Majids: Crabs with Stylish Hats

Aggregation of large spider crabs Leptomithrax gaimardii, photographed by Peter Fuller.

The subjects of today's post, the Majidae, commonly go by the names of spider crabs or decorator crabs. The first of those names might sound like some people's ultimate nightmare, but I doubt that anyone could complain about the latter. Majids are characterised by having a carapace longer than wide, often with a covering of bristly hooked setae and relatively long legs (hence the name 'spider crab'). They get their alternate name of 'decorator crab' from the habit of many species of using the aforementioned hooked setae to attach algae and other bits of organic matter to themselves. The primary purpose of this adornment is to provide camouflage, and a decorated spider crab can be inordinately difficult to see when not moving. A secondary use of the crab's organic covering, however, is that they will also feed on material from it in times of need*.

*It is perhaps fortunate for Gaga that the question was never raised of her doing the same.

Triangle crab Eurynolambrus australis, from here.

The circumscription of the Majidae is more than a little fluid: at times, it has been used to include all the spider crabs of the superfamily Majoidea, but the more common practice these days is to divide the majoids between a number of families. Unfortunately, authors have disagreed about what those families should be. Ng et al. (2008) united the subfamilies Majinae and Mithracinae within the Majidae on the basis of shared features such as a well-developed protective orbit around the eyestalk. However, a direct relationship between majines and mithracines is not currently supported by molecular (Hultgren & Stachowicz 2008) or larval (Marques & Pohle 1998) data, though both these latter data sources are themselves limited by the relatively small number of studied taxa. Two smaller subfamilies included by Ng et al. (2008) in the Majidae, the Planoterginae and the isolated species Eurynolambrus australis, have not yet been analysed molecularly. Eurynolambrus australis is a particularly unusual little majid, so much so that it looks more like a parthenopid than a majid. Eurynolambrus also lacks hooked setae and so does not decorate itself; instead, it relies for disguise on its resemblance in colour to the coralline algae amongst which it lives (and on which it primarily feeds, though it is omnivorous overall—Woods & McLay 1996). Ng et al. placed it in the Majidae nevertheless owing to the resemblance of its larval stages to those of Majinae.

Channel clinging crab Mithrax spinosissimus, photographed by Nick Hobgood.

The two main subfamilies, the Majinae and Mithracinae, can be distinguished by the development of the orbit around the eyestalk. In the Mithracinae, the orbit is broadly expanded both above and below (with the lower margin formed from an expansion of the basal antennal segment), almost entirely enclosing the eyestalk and giving the front of the carapace a distinctly broad appearance in dorsal view. In the Majinae, the basal antennal segment is not expanded to form an underside to the orbit, so the eyestalks are contained from above only (Davie 2002). The Majinae are most diverse in the Indo-West Pacific, with only a handful of genera found outside this region. Some majines are quite large: the Australian Leptomithrax gaimardii reaches a leg-span of about 70 cm. The Mithracinae are more pantropical inhabitants of shallow water reefs.

REFERENCES

Davie, P. J. F. 2002. Zoological Catalogue of Australia vol. 19.3B. Crustacea: Malacostraca: Eucarida (part 2): Decapoda—Anomura, Brachyura. CSIRO Publishing: Collingwood (Australia).

Hultgren, K. M., & J. J. Stachowicz. 2008. Molecular phylogeny of the brachyuran crab superfamily Majoidea indicates close congruence with trees based on larval morphology. Molecular Phylogenetics and Evolution 48: 986-996.

Marques, F., & G. Pohle. 1998. The use of structural reduction in phylogenetic reconstruction of decapods and a phylogenetic hypothesis for 15 genera of Majidae: testing previous larval hypotheses and assumptions. Invertebrate Reproduction and Development 33 (2-3): 241-262.

Ng, P. K. L., D. Guinot & P. J. F. Davie. 2008. Systema brachyurorum: part I. An annotated checklist of extant brachyuran crabs of the world. Raffles Bulletin of Zoology 17: 1-286.

Woods, C. M. C., & C. L. McLay. 1996. Diet and cryptic colouration of the crab Eurynolambrus australis (Brachyura: Majidae) at Kaikoura, New Zealand. Crustacean Research 25: 34-43.

The Grapsidae: From Sea to Shore

Sally Lightfoot, Grapsus grapsus, photographed by Victor Burolla. The vernacular name refers to their walking on the points of their legs.

In a post from back in 2008, I wrote about the group of crabs known as the Grapsoidea. As described in that post, the classification of the Grapsoidea has been shuffled in recent years, and the subjects of today's post, the Grapsidae, would have previously been classed as the Grapsinae within a larger Grapsidae. The more restricted Grapsidae has been supported by numerous recent analyses, both morphological (Karasawa & Kato 2001) and molecular (Schubart et al. 2000). Morphologically, grapsids are united by having an expanded anterolateral corner to the merus* of the third maxilliped, oblique ridges on the lateral surfaces of the meri of the pereiopods, and (in many species) oblique ridges on the dorsum of the carapace (Karasawa & Kato 2001). Studies of the larvae of grapsids have also identified distinctive characters by which grapsid larvae can be distinguished from those of other grapsoids (Cuesta & Schubart 1999).

*The merus is the first elongate segment of crustacean appendages, corresponding to the femur of other arthropods. The maxillipeds are feeding appendages; the pereiopods are the walking legs.

The Columbus crab Planes major, photographed by Denis Riek. This species comes in a wide range of colours, from brown to blue to almost white; the page linked to shows a number of examples.

Most grapsids are intertidal shore-dwellers, but there are some exceptions. Species of the genus Planes, known as Columbus crabs, are small oceanic forms. They live on objects floating in the open water: seaweed, driftwood and other debris, or even other animals such as by-the-wind sailors or turtles (Spivak & Bas 1999). Columbus crabs differ from other grapsids in having flattened pereiopod meri for swimming, and two of the three species lack oblique ridges on the carapace. The aforementioned phylogenetic analyses also agree in placing Planes as the sister group to other grapsids analysed.

Geograpsus grayi, from here.

Also distinctive are species of the genus Geograpsus, which are one of a number of crab groups to have developed a terrestrial lifestyle, found on islands of the Indo-Pacific and Atlantic. In the Indo-Pacific G. crinipes, it has been shown that dense bunches of setae between the second and third walking legs are long enough to contact the ground when the animal sits back on its haunches (McLay & Ryan 1990). Water on the surface of the ground is drawn up through the setae by capillary action and conducted into the gill chamber, keeping the gills damp and functioning. Terrestrial Geograpsus retain marine larvae as do many other terrestrial crabs; the larval development has been studied for the eastern Pacific G. lividus which goes through nine larval stages (eight zoeae and the megalopa) over the period of two months (Cuesta et al. 2011). This happens to be the longest developmental pathway of any known crab: the previous confirmed maximum was eight larval stages.

REFERENCES

Cuesta, J. A., G. Guerao, C. D. Schubart & K. Anger. 2011. Morphology and growth of the larval stages of Geograpsus lividus (Crustacea, Brachyura), with the descriptions of new larval characters for the Grapsidae and an undescribed setation pattern in extended developments. Acta Zoologica 92 (3): 225-240.

Cuesta, J. A., & C. D. Schubart. 1999. First zoeal stages of Geograpsus lividus and Goniopsis pulchra from Panama confirm consistent larval characters for the subfamily Grapsinae (Crustacea: Brachyura: Grapsidae). Ophelia 51 (3): 163-176.

Karasawa, H., & H. Kato. 2001. The systematic status of the genus Miosesarma Karasawa, 1989 with a phylogenetic analysis within the family Grapsidae and a review of fossil records (Crustacea: Decapoda: Brachyura). Paleontological Research 5 (4): 259-275.

McLay, C. L., & P. A. Ryan. 1990. The terrestrial crabs Sesarma (Sesarmops) impressum and Geograpsus crinipes (Brachyura, Grapsidae, Sesarminae) recorded from the Fiji Is. Journal of the Royal Society of New Zealand 20 (1): 107-118.

Schubart, C. D., J. A. Cuesta, R. Diesel & D. L. Felder. 2000. Molecular phylogeny, taxonomy, and evolution of nonmarine lineages within the American grapsoid crabs (Crustacea: Brachyura). Molecular Phylogenetics and Evolution 15 (2): 179-190.

Spivak, E. D., & C. C. Bas. 1999. First finding of the pelagic crab Planes marinus (Decapoda: Grapsidae) in the southwestern Atlantic. Journal of Crustacean Biology 19 (1): 72-76.

Crabs That Cannot Scratch Their Heads (Taxon of the Week: Parthenopidae)

An elbow crab amongst seaweed, showing both its long reach and well-developed camouflage. Photo from Wild Shores of Singapore.

Lift up one arm, and bend your elbow. Reach with your fingers to a point on your back, between your shoulder-blades. Scratch. Not only will that work wonders for any annoying tingle that you might have been feeling, but you have just demonstrated your superior flexibility to an elbow crab.

Crabs of the family Parthenopidae are found in tropical and subtropical coral reefs and shelly sea bottoms. Most species have bodies that are roughly triangular in shape, and often highly ornamented with lumps, bumps and spines (this ornamentation makes them very difficult to see among coral and rocks; it also encourages the growth of algae and other camouflaging organisms on the crab). They also usually have very large and long chelipeds (pincers), which make it easy to see how they got the name of 'elbow crabs'. The merus (the 'upper arm' part of the cheliped) is proportionally much longer than in many other crab families, giving parthenopids a real gorilla-ish look (I found one website that labelled a parthenopid of the genus Daldorfia as the "King Kong crab"). Despite their extraordinary size and length, however, the range of mobility of an elbow crab's chelipeds is limited, hence the point about back-scratching above. An elbow crab cannot reach the middle part of the top of its carapace.


Furtipodia petrosa, a rather adorable-looking parthenopid from Guam that resembles a sponge-covered rock. Furtipodia is also one of a number of parthenopids in which the walking legs are hidden by the carapace, improving the disguise. Photo from here.

This lack of cheliped mobility is one of the features distinguishing members of the Parthenopidae from the spider crabs of the Majidae, which have a broadly similar superficial appearance (Ng & McLay, 2003). Other distinct features of the family include the fusion of the third to fifth segments of the male abdomen* (Tan & Ng, 2007); also, while female majids have a high-domed abdomen that forms an entirely enclosed brood chamber for her eggs, the parthenopid female's abdomen does not entirely seal the eggs away from the outside world. The similar adult appearance of Parthenopidae and Majidae, with their triangular bodies and pointed snouts, lead most early authors to regard them as closely related, but the similarities are now thought to be convergent. The larvae of parthenopids are more similar to those of other families than majids (Yang, 1971), while phylogenetic studies do not support their association (Brösing, 2008).


Normal parthenopids are remarkable enough, but Lambrachaeus ramifer looks like something out of a Japanese video game (making it appropriate that I found this photo on a Japanese website). This individual is a female carrying eggs - they're the orange mass on her underside.

The subfamilial classification of Parthenopidae was reviewed by Tan & Ng (2007) who recognised only two subfamilies of elbow crabs, the Parthenopinae and Daldorfiinae (earlier authors recognised more - some have been moved to other families, others have been synonymised). The two subfamilies are distinguished by only a single character, the relative length of the antennal segments, and a more formal analysis is still required to test their distinction. A separate subfamily had previously been recognised for the very distinctive Indo-Pacific species Lambrachaeus ramifer which has the front of the carapace extended forward into a long neck (Ng & McLay, 2003), but Tan & Ng (2007) placed this species in Parthenopinae, noting that it had been separated on the basis of its own peculiar autapomorphies rather than by lack of the features of other subfamilies.

*If you don't know where to find the abdomen of a crab, then look at the underside of one the next time you're able to. The much reduced abdomen is turned forwards and held on the underside of the cephalothorax. In males, it is a small, narrow segmented strip. In females, it is much larger and broader, and is used to hold her eggs.

REFERENCES

Brösing, A. 2008. A reconstruction of an evolutionary scenario for the Brachyura (Crustacea) in the context of the Cretaceous-Tertiary boundary. Crustaceana 81 (3): 271-287.

Ng, P. K. L., & C. L. McLay. 2003. On the systematic position of Lambrachaeus Alcock, 1895 (Brachyura, Parthenopidae). Crustaceana 76 (8): 897-915.

Tan, S. H., & P. K. L. Ng. 2007. Descriptions of new genera from the subfamily Parthenopinae (Crustacea: Decapoda: Brachyura: Parthenopidae). Raffles Bulletin of Zoology Supplement 16: 95-119.

Yang, W. T. 1971. The larval and postlarval development of Parthenope serrata reared in the laboratory and the systematic position of the Parthenopinae (Crustacea, Brachyura). Biological Bulletin 140: 166-189.

Kneel before the Shrimp Queen

A pair of commensal snapping shrimps Synalpheus on their host crinoid. Photo from here.

As a child, snapping shrimp were one of my favourite things to find under rocks at the beach. The characteristic bang made by their enlarged pincer snapping shut never fails to fascinate. This 'snap' can often be heard for some distance, and the explosive force generated by it can be strong enough to stun small animals that get too close. Snapping shrimp form the family Alpheidae, and Synalpheus, with well over a hundred described species and counting, is one of the larger genera in that family.

Synapheus has a pantropically-centred distribution. Though it seems to be more abundant in the east Pacific and Atlantic Oceans than in the Indian, I'd be a little suspicious of the role collection bias has played in this. The various species of Synalpheus are retiring animals by nature, and sequester themselves in cryptic habitats, all the better to defend themselves against would-be intruders with that impressive claw. The best-known species of Synalpheus live within the body cavity of other animals such as sponges or corals, and a few species live on the underside of crinoids (VandenSpiegel et al., 1998). It is debatable to what extent the relationship between Synalpheus and their host should be regarded as commensal (with the shrimp feeding on food particles brought in by the host) or parasitic (with the shrimp feeding directly on the host tissue), as evidence exists for Synalpheus individuals doing both. Dardeau (1984) suggested that Synalpheus species could be divided into three broad levels of host association, from group I (generally free-living or opportunistically commensal species with very low or no host specificity) to group III (invariably commensal species with high host specificity). Many commensal-living individuals will do so as male-female pairs, aggressively excluding any conspecific competitors that attempt to settle in their home. Other species may be more tolerant, with numerous individuals in a single host.


Colonial Synalpheus on a sponge. Photo from Biology-Blog - this would appear to be a laboratory colony, with dabs of identifying paint on the individuals.

The most remarkable association of all, though, is found in certain species of what is called the Gambarelloides species group (after the species Synalpheus gambarelloides). The Gambarelloides group is a morphologically distinct association of species (most notably, they have a dense brush of setae on the smaller pincer) that was separated by Ríos & Duffy (2007) from the remainder of Synalpheus as their new genus Zuzalpheus. This separation was debated by Anker & De Grave (2008), but the complaint does not seem to concern the integrity of 'Zuzalpheus' itself, but that of the remainder of Synalpheus if the Gambarelloides group species are not included. Some of the group III sponge-dwelling species in this group (using Dardeau's grouping) form large colonies with hundreds of individuals in a single sponge. It was only recognised as recently as 1996 (Duffy et al., 2000, 2002) that these Synalpheus colonies actually qualify as eusocial, in the manner of bees and ants, representing the only known occurrence of eusociality outside insects other than mole rats. Reproduction within the colony is conducted by a single queen, though it remains unknown how the queen of a colony is established, and how she prevents other members of the colony becoming reproductive. The sexual ratio of the remainder of the colony remains unknown, as males are indistinguishable from non-egg-bearing females (and gender may be environmentally-determined rather than genetic), but the colony does include a number of larger individuals (called "males" by Duffy et al., 2002) that seem to be primarily responsible for the colony's defense, moving about the sponge more than the smaller juveniles seemingly on the lookout for intruders. The queen plays little part in defending the colony, and in one eusocial species, Synalpheus filidigitus, she lacks the large snapping pincer of the other individuals (Duffy et al., 2002). It is not yet established how fertilisation of the queen occurs, but allozyme analysis suggests that there may be only a single reproductive male in the colony (Duffy et al., 2000).

Phylogenetic analysis of the Gambarelloides group by Duffy et al. (2000) found that eusociality has evolved at least three times within the group. They suggested that it may have evolved as a response to severe competition for habitat. Where eusocial shrimps are found, almost all suitable hosts are home to a colony, so unoccupied homes are few and far between (offhand, how new colonies do become established is yet another unknown factor - eusocial Synalpheus lack a planktonic larval stage, so hatching offspring remain in the parent colony). A colonial group may be more effective at defending their host against would-be usurpers than a solitary individual or pair would be. With the large "soldiers" defending her, the queen is able to spend more time feeding and reproducing, safely hidden within the sponge.

REFERENCES

Anker, A., & S. De Grave. 2008. Zuzalpheus Ríos and Duffy, 2007: a junior synonym of Synalpheus Bate, 1888 (Decapoda: Alpheidae). Journal of Crustacean Biology 28 (4): 735-740.

Dardeau, M. R. 1984. Synalpheus shrimps (Crustacea: Decapoda: Alpheidae). I. The Gambarelloides group, with a description of a new species. Memoirs of the Hourglass Cruises 7 (2): 1-125.

Duffy, J. E., C. L. Morrison & K. S. Macdonald. 2002. Colony defense and behavioral differentiation in the eusocial shrimp Synalpheus regalis. Behav. Ecol. Sociobiol. 51: 488-495.

Duffy, J. E., C. L. Morrison & R. Ríos. 2000. Multiple origins of eusociality among sponge-dwelling shrimps (Synalpheus). Evolution 54 (2): 503-516.

Ríos, R., & J. E. Duffy. 2007. A review of the sponge-dwelling snapping shrimp from Carrie Bow Cay, Belize, with description of Zuzalpheus, new genus, and six new species (Crustacea: Decapoda: Alpheidae). Zootaxa 1602: 1-89.

VandenSpiegel, D., I. Eeckhaut & M. Jangoux. 1998. Host selection by Synalpheus stimpsoni (De Man), an ectosymbiotic shrimp of comatulid crinoids, inferred by a field survey and laboratory experiments. Journal of Experimental Marine Biology and Ecology 225 (2): 185-196.

Getting Crabs

The purple shore crab Leptograpsus variegatus of the southern subtropical Indo-Pacific ocean. Photo by Benjamint444.

When I was but an ickle lad, and my family would camp over Christmas at the beach by the estuary beneath the house of my great-grandparents, I would spend many hours turning over rocks and catching the crabs that I found underneath them. The most common variety I would find was the tiny grey-brown mud crab (Helice crassa), which could be handled easily, but if I managed to turn over one of the really big rocks then I would be able to find the larger purple shore crabs (Leptograpsus variegatus), which required a more careful approach lest they inflict great pain. One thing I didn't know at the time about either animal, however, was that they were both members of the superfamily Grapsoidea.

Grapsoidea is a grouping of crabs including at least seven families. The classification of Grapsoidea is currently undergoing something of a revision, and has shifted about a little in recent years. While most grapsoids were once included in the single family Grapsidae, the recognition of the latter as paraphyletic to the Gecarcinidae has lead to the elevation of the various prior subfamilies of Grapsidae to separate families. The family Glyptograpsidae was only established in 2002 (Schubart et al., 2002), while the genus Xenograpsus was moved into its own family within the past year (Ng et al., 2007). Other families in the group are Sesarmidae, Varunidae and Plagusiidae. The majority of grapsoids are found on the shoreline, but some (such as the Chinese mitten crab Eriocheir sinensis) move into fresh water. At least one genus, Planes (Grapsidae), is pelagic, while Xenograpsus has been found to depths of 270 m (McLay, 2007). Xenograpsus is found in association with hydrothermal vents, and populations of X. testudinatus living on sulphur vents near Taiwan make their living by feeding on the rain of dead zooplankton killed by toxic discharges from the vents (Ng et al., 2007).


Gecarcoidea natalis, Christmas Island red crab migration. Photo from here.

Some members of the Gecarcinidae live their adult lives terrestrially as adults on tropical islands. Nevertheless, all grapsoids (as far as I can tell) retain the ancestral state of marine planktonic larvae, so all terrestrial gecarcinids must return to the coast to spawn. The Christmas Island red crab, Gecarcoidea natalis has become renowned for the vast numbers that can be seen in its mass migrations, as the entire island's population of crabs (more than 40 million when estimated in 1995 - Adamczewska & Morris, 2001) moves down to the coast over the course of a week or so. Tragically, recent years have seen a population explosion on Christmas Island of the introduced yellow crazy ant* (Anoplolepis gracilipes), which was estimated to have killed off some 15 million-plus crabs by 2003 (O'Dowd et al., 2003), and has essentially eliminated crab populations wherever it has established colonies. Foraging crabs are attacked in large numbers by crazy ants defending their nests, and poisoned with large amounts of formic acid. Crazy ants will also occupy crab burrows, removing their former inhabitants with extreme prejudice. Not only are resident crabs killed, but crabs migrating from elsewhere have been destroyed as they crossed crazy ant-infested locations on their way to the coast. Where red crabs have been eliminated, the forest vegetation structure has begun to change significantly, as seedlings that would have once been grazed by crabs are able to establish a dense undergrowth.

*So called because of the seemingly random way in which they wander about when foraging.


Xenograpsus testudinatus at the base of a sulphur vent. Photo from here.

The Grapsoidea are closely related to another shore-crab family, the Ocypodoidea, and apparently species included in these two superfamilies were once united (back in the 1800s) under the taxon name Catometopa (Schubart et al., 2006), a name that I think deserves resurrection (just try saying it a couple of times - "Catometopa!"). While it seems to be universally accepted that these two superfamilies form a clade, the molecular phylogenetic analysis of Schubart et al. (2006) indicated that each of the "superfamilies" was polyphyletic within this clade, and recommended that they not be recognised as distinct. So far, I haven't been able to find what are the characters that are supposed to separate the two groups. Davie & Ng (2007) stated that morphological data maintained the monophyly of Grapsoidea, but omitted to cite any details in support of this statement.

REFERENCES

Adamczewska, A. M., & S. Morris. 2001. Ecology and behavior of Gecarcoidea natalis, the Christmas Island red crab, during the annual breeding migration. Biological Bulletin 200: 305-320.

Davie, P. J. F., & N. K. Ng. 2007. Two new subfamilies of Varunidae (Crustacea: Brachyura), with description of two new genera. Raffles Bulletin of Zoology Supplement 16: 257-272.

McLay, C. 2007. New crabs from hydrothermal vents of the Kermadec Ridge submarine volcanoes, New Zealand: Gandalfus gen. nov. (Bythograeidae) and Xenograpsus (Varunidae) (Decapoda: Brachyura). Zootaxa 1524: 1-22.

Ng, N. K., P. J. F. Davie, C. D. Schubart & P. K. L. Ng. 2007. Xenograpsidae, a new family of grapsoid crabs (Crustacea: Brachyura) associated with shallow water hydrothermal vents. Raffles Bulletin of Zoology Supplement 16: 233-256.

O'Dowd, D. J., P. T. Green & P. S. Lake. 2003. Invasional 'meltdown' on an oceanic island. Ecology Letters 6 (9): 812-817.

Schubart, C. D., S. Cannicci, M. Vannini & S. Fratini. 2006. Molecular phylogeny of grapsoid crabs (Decapoda, Brachyura) and allies based on two mitochondrial genes and a proposal for refraining from current superfamily classification. Journal of Zoological Systematics and Evolutionary Research 44 (3): 193-199.

Schubart, C. D., J. A. Cuesta & D. L. Felder. 2002. Glyptograpsidae, a new brachyuran family from Central America: larval and adult morphology, and a molecular phylogeny of the Grapsoidea. Journal of Crustacean Biology 22(1): 28-44.

Reference Review: The Secret of Bubba-Gump's Success

Dardeau, M. R., & R. W. Heard Jr. 1983. Crangonid shrimps (Crustacea: Caridea), with a description of a new species of Pontocaris. Memoirs of the Hourglass Cruises 6 (2): 1-39.

The Great Biological Survey has a long tradition in taxonomy. A collection of researchers and their associates travel to a far-off exotic location* where they spend their time greedily grabbing specimens of everything they can possibly find, before heading back home where the fruits of their labours are sorted, preserved and (hopefully) identified to give an extensive view of the biodiversity of the area surveyed.

*Well, not necessarily that far-off or that exotic. But it can be, and probably a lot more students are drawn in by the prospect of trips to central Africa or the depths of the Amazon than the small patch of remnant bush in the local council park.

Biological surveys are alive and well - I've commented on the results of recent examples here and here, and a current project to recreate the Beagle voyage of Charles Darwin plans to run one on the way (though [a] they're talking about DNA barcoding, a concept that rather raises my hackles - more on that later - and [b] hopefully the captain doesn't shoot himself this time around). Marine biology in particular has a proud history of surveying expeditions, with such examples as the Challenger to look back to.

The "Hourglass" survey began in Western Florida in 1965 and lasted for 28 months, during which samples were taken at regular intervals from stations on the continental shelf of west Florida. Results from this survey were published in a series called Memoirs of the Hourglass Cruises that came to my attention after I picked up a pile of issues of it that had been put into the "free to a good home" pile at the university library. Together, the various articles provide fairly good coverage of the marine fauna of the northern Gulf of Mexico. The Dardeau & Heard (1983) issue is typical in that it not only covers the Hourglass specimens, but takes the opportunity to review the entire Gulf of Mexico fauna (seeing as only one species of Crangonidae, Pontophilus gorei, actually turned up in the Hourglass survey, it could have been a very short paper otherwise). The one aspect that caught my eye was the description of the new species Pontocaris vicina. This species does not seem to be uncommon if the distribution records listed by Dardeau & Heard are to be believed, but had previously not been recognised as distinct from Pontocaris caribbaea. According to Dardeau & Heard, "The two species must have similar but not identical ecological requirements; although taken in successive trawl hauls, they were never taken together in the same haul".

Credits: The photo at the top comes from Wikipedia. Though a crangonid, it is not one of the Gulf of Mexico species. Rather, it is the north-east Atlantic Crangon crangon, one of the more commonly fished shrimp species in Europe.