect of outgroupselection and increased taxon sampling on tree topology". Molecular Phylogenetics and Evolution 31 (1): 89–95. doi:10.1016/j.ympev.2008.05.006. 
  34. ^ Barucca, M.; Olmo, E., Schiaparelli, S., & Capana, A. (2004). "Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia) based on mitochondrial 16S and 12S rRNA genes". Molecular Phylogenetics and Evolution 31 (1): 89–95. doi:10.1016/j.ympev.2003.07.003. 
  35. ^ Matsumoto, M.; Hayami, I. "Phylogenetic analysis of the family Pectinidae (Bivalvia) based on mitochondrial cytochrome C oxidase subunit". Journal of Molluscan Studies 66 (4): 477–488. 
  36. ^ Saavedra, C.; Peña, J.B (2006). "Phylogenetics of American scallops (Bivalvia: Pectinidae) based on partial 16S and 12S ribosomal RNA gene sequences". Marine Biology 150 (1): 111–119. 
  37. ^ Matsumoto, M.; Hayami, I. "Phylogenetic analysis of the family Pectinidae (Bivalvia) based on mitochondrial cytochrome C oxidase subunit". Journal of Molluscan Studies 66 (4): 477–488. 
  38. ^ Pamilo, P.; Nei, M. (1988). "Relationships between gene trees and species trees". Molecular Biology and Evolution 5 (5): 568–583. 
  39. ^ Wu, C.I. (1991). "Inferences of species phylogeny in relation to segregation of ancient polymorphisms.". Genetics 127 (2): 429–435. PMC 1204370. 
  40. ^ Matsumoto, M.; Hayami, I. "Phylogenetic analysis of the family Pectinidae (Bivalvia) based on mitochondrial cytochrome C oxidase subunit". Journal of Molluscan Studies 66 (4): 477–488. 
  41. ^ Waller, T.R., 1998. Origin of the Molluscan Class Bivalvia and a Phylogeny of Major Groups. Pp. 1-45. In: P.A. Johnston & J.W. Haggart (eds), Bivalves: An Eon of Evolution. University of Calgary Press, Calgary. xiv + 461 pp.

External links[edit]