Pisaster ochraceus arm length conversion using center or madreporite

Conversion for Pisaster ochraceus Arm Length MeasurementsTo enable P. ochraceus size comparisons between California and Oregon and to allow other researchers to easily convert between arm lengths using different published methods, we measured arm lengths of 25 sea stars ranging in arm length from ~5-200mm at each of 6 sites in Oregon (see manuscript) using both measurement approaches. To determine whether site influenced this conversion, we first ran a linear model with madreporite measure as the response variable and site and center measure as the interacting factors. No interacting effect of site and arm measurement from center to arm tip was found (F5,138 = 0.64, P = 0.672), suggesting this metric is consistent geographically, at least within Oregon. We had no data for California. So, we used a simple linear regression (R2 = 0.97, P < 0.001) to convert madreporite measures to center measures for all our data. Conversion formulas in centimeters are: [madreporite arm length = 4.074 + (1.060*center arm length)] or [center arm length= -0.729 + (0.914*madreporite arm length)].

紫海盘车（Pisaster ochraceus）腕长测量转换方法
为实现加利福尼亚州与俄勒冈州两地紫海盘车的体型对比，并便于其他研究者基于已发表的不同测量方法实现腕长的便捷转换，我们针对俄勒冈州6个采样点（详见论文手稿）的每处站点，分别采用两种测量方案，对25只腕长范围约5~200mm的海盘车进行了腕长测量。
为探究采样点是否对转换结果存在影响，我们首先构建了线性模型：以筛板（madreporite）测量值作为响应变量，以采样点与中央腕长测量值作为交互因子。分析结果显示，未发现采样点与腕尖至中央的腕长测量值之间存在交互效应（F₅,₁₃₈=0.64，P=0.672），表明该测量指标在地理上具有一致性，至少在俄勒冈州范围内如此。
目前我们尚未获取加利福尼亚州的相关数据，因此针对全部数据集，我们采用简单线性回归（R²=0.97，P<0.001）实现筛板测量值到中央腕长测量值的转换。以厘米为单位的转换公式如下：
筛板腕长 = 4.074 + (1.060 × 中央腕长)，或 中央腕长 = -0.729 + (0.914 × 筛板腕长)。