Antennular specialization in cyprids of coral associated barnacles

TY - JOUR

T1 - Antennular specialization in cyprids of coral associated barnacles

AU - Brinckner, I.

AU - Høeg, Jens Thorvald

PY - 2010/8

Y1 - 2010/8

N2 - We used video, light and scanning electron microscopy to study the cypris larvae in species of coral inhabiting barnacles (Pyrgomatidae) in search of adaptations to settlement on their highly unusual substratum. Species studied were Savignium crenatum, Trevathana jensi, Trevathana margaretae, Trevathana mizrachae and Trevathana sarae. In all five species the third antennular segment was shaped like a spearhead with only an extremely narrow attachment disc. This morphology represents the most extreme antennular specialization known from cirripedes, and it is not even matched by those parasitic barnacles that use the antennule for active penetration of cuticles. Compared to the third segment, the first, second and fourth segments exhibit no obvious specializations, and the armament of sensory setae is also as very comparable to that seen in balanomorphan cirripedes. The coral barnacles also have the nauplius eye, compound eyes, frontal filaments, lattice organs and cement glands known from other barnacles. Only T. sarae differed by having two unusually shaped setae terminally on the fourth segment. Video observations showed that the coral barnacle cyprids display the exploratory walking behaviour known from cyprids settling on hard bottom substrata. We interpret the pointed structure of the third antennular segment as an adaptation to penetrate through live coral tissue. Projecting this character onto a recent phylogenetic tree of balanomorphan species indicates that it is an apomorphy for a large clade of coral inhabiting barnacles.

AB - We used video, light and scanning electron microscopy to study the cypris larvae in species of coral inhabiting barnacles (Pyrgomatidae) in search of adaptations to settlement on their highly unusual substratum. Species studied were Savignium crenatum, Trevathana jensi, Trevathana margaretae, Trevathana mizrachae and Trevathana sarae. In all five species the third antennular segment was shaped like a spearhead with only an extremely narrow attachment disc. This morphology represents the most extreme antennular specialization known from cirripedes, and it is not even matched by those parasitic barnacles that use the antennule for active penetration of cuticles. Compared to the third segment, the first, second and fourth segments exhibit no obvious specializations, and the armament of sensory setae is also as very comparable to that seen in balanomorphan cirripedes. The coral barnacles also have the nauplius eye, compound eyes, frontal filaments, lattice organs and cement glands known from other barnacles. Only T. sarae differed by having two unusually shaped setae terminally on the fourth segment. Video observations showed that the coral barnacle cyprids display the exploratory walking behaviour known from cyprids settling on hard bottom substrata. We interpret the pointed structure of the third antennular segment as an adaptation to penetrate through live coral tissue. Projecting this character onto a recent phylogenetic tree of balanomorphan species indicates that it is an apomorphy for a large clade of coral inhabiting barnacles.

KW - Faculty of Science

U2 - 10.1016/j.jembe.2010.04.015

DO - 10.1016/j.jembe.2010.04.015

M3 - Journal article

SN - 0022-0981

VL - 392

SP - 115

EP - 124

JO - Journal of Experimental Marine Biology and Ecology

JF - Journal of Experimental Marine Biology and Ecology

IS - 1-2

ER -