new A comparison of the labrum-paragnath complex in five species of calanoid copepodsfileset

Although some information is available on how calanoid copepods collect and handle food, there is very little information on the labrum and paragnaths, structures that are the last to receive food before trituration and ingestion. Five species were used to examine the nature of and differences between the labrum-paragnath complex, species with a variety of feeding modes ranging from detritivore to carnivore. The nature of the complex ranged from very simple in Eucalanus bungii bungii Johnson, 1938, to the heavily sclerotized labrum and paragnaths of the carnivore Paraeuchaeta elongata (Esterly, 1913) with its specialized anterior labral lobe. The labrum, which provides a semi-enclosed space for trituration by the mandible gnathobases, is hood shape while the columnar-shaped paragnaths, which hold and help move food towards the mandible gnathobases, contain setule and spicule armature elements. Not only the shape of the complex, but also its orientation are suggested to play roles in dictating dietary choices. The range of structures, from the simple complex of Eucalanus bungii bungii to the beak like complex of Heterorhabdus tanneri (Claus, 1863), along with its claw-like gnathobase armature, provide an indication of the morphological diversity found in the labrum-paragnath complex of calanoid copepods.

尽管目前已有部分关于哲水蚤目桡足类（calanoid copepods）获取与处理食物方式的研究，但针对其上唇（labrum）与副颚（paragnaths）的相关记载却极为匮乏——这两类结构是食物在被磨碎（trituration）与摄食（ingestion）前最后接触的器官。本研究选取5种具有多样摄食模式（从腐食性到肉食性）的哲水蚤目桡足类，对上唇-副颚复合体的结构特征与种间差异展开考察。该复合体的结构复杂度跨度极大：1938年由Johnson命名的南极真哲水蚤（Eucalanus bungii bungii）的复合体结构极为简单；而肉食性的长近哲水蚤（Paraeuchaeta elongata, Esterly, 1913）则拥有高度硬化的上唇与副颚，且具备特化的上唇前叶结构。上唇呈兜帽状，可为大颚基节（mandible gnathobases）的磨碎动作提供半封闭空间；而呈柱状的副颚则用于夹持并协助将食物推送至大颚基节，其表面分布有小刺（setule）与骨针（spicule）状的附属刺突结构。研究表明，不仅上唇-副颚复合体的形态，其空间朝向也会对物种的食性选择产生影响。从南极真哲水蚤的简单复合体，到1863年由Claus命名的坦纳异肢水蚤（Heterorhabdus tanneri）的喙状复合体，再加上其爪状大颚基节附属刺突结构，这些多样的特征均体现了哲水蚤目桡足类上唇-副颚复合体的形态多样性。