Adult and Larval Stomatopod Crustaceans Occurring in Hawaiian Waters1 SIDNEY JOSEPH TOWNSLEy2 INTRODUCTION t~on of the Bernice P. Bishop Museum, found Sl X genera and eight species from Hawaii: THE STOMATOPODA constitute the only order belonging to the division Hoplocarida of the Squilla oratoria, S. alba, Pseudosquilla ciliata, malacostracan Crustacea. All living forms are P. oculata, Coronida sinuosa, Lysiosquilla macu­ ~do~todactylus included in a single family, the Squillidae, lata,. hanseni, and Gonodactylus Since th at time no extensive studies whose characteristics are the same as those guerlnJ. of the order. The order, according to Bigelow have been made on specimens from Hawaii, (1894), may be defined as Crustacea which but occasional reports of previously recorded ~pecies fr~m have these characteristics : the stalked eyes and this region have found their way anrennules are borne upon distinct mo vable into .the ht.erature. In addition to these eight segments; the adult rostrum is separated from speCles which have been again collected dur­ the carapace by a movable joint; the carapace _ ing the progress of thi s study, I have found is small and does not cover the last four tho­ two species which have not been recorded fr~.m racic somites; the first five pairs of thoracic this region previousl y, namely, Squilla appendages are not biramous and serve as boops and an undescribed species of Squilla. accessory mouth parts, with the second pair Stomatopods are usually found in very shal­ strongly developed into large raptorial limbs ; low water, but some species occur at greater the last three pairs of thoracic appendages depths. I have collected Gonodactylus guerini are adapted for walkin g, are biramous and bear in Hawaii only at depths over 100 meters, and a lateral segment upo n the penultimate seg­ Kemp (1913) reports th at Squilla leptosquilla ment; the abdomen is well developed; fila­ was dredged by the "Investigator" at a depth mentous gills are carried upon the exopod of of 370-419 fathoms . The adults are bottom the first five abdominal appendages; the sixth dwellers where the y may burrow into the sub­ ~nh ab i~ abd ominal appendages, the uropod s, with the strate .or crevices in coral. They are telson, act as a powerful tail fan. seclusive In their habits and durin g the day At the present time the six recognized gen­ are usually found either in their burrows or era have a world -wide distribution , bein g but a short distance away. At times they wan­ found in the tropical , subtropical, and rem­ der some distance from the ir burrows, as is perate waters of the Atlantic, Pacific, and In­ shown by the fact that the y are occasionally dian oceans. All six genera are represented in captured in crab nets and at submersible lights the Hawaiian fauna. Edm ondson (1921), re­ used for collecting at night. Inasmuch as the porting upon the stomatopods in the collec- burrows are quite deep (a foot or more below the surface), and because the animals retire 1 C ontr ibuti o~ No, 37, Hawaii Marine Laboratory, Prep ar e ~ as partial !.equirement for the M .S. degree. to the bottom of them at the least alarm University of H awaii. Manuscript received November stornatopods are .quite difficult to collect ; 14, 1951. 2 Graduate assistant, Osborn Zoological Laborator y consequently, the gro up has been studied Yale University. ' very little, the most notable works being those 399 400 PACIFIC SCIENCE, Vol. VII, October, 1953 of Miers (1880), Brooks (1886), Bigelow withstanding their great abundance, only two .(1894), and Kemp (1913). Of these works, or three early larval forms have been traced the most useful for the identification of the to their adult counterpart. Their long plank­ Hawaiian species has been Kemp's mono­ tonic existence easily accounts for the world­ graph on the Indo-Pacific species. wide distribution of the genera and the pres­ Stomatopods are carnivorous and readily ence of species such as Pseudosquilla ciliata seize any flesh held in front of their burrows . in the Pacific Ocean , Indian Ocean, Red Sea, This behavior has provided the most satis­ and Atlantic Ocean . At present there appear factory means for capturing them , as they can to be onl y two species which are endemic in be lured from their burrows by suspending Hawaii, namely, Coronida sinuosa and Squilla fish flesh a short distance away and captured calumnia n. sp. when they attack the flesh. Considerable dex­ Attempts were made to rear larval spec­ terity is necessary, however , as they withdraw imens, collected in plankton tows, in the lab­ rapidly into their burrows . It has been im­ oratory, but this proved to be impos sible as possible to keep more than one specimen at their period of survival in captivity was very a time in small aquaria as they are highly short, and none of the larvae ever molted cannibalistic. while in an aquarium . Because rearing of the It is doubtful whether the adults often serve larvae was unsuccessful, it was necessary to as food for other animals, although they may study specimens collected in plankton tows occasionally be found in the stomach con ­ and at night light stations and material from tents of fish; bur the planktonic larval stages the stomach contents of pelagic fishes. which compose a substantial proportion of The earlier authors such as Miers (1880), the neritic plankton form a considerable part in their work on larval sromatopods, were ofthe diet of pelagic fishes. content with bestowing separate generic and Instead of carrying their incubating eggs trivial names upon the larvae. If the adult attached to the abdominal appen dages, as do genus to which the larval specimens belonged most Malacostraca, the stomatopods deposit was known, they added the suffix -erichthus them at the bottom ofthe burrows where they to the first syllable of the adult genus plus are aerated by currents of water produced by a trivial designation .(except in the case of the abdominal appendages of the parent. alima of Squilla). Thus Pseuderichthus communis These appendages are paddle shaped and con­ Hansen, according to this system of classifi­ form to the cylindrical shape of the hole . cation, represented the larval form of a species The eggs perish when they are deprived ofthis of Pseudosquilla. Because no keys to these constant current of water, and, as the female individual larval species were included, future will not remain with the eggs when placed authors found it difficult to identify specimens in an aquarium, no larvae have been reared in their possession with those which had been from the egg in captivity. previously described , and new larval species The young do not hatch as nauplius larvae. were erected to compensate for this. Claus All known forms hatch in an advanced stage (1872) and Brooks (1886) have done the most which bears many adult characteristics , but notable works on the larval forms . Giesbrecht it is difficult to assign the early larvae properly (1910), Foxon (1932), and Gurney (1942) because the diagnostic characters do not ap­ have reviewed the works of Claus and Brooks pear until later. and expanded their results to include other The larvae are delicate, transparent organ­ unidentified larvae. However, I have found isms which lead a planktonic existence. The that the material has not been adequately larval life is long, and they pass through many simplified below the level of the genus, be­ molts before reaching the adult stage. Not- cause in many cases they have retained the Hawaiian Stornatopods - TOWNSLEY 401 previously assigned generic and rrivial names The present study was undertaken because of rhe larvae, thus making it difficult to as­ recent investigations on the feeding hab its of certain the relationship of these species to pelagic fishes have shown that the larval stages those collected in Hawaii. Most of the larvae of the Stornatopoda 'rank second in impor­ belonging to a particular genus resemble one tance as food for certain species of tu na in another so closely that it is virtually impossi­ the Hawaiian area, and that they are signifi­ ble to place them in their proper specific cant in the diet of several other pelagic fishes. category without rearing them to maturity. Inasmuch as the adult stages of the pelagic Because of these difficulties, I have not tried larvae involved are found on the reefs and to relate the Hawaiian larval forms with those shores of the Islands , it is apparent that the ofthe previously described species, but where general economy of the neritic waters in the it has been possible I have attempted to cor­ vicinit y is influenced to some extent by the relate them with their proper adult species. productivity ofthe reef and shore fauna. These The specific identification of the larvae was two points suggest a third, namely, that pe­ made in the manner used by Claus (1872) lagic fishes may be influenced to venture close and Brooks (1886) in which three methods to shore because of the increased food supply were emplo yed: (1) a comparison of larval there. stages with posdarval forms which show char­ In order to assess objectively the impor­ acteristics of both the larvae and adults, in tance of these larval stages in the general this manner working from the adult back economy of the neritic realm, it is necessary through the larval series to the earliest iden­ to be able to identify the species involved, tifiable stage; this is by far the most accurate so that a rapid qualitative andquantitative means of identification, except, of course, analysis ofboth the plankton and the stomach where rearing of the larvae to the adult has.