Spatial and genetic investigation of aggregation inIschnochiton(Polyplacophora; Neoloricata; Ischnochitonina; Ischnochitonidae; Ischnochitoninae) species with different larval development

Abstract

Many species are aggregated at some spatial scale but for some species, due to habitat or behaviour, aggregation can be difficult to assess quantitatively. Here, aggregation of chiton species (Polyplacophora; Neoloricata; Ischnochitonina; Ischnochitonidae; Ischnochitoninae; Ischnochiton) living under boulders in intertidal boulder fields was investigated at several relatively small spatial scales. Closely related species were found to be aggregated at the level of individual boulders, but evidence for grouping at the larger scale of patches of boulders varied.When organisms are mobile, dispersal can have an important influence on spatial patterns. Some organisms, such as marine invertebrates, have a highly dispersive larval phase that can influence spatial patterns of adults, particularly where the adult is sessile or relatively sedentary. Aggregation was compared in two species to test whether different modes of larval development influence spatial pattern.There was some evidence that species with a planktonic larva were even more aggregated than expected, in contrast to predictions based on this mode of development. Both types of larval development (planktonic and non-planktonic) produce larvae with short development times in these species, so one possible explanation for the grouping habit of these chitons is that they do not disperse, at all, from their natal boulder. The complexity of the boulder field habitat and the cryptic behaviour of these chitons may also contribute to a lack of dispersal. A simple application of a genetic method indicated, however, that philopatry at this scale is unlikely.

Biofluorescence reveals hidden patterns in chitons with implications to visual ecology

“…Observ.). It seems that their spatial distribution patterns are comparable to those of other chiton species, with the majority of boulders being unoccupied and only a few being occupied (Chapman, 2002; Palmer, 2012).…”

Habitat use of inter‐tidal chitons – role of colour polymorphism

“…Many inter‐tidal molluscs, such as limpets and snails and even some chitons such as Ischonochiton , display aggregation behaviours that can result in patches with densities as high as 84 individuals per rock (Chapman & Underwood ; Grayson & Chapman ; Palmer , ). This behaviour is considered to be a mechanism for reduction of desiccation stress (Levings & Garrity ) or wave action disturbance (Feare ).…”

“…Otaíza & Santelices ; Aguilera & Navarrete , ; Jörger et al . ; Palmer ). Here, we studied for the first time colour polymorphism in the common and widespread North Atlantic and Mediterranean chiton Lepidochitona cinerea , as well as in other less studied species.…”

The complete mitochondrial genome and phylogenetic analysis ofIschnochiton hakodaensis(Carpenter, 1893)

“…Chitons are marine molluscs with eight articulated shell plates encircled by a muscular girdle (Palmer 2012). Ischnochiton hakodaensis is an important species of chitons, which plays a vital role in the intertidal and subtidal ecosystems (Dou et al 2018).…”