Peer Aquatic Biology
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Specimens of Thylacodes decussatus in Belize often occur in shallow water at snorkeling depth, while specimens in the Florida Keys were found almost exclusively during scuba diving.
The operculum is also missing from Thylacodes decussatus, and the species has undergone a parallel evolution of the non-operculate marine worm-snail genera Thylacodes, so it also lacks an operculum (trapdoor) that closes the tube.
Color in life: polychromatic:
Orange-colored morph observed in Belize, St. Thomas, Florida Keys and the Bahamas:
Head-foot, tentacles and mantle edge opaque orange; pedal plate and “snout area” with fine black surface pigment; fine dark brown pigment spots, which are roughly arranged in transverse lines on the exposed surface of the foot and in longitudinal lines on the sides of the foot and neck radiating from the area around the mouth, running along the muzzle and side of the head; outermost edge of mantle always without black pigmentation; narrow black pigment band immediately behind the outer edge of the mantle; mantle edge with a pattern of two black lines forming forming open “V” shapes, with the area surrounding the two black lines lined with lighter orange pigment; posterior dorsal surface of the mantle mottled with opaque black, white, and orange pigment spots on a pale brown background.
Gray Morphe observed in Belize, St. Croix and Florida Keys:
Foot mottled in off-white with fine olive-gray dots and dotted lines between pure white longitudinal spots; mantle edge with black “open V” pattern as above; additionally black circles at the edge of the concave lateral foot zones; the orange color is restricted to the mantle margin (between and adjacent to the double black markings) and small clusters of orange pigment around the mouth, on the tentacles, and sometimes along the pedal plate; the circles in the concave lateral zone of the head-foot are often filled with yellow. Juveniles with more pronounced black pigment on the head.
Distribution:
Known from southern Florida, the Bahamas, and the Caribbean. Live specimens of both color morphs were observed during this study along the entire Florida Keys archipelago (Carysfort Reef to Dry Tortugas), the Bahamas, the US Virgin Islands, and Belize. Verified shells have been sighted in many other locations throughout the Caribbean, including St. Lucia, Ominica, and Venezuela. Records from North Carolina (Abbott, 1974) and Brazil (see taxonomic notes below) remain to be verified. Not reported from Bermuda (see Thylacodes bermudensis n. sp., above). Historical Indo-Pacific records for this species (e.g., from Sowerby, 1892 for South Africa) are in error.
Etymology:
The generic name “Cayo” is the Spanish term for a small flat island in the Caribbean and surrounding regions, corresponding to “key” in Florida, “cay” in the Bahamas and “caye” or “cay” in Belize. Here, the term refers to the locations of the four currently known species of this genus, Looe Key in the barrier reef of the Florida Keys and Carrie Bow Cay in the Belizean reef.
Etymology:
The specific name “galbinus” is derived from Latin and means “greenish-yellow”, which refers to the vivid coloration from head to tail.
Literature reference:
Bieler R, Collins TM, Golding R, Granados-Cifuentes C, Healy JM, Rawlings TA, Sierwald P. 2023. Replacing
mechanical protection with colorful faces–twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard,
1770) and Cayo n. gen. (Gastropoda: Vermetidae). PeerJ 11:e15854 http://doi.org/10.7717/peerj.15854
Bieler R, Collins TM, Golding R, Granados-Cifuentes C, Healy JM, Rawlings TA, Sierwald P. 2023. Replacing
mechanical protection with colorful faces–twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard,
1770) and Cayo n. gen. (Gastropoda: Vermetidae). PeerJ 11:e15854 http://doi.org/10.7717/peerj.15854
CC BY 4.0, open access
The operculum is also missing from Thylacodes decussatus, and the species has undergone a parallel evolution of the non-operculate marine worm-snail genera Thylacodes, so it also lacks an operculum (trapdoor) that closes the tube.
Color in life: polychromatic:
Orange-colored morph observed in Belize, St. Thomas, Florida Keys and the Bahamas:
Head-foot, tentacles and mantle edge opaque orange; pedal plate and “snout area” with fine black surface pigment; fine dark brown pigment spots, which are roughly arranged in transverse lines on the exposed surface of the foot and in longitudinal lines on the sides of the foot and neck radiating from the area around the mouth, running along the muzzle and side of the head; outermost edge of mantle always without black pigmentation; narrow black pigment band immediately behind the outer edge of the mantle; mantle edge with a pattern of two black lines forming forming open “V” shapes, with the area surrounding the two black lines lined with lighter orange pigment; posterior dorsal surface of the mantle mottled with opaque black, white, and orange pigment spots on a pale brown background.
Gray Morphe observed in Belize, St. Croix and Florida Keys:
Foot mottled in off-white with fine olive-gray dots and dotted lines between pure white longitudinal spots; mantle edge with black “open V” pattern as above; additionally black circles at the edge of the concave lateral foot zones; the orange color is restricted to the mantle margin (between and adjacent to the double black markings) and small clusters of orange pigment around the mouth, on the tentacles, and sometimes along the pedal plate; the circles in the concave lateral zone of the head-foot are often filled with yellow. Juveniles with more pronounced black pigment on the head.
Distribution:
Known from southern Florida, the Bahamas, and the Caribbean. Live specimens of both color morphs were observed during this study along the entire Florida Keys archipelago (Carysfort Reef to Dry Tortugas), the Bahamas, the US Virgin Islands, and Belize. Verified shells have been sighted in many other locations throughout the Caribbean, including St. Lucia, Ominica, and Venezuela. Records from North Carolina (Abbott, 1974) and Brazil (see taxonomic notes below) remain to be verified. Not reported from Bermuda (see Thylacodes bermudensis n. sp., above). Historical Indo-Pacific records for this species (e.g., from Sowerby, 1892 for South Africa) are in error.
Etymology:
The generic name “Cayo” is the Spanish term for a small flat island in the Caribbean and surrounding regions, corresponding to “key” in Florida, “cay” in the Bahamas and “caye” or “cay” in Belize. Here, the term refers to the locations of the four currently known species of this genus, Looe Key in the barrier reef of the Florida Keys and Carrie Bow Cay in the Belizean reef.
Etymology:
The specific name “galbinus” is derived from Latin and means “greenish-yellow”, which refers to the vivid coloration from head to tail.
Literature reference:
Bieler R, Collins TM, Golding R, Granados-Cifuentes C, Healy JM, Rawlings TA, Sierwald P. 2023. Replacing
mechanical protection with colorful faces–twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard,
1770) and Cayo n. gen. (Gastropoda: Vermetidae). PeerJ 11:e15854 http://doi.org/10.7717/peerj.15854
Bieler R, Collins TM, Golding R, Granados-Cifuentes C, Healy JM, Rawlings TA, Sierwald P. 2023. Replacing
mechanical protection with colorful faces–twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard,
1770) and Cayo n. gen. (Gastropoda: Vermetidae). PeerJ 11:e15854 http://doi.org/10.7717/peerj.15854
CC BY 4.0, open access
