Macrophthalmus, Desmarest, 1823

Barnes, R. S. K., 2010, A Review Of The Sentinel And Allied Crabs (Crustacea: Brachyura: Macrophthalmidae), With Particular Reference To The Genus Macrophthalmus, Raffles Bulletin of Zoology 58 (1), pp. 31-49 : 33-37

MACROPHTHALMUS SPECIES (MALES)

1. With stridulatory apparatus; i.e. with short horny ridge on inner margin, or on inner surface near inner margin, of cheliped merus, & lower orbital border with small number of large triangular protuberances along its outer section occupying at least one fifth of that margin ................................................................ 2

– Without such stridulatory apparatus, although lower orbital border may be regularly serrated by granules ...................... 7

2. Carapace and propodus of fourth pereiopod with large spines or spiniform tubercles .......................................... M. dentipes [Very large (up to 80+ mm carapace breadth) inhabitant of soft mudflats around the Arabian Gulf and Arabian Sea. This species was previously widely known under the name M. pectinipes Guérin, 1839 (Holthuis 1995) .]

– Carapace and propodus of penultimate pereiopod without large spines or spiniform tubercles ................................................ 3

3. Inner surface of palm of chela with large spine near articulation with carpus ................................................................ M. erato [Small (<15 mm carapace breadth) inhabitant of stony mudflats or those with mangrove pneumatophores along the northern shores of the eastern Indian Ocean, eastern Malesia and the South China Sea.]

– Inner surface of palm of chela without spines ..................... 4

4. Anterolateral teeth of carapace narrowly separated from each other, their external margins forming a smooth curve ............ .......................................................................... M. tomentosus [Large (up to 35+ mm carapace breadth) Malesian mudflat species occurring from Andaman Sea and Taiwan, through the Philippines to New Caledonia.]

– Anterolateral teeth, or at least external orbital angles and second lateral teeth, separated from each other by wide V- or U-shaped gap, so anterolateral carapace margins appearing jaggedly toothed ................................................................................... 5

5. Inner surface of palm of chela with mat of hair; outer surface of palm and index with row of granules near to and subparallel with lower margin ............................................. M. quadratus [Small (<12 mm carapace breadth) inhabitant of burrows or crevices beneath driftwood, stones or around mangrove pneumatophores in scattered localities from Thailand to Ryukyu Islands, and through Malaysia and Indonesia to New Caledonia.]

– Inner surface of palm of chela without mat of hair; outer surface of palm and index without row of granules near lower margin .................................................................................... 6

6. Greatest carapace breadth across external orbital angles and/or second lateral teeth; index of chela not deflexed .................... ....................................................................... M. boteltobagoe [Very small (<10 mm carapace breadth) inhabitant of holes excavated by e.g. sipunculans in limestone rocks and on gravelly mudflats from Taiwan and the Ryukyu Islands, Hong Kong to New Guinea.]

– Greatest carapace breadth across third lateral teeth; index of chela noticeably deflexed .................................... M. holthuisi [Very small (<10 mm carapace breadth) inhabitant of mud-filled depressions in or around mangrove habitats from the Ryukyu Islands, through Indonesia, to New Guinea.]

7. Ocular peduncles with a thin terminal filament (style) projecting distally beyond the cornea .................................................... 8

– Ocular peduncles without a style .......................................... 9

8. Cornea projecting beyond tip of external orbital angles for only half its length at most; style short ......................... M. graeffei [Medium-sized (up to ca. 25 mm carapace breadth) species known mainly from scattered sublittoral localities from Samoa, New Caledonia and New Guinea to the Red Sea and Arabian Gulf, and now also established in the eastern Mediterranean from Israel to the Aegean Sea.]

– Ocular peduncles extremely elongate so that whole cornea located well beyond carapace lateral margins; style long (subequal to rest of peduncle in length) and segmented ......... ....................................................................... M. ceratophorus [Large (up to 45+ mm carapace breadth) species known only from limited sublittoral material from southern Japan to Taiwan and in Seychelles.]

9. Ocular peduncles extremely elongate, at least half of length of cornea located beyond lateral carapace margins ................ 10

– Cornea not extending beyond lateral margin of carapace for half length of cornea, if at all ............................................. 17

10. Carapace at least twice as broad as long; cheliped merus with long spines on all its margins ......................... M. transversus [Medium-sized (carapace breadth up to ca. 25 mm) species known from soft intertidal sediments around the Bay of Bengal, Andaman Sea and Strait of Malacca.]

– Carapace less than twice as broad as long; cheliped merus with or without granules or tubercles but never with long spines .. .............................................................................................. 11

11. Ocular peduncle projecting beyond lateral carapace margin for less than 25% of its length, so that cornea located beyond lateral carapace margin for no more than its total length ....... .......................................................................... M. ryukyuanus [A very small species (up to 10mm carapace breadth) known only from two specimens dredged from a depth of some 20 m off one of the Ryukyu Islands, Japan.]

– Ocular peduncle projecting beyond lateral carapace margin for at least 25% of its length, so that cornea located beyond lateral carapace margin for more than its own length ................... 12

12. Terminal segments of last pereiopod flattened and paddleshaped; with furrow demarcating the front from remaining carapace .................................................................. M. latipes [Known only from sublittoral material from Seychelles and Maldives; insofar as is known, very small (<10 mm carapace breadth).]

– Terminal segments of last pereiopod not especially flattened nor paddle shaped; no furrow separating the front from remaining carapace ............................................................................... 13

13. With 4 distinct anterolateral carapace teeth; length of cheliped merus> carapace length ............................. M. philippinensis [Small (<12 mm carapace breadth) inhabitant of sublittoral sediments; known only from limited material from the Philippines, Vietnam and Taiwan.]

– With no more than 3 anterolateral carapace teeth; length of cheliped merus <carapace length ....................................... 14

14. Ocular peduncles extend beyond tip of external orbital angle for <36% of their length and for less than a distance equal to twice length of cornea ............................................. M. milloti [Medium-sized (up to 20+ mm carapace breadth) inhabitant of intertidal soft sediments from east Africa to Hawaii and northern Australia.]

– Ocular peduncles extend beyond tip of external orbital angle for> 38% of their length and for more than a distance equal to twice the length of the cornea ........................................ 15

15. With poorly differentiated teeth on cutting margins of chelae; lower margin of index concave; may attain a carapace breadth of> 35mm ...................................................... M. telescopicus [Large inhabitant of mostly subtidal soft sediments from scattered localities throughout the western and central Pacific Ocean.]

– With distinct teeth on cutting edges of chelae; lower margin of index straight or convex; carapace breadth <25 mm ........ 16

16. Lower margin of index of chela straight; second and third anterolateral teeth of carapace spiniform and sharp; branchial regions with soft pubescence ................................. M. serenei [Medium-sized (up to some 25 mm carapace breadth) inhabitant of mostly intertidal soft sediments from scattered localities from the Red Sea and East Africa to southern Japan, the Tuamotus and Lord Howe Island.]

– Lower margin of index of chela with distinct convexity; second and third anterolateral teeth of carapace indistinct and lamellar; branchial regions naked (sublittoral) ............ M. microfylacas [Small (<15mm carapace breadth) inhabitant of coralline sediments from shallow sublittoral localities in Japan.]

17. Carapace with 4 or 5 anterolateral teeth, external orbital angle largest and marking position of greatest carapace breadth; carapace smooth and shiny ................................. M. dentatus [Small (<15 mm carapace breadth) inhabitant of sublittoral sites scattered through the South China Sea from Hainan Island to Timor.]

– Carapace with 2–4 anterolateral teeth, if 4 present then carapace surface heavily granular and external orbital angles not marking position of greatest carapace breadth .................................. 18

18. Central region of epistome with a protuberance ................ 19

– Central region of epistome straight or with a concavity .... 31

19. Inner surface of palm of chelae with at least 1 spine near articulation with carpus ....................................................... 20

– Inner surface of palm of chelae without spines .................. 27

20. Merus of cheliped with granules or tubercles on its margins, but without spines except, in some, around distal angle of inner margin .................................................................................. 21

– Merus of cheliped with spines on some or all of its margins, not counting any around distal angle of inner margin ....... 22

21. External orbital angle very small and projecting less than second anterolateral tooth ............................................ M. grandidieri [Large (up to 35 mm carapace breadth) inhabitant of muddy sandflats and seagrasses along eastern coast of Africa from South Africa to Gulf of Oman.]

– External orbital angle elongate and more or less projecting equally with second anterolateral tooth .................. M. brevis [Medium-sized (up to 30 mm carapace breadth) inhabitant of firm muddy sandflats from Bay of Bengal to Ryukyu Islands and Malesia.]

22. Cutting margin of index of chelae with 2 teeth, one near tip; external orbital angle and second anterolateral tooth separated by wide incision .................................................................. 23

– Index of chelae with 1 tooth on its cutting margin, without one near tip; external orbital angle and second anterolateral tooth separated by a narrow incision ........................................... 24

23. Lines of tubercular granules on branchial regions hook-shaped; dactylus of chelae with mat of hair over whole or almost whole of inner surface ................................................ M. laevimanus [Medium-sized (carapace breadth> 25 mm) inhabitant of muddy sandflats around the Bay of Bengal and Strait of Malacca.]

– Granules on branchial regions in clumps or lines but not in hook-shaped rows; inner surface of dactylus of chelae without mat of hair ................................................................ M. laevis [Large (carapace breadth> 30 mm) inhabitant of muddy sandflats in the Arabian Gulf and Arabian Sea.]

24. Second anterolateral tooth projecting markedly beyond external orbital angle ......................................................................... 25

– External orbital angle projecting as far as second anterolateral tooth ..................................................................................... 26

25. External orbital angle projecting <half as far as second anterolateral tooth; tip of cornea projecting distinctly beyond tip of second anterolateral tooth; index of chela with distinct quadrangular tooth on cutting margin ... M. sulcatus sulcatus [Medium-sized (up to 30mm carapace breadth) inhabitant of muddy sandflats in Arabian Gulf and Arabian Sea.]

– External orbital angle projecting> half as far as second anterolateral tooth; tip of cornea not projecting beyond tip of second anterolateral tooth; index of chela with indistinct, very low to slightly dome-shaped tooth on cutting margin ............. .......................................................... M. sulcatus malaccensis [Medium-sized (up to 30 mm carapace breadth) inhabitant of muddy sandflats in the Bay of Bengal and western Malesia, where it replaces M. sulcatus sulcatus .]

26. Outer surface of palm of chela with large hemispherical tubercles over upper half ............................................... M. abbreviatus [Large (up to 35+ mm carapace breadth) inhabitant of muddy sandflats from South China Sea to southern coasts of Korea and Japan. Before 1981, M. abbreviatus was widely known under the name M. dilatatus (de Haan, 1835) .]

– Outer surface of palm of chela finely granular, without hemispherical tubercles over upper half ............ M. crassipes [Large (carapace breadth> 35 mm) inhabitant of muddy sandflats from northern and eastern Australia to the Carolines and Hainan Island.]

27. External orbital angle larger than and projecting beyond second anterolateral tooth; carapace breadth twice carapace length; branchial regions with clumps of granules ......................... 28

– External orbital angle smaller than and not projecting as far as second anterolateral tooth; carapace breadth 1.5 × carapace length; branchial regions without clumps of granules (although rows of granules may be present) ....................................... 30

28. Chelae large & elongate (equivalent to those of other species) with clearly differentiated teeth on cutting margins of fingers ............................................................................. M. convexus [Large (carapace breadth up to 35 mm) inhabitant of high-level sand- or mudflats from the Andaman Sea and Ryukyu Islands, through Malesia to Hawaii, the Tuamotu Archipelago and Queensland.]

– Chelae small and feeble (as in female Macrophthalmus ) with poorly differentiated or no teeth ......................................... 29

29. Index of male chela with poorly differentiated, long low tooth along proximal half of cutting margin; tip of male first pleopod prolonged ........................................................ M. parvimanus [Medium-sized (carapace breadth up to 30 mm) inhabitant of mudflats at scattered localities from East Africa through the Indian Ocean and Malesia as far east as the Solomon Islands.]

– Index of male chela with small, quadrangular tooth in centre of cutting margin; tip of male first pleopod truncated ............ ........................................................................ M. consobrinus [Medium-sized (carapace breadth up to 30 mm) inhabitant of river-mouth mudflats in the Gambier Islands in the Central Pacific Ocean.]

30. Index of chela without a tooth on cutting margin; outer surface of palm and index of chela with longitudinal ridge near to and subparallel with lower margin ............................. M. latifrons [Medium to large (up to 30+ mm carapace breadth) mudflat species restricted to south-eastern Australia.]

– Index of chela with a large, wedge-shaped tooth on cutting margin; outer surface of chela without longitudinal ridge near lower margin ............................................................ M. teschi [Medium-sized (up to 25 mm carapace breadth) inhabitant of mudflats through western Malesia.]

31. Merus and ischium of external maxilliped subequal (length of ischium <1.4×length of merus); front broad (its breadth across base of ocular peduncles> 20% of distance between tips of external orbital angles) ........................................................ 32

– Merus of external maxilliped distinctly smaller than ischium (length of ischium> 1.5 × length of merus); front narrow (its breadth across bases of ocular peduncles <18% of distance between tips of external orbital angles) .............................. 34

32. Cheliped carpus with large pointed protuberance on upper margin; medium to large-sized (up to 30+ mm carapace breadth); restricted to New Zealand..................................... M. hirtipes [Associated with low-tidal level sandy mudflats and with the seagrass Zostera sp. in estuaries and lagoons; often relatively nomadic and not occupying permanent burrows.]

– Cheliped carpus without protuberance on upper margin; small (<15 mm carapace breadth); not occurring in New Zealand. .............................................................................................. 33

33. Carapace surface granular ....................................... M. boscii [Widespread species usually occurring under stones, in rock crevices or in sandy tide-pools at high tidal levels in rocky areas from eastern shores of Africa to Japan, Australia and Fiji.]

– Carapace surface without granules ................ M. punctulatus [Inhabitant of high-shore mud and stony areas, restricted to south-western and eastern Australia.]

34. Inner surface of palm of chelae without mat of hair .......... 35

– Inner surface of palm of chelae with mat of hair concealing at least part of surface ............................................................. 38

35. Dactylus of chela with very large tooth near centre of cutting margin; inner surface of palm of chelae with longitudinal row of hairs near to and subparallel with upper margin ................ ................................................................................ M. barnesi [Known only from limited material from depths of 10+ m from Taiwan, Philippines, New Guinea and Seychelles; existing material probably of no more than young adults, <25 mm carapace breadth.]

– Dactylus of chela with tooth near base of cutting margin; inner surface of palm of chelae without row of hairs as above .. 36

36. Branchial regions of carapace without distinct longitudinal rows of granules; carapace margins smoothly converging anteriorly ...................................................... M. abercrombiei [Only five specimens of this species currently known, from the shores of the Torres Strait and Gulf of Carpentaria; existing material obtained from the shallow sublittoral and (though adult) is <20 mm carapace breadth.]

– Branchial regions of carapace with distinct longitudinal rows of granules; carapace margins not smoothly converging anteriorly ............................................................................. 37

37. External orbital angle rectangular, not projecting as far as second lateral tooth and not directed anteriorly ............ M. japonicus [Large (up to 40 mm carapace breadth) inhabitant of mudflats from Japan and Korea to Singapore. Tai & Song (1984) divided this species into two subspecies but stated that ‘In many areas, there are intermediate forms. Absolute separation of these forms is often impossible.’: for these reasons, this proposed subdivision is not followed here.]

– External orbital angle pointed, directed partly anteriorly and projecting as far as second lateral tooth (sibling species of the above, differentiated more behaviourally than morphologically) .................................................... M. banzai [Medium-sized (up to 30 mm carapace breadth) inhabitant of mudflats from Japan and Korea to Taiwan and south coast of China.]

38. Carapace with concave granular row on each protogastric region ................................................................... M. definitus [Large (exceeding 30 mm carapace breadth) inhabitant of mudflats from the Andaman Sea and around the western rim of the Pacific Ocean from the Ryukyu Islands to the Solomon Isles and Queensland.]

– Carapace without concave granular rows on protogastric regions ................................................................................. 39

39. Greatest carapace breadth across external orbital angles, where breadth> 1.7 times carapace length; outer surface of palm and index of chela with longitudinal ridge near lower margins; index deflexed ................................................................. M. setosus [Large (up to 40mm carapace breadth) mud-burrowing species restricted to east coast of Australia.]

– Carapace broadest posterior to external orbital angles, where breadth <1.7 times carapace length; if longitudinal ridge present on outer surface of palm and index of chela then index not deflexed ............................................................................... 40

40. Whole inner surface of palm of chela obscured by mat of hair ....................................................................................... 41

– At least part of inner surface of palm of chela free from thick hair ....................................................................................... 42

41. Central region of epistome straight; index with large wedgeshaped tooth on its cutting margin .......................... M. teschi [Medium-sized (up to 25 mm carapace breadth) inhabitant of mudflats through the Bay of Bengal and western Malesia.]

– Central region of epistome with distinct concavity; index with low poorly-differentiated tooth on cutting margin .................. ............................................................................ M. depressus [Large (up to 35+ mm carapace breadth) inhabitant of mudflats through the western Indian Ocean.]

42. Inner surface of palm of chela with longitudinal band of hair along upper half; index of chela deflexed ....... M. pistrosinus [Medium to large-sized (carapace breadth>30+ mm) inhabitant of sandy mudflats in Shark Bay , Western Australia.]

– Hair on inner surface of palm of chela not as above; index of chela scarcely or not at all deflexed ................................... 43

43. Outer surface of index of chela with longitudinal granule-capped ridge running along centre, subparallel with lower margin .... ................................................................................ M. crinitus [Medium-sized (up to 25 mm carapace breadth) inhabitant of mudflats scattered from the Gulf of Aden, through Malesia to southern Japan.]

– Outer surface of index of chela without longitudinal ridge .... .............................................................................................. 44

44. Cutting margin of index of chela with a differentiated tooth; carapace breadth <40 mm .................................................. 45

– Cutting margin of index of chela without a differentiated tooth, except in individuals of> 45 mm carapace breadth .......... 47

45. Carapace with thick hair laterally and longitudinal rows of hairs on branchial regions ....................................... M. darwinensis [Little-known inhabitant of mangrove-associated mudflats in northern Australia and New Caledonia, all existing material <15 mm carapace breadth.]

– Carapace without thick lateral hair and without longitudinal rows of hairs branchially ..................................................... 46

46. Cutting margin of index of chela with distinct, tall, prominent tooth .......................................................... M. leptophthalmus [Known for certain only from northern shores of the Bay of Bengal; limited existing material all <25mm carapace breadth.]

– Cutting margin of index of chela with indistinct, long, low, crenulated tooth .................................................. M. dagohoyi [Small (<20 mm carapace breadth) inhabitant of shallow subtidal organic muds in Bohol, Philippines.]

47. Carapace smooth to naked eye; inner surface of dactylus of chela without mat of hair .................................... M. pacificus [Medium-sized (up to 25 mm carapace breadth) inhabitant of (often mangrove-associated) mudflats around the western Pacific rim from Korea to northern Australia and Samoa, and on both sides of the Malay-Thai peninsula (and possibly India).]

– Carapace surface heavily granular; inner surface of dactylus of chela heavily haired ............................................ M. latreillei [Very large (up to 60+ mm carapace breadth) inhabitant of low shore and subtidal muds from Mozambique to Japan and Australasia.]