Morphology and development of <Emphasis Type="Italic">Pteromalus cerealellae</Emphasis> (Ashmead) (Hymenoptera: Pteromalidae) on <Emphasis Type="Italic">Callosobruchus maculatus</Emphasis> (F.) (Coleoptera: Chrysomelidae)

Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is an ectoparasitoid of several stored-product insect pests. Very little information has been published on its biology and development in host larvae, which typically are concealed within seeds. We documented the development of P. cerealellae within fourth instar larvae of its concealed host, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting cowpea seeds. The preimaginal life stages of the parasitoid were characterized for the first time using morphological structures revealed by microscopic techniques including scanning electron microscopy. Pteromalus cerealellae produces hymenopteriform eggs and larvae. Eggs hatch into 13-segmented first instar larvae with peripneustic condition of spiracles. The larvae have simple, tusk-like mandibles, whereas the mandibles of the pupae and the adults are of the conventional toothed types. Using statistical analyses of the sizes of the larval mandibles and head capsules in conjunction with reliable characters such as the number of exuviae on the body of parasitoid larvae, cuticular folding, and excretion of the meconium, we recorded four larval instars for P. cerealellae. The data showed significant positive correlations between larval mandible lengths and widths of larval head capsules, as well as between mandible lengths and larval instars, suggesting that mandible length is a good predictor of the number of instars in P. cerealellae. Developmental time from egg to adult emergence was ∼12 d for females and ∼11 days for males at 30 ± 1°C, 70 ± 5% r.h. and 12L:12D photoperiod.     

Spectral cathodoluminescence analysis of hymenopteran mandibles with different levels of zinc enrichment in their teeth

The inclusion of Zn in insect mandibles affects their hardness and is functional to their use during feeding or reproducing. However, little is known on the chemical/structural base of Zn enrichment. Here, we found that cathodoluminescence (CL) technique revealed two different types of CL spectra in the mandibles of Hymenoptera, depending on the Zn enrichment level assessed by Energy Dispersive X-ray Spectroscopy (EDS). Individuals having negligible traces to low % of Zn in their mandible teeth (≤3 wt%) presented a wide band of luminescence in the visible range which resembled those observed in the CC structures of graphite. This spectrum is probably characteristic for un-enriched cuticle, since it did not differ from those obtained from the Zn-lacking inner part of mandibles. Individuals with moderate to high % of Zn in their mandible teeth (≥7 wt%), instead, presented additional CL peaks in the ultraviolet range. Comparisons with different minerals of Zn suggest that these peaks could be related with OZnO bonds, with hydroxyl groups and with zinc-chlorine links (in agreement with Cl high levels detected by the EDS). Being a non-destructive technique, CL allows large comparative studies of the chemistry of metal-enriched insect cuticle even using unique specimens, such as those deposited in Natural History Museums.     

A comparative study on the dental health status of five precolumbian Peruvian cultures.

In a survey of dental health status of ancient Southern Peru, 101 skeletal remains were studied from five cultures: Paracas, Nazca, Tiahuanaco, Ica, and Inca. The Paracas and Ica cultures exhibited more missing antemortem teeth per mandible than the other cultures. Frequency of missing one or more third molars was less than expected and not as high as reported in peoples of Mongoloid heritage. The Paracas, Ica and Nazca, "coastal" cultures had a higher caries incidence than the "inland" cultures. Whether this relates to some difference in diet or water supply remains unresolved and warrants further investigation. Moderate attrition was noted in all the Precolumbian cultures but pulpal involvement was not observed. Osteitis, noted in all the cultures, was more pronounced in the Nazca, Paracas and Ica cultures. There appeared to be a direct relationship between caries involvement and the number of missing antemortem teeth to osteitis. Calculus was heavier in the Paracas and Ica cultures. In addition, the Paracas culture exhibited a dark brown stain on the teeth which may imply some difference between the cultures in either the food, water or social habits.     

Molecular evidence for the gnathobasic derivation of arthropod mandibles and for the appendicular origin of the labrum and other structures

 Mandibles are feeding appendages functioning as ”jaws” in the arthropod groups in which they occur. Which part of this appendage is involved in food manipulation (limb tip versus limb base), has been used to suggest phylogenetic relationships among some of the major taxa of arthropods (myriapods, crustaceans, and insects). As a way to independently verify the conclusions drawn from previous morphological analyses, we have studied the expression pattern of the gene Distal-less (Dll), which specifies the distal part of appendages. Our results show, in contrast to the traditional view, that both insect and crustacean adult mandibles are gnathobasic, handling food with the basal portion of the appendage. Furthermore, as is evident by the reduction in the number of Dll-expressing cells in the later developmental stages, adult diplopod jaws are also gnathobasic. Thus, jaws of all mandibulates (myriapods, crustaceans, and insects) seem to have a similar gnathobasic structure. We have also found that Dll is expressed in the labra of all arthropod taxa examined, suggesting that this structure is of appendicular derivation. Additionally, the spinnerets and book lungs of spiders, long considered on other grounds to be modified appendages, express Dll, confirming this interpretation. This study shows that, in addition to their use in phylogenetic and population genetic studies, molecular markers can be very useful for inferring the origins of a particular morphological feature. Received: 12 January 1998 / Accepted: 23 March 1998     

Jaw growth and replacement in<Emphasis Type="Italic"> Ophryotrocha labronica</Emphasis> (Polychaeta,Dorvilleidae)

Ophryotrocha labronica, as typical for Eunicida, has a complex jaw apparatus consisting of ventral mandibles and dorsal maxillae. Mandibles are not replaced but are retained throughout life. Larval mandibles have adult-sized cutting plates but their proximal shafts lengthen and enlarge as the worm grows. The maxillary apparatus of O. labronica undergoes three moults or replacements. The initial, or larval maxillae, consisting of two paired basal plates and two paired free denticles, develop in the unreleased larvae. They are replaced in the 5-setiger juvenile by the P1-maxillae consisting of falcate forceps and six denticles. The second moult occurs in the 8- to 9-setiger juveniles and results in the P2-maxillae with bidentate forceps and seven denticles, and the third and final moult results in the K-maxillae and seven denticles. The K-maxillae develop in 9- to 12-setiger males and 13- to 15-setiger females and are not replaced but enlarge proximally. Thus the K-forceps can be traced back through the P2-forceps, P1-forceps, to the larval basal plates, indicating the apomorphic state of the K-forceps. Three pulp cavities, separated by darker fusion lines are visible in weakly sclerotised young K-forceps suggesting the fusion of three separate elements. It is concluded that the Ophryotrocha forceps are homologous to the superior and probably inferior basal plates of other dorvilleids. The internal structure of the Ophryotrocha forceps demonstrates that they are not homologous to the labidognath maxilla I as has been suggested.     

Relationship between the mandibular condyle and the occlusal plane during hominid evolution: Some of its effects on jaw mechanics

A selection of mandibles from recent higher primates, fossil hominids, and hominoids has been studied from photographs of skulls, reproductions, and material published by others, all viewed in the sagittal plane. Tracings of each mandible were constructed so that the dentitions were all scaled to the same length (d) and superimposed. The (scaled) positions of the articular surfaces of the condyles (J = joint point) were compared. The height of each J point above the scaled dentition (h = effective condyle height) and its distance behind the dentition (r = effective ramus width) were compared. With very few exceptions d r > d/2. There was a poor correlation between r and the amount of prognathism. The position of the J point with respect to the occlusal plane was different for different groups within the material analysed and could prove to be a useful tool to help improve the reconstruction of fragmented fossil material. Some examples are given. A. afarensis and Homo habilis shared a low and anterior J point (r ～ d/2). The later australopithecines evolved a high and anterior J point, whereas that of Homo erectus was raised and displaced posteriorly (r ～ 3d/4). The value of r was increased to d in the Neanderthals, and recent man has moved the J point forward again. The effect of the position of the J point, the slope of the preglenoid plane, and the curve of Spee on the relationship between upper and lower postcanines when the jaw is opened and then closed to process food have been analysed. The results show that the position of the J point affects the way in which the mandible moves, and this may be related to changes in diet during evolution.     

New hominid fossils from the Swartkrans formation (1979-1986 excavations): craniodental specimens

Seventy-two individually numbered hominid craniodental fossils from recent excavations at Swartkrans are described. All derive from in situ decalcified breccia and/or unconsolidated sediments. A total of 20 specimens, representing 13 to 16 individuals derive from Member 1 "Lower Bank," two teeth derive from sediments along the Member 1-2 Interface, 38 fossils representing 19 to 24 individuals come from Member 2, and 12 teeth representing 9 to 11 individuals derive from Member 3. All but four of the specimens are attributable at the generic level; one specimen from Member 1 "Lower Bank" and five specimens from Member 2 are attributed to Homo, while the others represent Paranthropus. The proportional representation of Homo in the Swartkrans Formation is markedly higher in Member 2 (c. 33%) than in the Member 1 "Lower Bank" (c. 8%) and Member 1 "Hanging Remnant" (c. 5%) samples.     

New hominids from East Turkana,Kenya

Thirty-five new fossil hominid specimens are described. They were recovered from the Plio-Pleistocene sediments to the east of Lake Turkana (formerly Lake Rudolf). They include cranial and mandibular parts, teeth, and postcranial bones of upper and lower limbs. Parts of a single skeleton are also described. All of the specimens are described in anatomical detail and selected measurements are given. Some of the specimens are illustrated. It is proposed that they should be attributed to the family Hominidae, with genus and species undetermined until detailed comparative studies have been undertaken.     

Morphology of Afropithecus turkanensis from Kenya

Forty-six specimens of a large Miocene hominoid, Afropithecus turkanensis, recently recovered from northern Kenya preserve many morphological details that are described. The specimens include cranial, mandibular, and postcranial parts. They are compared briefly with other Miocene hominoids. It is suggested that Afropithecus may have affinities with Heliopithecus, Kenyapithecus, and the large hominoid from Moroto and Napak, although it is noted that the comparative material is limited in the number of common anatomical parts preserved.     

Morphology of Turkanapithecus kalakolensis from Kenya

The type specimen of Turkanapithecus kalakolensis recently recovered from northern Kenya preserves a partial cranium and mandible. This specimen, together with postcranial elements that are probably associated with it, and two additional specimens are described. The collection is compared with other Miocene hominoids.