Eye and clasper damage influence male mating tactics in the horseshoe crab, Limulus polyphemus

Abstract

In the horseshoe crab mating system, mated pairs are frequently accompanied by unattached satellite males as they spawn on intertidal beaches. Previous studies have shown that males locate females visually using their lateral (compound) eyes, and that attached (mated) males generally have less heavily worn or damaged carapaces than unattached males. The purpose of this study was to investigate the influences of lateral eye condition and clasper abnormalities on male mating tactics. Sexually mature males had two kinds of eye damage: deterioration caused by disease, and overgrowth by sessile invertebrates, such as bryozoans, mussels, and tube-building polychaetes. The lateral eyes of attached males had significantly less decay than unattached males. On the other hand, coverage of the lateral eyes by encrusting invertebrates was more extensive among attached than unattached males. Although overgrowth did not appear to impair a male's ability to pair with a female as severely as eye decay, it is conceivable that amplexus may have occurred before epibiont coverage was sufficient to obscure vision. Male crabs that were experimentally "blindfolded" by painting their lateral eyes with black nail polish were less likely to reattach to a female than controls. Appendage injuries were more frequent among unattached males than among attached males; in particular, 6.4% of unattached males but 0.0% of attached males had damaged claspers (the modified first legs required for amplexus). Unattached males in the population were "older," as judged by the degree of carapace wear, than attached males. Severe visual impairment and/or clasper damage may explain the reduced pairing success of older male horseshoe crabs, and underlie their choice of the alternative satellite male mating tactics.

Abnormal xiphosurids, with possible application to Cambrian trilobites

“…Damaged pretarsus, apotele sections and processes of pushing legs are the most documented appendage injuries (van der Meer Mohr, 1935, 1941. Damaged and amputated walking legs and the loss of male pedipalps have also been noted (Bursey, 1977;Schaller et al, , 2005Duffy et al, 2006). Such injuries can persist through multiple moulting events (Itow et al, 1998a).…”

“…Those abnormalities to extant xiphosurids that have been documented are mostly telson teratologies (Table 1) (Shuster Jr, 1982, 2009Botton and Loveland, 1989;Shuster Jr and Sekiguchi, 2004). Injuries to female opisthosomal sections and cephalothoracic appendages have been documented and are records of injuries incurred during mating, burrowing, or other activities (Brockmann, 1990;Schaller et al, , 2005Duffy et al, 2006;Shuster Jr, 2009). There is also one documented example of Limulus polyphemus with a substantially buckled cephalothoracic margin (Jell, 1989).…”

Conservation status of the American horseshoe crab, (Limulus polyphemus): a regional assessment

“…In addition, unattached males come to the shore and gather around nesting pairs as satellites (Cohen and Brockmann 1983;Brockmann and Penn 1992). Males in amplexus do not differ in size from unattached males, but they are in better condition, more active, have a higher sperm concentration, remain attached longer and probably are younger (more recently molted into the adult) than satellite males (Cohen and Brockmann 1983;Brockmann and Penn 1992;Loveland and Botton 1992;Brockmann 2002;Duffy et al 2006;Sasson et al 2012). Satellite males are rare in some populations, including the Florida Atlantic and the northern coast of the Yucatán Peninsula including Chuburná and Chabihau (unpublished data J. Gutiérrez and J. Zaldívar-Rae, Anáhuac Mayab University).…”

Opsin1-2, Gqα and arrestin levels at Limulus rhabdoms are controlled by diurnal light and a circadian clock

“…Perhaps it is because Limulus use their LEs to find mates when they spawn (Barlow et al, 1982;Duffy et al, 2006;Schwab and Brockmann, 2007;Saunders et al, 2010), and they spawn during the day and night (Cohen and Brockmann, 1983). Thus, their LEs must function optimally under both very low and very bright light conditions.…”