Hermit crabs Calcinus of the world (Anomura: Diogenidae)


Character List


#2. <References>/

Shield and cephalic appendages

#3. Ocular scale/
1. with a single terminal spine/
2. with several terminal spines/

Unusual armament sometimes observed (e.g. usually 1 spine in Calcinus latens, but up to 3 spines in few abnormal specimens)

#4. <Size>/
1. small species, shield length does not exceed 2–3 mm/
2. species of normal size, i.e. shield length often greater than 2–3 mm/

The only remarkably small species within the genus are Calcinus revi, C. areolatus, and C. paradoxus

#5. Anterodorsal plate of branchiostegite/
1. with row of spinules on dorsal margin/
2. unarmed on dorsal margin or with 1–2 spinules subproximally/

Character recently introduced by Asakura & Tachikawa (2000) to separate C. revi and C. kurozumii. Not mentioned in descriptions of other species. (This plate situated laterally on the head, just under dorsal shield).

Chelipeds (P1)

#6. Upper margin of right chela/
1. smooth/
2. tuberculated or spinous/

Only 2 Indo-West Pacific species (out of 34) have a smooth upper margin on this chela. This character is also present in the 3 eastern Pacific species (C. californiensis, C. explorator, C. obscurus) and 1 western Atlantic species (C. tibicen).

#7. Outer face of left palm/
1. regularly convex/
2. with longitudinal depression(s)/
3. with 2–3 subcircular depressions/

Most of the species (38 out of 42) have the outer face of left palm regularly convex.

#8. Fingers of left chela/
1. with pearl-like tubercles on outer face/
2. with square-like tubercles on outer face/

This character used to separate C. elegans and C. orchidae. Not known for other species.

Ambulatory legs (P2-P3)

#9. Dorsolateral margins of P3 propodi/
1. slightly carinated/
2. rounded/

Dorsal margin of P3 propodus is slightly carinated only in Calcinus obscurus, C. seurati, and C. tibicen. It is rounded in all other Indo-West Pacific Calcinus.

#10. Dactyl of P3 <relative length>/
1. subequal to propodus or slightly shorter/
2. distinctly shorter than propodus/

Not a very good character because of large intraspecific variations and difficulty to accurately measure the length of dactyl and propodus. However, in some species, such as C. guamensis, dactyl seems to be always much shorter than the propodus (i.e. 0.5–0.7 times as long as propodus, versus 0.6–1.1 for species with dactyl subequal or slightly shorter to propodus).

#11. Distal pilosity of P3/
1. weak, similar to distal P2/
2. more prononced than on distal P2, but not forming a dense brush of setae/
3. dense, forming a brush of setae/

Setation of distal P3 is not always easy to appreciate due intraspecific variations. Rather arbitrarily 3 states are defined here. In case of doubt try succesfully states 1–2, or states 2–3.

#12. Ventral margin of P3 dactyl <armament>/
1. with less than 10 spines/
2. with 10 spines or more/

Ventral margin of P3 dactyl has more than 10 spines only in C. vanninii.

Armament of telson

#13. Left lobe of telson <armament>/
1. unarmed/
2. with a single spine/
3. with several spines disposed on posterior margin only/
4. with several spines disposed on posterior and lateral margins/

Spines disposed on margins of left and right lobes of telson are sometimes difficult to observe. Calcinus tropidomanus would be the single species with an unarmed telson. Among the remaining species, unusual armament are sometimes observed, i.e. 0–2 spines for species that usually have only one spine on each lobe, or a single spine for species that usually have several spines on each lobe.

#14. Right lobe <of telson; armament>/
1. unarmed/
2. with a single spine/
3. with several spines/


#15. Shield <color>/
1. orange/
2. white or cream/
3. green-olive/
4. pale violet/
5. purple-brown/
6. pale brown to red brown/
7. with a patch on disal half/

Color of the shield quite variable and difficult to appreciate. Not a strong character.

#16. Ocular peduncle <color pattern>/
1. uniformly colored/
2. multicolored with narrow ring close to cornea/
3. multicolored without narrow ring close to cornea/
4. with spots/

Terminal ring only 1/4 or less of peduncular length. It is often white but can also be cream, blue, or darker. Only two species have spots on the ocular peduncle (Calcinus sp. nov. Poupin, in prep. and C. tubularis)

#17. Detailed coloration of ocular peduncle:/
1. green-olive/
2. pink-gray/
3. white to pale orange/
4. brown with pink tinge proximally, narrow cream ring close to cornea/
5. pale-orange to red-orange with white ring close to cornea/
6. brown, burgundy or purple, with narrow white ring close to cornea/
7. black on proximal 3/4 (including a small blue area); blue on distal 1/4/
8. cream, with large black patch or ring/
9. white, gradually turning to blue on distal half/
10. bright blue, with narrow dark ring proximally/
11. proximally dark red-orange, grading to cream distally/
12. proximally deep brown grading to paler distally/
13. proximally pink, grading to pale pink or white distally/
14. proximal 3/4 dark brown, distal 1/4 blue, with paler ring close to cornea/
15. proximally pink, medially orange, narrow white ring close to cornea/
16. dark narrow ring proximally, basal 2/3 green-olive, distal 1/3 white/
17. dark brown proximally, distal half blue, narrow dark ring close to cornea/
18. orange narrow basal ring, sky-blue ring on proximal 1/3, distal 2/3 orange/
19. brown proximally, distal 1/4 and latero-ventral surfaces orange, narrow blue ring close to cornea/
20. bright orange with white spots and distal white ring close to cornea/
21. basal narrow orange ring, gray-blue band proximally, gradually turning to orange distally/

Usually a good character to separate the Calcinus species, although unusual coloration are not uncommon. For example in Calcinus guamensis ocular peduncle is usually gray with a large black patch. This patch is however of variable extension, and sometimes is totally missing. Color tones are also subject to variation (white to gray; pale brown to dark brown ...).

#18. Distal antennular peduncle <color>/
1. black/
2. white to cream/
3. white-violet/
4. brown/
5. blue or dark blue/
6. purple or burgundy/
7. yellow-orange/
8. dark green/

Ultimate segment of antennular peduncle can have different colors. For example, in C. nitidus, distal half of ultimate segment is yellow-orange and proximal half is blue-black. In that case enter color of distal half only (i.e. yellow-orange).

#19. Distal antennal peduncle <color>/
1. black/
2. white/
3. blue/
4. brown/
5. green/
6. burgundy/
7. yellow-orange/

In some species, distal segment of antennal peduncle has a coloration different than proximal segments. For example, in Calcinus guamensis distal segment is black and proximal segments are cream. In that case, enter coloration of distal segment (i.e. black).

#20. Chela <outer face, color pattern>/
1. uniformly colored, often grading to paler distally/
2. with submedian patch or spot on outer face/
3. with red spot at base of dactyl/
4. with brown, dark orange or red patches/
5. with several spots/

#21. Ambulatory legs (P2 & P3) <color pattern>/
1. without ring(s) or spot(s)/
2. with spots/
3. with ring(s)/
4. with longitudinal bands/
5. with spots and ring(s)/
6. with ring(s) and longitudinal bands/

White or paler areas and tip of dactyls (and propodi) are not considered as 'rings'. For example, legs of C. dapsiles are pink to purple brown with white areas on distal dactyls and propodi. In that case choose state 1: without ring(s) or spot(s).


#22. <Habitat>/
1. intertidal rocky shores/
2. facultative associates of corals (e.g. Pocillopora, Acropora)/
3. shallow-waters <1–20 m>/
4. deep <20–150 m>/

Geographic distribution

#23. <Geographic distribution>/

#24. <Worldwide Distribution>/
1. Indo-West Pacific/
2. East Pacific/
3. West Atlantic/
4. East Atlantic/


#25. <Remarks>/

Cite this publication as: J. Poupin (2003, Internet). - Hermit crabs Calcinus of the world (Anomura, Diogenidae). Descriptions, Illustrations, Identification, and Information Retrieval, using the DELTA format.