Gunnar Thorson's world-wide collection of prosobranch egg capsules: Muricidae

Abstract

Egg capsules from 56 species in Muricinae, Ocenebrinae, Ergalataxinae, Trophoninae, Thaidinae, and Rapaninae are described and illustrated. These descriptions demonstrate the degree to which muricid egg capsules exhibit features diagnostic oftaxa in the subfamilies and emphasize variation in protective strategies employed during spawning. Non-random patterns of sutures appearing on all muricid egg capsules are used to categorize the very diverse forms into two major types: (1) vasiform capsules, which are deposited with alignment of the sutures nearly perpendicular to the anterior-posterior axis of the spawner's foot, and (2) ampulliform capsules, which are positioned with alignment ofthe sutures approximately parallel to the anterior-posterior pedal axis. Bulliform capsules appear to be the simplest type of vasiform capsule.

Consistent occurrence of sutural patterns is shown for most subfamilies and genera. Muricines, muricopsines, ergalataxines, and trophonines, for which egg capsules are known, deposit a variant of the vasiform type. All described ocenebrine and rapanine egg capsules have the ampulliform sutural pattern. Thaidine genera have either ampulliform or vasiform capsules, with one exception. Thais includes at least two species with capsules that are not typical of congeners.

Species in related genera and congeners often deposit eggs in capsules with similar shapes; however, many exceptions exist. Diverse subfamilies with several species having egg capsules with similar shapes could be examples of convergence as well as common origin. The number of these exceptions suggests that shape and sculpture (other than the sutures) of egg capsules are only occasionally diagnostic of muricid genera.

Muricid egg capsules have species-specific morphologies, with few exceptions. Specific characteristics include shape and sculpture with the latter being most distinctive. Bulliform capsules occurring in four subfamilies are exceptional in that they usually do not have species-specific morphologies. Other exceptions reported in this paper are expected to be less prominent when the taxonomy of affected taxa is revised and errors in identification are corrected.