Daylithos, Salazar-Vallejo, 2012

Salazar-Vallejo, Sergio I., 2012, 3562, Zootaxa 3562, pp. 1-62 : 42-43

Daylithos n. gen.

Type species: Stylarioides parmata Grube, 1877 .

Gender: Masculine.

Diagnosis: Body anteriorly swollen, with a posterior, often depressed cauda. Cephalic cage well developed. Dorsal shield over chaetigers 1–4, without an articulated anterior plate, not continued ventrally. Body papillae minute, arranged in distinct belts, at least in anterior chaetigers. Anterior neuropodia with multiarticulate capillaries, sometimes aristate. Posterior neurohooks falcate, simple, sometimes flanged. Posterior end often with many neurohooks. Boring in hard or compact substrates.

Etymology. This genus is named after the late Dr. John H. Day, one of the most productive and diversified polychaete scientists; he started by studying early development and then moved to do taxonomy of many different groups, especially those collected in South Africa. His studies on flabelligerids were very useful and changed the general understanding of the group, especially by clarifying some features of the eversible anterior end. The name is a combination of his last name with the Greek word for stone (lithos, masculine), because of the stone-like appearance of the dorsal shield of the species included in the genus.

Remarks. Daylithos n. gen., and Semiodera Chamberlin, 1919 are very similar; however, they have several differences. In Daylithos there are no pseudocompound hooks in chaetigers 3–7, the cauda is often flat, and all far posterior neuropodia have 3–7 falcate hooks, arranged in a -pattern; Semiodera , in contrast, has pseudocompound hooks in some anterior chaetigers, the cauda is cylindrical, and all far posterior neuropodia have only 1–2 falcate hooks. Additional differences relate to the arrangement of branchial filaments and to the relative position of palps, although these would require dissection to observe them. Semiodera has branchial filaments arranged in two lateral spirals and the palps are present over the mouth, whereas in Daylithos , the branchial filaments are arranged in two lateral groups, each with six or more irregular rows of filaments, and the palps arise below the mouth. The type species name, in order to agree in gender with the genus-group name has to be modified (ICZN 1999, Art. 31.2) if it is in a nominative singular, as is the case for parmata , feminine being modified to parmatus , masculine.

It should be emphasized, however, that since the species of Daylithos may also be able to bore into living corals, there may be many more species than currently recognized. Thus, it seems unlikely that, Daylithos parmatus ( Grube, 1877) n. comb., occurs throughout the Indian and Western Pacific oceans, associated with several different coral genera. Although as intertidal rocks (and sediments) were widely employed for ballasting ships ( Blakemore 2007), this could have led to the widespread dispersal of the species, although this seems unlikely given that this early form of ballasting early shipping was during a time when there was little shipping in these coral reef areas. A more detailed study of flabelligerids boring into a variety of coral species is required to determine if a single or multiple species are involved.

Some features might be relevant for finding out any specific differences in future studies. The coral species must be noticed because some selectivity has been found in Caribbean serpulid larvae ( Marsden & Meeuwig 1990), and a similar mechanism may operate with boring flabelligerids. This intriguing ecological process deserves further studies because corals are capable of eating planktonic larvae and this would avoid their settlement on living corals. Other potentially useful features may be the color, type and relative size of sediment particles present in the dorsal shield, as found in some oweniids ( Koh & Bhaud 2003). Additionally, the pattern of number of neurohooks per chaetiger of each body region may be useful, but it has not been evaluated in this study, as there was insufficient material.