Spurilla braziliana MacFarland, 1909

イロミノウミウシ Spurilla braziliana
Photographed by
黒田貴司
Location
Boso Peninsula, Japan
Date
2014/03/09
Length
15mm
Depth
1.0m
Water temperature
18.0℃

MORPHOLOGY

The body is elongate and moderately broad, tapering gradually to the posterior end. The anterior foot corners extend into tentaculiform processes. The body colour is variable. This variability results from ontogenetic changes (Domínguez et al., 2008). The youngest individuals are cream white (Fig. 4D), whereas the adults have a coloration that ranges from pale orange to vermillion red (Fig. 4C, E). White spots occur all over the dorsum (from the head to the posterior end) in both juveniles and adults. Depend- ing on the specimen, these white spots can be more or less conspicuous. Right behind the rhinophores and behind the pericardium, the white spots can form a confluent patch. A reticulate pattern produced by the presence of zooxanthellae is usually absent, or at least not easily distinguishable, but when present it is restricted to both sides of the head, just below the rhinophores, as a short branch (Fig. 4E), as well as on the insertions of the cerata (Fig. 4D–E).
The rhinophores, the oral tentacles, and the foot corners have the same colour as the rest of the body. The rhinophores are perfoliate, bearing 11–14 lamellae with a white apex. They are somewhat shorter than the oral tentacles. The coloration of the tips of the oral tentacles is lighter than the background.
The cerata length varies depending on the size of the animals. Adults have short and thick cerata, and their tips are curved inwards. The cerata of the juveniles are long, thin, and slightly curved inwards (Fig. 4D). The cerata are arranged in up to nine arches, leaving a distinct gap between pre- and post- pericardial groups. They extend from behind the rhinophores to the posterior end of the body. Each arch contains between five and 26 cerata, decreasing in size towards the foot. The apices of the cerata are translucent white. The cerata are translucent, light brown (juveniles), or bluish dark grey or dark green (adults), with the ramifications of the digestive gland visible through the ceratal wall. All the specimens have white markings all over the ceratal surfaces, although their density and size vary. Only the vermillion red specimens have a vermillion red band on the distal third of the cerata. The anus is cleioproctic and is located within the second right
ceratal arch. The genital opening is located within the cerata of the anteriormost group on the right.

DISTRIBUTION

Originally described from Alagoas, Brazil (MacFarland, 1909), this species has been reported (under the name of S. neapolitana) from the western Atlantic Coast: the Caribbean Sea (Valdés etal., 2006), Florida, Mexico, Colombia, Cuba (the present
Er. Marcus, Aeolidiella albopunctata Lin, 1992: 184, figs 4–5.
Spurilla
var. braziliana 1955: 184, pl. 29, figs 270–274.
© 2014 The Linnean Society of London, Zoological Journal of the Linnean Society, 2014, 170, 132–154
study), Jamaica (Miloslavich et al., 2010), Puerto Rico (Miloslavich et al., 2010), and in the northern part of the Magellanic Province (Forcelli, 2000). It has also been reported from the Pacific: Hawaiian Islands (Kay, 1979; Gosliner, 1980; Pittman & Fiene, 2013), the Pacific coast of Costa Rica (Camacho-García et al., 2005), Peru (Uribe & Pacheco, 2012), Japan (Hamatani, 2000), China (Lin, 1992), and Australia (Willan, 2006).

References