Английская Википедия:Atlanta lesueurii
Шаблон:Short description Шаблон:Speciesbox
Atlanta lesueurii is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.[1]
Description
The maximal shell size of Atlanta lesueurii appears to vary geographically (from 2 mm in Hawaiian and eastern Australian waters to 6 mm in the tropical western Pacific).[2] The shell is transparent, thin and fragile, with a smooth surface (lacking raised sculpture). The spire is very small, somewhat elevated and compact, consisting of about 2½ whorls.[2] Spire sutures are deep, with the result that the whorls are somewhat rounded in profile and can easily be distinguished.[2] After metamorphosis the outermost whorl enlarges and inflates rapidly and the keel becomes progressively taller, becoming very tall in large adults and having a truncate leading edge.[2] The keel base and spire sutures are colorless.[2]
Main features for the recognition of this species are the protoconch composed of just 2¼-3 convex whorls, separated by an incised suture and the absence of any ornament.[3] The first teleoconch whorl expands rapidly and bears a well-developed flange-like keel.[3] In the largest specimens the final three quarters of the teleoconch separates from the penultimate whorl.[3]
Eyes are type b, with a large lens.[2] The Operculum is the type b.[2] Radula is type I, with a narrowly triangular shape.[2]
Atlanta lesueurii is the large species in the genus Atlanta, but Atlanta peronii is larger.
Atlanta lesueurii resembles closely Atlanta oligogyra, in which, however, the first whorls are separated by a superficial suture and the shell remains much smaller.[3]
Overview of description:
- Maximal shell size appears to vary geographically, between 2 and 6 mm[2][4]
- Shell transparent with a thin, fragile walls[2]
- Shell surface smooth; lacking surface sculpture[2]
- Spire compact, consisting of about 2½ whorls[2]
- Spire sutures incised, enabling distinction of whorls[2]
- Keel tall, with a truncate leading edge[2]
- Eyes type b; lens large[2]
- Operculum type b[2]
- Radula type I, narrowly triangular shape[2]
Distribution
Atlanta lesueuri has a Recent circumglobal tropical/subtropical distribution.[3]
The first fossil specimens of Atlanta lesueurii has been found from Pliocene in Tiep, Roxas (map) and Anda, Pangasinan, Luzon, Philippines in 2001 (published in 2007).[3]
Ecology
Vertical distribution in Hawaiian waters is restricted to upper 150 m, with most individuals in the upper 100 m and some evidence for nocturnal migration into the upper 50 m.[2]
Vertical migration
Diel vertical distribution patterns of Atlanta lesueurii (among the 13 species of heteropods in the study) were investigated off leeward Oahu, Hawaii in waters overlying a bottom depth of 2,000 m (between 9 and 11 km off the coast) by Seapy (1990).[2] Heteropods were collected during day and night periods using paired, opening-closing BONGO nets at 50-m depth intervals between the surface and 200 m and at 200–300 m and 300–400 m.[2] Three or four replicated tows were taken in each depth interval.[2] Atlanta lesueurii was found to be the most abundant species, with a maximal density of 59 individuals per 1,000 m3 in a daytime 0–45 m depth interval.[2] The species ranged from the surface to 140 m during both day and night periods.[2] There was an apparent partial populational migration from a depth interval of 45–90 m during the day to 0–45 m at night.[2] However, high variability in densities between the replicated tows in each of the depth intervals resulted in statistically non-significant differences between day and night periods for each of the depth intervals.[2]
In a subsequent study off leeward Oahu (Seapy, 2008), duplicate tows were taken with a MOCNESS multiple, opening-closing net system during day and night periods at three stations located 1, 5 and 15 nm off the island in fall and spring sampling periods.[2] Mean densities were computed (as numbers of individuals beneath 100 m2 of ocean surface) during day and night periods at each station.[2] As in the 1990 study, Atlanta lesueurii was the most abundant species in the fall, although it was a close second to Atlanta plana in the spring.[2] Comparisons were made using the nighttime density data to avoid issues such as daytime net avoidance and to include increased nighttime abundances resulting from possible nocturnal vertical migrator species.[2] Atlanta lesueurii was found to be most abundant at the offshore (15 nm) station during both seasons.[2] Offshore to inshore abundance decreased most dramatically in the fall; from mean nighttime densities of 480 (15 nm) to 124 (5 nm) to 37 (1 nm) individuals beneath 100 m2 of ocean surface.[2] At the 15 nm station the species ranged downward to the greatest depths; to the 120–160 m depth interval in the spring and to the 80–120 m depth interval in the fall.[2] Clear evidence for nocturnal vertical migration was only seen in the spring at the 1-nm station (10-m depth interval tows were taken in the upper 100 m at this shallow-water station).[2] Highest abundances were recorded between 60 and 30 m during the day to 30 m to the surface at night.[2]
References
This article incorporates CC-BY-3.0 text from references.[3][2] Шаблон:Reflist
- ↑ Шаблон:WRMS species
- ↑ 2,00 2,01 2,02 2,03 2,04 2,05 2,06 2,07 2,08 2,09 2,10 2,11 2,12 2,13 2,14 2,15 2,16 2,17 2,18 2,19 2,20 2,21 2,22 2,23 2,24 2,25 2,26 2,27 2,28 2,29 2,30 2,31 2,32 2,33 2,34 Seapy R. R. (2009). Atlanta lesueurii Gray 1850. Atlanta lesueuri Souleyet 1852. Version 29 October 2009. http://tolweb.org/Atlanta_lesueurii/28765/2009.10.29 in The Tree of Life Web Project, accessed 20 August 2010.
- ↑ 3,0 3,1 3,2 3,3 3,4 3,5 3,6 Шаблон:Cite journal
- ↑ Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". PLoS ONE 5(1): e8776. Шаблон:Doi.
