臺灣東部海岸之海參新種：形態特徵、粒線體基因體與生長模式分析

Abstract

本研究闡述一種在臺東海岸發現的新物種海參，其外觀特徵為黑色的圓柱形身體、柔軟的表皮，腹側具有呈三縱列排列的管足，背側有許多均勻分佈的疣足，口部具約20個呈樹枝狀的攝食觸手，收縮時呈楯狀；利用掃描式電子顯微鏡觀察，在管足、觸手、縱肌以及體背側可發現棒狀和末端分支的棒狀骨針；解剖構造顯示其缺乏居維葉氏管，上述特徵表明此海參應為尚未發現的物種。此新種海參的粒線體基因體共有15,720個鹼基對，由37個基因構成，包括13個蛋白質編碼基因、2個核糖體RNA基因、22個轉運RNA基因，以及一個非編碼控制區；粒線體基因體的AT-skew (0.04) 和GC-skew (−0.17) 分別為正值和負值，與大多數已定序的棘皮動物相同。親緣關係分析顯示此新種海參位於海參科物種構成的單一支序群，與同屬海參目的刺參科分為不同支系。本研究結合形態和分子證據，將該物種分類於海參目海參科，並透過其獨特的骨針組成，將其歸類至海參屬下的賽倫參亞屬。本研究亦分析此海參的體長與體重關係，顯示此海參為負異速生長，與在其他海參中觀察到的生長模式相似。本研究首次發現並闡述一未被記錄的海參物種，提出新的學名，且為臺灣定序海參完整粒線體基因體之先驅，並進行野外族群調查，提供關於此新物種的生態棲位和演化關係的見解。

This study describes a newly discovered sea cucumber species from the eastern coast of Taiwan and focuses on its morphological characteristics, growth patterns, and complete mitochondrial genome. The species is characterized by a black, cylindrical body and soft skin. Tube feet are arranged in three adjacent rows, and the dorsal side is covered with multiple evenly distributed papillae. The species has approximately 20 dendritic tentacles that appear peltate-like when contracted. Scanning electron microscopy showed that only rod-shaped or terminally branched rod-shaped ossicles are present in the tube feet, tentacles, longitudinal muscles, and dorsal body. Internal anatomy shows the absence of Cuvierian organs. The complete mitogenome comprises 15,720 base pairs and contains 37 genes, including 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a single control region. The AT-skew (0.04) and GC-skew (−0.17) in the mitogenome are positive and negative, respectively, consistent with most sequenced echinoderms. Phylogenetic analysis based on mitochondrial amino acid sequences places this species within the Holothuriidae family. Based on both morphological and molecular data, the new species is classified as Holothuriida: Holothuriidae. The dermal ossicle compositions support its classification as subgenus Selenkothuria of Holothuria. The length-weight relationship index and growth coefficient indicate negative allometric growth, similar to patterns observed in other holothurians. Our research offers insights into the ecology and evolution of a previously unrecognized sea cucumber species.