Feng W et al. (2019), Reproduction and population structure of the se...

ECB-ART-46862

PLoS One 2019 Jan 01;141:e0209858. doi: 10.1371/journal.pone.0209858.

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Reproduction and population structure of the sea urchin Heliocidaris crassispina in its newly extended range: The Oga Peninsula in the Sea of Japan, northeastern Japan.

Feng W , Nakabayashi N , Narita K , Inomata E , Aoki MN , Agatsuma Y .

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Ocean warming has facilitated the range expansion of commercially important sea urchin species to higher latitudes. Heliocidaris crassispina was recorded to extend northward to Toga Bay along the Oga Peninsula, Japan following an increase in seawater temperatures, and replacement of local sea urchin species Mesocentrotus nudus. In order to identify evidence of adaptation occurring in response to a range extension of H. crassispina to the newly extended environments, we randomly collected 106 H. crassispina in August 2014 in Toga Bay, determined the growth and age composition and examined gonad traits (size, color and development). To confirm the gonad development, 30 H. crassispina with > 30 mm diameter were collected in July, August and September 2017. We found slower growth in the extended range than the central range. More delayed gonad development of males than those of females and a large variety of developmental stages in the acini of testis indicated that the spawning of both sexes of the sea urchins were asynchronous. In terms of gonad color, L* (lightness) values increased with increasing GI, while b* (yellowness) values decreased with increasing age. The population consisted of seven year-classes from 2006 to 2012, suggesting persistent juvenile recruitment. Long-term water temperature data indicated that the range extension of H. crassispina was due to ocean warming, in particular during the summer spawning season.

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Genes referenced: LOC100887844 LOC115925415

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References [+] :

Cochran, Environmental regulation of the annual reproductive season of Strongylocentrotus purpuratus (Stimpson). 1975, Pubmed, Echinobase

	Fig 1. Flow diagram of the assays and the samples that were evaluated.
	Fig 2. Size-frequency distribution (a) and year class composition (b) of Heliocidaris crassispina collected in August 2014.Roman numerals indicate ages.
	Fig 3. Number of acini at different gonad development stages per 10 acini and number of gonad developmental stage of Heliocidaris crassispina by sex in August 2014 and July–September 2017.Data indicate means ± SE. One and two asterisks indicate significant sexual differences at p < 0.05 and p < 0.01, respectively.
	Fig 4. Histology of a testis (a) and ovary (b) with different development stages of acini in Heliocidaris crassispina.Scale bars represent 500 μm.
	Fig 5. Percentage area of acinar components of female (n = 38) and male (n = 27) Heliocidaris crassispina at different gonad developmental stages.(a) Acinar component in ovary: nutritive phagocytes (NPs), oocytes, ovum, unoccupied lumen. (b) Acinar component in testis: NPs, spermatocytes, spermatozoa, unoccupied lumen. Urchins were collected in August 2014.
	Fig 6. Gonad indices (mean ± SE) of Heliocidaris crassispina by sex in August 2014 and July–September 2017.Asterisks indicate significant sexual differences (p < 0.05). A and B indicate significant differences among months (p < 0.05).
	Fig 7. Gonad color (L, a, b*) (mean ± SD) of female and male Heliocidaris crassispina collected in August 2014.Asterisks indicate significant sexual difference (p < 0.05).
	Fig 8. Sea surface temperature off Unosaki (39°51´N, 139°48´E), along the Oga Peninsula, Akita Prefecture.Monthly averages for 34 years (1984–2017) (a), and deviations from the average from 2006 to 2009 (b), 2010 to 2013 (c) and 2014 to 2017 (d). X-axis represents months from January (J) to December (D).